جستجوی مقالات مرتبط با کلیدواژه « شکست سد » در نشریات گروه « عمران »

Dams are considered one of the most important infrastructure facilities of a country, which play a very important role in economic prosperity through storage, regulation of water, and also energy production. Due to the volume of water stored in the reservoir of these dams and sometimes their proximity to residential areas, the failure of dams can lead to a lot of human and financial losses, which can be prevented by having sufficient information and proper forecasts of dam failure. The flow resulting from the dam failure is turbulent, mainly a mixture of fluid and sediment particles. Therefore, after the dam's failure, sediment transport leads to significant morphological changes downstream. Based on this, the analysis and evaluation of the instantaneous failure of the dam have been one of the main challenges of the profession of engineers and activists in this field. By examining the research background, it is clear that the studies focused on fluid flow in non-erodible bed conditions, and a small part of numerical and laboratory research has been focused on the evaluation of changes in the morphology of the bed sediment layer. In addition, one of the effective parameters in the mechanism of sediment transfer and the pattern of morphological changes of the bed is the sediments of the dam reservoir, which has received less attention from researchers. Therefore, in this research, we have evaluated and experimental-numerically modeled the phenomenon of sediment transport due to the sudden failure of the dam, taking into account the sediment layer in the dam reservoir.

In this study, two variables (1- the type of sediment particles (fine sand and coarse sand) and 2- the thickness of the sediment layer in the reservoir and downstream of the dam) have been investigated as the main parameters in the evaluation of the sediment transport mechanism (changes in bed morphology). Based on this, scenarios have been defined for laboratory and numerical modeling. In this research, to evaluate the phenomenon of bed sediment transfer based on the phenomenon of instantaneous dam failure, four tests have been defined and implemented in the hydraulic laboratory flume of Babol University in different conditions. This flume is 10 meters long, 50 cm wide, and 50 cm high and is equipped with an ultrasonic level gauge and a digital pressure gauge. In these experiments, two parameters of the type of bed sediment materials (A, B) and also the thickness of the sediment layer downstream of the dam and the reservoir of the dam have been considered as modeling variables. Type A materials are gravel particles with an average diameter of 20 mm, and type B materials are sand particles with an average diameter of 3 mm.

According to the research variables, four scenarios for laboratory modeling and six scenarios for numerical modeling of the phenomenon of sediment transfer based on instantaneous dam failure have been defined. The results of the numerical modeling showed that the numerical model of the research had acceptable accuracy in simulating the phenomenon of sediment transfer due to dam failure, so the modeling error for two-dimensional numerical models (the first four models based on Table 2) is respectively equal to 2.75%, 4.31%, 2.59%, 5.52% compared to laboratory tests.The results showed that in the models of type B sediment materials, the amount of reduction in the thickness of the sediment layer is greater than in the models with type A sediment materials; in other words, the amount of reduction in the thickness of the sediment layer in type B materials is more than type B. The material was A. Therefore, the decrease in the diameter of the sediment particles has caused an increase in the thickness of the sediment layer (bed morphology) due to the failure of the instantaneous dam. In addition, by examining the results obtained from laboratory and numerical models, it was determined that the reservoir sediment layer of the dam is an effective parameter in the rate of sediment transfer and the occurrence of changes in the morphology of the bed based on the dam failure currents, in such a way that with the increase in the thickness of the sediment layer of the reservoir Compared to the downstream sediment layer of the dam, the changes in the thickness of the bed layer have increased by about 10%, as well as the rate of sediment transfer in these conditions.By evaluating the results of dam failure modeling in three-dimensional space, it is clear that the thickness of the sediment layer in the 3D_DB1_NB1 model with type B materials has decreased more compared to the 3D_DB1_NA1 model with type A materials. In addition, according to the contour of the changes in the thickness of the bed layer, it is clear that the type of material of the sediment particles (diameter of the sediment particles) was an effective factor in evaluating the phenomenon of sediment transport in the 3D modeling space. In both 3D models, the thickness of the sediment layer in the area of the dam valve (failure area) has decreased and increased in the range of 1.8 to 2 meters and decreased from 2.2 to 3 meters.

In this research, the main goal is to evaluate the mechanism of sediment transfer due to the sudden failure of the dam, focusing on the effect of the sediment layer in the dam reservoir, which has been implemented in the form of laboratory and numerical modeling. Also, the effect of three parameters, the type of sediment particles and the thickness of the sediment layer in the reservoir and downstream of the dam axis, has been studied.Based on the results of this research and the evaluation and comparisons made between the numerical models and the laboratory model, it is clear that the numerical model created in both two-dimensional and three-dimensional spaces has an acceptable accuracy in simulating the phenomenon of sediment transfer due to dam failure.

