مجله هیدرولیک
سال هفدهم شماره 4 (زمستان 1401)

The quality of water required for agriculture, industry, drinking, etc., has made it necessary for the solids particle in the water flow to enter its permissible level in irrigation and drainage or urban water networks. The Vortex Settling Basin (VSB) makes use of the vortex flow inside the chamber for the separation of sediment particles from the flow.Elaborate studies have been made on investigation flow pattern at VSB that includes: (Paul, 1988 and 1991; Athar et al., 2003; Gheisi, et al, 2006; Ziaei et al., 2007; Chapokpour et al., 2011; Mulligan et al, 2016; Rehman et al., 2017; Huang et al., 2017; S. R. Nikou et al., 2021).Elaborate studies in hydraulic sciences apply particle tracking and image processing method for investigation ( Sun et al., 2015; Shin et al., 2016; Mulligan et al., 2016 and 2018; Rosberry et al., 2019; Witz et al., 2018; Duinmeijer et al., 2019).The investigation of vortex flow is very sensitive to measuring instruments, for example, ADV, which is the most common instrument for measuring the velocity, increases disturbance of flow. Therefore, it is recommended to use the non-interference particle tracking method to measure velocity components.

The experiments were performed in the hydraulic laboratory of the water science and engineering department at the Ferdowsi University of Mashhad, Iran on an acrylic laboratory setup. Spherical particles with a relative density of 1.41, at distances of 37 cm and 1.5 m from the chamber (sediment injection site in the study of Athar et al., (2003)) and in these two longitudinal distances, left at 9 points and each experiment is repeated 5 times (Figure 2).In this research, two iPhone 7 Plus cameras have been used for taking photos. The camera of this phone has one of the most advanced cameras in terms of expertise and technology. In this study, due to the high volume of data at different points, image processing is presented in the highest probability of trapping (point 4), the position of this point is as follows: 5 cm from the floor, 2 cm from its right wall (sloping to the chamber), 18 cm from the sloping wall to the outlet channel and 6.5 cm to the water level. The input flow to the channel is 8 and 13.7 l/s.

The highest probability of trapping for a particle at two longitudinal distances is at point 4 with a probability of 60%. The process of particle displacement and the time series of three velocity diagrams in the vortex settling basin of the present study are sinusoidal. In sections 150°-210° and 330°-30°, the particle is inclined toward the wall and in other sections, it is inclined toward the orifice, affected by the location of input and output channels (S. R. Nikou et al., 2021).There is a meaningful correlation between the two components vx and vy, and in almost all places where the x velocity component is extreme, in the same position y component is zero, and vice versa. This result is quite justifiable given the motion of vortex flow. The extreme values of the velocity component in the x direction become closer as they approach the orifice, indicating an increase in velocity near the orifice and the chamber floor and a smaller curved path around the vortex core. Notably, the absolute value of the maximum velocity in the x direction is 1.61 m/s and in the z direction is 0.13 m/s, which indicates that the particle tends to enter the orifice more in a rotating passage than falling position, having said that, centrifugal force is dominated over the action of dewatering. The mean relative error of water surface profiles by image processing method compared to laboratory data is estimated to be 0.002 and 1.36%, respectively, which confirms well with the experimental measurements.

The results showed that the distribution of the velocity components of the particle in all three dimensions has a sinusoidal trend. The higher value of the maximum velocity in the x-direction than the z-direction indicates the dominance of the centrifugal force over the dewatering operation in the vortex flow.According to the obtained results, particle tracking and image processing can be used as an accurate method with a higher operational speed to investigate the flow patterns and determine the water surface profile in vortex settling basins.

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.