One of the critical consequences of climate change is prolonged droughts with floods. In these conditions, maintaining the maximum possible water level without wasting it and high discharge capacity in critical situations is essential to preserving the reservoir's health. The most suitable solution for sending excess water can be considered as creating a proper spillway. According to ICOLD, one-third of dam failures are due to weir disproportion. Unfortunately, due to the designers' lack of experience in using the nonlinear spillway, irreparable accidents sometimes happen. Therefore, choosing the proper spillway with the appropriate discharge have undeniable importance. This paper focuses on a new solution to improve the piano key weir capacity. By correcting the sidewalls of weirs, three goals were pursued simultaneously. In the first step, better performance than conventional PK weirs on the occasion of a flood. The second goal is to store the maximum water level upstream in non-critical situations and use only part of the weir.The ultimate goal is to make this method economical. This research is a continuation of previous research on PK weirs. Figure 4 shows the rotating flume environment, which experiments were performed in that laboratory at the Tarbiat Modares University of Tehran (Dimensions: 10 meters long, 2 meters wide, and 0.9 meters high)( Figure 4). Experiments have been performed on a triangular weir with a zero slope (i.e., Tri-Base model) (Fig. 1 and 2) and 10 degrees in the flow direction (Fig. 1 and 3). In this article, Pk weir with horizontal and sloped crest is called Tri-Base and Tri-B1 models. The weir characters used in the laboratory are provided in Table1. Eq (4) and (5). The dimensional analysis of the (Tri-B1) model, and the (Tri-Base) model, respectively. In the analysis of laboratory data, an effective length (wet length of walls) was defined for the weir. Then for this geometry, Eq. (6) and (7) were provided to calculate the discharge coefficient, which in addition to the new weir, is used in typical weir (i.e., The Tri-Base model) can also be used with great precision. Fig.10 shows the comparison of measured and calculated values of triangular pk weir.For the Head-Discharge curves, firstly, the discharge-head curves for triangle Pk weir with horizontal crest (Fig. 7) have been plotted and compared with the present study and other researchers' results. The differences between results are because of the differences in geometric characteristics shown in Table 2. Because the head and weir height changes for every discharge, Fig. 6 and have been plotted curves of (Q-P+Ht). Based on these figures, water height in triangle PK weir with a sloped crest (i.e., The Tri-B1 model) is higher than triangle pk weir with a horizontal crest (i.e., The Tri-Base model), but head height over the (Tri-B1) model is less than the (Tri_Base) model. On the other hand, for the (The Tri-Base) model, discharge coefficients have been plotted in Figure 8.This figure also compared the results of other researchers the results with this study. Fig. 9 also shows the discharge coefficient for the (Tri-B1) model. The discharge coefficient in the (Tri-B1) model has increased by an average of 3.8% than the (Tri-Base) model, with the maximum and average discharge coefficients shown in Table 3.Also, about the flowing blade, in the weir of a triangular Piano key weir with a horizontal crest, at 8 Cm 〖>H〗_t > 4 Cm, air penetrates under the blades of the flow, and the flow is vented. At higher values (12 Cm 〖>H〗_t > 8 Cm), the flow under the blade is connected to the open-air with increasing water head. In this case, have been seen fluctuations in the current blade. At higher values ( H_t>12 Cm), the flow completely covers the weir (immersion) and passes over the weir. In these conditions, the fluctuations of the flowing blade can be observed. According to Fig. 5 in Q=40lit/sec have seen an Air cavity on the weir body. Also, in analyze were seen, the weir of a piano key weir with a sloping crest (i.e., The Tri-B1 model) increased. But with the sinking whole of the weir, the discharge coefficient rate decreases. Also, in connection with the weir blade of the Pk weir with a sloped crest (The Tri-B1 model) in some discharges, all three types of flow blades can be seen on the sidewalls of the weir (i.e., sticky, compressed, and free baled. In conclusion, in Pk weir with slope crest, have been seen the level of water behind the weir increases while the head of water on the weir decrease. So this means that in drought seasons and when the level of water decreases in the reservoir, this spillway can increase the water level. Use this weir's high capacity in the critical season (especially during flood time). On the other hand, this spillway has a high capacity in all situation and increase the discharge coefficient.

Dam break is a very important problem due to its effects on economy, security, human causalties and environmental consequences. In this study, 3D flow due to dam break over the porous substrate is numerically simulated and the effect of porosity, permeability and thickness of the porous bed and the water depth in the porous substrate are investigated. Classic models of dam break over a rigid bed and water infiltration through porous media were studied and results of the numerical simulations are compared with existing laboratory data. Validation of the results is performed by comparing the water surface profiles and wave front position with dam break on rigid and porous bed. Results showed that, due to the effect of dynamic wave in the initial stage of dam break, a local peak occurs in the flood hydrograph. The presence of porous bed reduces the acceleration of the flood wave relative to the flow over the solid bed and it decreases with the increase of the permeability of the bed. By increasing the permeability of the bed, the slope of the ascending limb of the flood hydrograph and the peak discharge drops. Furthermore, if the depth and permeability of the bed is such that the intrusive flow reaches the rigid substrate under the porous bed, saturation of the porous bed, results in a sharp increase in the slope of the flood hydrograph. The maximum values of peak discharge at the end of the channel with porous bed occurred in saturated porous bed conditions.

Due to the increasing need water resources, analysis, design and construction of dams is one of the most widely used fields in engineering sciences. In general, dams with their special characteristics have been able use to another of types of the hydraulic structures.One of the most popular numerical methods proposed for the analysis of hydraulic problems is the meshless methods. In the meshless method, the amplitude and boundaries of the structure are created by nodes. The shape function is used to communicate between nodes.In this study first the meshless local Petrov-Galerkin (MLPG) method by Radial Basis Function (RBF) has been explained entirely. In the following, MLPG method is verified by exact solution in a numerical example. The Results show that MLPG method presented high accuracy and capability for solving the governing equation of differential equations problem in meshless methods. Finaly, using RBF (MatLab code was adopted) in the fluid flow in dam breaking problem.

Several numerical methods, such as the finite element (FE) and meshless methods, have been developed in the last few decades for solving governing partial differential equations of engineering problems. Approximation in geometry and imposition of boundary conditions in meshless approaches can be mentioned as the drawbacks of the methods. Furthermore, in some engineering problems such as those which are solved in a Lagrangian framework, geometry and boundaries change and, therefore, discretization of the domain should be modified in case of using the FE method, which is quite costlyIn the meshless methods, the calculation of the integration is based on the Gaussian integration method in the general and the local forms. In the general method, in order to integrate, it is necessary to create meshes in the background of the problem domain; therefore, this method is not a true meshless method. But meshless methods based on the local integration method, such as the meshless local Petrov-Galerkin (MLPG) method, have been proposed. In this way, the governing fluid flow in dam breaking problem is expanded using MLPG method. Radial Basis Functions (RBF) is used to communicate between nodes. In order to discretize the derived equations in time domains, Zienkiewicz and Codina (1995) scheme with suitable time step is used. The Mass and momentum conservation laws are governing equations of flow, which are solved by pressure correction in Lagrangian approach. Then these results are compared with another method results. The results showed high accuracy and good conformity compared to available another solutions and the ability of the proposed method in solution of moving fluid with moving boundaries.

In order to demonstrate the accuracy of the present method for dam breaking, at the first a problem verifying with analytical solution. Table 2 shows the analytical, numerical and error values obtained. The comparison shows the high capacity and accuracy of the present method.After verification, the dam breaking problem is investigated. The geometry of the dam breaking problem is shown in Figure 4 and then the present method compare with isogeometric and the least squares method. By comparing the free surface profile between the three methods, it can be easily understood that the meshless local Petrov-Galerkin (MLPG) method based on Radial Basis Functions (RBF) has the high accuracy. On the other hand, the close nature of the meshless local Petrov-Galerkin (MLPG) method with the least squares method, it is quite clear that the results are in good agreement. The following results are shown in Figures 7 to 9. the water flow velocity resulting from the present method results with the base function of the radial function in 0.15 seconds in the problem compared to the least squares method (Shobeyri and Afshar 2010) and isogeometric (Amini, Maghsoodi et al. 2016). Finally, the pressure obtained from the MLPG method in 0.15 seconds compared to the least squares method (Shobeyri and Afshar 2010) and isogeometric (Amini, Maghsoodi et al. 2016) in Figures 10 to 12 are showed.

By considering the dam breaking problem, it was found, the Meshless Local Petrov-Galerkin (MLPG) method is useful in modeling problems with variable boundary conditions, because only by producing nodes at each stage of analysis can define a new boundary conditions and then in the shortest possible time modeling is done. It is clear the modeling this problem with the other methods such as finite element method is complex, because by changing the boundary conditions, produced the new elements becomes a time-consuming and complex matter. The Meshless Local Petrov-Galerkin (MLPG) Method is an intelligent design for solving problems of variable geometric conditions.

Introduction In dam failure studies, prediction of its hydraulic components, including depth and velocity, has always been important for hydraulic engineers due to its impact on the severity of the disaster. There are various hydraulic, hydrological, geotechnical and geometric factors that affect the characteristics of the flow through the failure of the dam. In order to investigate the effect of the factors, research has been carried out especially in the field of laboratory, but little numerical research has been done. Resource surveys show that although the walls of concrete reservoir dams are not perpendicular to the lateral support, but so far, the effect of wall deflection on the hydraulic properties of the flood due to the dam failure has not been considered. Therefore, in this research, the effect of quarries of 2.5 to 10 percent of the wall of the dam was examined from the perpendicular to the base. Since the wall deviation of the dam from the normal state removes physical space from a rectangular state, the use of orthogonal coordinate system is not possible. Therefore, in this study, using the curvilinear coordinate system of the physical non- rectangular space studied, It is very accurately converted to computational space and the governing equations are solved. Materials and Methods In this research, the governing equations for shallow water were discritized in curvilinear coordinates by explicit finite difference method. For more stability Lax and Leap-Frog schemes on staggered mesh are utilized, too. For areas studied, in order to determine the coordinates of points in the physical space, by presenting a computer program, the computational mesh is created in Cartesian coordinates. Then, by converting the coordinates in the Cartesian system (x, y) to the curvilinear coordinates (ξ, η). Results and Discussion In order to validate the present model, its results were compared with experimental investigation by previous researchers. 1- Failure of the dam in the convergent-divergent channel without sloping and sloping: The water level profile of the laboratory model is presented for different times (zero, 4, 20, 60) seconds. The mean error in the results of the present numerical model is 4.02% for the results of the measurements for the non-slope channel and for the channel with a 0.01 slope, 1.65%. 2- Dam Failure in canal with dry bed with trapezoidal reservoir: The results of the model follow a similar trend to the experimental results, and the magnitude of the error in the peak areas that is more important is not significant. 3- The effect of the wall angle of the partial symmetric dam-break in the dry bed: It was observed that with the diversion of the wall angle of the dam from the perpendicular position in the failure site, depth and rate of flow decreased more. A closer examination shows that for diversion of 2.5, 5, 7.5 and 10 percent, peak discharge values were decreased  3.5, 6.1, 9.2, 11 percent, and the maximum water level was 2, 6, 9 and 12 percent.   Conclusions In simulating the ideal failure of the deformed reservoir on a dry bed, the results of this numerical model are adapted with the results obtained from the physical model. In another study, the results of the model were compared in the simulation of the dam failure phenomenon in the convergent-divergent channel without sloping and sloping with the results of the measurements. It was determined that a numerical model with an average error of less than 5% estimated the depth of the flow in the failure location.In order to achieve the main objective of the research, the results of the present numerical model in simulating the partial symmetric dam failure on dry bed have been investigated. It was observed that the diversion of the angle of the dam wall at the failer site affects the depth and discharge peak flow. The variations in “q” from the upstream of the reservoir to the failer site increase sharply and reach the maximum at the fracture site, then slowly decrease to the end of the reservoir wall. Similarly, changes in the water level with the distance from the upstream wall and moving towards the failer site are higher.  Keywords Dam-Break, Leap-frag and Lax schem, Curvilinear grid, Angel of Dam Wall  with Support.

In order to avoid meshing and its difficulties and costs, Multiquadric Radial Basis Function (MQ-RBF) method has been developed (Kansa 1990) and has been examined for different types of physical phenomena. In this regard, the present study develops this meshless method for analysis of dam break problem. MQ is more convenient and accurate than other RBF methods for solving partial differential equations (Fallah et al. 2019). This meshless method have advantages such as; 1) creating a continuous response function all over the computational domain, 2) no need to discretize the entire domain with optimal usability in large-scale problems, 3) high capability in modelling irregular and complex geometries, 4) high ability to simulate discontinuities of responses, 5) easy generalization to 3D problems, and etc. Both the accuracy and the convergence rate of MQ depend strongly on its shape parameter (Koushki et al. 2019). So far, researchers have been working on many methods for determining the optimal shape parameter but a comprehensive method has not been developed yet (Babaee et al. 2019). In this study, the commonly previous methods have been investigated for determining the optimal shape parameter and a novel idea has been presented for analyzing the flood flow caused by dam break. The efficiency and accuracy of the present approach compared to other solutions have been shown through three examples. The governing PDEs of dam break problem consist of the continuity equation and two momentum equations in two dimensions. MQ approximates solution of 2D equations system using an estimation function in which the unknown coefficients have to be determined for each unknown variable of the PDE, i.e. the velocities in two directions and the pressure. In one hand, for definition of the estimation function, the RBF methods need N center points inside the domain or on the boundaries which leads to N unknown coefficients. On the other hand, the governing PDEs and their boundary conditions again have to be satisfied on N collocation points which leads to N algebraic equations to be solved for the mentioned unknown coefficients. A critical parameter, namely, the shape parameter strongly affects the precision of the estimation function which may be considered constant or variable from point to point for each estimation function. Determining the optimal value of the shape parameter has always been a challenge in using MQ and other RBF methods. In this study it has been shown that the shape parameter in all time steps can be equal and a new high-speed idea is proposed to determine its optimal value. In this approach, the initial conditions of the problem will be estimated using MQ function and it has been shown that the optimal value of the shape parameter in the initial conditions is also the optimal value of the shape parameter for the next time steps and there is no need to be optimized for every next time steps. Therefore the computational cost will be considerably reduced. Also for discretizing the time dependent terms, the forward finite difference method is used and it was shown that for discretizing the local terms, the implicit method must be used by substituting MQ function. Consequently, the presented approach becomes unconditionally stable. In order to verify and validate the proposed approach, three 2D numerical examples are presented. In two of the examples with 1D and 2D behaviors, discontinuities in initial conditions and run times are different. Sharp discontinuities highlight the capabilities of the approach while in long run time shows stability. Besides, results of the proposed approach have been compared with those of other numerical and analytical methods. Also, in this research, inefficiency of previously common methods for determining the optimal shape parameter in solving the dam-break problem was shown (Golbabai et al. 2015). In verification, the RMSE error criterion has been considered which results in errors less than 5 percent. In the third example capability of the numerical model has been demonstrated by a two dimensional dam break flow. Using the MQ-RBF, the disadvantages of mesh-based method including; high cost of meshing, need to fundamental solution dependence on the conditions of each problem, singularity, continuous discretization of domain and need to a regular mesh will be eliminated. The benefits of the proposed idea for the optimal value of the shape parameter respect to existing methods include 1) independency of a secondary solution of the problem, 2) solving problem using just one set of computational centers, 3) independency of the geometry and physics of the problems, 4) needless to optimize the shape parameter at every time step, 5) low computational cost and 6) convenient to use. Finally result of several different examples compared to other numerical and analytical methods showed acceptable accuracy of the present approach.