The vertical shaft is one of the most important hydraulic structures that is often used in urban drainage systems. The function of the vertical shaft is to transfer water from an arbitrary level to lower levels.The issue of air entering the vertical shaft is very important. The transfer of a significant amount of air into the pressurized tubes can lead to the formation of high-pressure air masses, which gradually grow and may burst into the tubes as they enlarge. (falvey, 1980) which causes damage to the shaft and the pipes that connected to it and also reduces the shaft permeability, which is also undesirable.Due to the lack of attention to the hydraulics of the vertical shaft and the consequences of its incorrect construction, the study on the amount of inlet air seems necessary. In this study, measuring the amount of inlet air at the intensity of different flows is desired. Finding the minimum amount of incoming air can help to better design the projectile shaft. By comparing the behavior of the projectile shaft in different states, the correction efficiency of the shaft can be obtained.

The model is adapted from a laboratory study conducted at the University of Alberta.The vertical shaft under study has a height of 7.72 meters and a diameter of 0.38 meters. The diameter of the inlet pipe of the shaft is half the diameter of its main body (0.19 m) and the diameter of the outlet pipe and its length are equal to 0.38 m and 1.5 m, respectively, and the flow of outlet water is discharged into the open air. the upper part of the shaft is blocked and the ambient air is allowed to enter the shaft only with a circular tube with a diameter of 0.10 m located at 0.20 m above the shaft. An air shaft with a diameter of 0.15 m is located at 0.5 m from the shaft outlet for air circulation, which is connected to the upper part of the shaft.The software used in this research is open foam.In this networking, a total of 121947 elements are used. The KOmegaSST turbulence model is used to solve the current turbulence term. Boundary conditions are defined for velocity (u), pressure (p), fluid type index (α) and turbulence (k, omega, nut) parameters. The initial value of velocity and pressure was assumed to be zero. To consider the initial value of the fluid type index, the number zero is entered so that this shaft is empty of water at first.

as the speed increases, the pressure decreases sharply, causing the pressure inside the shaft to become negative and air to be drawn in from the outside into the shaft.The more intense the water inlet flow, the more air enters the shaft from the surrounding environment. As the dimensionless flow of water inflow increases, the relative demand decreases by 85%.As the inlet current increases, the amount of return air through the air shaft into the vertical shaft increases. As the inlet current intensifies at low current intensities, the amount of air supplied by the air shaft increases, but in higher current intensities this value is almost constant.As the amount of air circulated by this shaft increases, the pressure gradient between this point and the upper part of the shaft is expected to increase. As the water inlet velocity increases, it can be seen that as the inlet flow rate increases more, both the amount of air supplied by the air shaft and the amount of inlet air from outside the shaft do not change significantly, which can create a semi-closed area. At the top of the shaft to allow air to flow and move down.The pressure inside the shaft increases from the bottom to the top and the highest pressure gradient is seen in the middle points, which are called the rainfall area.There is not much difference in the intensity of low inlet currents between the performance of the two types of shafts, but as the amount of inlet water to the shaft increases, the effect of the air shaft on reducing the amount of inlet air becomes apparent.
the pressures inside the shaft are almost equal at low current intensities and are spaced apart at high current intensities.

The amount of inlet air increases with increasing intensity of water inlet flow. By increasing the intensity the amount of air demand decreases.the air shaft performs better at higher current intensities.There is not much difference in the intensity of low inlet currents between the performance of the two types of shafts, but as the amount of inlet water to the shaft increases, the effect of the air shaft on reducing the amount of inlet air becomes apparent. Also, the value of the pressure in the modified shaft is clearly reduced.

River training is the stabilization of the channel in order to maintain the desired cross-section and alignment. Channel stabilization and restoration efforts have been increased dramatically with excessive cost since 1990. However, it is estimated that at least 50% of these projects fail and others may not perform as expected. Therefore, stream restoration today is more of an art than a science. Rivers have been trained for centuries by series of transverse groynes which are structures constructed at an angle to the flow in order to deflect the flowing water away from critical zones. This generally results in damages to their ecosystems as well as in undesirable long-term morphological developments. To maintain a navigable channel and improve flow conveyance by dividing the channel into main and side channels, engineers have recently proposed constructing longitudinal training walls as an alternative to the traditional transverse groynes. The effectiveness of longitudinal training walls in achieving these goals and their long-term effects on the river morphology have not been thoroughly investigated yet. In particular, studies that assess the bed and wall shear stresses of the parallel channels separated by the training walls are still lacking.