Investigation of multi-physics problems such as flow-structure interaction (FSI) in free surface is very important in mechanical engineering, whereas numerical simulations of such problems have been widely conducted by researchers. The implementations of CFD in engineering applications are most of the time based on the Eulerian description. In this method, one can focus on flows at a fixed spatial point x at time t and any flow variable Φ is expressed as Φ (x, t). This description has been studied for over fifty years and is clearly understood. Most of commercial codes have been developed by using finite difference, finite element and finite volume approaches. Simulating free surface flow with most Eulerian CFD methods is potentially very difficult as explicit treatment of the free surface is required. Moreover, The problems of most Eulerian and mesh-based numerical methods for complex free surface deformations involves difficulties and complexities of various boundaries remeshing as well as moving boundaries and exact determination of free- surface fluid. Another description of study of CFD is the Lagrangian method where one can follow the history of an individual fluid parameter through the time. In the Lagrangian methods, any flow variable is expressed as Φ (x0, t), where the point vector x0 of the particle at the reference time t = 0. Smoothed Particle Hydrodynamics (SPH) is a meshless and fully Lagrangian method which is able to simulate the FSI problems due to its simplicity and capability, as there is no special treatment needed for the free surface. The current problem in hydrodynamic science and fluid engineering is studied as a complex phenomenon in free-surface flow. Smoothed Particle Hydrodynamics (SPH) is a flexible Lagrangian and meshless technique for CFD simulations initially developed by Lucy (1977) and Gingold and Monaghan (1977) to simulate the nonaxisymmetric phenomena in astrophysics. In recent years, the SPH method has been very popular in fluid mechanics, e.g. multiphase flows,3 heat conduction,4 underwater explosions, free-surface flows, etc. In this method, each particle carries an individual mass, position, velocity, internal energy and any other physical quantity. The Lagrangian nature of SPH would lead this method to be well suited to problems with large deformations and distorted free surfaces. Simplicity, robustness and relative accuracy in comparison with other numerical methods are the main advantages of using SPH.10 Moreover, the SPH method can handle fully nonlinear, multiply-connected free-surface problems and extend computations beyond wave breaking, which need complex treatments in other grid-based methods, e.g. Volume of Fluid (VoF).In this approach the computational domain is formed by a set of particles. Each particle represents macroscopic volume of fluid conveying information about the mass, density, pressure, speed, position and the other parameters related to the nature of the flow. However, the computational cost is a disadvantage of SPH because the time step is small because of the explicit integration scheme in a weakly compressible formulation. This method has been successfully applied to a range of free-surface problems which involve breaking and splashing up There is a choice of SPH formulation in the literature mostly expressed in weakly compressible forms where pressure is obtained from the equation of state In this research, SPH is used to investigate the flow-structure interaction in free surface. First, the simulation of dam break problem on a dry and infinite bed is shown and compared with the experimental data. Then, and after implementing the governing equations, the vibration of a beam is studied. Finally, the dam break problem on an elastic gate is shown. Comparison between the SPH results and available numerical and experimental data shows that the SPH method is useful method for simulating the FSI problem.

In this study first the meshless local Petrov-Galerkin (MLPG) method by Radial Basis Function (RBF) has been explained entirely. In this way the governing channel flow expression that is expanded. The Results show that MLPG method presented high accuracy and capability for solving the governing equation of the problem. Also, The seepage problem in steady state form is analyzed by the written code in MatLab . On the other hand the velocity field is approximated in middle of nodes by RBF (MatLab code was adopted) in the uniform flow in a sloped channel problem. Finally in the fluid flow in dam breaking problem, the Mass and momentum conservation laws are governing equations of flow which are solved by pressure correction in Lagrangian approach and compared with another methods results. The obtain results explain that Application of meshless method in Fluid flow modeling in hydraulic Problem the applicability and efficiency of the meshless local Petrov-Galerkin method by Radial Basis Function method.

Flooding caused by dam failure is been one of the most awful events in the past two centuries. In this type of flooding, a considerable amount of water releases in the river downstream in a short time and causes huge waves in the coastal. Due to the nature of wave, the use of mathematical models is common for simulating advancing and spreading of flood caused by it. In this case study, the subsequences of the flood volume released by the failure of Mirza Shirazi storage dam that is under construction (in Fars province) and estimating of damage with respect to two probable dam break scenarios: 1) immediate failure due to overtopping; and 2) gradual failure due to overtopping, is been investigated. In immediate failure scenario, calculated peak of flood discharge at the point of failure was 118,000 m3/s and in gradual failure was 80,000 m3/s. The average velocity of water in the river bed in immediate failure scenario is 10.2 m/s and in gradual failure scenario is 5.06 m/s. The result estimated damage cost of flood caused by dam break, in scenario of gradual failure is 5578 billion Rials and in immediate scenario is 9136 billion Rials.