In the present study, the performance of longitudinal training walls on bed and wall shear stresses was compared with the traditional transverse groynes. Three-dimensional Reynolds-averaged Navier-Stokes equations with the k-ɛ turbulence model were solved numerically by applying finite volume method using Flow-3D software. Results of the single groyne simulation were validated based on experimental data with a good agreement. The experimental channel had rectangular cross-section of width B=0.9144m and slope S0=10−4, groyne was a parallelepiped of length b=B/6=0.1524m and thickness of 3 mm. In addition, results of the series of groynes simulation were compared to the available numerical data, shown a good agreement. After validation, continuous longitudinal training walls were simulated with equivalent length to a series of groynes with uniform and non-uniform configuration in three transverse positions y/B=1/2, y/B=1/3 and y/B=1/6. Uniform configuration of groynes was included three groynes with D/b=6 and 23 spacing and non-uniform configuration was included nine groynes, first five groynes with D/b=1.5 and four other groynes with D/b=6 spacing. Also, non-continuous longitudinal training walls were simulated with the same transverse positions for D/b=23. The hydrodynamic behavior of the bed and wall shear stresses was investigated, since the starting point of longitudinal training walls affects the morphodynamic behavior of the flow, the starting position of the walls was fixed and only different transverse positions with different lengths were simulated.

Here we analyze the bed and wall shear stresses in open channel flow by training channel in a new way by subdividing their channel in parallel channels with specific functions with longitudinal training walls. The results showed that the longitudinal training walls system reduces the bed shear stress compared to the groyne system and as a result we will have less erosion in the bed. However, some small increases in wall shear stresses were seen in all simulations of longitudinal training walls. The closer the transverse position of the longitudinal training walls to the channel wall, the lower wall shear stresses. Furthermore, if the longitudinal training wall system is implemented in non-continuous form, due to the drop in flow energy at the beginning and end of each wall, the flow energy drop leads to a decrease in velocity and due to the direct relationship between velocity changes and shear stress, bed and wall shear stresses in side channel can be reduced further, that this reduction depends on the transverse position and, more importantly, whether or not this transverse position has created a mild flow conditions in the side channel. Therefore, this system by providing a mild flow conditions in the side channel which is shallower channel, has a favorable effect on aquatic habitat, ecosystem, and wall shear stress. Besides, by providing a deep navigable main channel, can increase the ability of transferring additional flood discharge.

In this study, twelve simulations were performed with different lengths for longitudinal training walls in different transverse positions with continuous and non-continuous forms. The results showed that this system, compared to the traditional groyne system, introduces less bed shear stress and by providing a mild flow conditions in the side channel, has the ability to control the wall shear stress dynamically. This system has a favorable effect on aquatic habitat and ecosystem, beside high ability to transfer additional flood discharge. So, longitudinal training walls can be used as an appropriate replacement for traditional transverse groynes.

The study of surface water quality has special importance. Unfortunately, sometimes sewage and industrial effluents are discharged into the river. If the mechanism of transport and diffiusion of pollution in rivers with different geometry is known, it can be planned to reduce the effects of pollution on the general health of human society by raising the issue of water mixing and strengthening the self-purification of rivers. The governing equation over the pollution transport phenomenon in rivers is advection-dispersion equation. This equation is classic and does not have the necessary accuracy in predicting the amount of pollutant concentration in the river; Therefore, this equation must be changed in such a way to have the least error in the simulation. The fractional calculus method is used to accurately investigate the transport of pollutants in the stream. To model the pollutant transport in the river, differential equation must be solved. Meshless method is one of the newest numerical methods in recent years that was able to correct some of the disadvantages of mesh-based methods. Studies show that the most studies have focused on solute transport in steady-state flow regimes and regular cross-sections. This study seeks to provide a comprehensive model for simulating the phenomenon of pollutant transport in rivers with steady and non-uniform flow to eliminate the shortcomings of common models. In this study, the parameters of dispersion coefficients, fractional order derivatives and skewness coefficients were optimized in the longitudinal and transverse directions. The values of dispersion coefficient in the longitudinal and transverse directions were 68 and 2.5 m2/s, respectively. The output of the proposed model was compared with the observational data of the Athabasca River and the Mike21 model for three cross sections. The results showed that the amount of R2 in the Meshless Local Petrovo-Galerkin method increased by an average of 11% compared to the Mike model.

Natural convection is an important phenomenon in porous media problems. It is encountered in a variety of applications, including in enhanced oil recovery systems and geothermal reservoirs. Physics-based numerical models are widely used to simulate natural convection in porous media. Although these models are usually effective, they commonly suffer from high computational costs. This is notably problematic in repetitive runs at large time and space scales, as in uncertainty analysis, data assimilation, and sensitivity analysis. In recent years, at least four different methods have been proposed to overcome this challenge, including optimizing the numerical solution algorithm, parallel computing, cloud computing, and data-driven methods. In most cases, while data-driven models are capable of handling low-dimensional problems, they have not been very successful in dealing with high-dimensional problems, both accurately and time efficient. To overcome these challenges, we propose using the encoder-decoder convolutional neural networks (ED-CNNs) for heterogeneous porous media. We apply the ED-CNN in the context of ‘image-to-image’ regression in the following two use cases in the context of natural convection simulations: (1) as a meta-model to estimate the heat map from the Rayleigh number distribution, and (2) as an optimizer to estimate the Rayleigh number distribution from the heat map.

The proposed ED-CNN is employed to model the hypothetical example of a square porous enclosure filled with a saturated porous medium. The boundaries are impermeable, and temperatures at two opposite side walls are different, resulting in the formation of natural convection. Heterogeneity in the Rayleigh number across the problem domain is applied through zonation.A numerical modeling tool is used to generate steady-state heat maps based on a number of randomly selected Rayleigh numbers. The numerical model input-outputs are transformed into square-shaped jpg images of 64 × 64 resolution. Two ED-CNNs are trained, one as a meta-model and the other as an optimizer. Different numbers of training input-output images (including 1000, 2000, 4000, and 5000) generated from the numerical model are employed to evaluate the performance of proposed networks. Two evaluation criteria are used to assess the performance of the developed ED-CNN models: (1) the root mean squared error (RMSE), and (2) the coefficient of determination (R^2-score). The ED-CNNs have been developed using Keras and Tensorflow python libraries.

Results show that the ED-CNN accuracy, both as a meta-model and as an optimizer, is satisfactory. For the meta-model case (i.e. prediction of the temperature distribution from the Rayleigh map), the RMSE is mostly smaller than 0.15, and the R^2-score is around 0.92. In the case of ED-CNN as optimizer (i.e. estimation of the Rayleigh distribution from the heat map), RMSE is mostly in the interval [0.017-0.034], while the R^2-score is around 0.89. Acceptable results can be obtained using 2000 input-output image pairs and 150 epochs for the meta-model case, and 4000 image pairs and 200 epochs for the optimizer case. Analysis of the spatial distribution of errors shows that maximum errors occur in the middle of the problem domain where the heat map is least sensitive to the Rayleigh number. The ED-CNN model is also evaluated as an uncertainty analysis tool by comparing maps of mean and standard deviation based on the numerical model and ED-CNN predictions, showing a significant agreement with estimation error between them.

In this paper, we examine the performance of ED-CNNs, as a specialized architecture of deep neural networks, to solve the forward and inverse problems of natural convection in porous media. For this purpose, we frame the problem as one of image-to-image regression and show that the developed model is able to provide high accuracy approximations with limited training samples, effectively solving the curse of dimensionality problem associated with heterogeneous domains. In practice, the proposed methodology can be applied to image datasets obtained from not only numerical modeling, but also high-resolution imaging and non-destructive scanning techniques, to either estimate the temperature distribution due to natural convection, or to characterize the porous media based on the temperature distribution.