In this paper, the dam break phenomena has been simulated in curved rivers using 3D numerical model, Flow-3D. It utilizes the finite volume scheme for structured meshes was used for solving the unsteady Reynolds-averaged Navier-Stokes equations in conjunction with the RNG k-ε closure model. In the utilized software, the Fractional Area/Volume Obstacle Representation (FAVOR) method is used to inspect the geometry in the finite volume mesh. FAVOR appoints the obstacles in a calculation cell with a factional value between 0 to 1 as obstacle fills in the cell. Fluid surface shape is illustrated by volume-of-fluid (VOF) function F(x,y,z,t). With the VOF method, grid cells are classified as empty, full, or partially filled with fluid. Cells are allocated in the fluid fraction varying from zero to one, depending on fluid quantity. The pressure and velocity are coupled implicitly by using the time-advanced pressures and time-advanced velocities in the momentum and continuity equations, respectively. FLOW3D solves these semi-implicit equations iteratively using relaxation techniques. In this paper the GMRES technique has been used as pressure implicit solver. A flux surface is a diagnostic feature in FLOW-3D for computing fluid flow rates. It can be used to obtain time-dependent information about the flow in different parts of the domain. A typical flux surface is a 100% porous baffle with no flow losses, so it does not affect the flow in any way. This feature gives the opportunity to determine the flood hydrograph at various stations downstream of the dam. Effects of curve angle and radious of curvature on the flood wave propagation and unsteady flow features along the curved reach, downstream of the dam has been investigated. Results showed that at the initial instants of the dam break in the straight channel, due to the effects of the dynamic wave, flood hydrographs at the dam location and at a distance downstream of the dam have local peak values, while in the curved chnnel cases, the flood wave becomes unstable immediately after the dam break and the local peak occures just at the dam section. The curved reach decelerate the flood wave propagation compared to the straight channel. Effect of channel curvature on the movement of the flood wave along the inner bank is higher than the outer bank and also the centerline of the curved channel. By decreasing the central radious of the bend, slope of the rising limb of the hydrograph and also the peak discharge, attenuates. Furthermore, the peak discharge time reduces. Unlike to effects of the curvature of the bend, increasing the bend angle does not affect the peak discharge. Changing the bend curvature and curve angle has no effect on the falling limb of the flood hydrograph at various stations downstream of the dam.

Flooding induced by large dam breaks causes severe and heavy damages to human lives and civil facilities. Knowing the volume and direction of the ood spreading, due to the breaking of a certain dam, in advance, may allow us to specify the areas prone to ood damage and help the institutions in charge to be on full alert before catastrophe occurs. The main aim of this research is to study the in uence of the shape factor of a dam reservoir on a ood hydrograph, induced due to a dam break, by means of a physical model in the laboratory. Thus, the sudden dam break phenomenon has been modeled in the hydraulic laboratory of Amirkabir University of Technology. Dierent tests have been planned and carried out in the laboratory for shape factors ranging from 0.040 to 0.557. Hence, 7 series of reservoir with dierent dimensions and geometry have been built and tested. To measure the ow velocity and also the variations of water level at dierent points of the channel, the ADV speed meter and Ultrasonic and Micro sonic sensors were used, respectively. Having the variations of velocity and water level, the ow rate, due to dam break, is calculated and the corresponding hydrograph for each reservoir shape factor is obtained. Finally, the obtained hydrographs are evaluated and compared, and a correlation between the reservoirs shape factor and the Froude Number is developed. The experimental data were compared with those obtained from dierent actual dam break case histories. Although good agreement between the trends was found, large deviations from actual cases were observed. This may be due to several simpli ed procedures applied to the physical model developed in the laboratory to study the phenomenon. Thus, more sophisticated models with larger capabilities are needed to reach more accurate and reliable results in future research.

Smoothed Particle Hydrodynamic method is a Lagrangian numerical particle method, best fitted for free surface hydrodynamics. SPHysics is one of the most well-known computer models based on SPH. However, this open source code is limited to one-phase Newtonian fluid problems. In this research, after developing the standard serial SPH code to a two-phase non-Newtonian model, the movable bed dam break problem has been modeled. An added pressure term is used in the pressure equation of state. Afterward, the model has been used for various problems and the validity of results was evaluated by related numerical models and experiments. Finally, the model has been challenged with modeling of dam break movable bed material by non-Newtonian Bingham model and compared with MPS method and experimental results.

Mesh-free particle (Lagrangian) methods، such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH)، are the newest methods in computational fluid dynamics، which have been applied in flow problems with large deformations and inconsistency. The aim of ths research was to develop and improve the simulation of free surface flows، using the new method of weakly compressible MPS (WC-MPS). In the MPS method، pressure is determined by solving Poisson equation. This equation is solved implicitly، which needs too much computer time. In the present research، the WC-MPS method is used to calculate pressure. In this method، as in SPH method، the state equation is used. This equation is solved explicitly، which does not occupy too much computer time. To evaluate the proposed method، the famous applied flow problem of dam break is analyzed. The program is written in C language and validations are performed for this code. To compare the Lagrangian approach with Eulerian approach، dam break is modeled by using FLOW-3D software too. The results of modeling approaches and physical models showed that both approaches have acceptable accuracy in modeling the free surface flow، but the accuracy of Lagrangian approach، especially the WC-MPS، is more than Eulerian approach. The proposed methos had some pressure oscillations، which were analyzed thereafter. Simulation of free surface flows using Weakly compressible moving-particle semi-implicit methodMesh-free particle (Lagrangian) methods، such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH)، are the newest methods in computational fluid dynamics، which have been applied in flow problems with large deformations and inconsistency. The aim of ths research was to develop and improve the simulation of free surface flows، using the new method of weakly compressible MPS (WC-MPS). In the MPS method، pressure is determined by solving Poisson equation. This equation is solved implicitly، which needs too much computer time. In the present research، the WC-MPS method is used to calculate pressure. In this method، as in SPH method، the state equation is used. This equation is solved explicitly، which does not occupy too much computer time. To evaluate the proposed method، the famous applied flow problem of dam break is analyzed. The program is written in C language and validations are performed for this code. To compare the Lagrangian approach with Eulerian approach، dam break is modeled by using FLOW-3D software too. The results of modeling approaches and physical models showed that both approaches have acceptable accuracy in modeling the free surface flow، but the accuracy of Lagrangian approach، especially the WC-MPS، is more than Eulerian approach. The proposed methos had some pressure oscillations، which were analyzed thereafter. Simulation of free surface flows using Weakly compressible moving-particle semi-implicit method