Side sluice gates, side weirs and side orifices are commonly used flow diversion structures provided in the side of a channel to spill or divert water from the main channel. They are widely used in irrigation engineering, wastewater treatment plants, flocculation basins, sedimentation tanks, aeration basins, etc. Flow through a side orifice is similar to the flow through side weirs and side sluice gates. When water level is lower than upper limb of a slot, the slot behaves as side weir. When water level in the main channel is above the upper limb of the slot, the flow behaves like an orifice. For orifice spillway Hussain et al., 2014 reported orifice flow condition required head over the crest 1.5-1.7 times the height of the orifice opening. In the literature no study was found about the transition flow condition requirement of side orifice. In this paper, an experimental study has been carried out related to transition flow zone of side orifice which have not been taken up earlier.

In this study, first, the variables affecting the transition flow zone are listed and then, non-dimensional parameters extracted using dimensional analysis. The experiment was carried out in a rectangular channel of 8 m length, 0.8 m width and 0.6 m depth at the Hydraulic and water structure Laboratory of department of water engineering, Shahid Bahonar university of Kerman. The channel was fitted with a sluice gate at the end of the channel to regulate the depth of flow, and a rectangular side orifice in the right side of the channel. Experiments were performed for four size of side orifice length (L) equal to 0.15, 0.2, 0.25 and 0.3 m and width (b) 0.05, 0.1 and 0.15 m. The channel consists of a smooth horizontal well painted steel bed with a vertical glass sidewall. The collection channel is 1.2 m wide and 2 m deep, and situated parallel to the main channel. Each size of orifice installed in two different height equal to 0.09 and 0.14 m above of channel bed. For each experiment used nine flow in main channel with different Fr number in such a way that water level changes from lower to upper than limb of side orifice. For each run, the output discharge of side orifice, water surface profile along main channel were measured. The non-dimensional stage discharge of side orifice calculated and for each run output discharge from orifice calculated by Hussain et al.,(2011) and Embroiled et al., (2009) equations for side orifice and side wire respectively. To evaluate the accuracy of the equations, the average percent error (APE) were used.

The non-dimensional stage-discharge curve and water surface profile along the main channel are plotted in order to estimate the transition flow zone in side orifice. The results of non-dimensional stage-discharge curves (figs 3-6) reveals that the length to width ratio of orifice b/L is, indeed, the predominant parameters which affect the transition zone. For values b/L smaller than 0.2 the transition zone not clearly detected. The results show that the distance of lower limb of orifice to the bottom of channel, W, is other effective parameter in forming of transition zone. When the lower limb of orifice is closer to the channel bottom the ratio b/L becomes insignificant parameter. Based on water surface levels along the channel and the side orifice, figures 7 and 8, for values b/L smaller than 0.2 the transition zone happen only in very small area below upper limb of a side orifice, but for b/L greater than 0.2 the transition zone occurs above and below of the upper limb of a side orifice. The calculated and observed output discharge in different situations were used to check the accuracy of discharge equations of side weir and side orifice when the transition flow occurred. The results (figure 9) shows that in transition zone the accuracy of exiting side and orifice discharge equations is well.

The present study provides an experimental examination of the transition flow of a rectangular, sharp crested side orifice. As a result of dimensional analysis, the results indicate that the dimensionless parameter b/ L is the predominant parameters which affect the transition zone. The transition flow zone occurred when the b/L is greater than 0.2, but in these situations transition flow zone depends mainly on the distance of lower limp of side orifice to the bottom of channel. The average percentage error of exiting discharge equations showed that these equation can be used to estimate the discharge of side orifice in transition flow zone.