Preparing for the consequences of dam failure is very important and should be considered. The failure of a dam can have major effects, such as injury and loss of life, economic, property and environmental damage. More than a century, scientists have seriously studied the dam failure. Flooding caused by a dam failure can occur in a relatively short period. Downstream communities located close to the dam typically have short warning times. Numerical modeling of dam-break flood analysis due to the shallow water equations are often developed as the next one. Initial studies in this area were done by Ritter [1] Dressler [2] and Stoker [3]. In the last decade, remarkable progress has been made in the field of numerical modeling of dam failure. Bellos et al. [4] applied a two-dimensional numerical model to simulate flood waves resulting from the instantaneous break of dams. The McCormack two step predictorcorrector scheme was used for the solution of the transformed system of equations. Comparisons between computed and experimental data showed a satisfactory agreement. The rapidly varied unsteady flow caused by the failure of a dam in a rectangular dry bed horizontal channel has been studied by Hassanzadeh [5]. In the literatures, many researchers have investigated various aspects of dam failure. In this paper, dam break and its flood wave propagation was simulated using finite volume method in twodimensional vertical condition. Numerical results are compared with experimental results for the evaluation ofnumerical model. In this paper, dam break wave propagation in two-dimensional vertical state is simulated by FLUENT model. FLUENT provides comprehensive modeling capabilities for a wide range of incompressible and compressible, laminar and turbulent fluid flow problems. To permit modeling of fluid flow and related transport phenomena inindustrial equipment and processes, various useful features are provided. A very useful group of models in FLUENT is the set of free surface and multiphase flow models. For these types of problems, FLUENT provides the volumeof- fluid (VOF) model. Robust and accurate turbulence models are a vital component of the FLUENT suite of models. The turbulence models provided have a broad range of applicability, and they include the effects of other physical phenomena, such as buoyancy and compressibility. Particular care has been devoted to addressing issues of near-wall accuracy via the use of extended wall functions and zonal model [6]. In this paper, numerical model was tested by three different turbulence models, k-ε, k-ω, and RSM. By use of statistical analysis method, NRMSE, the best turbulence model for 2D dam break, was obtained the k-ε standard(Table 1). Dam break have always been regarded as an extremely risky event and hence the research programs, government planning and investment in coastal dams are of the utmost importance. In this paper, dam break induced wave propagation was simulated using FLUENT model in two-dimensional vertical state, and numerical results were compared with experimental data for the evaluation and verification of numerical model. Dam break was simulated in both dry and wet bed performance for different sizes of the grid mesh, different discretization schemes (such as First Order Upwind, Second Order Upwind, Quick and Power Law) and different turbulence models (k-ε standard,k-ε RNG, k-ε Realizable, RSM and k-ω). Results show that the turbulence k-ε standard model and the First Order Upwind scheme are more accurate than others. After testing the sensitivity and accuracy of the model, simulation is done for basin slopes of 0, 1% and 2% and the roughness of the substrate with coefficients 0.009, 0.015, 0.0185, and0.0198 performance and results were analyzed. The results showed that the numerical model can be used to simulate a dam break in both dry and wet beds and provides acceptable results.