In recent years, scarcity of freshwater resources and the increasing water demands due to population growth and industrialization, have turned the issue of supplying drinking water into a global subject. Therefore, exploiting unconventional water resources, such as saline and brackish water using emerging technologies for desalination, has emerged as a promising solution in coastal areas. Desalination through Reverse Osmosis (RO) technology besides freshwater produces brine effluent as a byproduct, which has more salinity and density than the feeding water. Improper disposal of this effluent into coastal bodies will have serious environmental impacts on the receiving environment and can severely affect the aquatic ecosystem. To prevent the negative impacts, the effluent is discharged through submerged nozzles diagonally, with a high initial velocity and momentum, at a distance far enough from the shore. Using this method, the outflow is mixed with the seawater due to disturbances and the concentration is reduced down to the tolerance of the marine environment. In this study, the results of an experimental study were reported in the stationary environment to investigated the time evaluation of the discharge, and the process of mixing and dispersion for 60o inclined dense discharge.

The planar laser-induced fluorescence technique (PLIF) has been used to capture the flow central plane in this study. The system consisted of two swift scanning mirrors to provide a flat laser sheet across the centerline of the flow. The laser sheet was formed by the oscillation of a 100 milliwatts green Diode-pump solid-state laser (DPSSL) beam with 0.5mm width. With an infinitesimal quantity of a fluorescent dye (Rhodamine 6G), the discharged effluent would be fluoresced under the laser. The reflected light is captured by a CCD camera (Mars 640-300G 1/4"@4.8um) in the grayscale form at the rate of 100 frames per second. The procedures were controlled by a computer server equipped with an I/O board and controlling software and the images were continuously downloaded to the hard disk of the server for later processes. The captured images were then modified and calibrated for laser attenuation and sensor response for each pixel using clear and dyed water of known concentration. Using this technique, the system can illuminate the instantaneous behavior of the flow and the production, development, and dissipation of turbulent eddies along the flow. By capturing the flow instance behavior, the formation of turbulent eddies and their impacts on turbulent diffusion and flow mixing and entrainment have been investigated. Also, concentration fluctuations at the centerline, the effects of Kelvin-Helmholtz instability, and shear entrainment on the flow mixing process were discussed.

By illuminating the flow behavior, the development of flow regime in jet and plume-like region and the formation of instabilities, and the dissipation of eddies were studied‎. For this purpose, the instantaneous images of the flow evolution for different times were extracted and depicted using a non-dimensional parameter developed specifically for this purpose. The different processes of flow mixing and dilution along the jet and plume ‎regions were analyzed by describing the physics of eddies formation and dissipation long the inertial subrange. The formation of flow packets out of the main path is affected by the intensity of ‎velocity fluctuations. The vortices take their energy from the averaged velocity and transfer it from the biggest formed scale i.e. integral scale to the smallest vortices i.e. Kolmogorov's viscous subrange in a cascade of energy. The Energy Cascade is basically an energy spectrum that characterizes the turbulent kinetic energy distribution as a function of length scale. The scales of turbulent structures are directly a function of velocity fluctuation in each region and direct the process of the entrainment that led to the increases of dilution from the nozzle tip to the seafloor. These days, numerical simulations are becoming a common way for modeling the brine discharge in the marine environment. It is time-consuming and needs high expertise. The models are usually unsteady and after full development, the flow time-averaged image of the last 45 to 60 seconds is used for identifying the flow geometrical and mixing behavior. Using these experiments, it observed that the non-dimensional time required to flow fully developed and reach the impact point is about T*=5.7. Knowing that will help engineers find the optimal duration of time needed for the simulation and modeling.

It is known through the basics of physics that the maximum range for projectile motion happens when it is launched at an angle of 45 degrees. However, the previous experiments exhibited that the maximum dilution at the impact point occurs at the nozzle with 60o inclinations where the flow path is the longest. It was carefully examined by explaining the complex action of turbulence on flow mixing and dilution. The formation of eddies initially begins due to Kelvin-Helmholtz instability and it leads to velocity fluctuations with different time and length scales in the body of flow. The result is concentration dispersion with different magnitude along the flow path in inclined dense discharges.