I‌n t‌h‌i‌s r‌e‌s‌e‌a‌r‌c‌h, a n‌e‌w m‌o‌d‌i‌f‌i‌e‌d m‌a‌t‌r‌i‌x s‌u‌b‌t‌r‌a‌c‌t‌i‌o‌n m‌e‌t‌h‌o‌d i‌s p‌r‌o‌p‌o‌s‌e‌d u‌s‌i‌n‌g s‌q‌u‌a‌r‌e t‌i‌m‌e-f‌r‌e‌q‌u‌e‌n‌c‌y r‌e‌p‌r‌e‌s‌e‌n‌t‌a‌t‌i‌o‌n‌s t‌o d‌e‌t‌e‌c‌t b‌r‌i‌d‌g‌e p‌i‌e‌r d‌a‌m‌a‌g‌e a‌n‌d i‌t‌s l‌o‌c‌a‌t‌i‌o‌n. T‌h‌e n‌e‌w p‌r‌o‌p‌o‌s‌e‌d m‌e‌t‌h‌o‌d i‌s c‌o‌n‌f‌i‌r‌m‌e‌d, u‌s‌i‌n‌g t‌h‌e s‌e‌i‌s‌m‌i‌c r‌e‌s‌p‌o‌n‌s‌e o‌f t‌h‌e 448 m‌e‌t‌e‌r l‌o‌n‌g G‌h‌o‌t‌o‌u‌r B‌r‌i‌d‌g‌e m‌o‌d‌e‌l, a‌n‌d c‌o‌m‌p‌a‌r‌e‌d w‌i‌t‌h c‌o‌r‌r‌e‌l‌a‌t‌i‌o‌n a‌n‌d l‌e‌a‌s‌t s‌q‌u‌a‌r‌e d‌i‌s‌t‌a‌n‌c‌e m‌e‌t‌h‌o‌d‌s. T‌i‌m‌e f‌r‌e‌q‌u‌e‌n‌c‌y p‌l‌a‌n‌s o‌f d‌a‌m‌a‌g‌e‌d a‌n‌d n‌o‌n-d‌a‌m‌a‌g‌e‌d b‌r‌i‌d‌g‌e m‌a‌t‌r‌i‌x e‌l‌e‌m‌e‌n‌t‌s a‌r‌e c‌a‌l‌c‌u‌l‌a‌t‌e‌d u‌s‌i‌n‌g r‌e‌d‌u‌c‌e‌d i‌n‌t‌e‌r‌f‌e‌r‌e‌n‌c‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n. T‌h‌e d‌i‌f‌f‌e‌r‌e‌n‌c‌e m‌a‌t‌r‌i‌x i‌s c‌a‌l‌c‌u‌l‌a‌t‌e‌d b‌y s‌u‌b‌t‌r‌a‌c‌t‌i‌o‌n o‌f c‌o‌r‌r‌e‌s‌p‌o‌n‌d‌i‌n‌g m‌a‌t‌r‌i‌x e‌l‌e‌m‌e‌n‌t‌s. T‌h‌e p‌o‌s‌s‌i‌b‌i‌l‌i‌t‌y o‌f a‌n e‌x‌i‌s‌t‌i‌n‌g d‌a‌m‌a‌g‌e i‌n‌d‌e‌x i‌s c‌a‌l‌c‌u‌l‌a‌t‌e‌d b‌y s‌u‌m‌m‌a‌t‌i‌o‌n o‌f a‌l‌l e‌l‌e‌m‌e‌n‌t‌s o‌f d‌i‌f‌f‌e‌r‌e‌n‌c‌e m‌a‌t‌r‌i‌c‌e‌s a‌n‌d t‌h‌e‌n n‌o‌r‌m‌a‌l‌i‌z‌i‌n‌g t‌h‌e‌m w‌i‌t‌h a m‌a‌x‌i‌m‌u‌m v‌a‌l‌u‌e. L‌i‌n‌e‌a‌r t‌i‌m‌e h‌i‌s‌t‌o‌r‌y a‌n‌a‌l‌y‌s‌e‌s a‌n‌d e‌a‌r‌t‌h‌q‌u‌a‌k‌e a‌c‌c‌e‌l‌e‌r‌a‌t‌i‌o‌n r‌e‌c‌o‌r‌d‌s o‌f S‌a‌n F‌e‌r‌n‌a‌n‌d‌o, L‌o‌m‌a P‌r‌i‌e‌t‌a a‌n‌d N‌o‌r‌t‌h‌r‌i‌d‌g‌e e‌a‌r‌t‌h‌q‌u‌a‌k‌e‌s a‌r‌e u‌s‌e‌d f‌o‌r s‌e‌i‌s‌m‌i‌c r‌e‌s‌p‌o‌n‌s‌e a‌n‌a‌l‌y‌s‌i‌s. I‌n p‌r‌e‌v‌i‌o‌u‌s r‌e‌s‌p‌o‌n‌s‌e a‌n‌a‌l‌y‌s‌e‌s o‌f t‌h‌e G‌h‌o‌t‌o‌u‌r B‌r‌i‌d‌g‌e, a‌s s‌t‌a‌t‌e‌d i‌n r‌e‌f‌e‌r‌e‌n‌c‌e [23], t‌h‌e t‌h‌i‌r‌d p‌i‌e‌r f‌r‌o‌m t‌h‌e l‌e‌f‌t i‌s c‌o‌n‌s‌i‌d‌e‌r‌e‌d m‌o‌r‌e v‌u‌l‌n‌e‌r‌a‌b‌l‌e t‌o s‌e‌i‌s‌m‌i‌c d‌a‌m‌a‌g‌e. T‌h‌e‌r‌e‌f‌o‌r‌e, f‌o‌r t‌h‌e p‌u‌r‌p‌o‌s‌e o‌f t‌h‌i‌s s‌t‌u‌d‌y, a r‌e‌d‌u‌c‌t‌i‌o‌n o‌f t‌h‌i‌r‌t‌y p‌e‌r‌c‌e‌n‌t i‌n t‌h‌e s‌t‌i‌f‌f‌n‌e‌s‌s o‌f t‌h‌a‌t p‌i‌e‌r i‌s c‌o‌n‌s‌i‌d‌e‌r‌e‌d, t‌o s‌i‌m‌u‌l‌a‌t‌e t‌h‌e s‌e‌i‌s‌m‌i‌c d‌a‌m‌a‌g‌e i‌n t‌h‌e d‌a‌m‌a‌g‌e‌d a‌n‌a‌l‌y‌t‌i‌c‌a‌l m‌o‌d‌e‌l. I‌t i‌s s‌h‌o‌w‌n t‌h‌a‌t t‌h‌e p‌r‌o‌p‌o‌s‌e‌d m‌e‌t‌h‌o‌d c‌o‌u‌l‌d s‌a‌t‌i‌s‌f‌a‌c‌t‌o‌r‌i‌l‌y i‌d‌e‌n‌t‌i‌f‌y t‌h‌e d‌a‌m‌a‌g‌e l‌o‌c‌a‌t‌i‌o‌n. F‌o‌r t‌h‌e s‌e‌i‌s‌m‌i‌c r‌e‌s‌p‌o‌n‌s‌e o‌f t‌h‌e t‌o‌p o‌f t‌h‌e b‌r‌i‌d‌g‌e p‌i‌e‌r‌s, t‌h‌e m‌a‌x‌i‌m‌u‌m e‌r‌r‌o‌r i‌n l‌o‌c‌a‌t‌i‌n‌g t‌h‌e d‌a‌m‌a‌g‌e i‌s 6 p‌e‌r‌c‌e‌n‌t, w‌h‌i‌l‌e, f‌o‌r t‌h‌e s‌e‌i‌s‌m‌i‌c r‌e‌s‌p‌o‌n‌s‌e o‌f t‌h‌e m‌i‌d‌d‌l‌e o‌f t‌h‌e b‌r‌i‌d‌g‌e p‌i‌e‌r‌s, i‌t i‌s 14 p‌e‌r‌c‌e‌n‌t. T‌h‌e t‌i‌m‌e-f‌r‌e‌q‌u‌e‌n‌c‌y r‌e‌p‌r‌e‌s‌e‌n‌t‌a‌t‌i‌o‌n‌s u‌s‌e‌d i‌n‌c‌l‌u‌d‌e: t‌h‌e s‌h‌o‌r‌t t‌i‌m‌e F‌o‌u‌r‌i‌e‌r t‌r‌a‌n‌s‌f‌o‌r‌m s‌p‌e‌c‌t‌r‌u‌m, w‌a‌v‌e‌l‌e‌t t‌r‌a‌n‌s‌f‌o‌r‌m s‌p‌e‌c‌t‌r‌u‌m, W‌i‌g‌n‌e‌r-V‌i‌l‌l‌e D‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n, C‌h‌o‌i-W‌i‌l‌l‌i‌a‌m‌s d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n, s‌m‌o‌o‌t‌h‌e‌d p‌s‌e‌u‌d‌o W‌i‌g‌n‌e‌r-V‌i‌l‌l‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n a‌n‌d r‌e‌d‌u‌c‌e‌d i‌n‌t‌e‌r‌f‌e‌r‌e‌n‌c‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n, w‌h‌i‌c‌h a‌r‌e f‌i‌n‌a‌l‌l‌y i‌d‌e‌n‌t‌i‌f‌i‌e‌d a‌s o‌p‌t‌i‌m‌a‌l p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e t‌i‌m‌e-f‌r‌e‌q‌u‌e‌n‌c‌y r‌e‌p‌r‌e‌s‌e‌n‌t‌a‌t‌i‌o‌n f‌o‌r b‌r‌i‌d‌g‌e s‌e‌i‌s‌m‌i‌c r‌e‌s‌p‌o‌n‌s‌e s‌i‌g‌n‌a‌l p‌r‌o‌c‌e‌s‌s‌i‌n‌g. R‌e‌d‌u‌c‌e‌d i‌n‌t‌e‌r‌f‌e‌r‌e‌n‌c‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n a‌n‌d W‌i‌g‌n‌e‌r-V‌i‌l‌l‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n a‌r‌e b‌o‌t‌h i‌n t‌h‌e C‌o‌h‌e‌n c‌l‌a‌s‌s, b‌u‌t r‌e‌d‌u‌c‌e‌d i‌n‌t‌e‌r‌f‌e‌r‌e‌n‌c‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n m‌e‌t‌h‌o‌d‌s a‌r‌e m‌o‌r‌e a‌p‌p‌r‌o‌p‌r‌i‌a‌t‌e f‌o‌r p‌r‌o‌c‌e‌s‌s‌i‌n‌g s‌e‌i‌s‌m‌i‌c b‌r‌i‌d‌g‌e t‌r‌a‌n‌s‌i‌e‌n‌t n‌o‌n‌s‌t‌a‌t‌i‌o‌n‌a‌r‌y r‌e‌s‌p‌o‌n‌s‌e s‌i‌g‌n‌a‌l‌s. T‌i‌m‌e-f‌r‌e‌q‌u‌e‌n‌c‌y p‌l‌a‌n‌e‌s h‌a‌v‌e b‌e‌e‌n c‌a‌l‌c‌u‌l‌a‌t‌e‌d a‌n‌d d‌y‌n‌a‌m‌i‌c s‌p‌e‌c‌i‌f‌i‌c‌a‌t‌i‌o‌n‌s o‌f t‌h‌e s‌y‌s‌t‌e‌m h‌a‌v‌e b‌e‌e‌n e‌s‌t‌i‌m‌a‌t‌e‌d. T‌h‌e p‌r‌o‌p‌o‌s‌e‌d a‌l‌g‌o‌r‌i‌t‌h‌m i‌s a s‌e‌i‌s‌m‌i‌c o‌u‌t‌p‌u‌t-o‌n‌l‌y m‌e‌t‌h‌o‌d. T‌h‌e‌r‌e‌f‌o‌r‌e, i‌t h‌a‌s t‌h‌e a‌d‌v‌a‌n‌t‌a‌g‌e o‌f n‌o‌t n‌e‌e‌d‌i‌n‌g t‌o d‌e‌f‌i‌n‌e t‌h‌e b‌r‌i‌d‌g‌e a‌n‌a‌l‌y‌t‌i‌c‌a‌l m‌o‌d‌e‌l a‌n‌d m‌e‌a‌s‌u‌r‌i‌n‌g s‌e‌i‌s‌m‌i‌c i‌n‌p‌u‌t l‌o‌a‌d‌i‌n‌g, a‌n‌d, a‌l‌s‌o, n‌o‌t n‌e‌e‌d‌i‌n‌g t‌o u‌s‌e h‌a‌r‌m‌o‌n‌i‌c f‌o‌r‌c‌e‌d v‌i‌b‌r‌a‌t‌i‌o‌n a‌n‌a‌l‌y‌s‌i‌s a‌f‌t‌e‌r e‌a‌r‌t‌h‌q‌u‌a‌k‌e o‌c‌c‌u‌r‌r‌e‌n‌c‌e f‌o‌r b‌r‌i‌d‌g‌e s‌e‌i‌s‌m‌i‌c d‌a‌m‌a‌g‌e d‌e‌t‌e‌c‌t‌i‌o‌n, a‌s i‌s g‌e‌n‌e‌r‌a‌l i‌n s‌o‌m‌e o‌t‌h‌e‌r m‌e‌t‌h‌o‌d‌s.

Smoothed Particle Hydrodynamic (SPH), a new generation of mesh-free numerical methods to model free surface flow, is of great interest among many researchers nowadays. In this paper, ISPH was applied to simulate free-surface flow around hydraulic structures in several classical cases including dambreak, flow over a sharp-crested weir, and simultaneous operation of weir and gate. Due to enforcing incompressibility of flow, Cummins and Rudmans (1999) projection method is used in these cases. Error curves are used to evaluate the sensitivity of ISPH to approximate pressure terms. Two pressure formulations for approximating the left-hand-side of the Poisson equation result in a similar and acceptable trend of error. Comparison of several classical flow cases results using ISPH with experimental data and FVM-VOF shows good agreement between them.

Dam break flood on a mobile bed is simulated using a two dimensional numerical model. The governing equations are solved in the framework of the finite volume method. In order to achieve a second order method both in time and space, the Mac Cormack predictor corrector scheme is used. To overcome the problem of unphysical oscillations the component-wise TVD technique is implemented which is a simple TVD method because it is not necessary to use the Jacobian matrix and its eigenvalues. In the study of mobile bed hydraulics it is necessary to pay due attention to the strong interaction between water and sediment and morphological river changes. Thus the conservation laws are solved in a coupled manner, i.e. the transport equations for water and sediment are solved simultaneously. The model has been verified by its application for different test cases and the results are satisfactory.

The possibility of dam failures due to seismic forces, bombardment, piping, overtopping, or mal-designing and construction considerations is probable and can result in the most notable human life losses and extensive property damages. The knowledge of the propagation of the flood waves resulted by dam failure and the resistance effects of bed roughness on the flow velocity variation in the downstream of the dams have an important role in the hydraulics of free surface flows. In the present paper the rapidly varied unsteady flow caused by the failure of a model dam in a rectangular sloping rough channel with dry down stream bed has been analyzed theoretically using the characteristic method on the dimensionless form by means of computer and compared with experimental data existing in the literature. It is concluded that the positive wave front and drying wave front are highly sensitive to hydraulic resistance, consequently increasing the bed roughness causes to decreasing the flow velocity. Also by approaching the positive wave front, the flow velocity increases and tends to the value of wave front velocity. Finally, comparison revealed that experimental data of rough sloping channel agreed closely with the theoretical one. Thus this latest method would provide more satisfactory results for sloping rough channels.