جستجوی مقالات مرتبط با کلیدواژه "میدان جریان" در نشریات گروه "فنی و مهندسی"

Heat management in the polymer membrane fuel cell is necessary to increase the rate of reactions, prevent the formation of hot spots, and prevent the membrane from drying out. In the polymer membrane fuel cell, in the polymer membrane fuel cell, there is a limitation in increasing and decreasing the temperature. The flow field affects the mass and heat transfer and consequently the current density, and the proper design of the flow field leads to the improvement of the fuel cell performance. Parallel flow channels with baffles can increase the transfer of reactants to the catalyst layer and reduces the maximum temperature, uniforms temperature distribution and improve battery performance. In this article, the numerical, three-dimensional and two-phase modeling of the fuel cell with channels along with baffles is discussed and its electrochemical and thermal performance is compared with the battery with simple parallel channels. The results show that the addition of the baffles improves the mass transfer from the channels to the gas diffusion layer and hence the reaction rate in the cell increases and leads to improved cell performance. Also, the presence of the baffles causes the maximum temperature of the fuel cell to decrease by more than 1 Kelvin and the temperature distribution becomes more uniform.

In this study, the flow field and the impingement heat transfer of fluidic oscillators at narrow spaces are investigated numerically. Simulations are performed in 2-D, incompressible, and unsteady conditions and the aim is to analyze the effects of the jet to wall distance, the external nozzle angle, the Reynolds number, and removing the external nozzle on the heat transfer performance. Also, for a comprehensive review, the results of the fluidic oscillator are compared with the results of the steady jet. To ensure the validity of the numerical simulations, two experimental researches are applied for the fluidic oscillator and the steady jet and a good agreement is observed between the present simulations and the experimental data. The results show that increasing the distance in fluidic oscillators causes a maximum decrease of about 11% at the Nusselt number of the stagnation point, while employing the various distances does not have a significant effect on the steady jet. In addition, the configuration of the different external nozzle angles affects the Nusselt number, but this influence does not have a monotonic behavior. Furthermore, the Nusselt number increases by removing the external nozzle. When the Reynolds number increases for the fluidic oscillator and the steady jet, the Nusselt number of the stagnation point increases by at least about 22 and 28%, respectively.

Aerodynamic interference is one of the phenomena that occurs when two flying objects pass near each other. In this case, the change in the pressure distribution on objects passing near each other causes a change in the aerodynamic forces. In this research, the numerical investigation of the flow field between two narrow bodies at a close distance and the pressure changes along them at supersonic speeds is done. The simulation was done in two-dimensional and three-dimensional form, and the k-omega sst was used to model the flow turbulence. The two slender bodies were placed next to each other at speeds of Mach 1.5, 3, and 4.5 and at intervals of 2, 3, and 4 times the diameter of the body. they were examined in two modes with relative motion and without relative motion. The results show that as the free flow velocity increases, the shock wave deforms from bow to oblique and is reflected between the two bodies.  Also, as the flow Mach number decreases and the distance between two slender bodies increases, the reflected shock wave becomes weaker. At Mach 1.5 the shock wave reflection between two bodies is not very noticeable, while at Mach 4.5 the shock wave is well reflected between two bodies. In the state of relative motion of two slender bodies, separation occurs at the shock wave reflection points and the number of shock wave reflections decreases compared to the state without relative movement.

Drain valves are usually constructed to control and drain flood, regulate flow, drain tank in critical cases, discharge sediment, and transfer current. Therefore, the study of their hydraulic conditions during design and operation should be considered by researchers and designers. As the height of the dam increases, the flow velocity in the semi-open valves of the dam also increases and as a result, the local pressure decreases, which consequently causes the cavitation phenomenon The presence of air near the rigid boundaries of the flow greatly reduces the destructive effect of cavitation and therefore the method of aeration and its effects and the percentage of air bubbles in the vicinity of these boundaries to prevent cavitation is one of the points to know the different types of aeration mechanism and bubble placement, and the type of valve according to the flow conditions. As mentioned, one of the phenomena that can endanger the safety of valves is cavitation. In these valves, the two-phase flow of air is transmitted at high speed. Due to the separation of the flow lines, a sharp drop in the downstream values of the valve occurs.

Siazakh rock dam is located in a place called Siazakh and at the junction of two tributaries of Ghezelozen river named Kaqli and Sheikh Haidar, 7 km from Divandere. The level of the dam on the riverbed is 1756 meters above sea level. The purpose of constructing this dam is to supply agricultural water, control and control river floods. In the middle of the duct, the control system is located, consists of an emergency sliding valve and a sliding service valve. The physical model of the valve includes a repair valve, a metal cover with a rectangular cross section, a duct inlet, a valve groove, a middle duct, an emergency valve, an emergency valve chamber, its grooves, a service valve, a vent between two valves and the entire downstream duct. In order to provide the required water height and required discharge, an open metal tank has been used. This tank is in the form of a cylinder with a diameter of 5 meters and a height of 6 meters.In order to measure the pressures on the valve, 8 piezometers are installed on the valve and all these piezometers are connected to the tightly connected hoses. The experiments were performed for four different heads. Two pumps and an outlet adjustment valve were used to adjust the head, so that only one pump was switched on at the lower heads and the output valve was bypassed to adjust the head. This time was chosen according to the turbulence of the air flow and minimizing its error by trial and error.

After adjusting the head, the service valve was placed in the pre-planned openings and the emergency valve was displaced so much that the most critical situation occurred. The criterion for detecting this critical state is the velocity of air suction from the aeration pipe between the two valves into the duct, which was measured by a hot wire. To measure the air velocity, the hot wire is placed inside the aeration tube in the center of the tube for one minute. After the desired time, the average inlet air velocity is recorded by the hot wire device. The results show that the most critical situation occurs when the jet passing under the emergency valve hits exactly the lower edge of the service valve. In this case, a severe disturbance occurs between the empty space of the two valves, which causes severe suction of air into the aeration pipe. According to observational experience, this condition is usually achieved when the percentage of emergency valve opening is up to about 5% less than the service valve opening.

The results of this study showed that when the emergency valve is broken in a certain opening and consequently the emergency valve enters the circuit, the most critical situation is when the amount of emergency valve opening is equal to the service valve. By measuring the amount of incoming air from the aeration tube in 24 different laboratory modes, and comparing them with different parameters, a relation was provided to determine the aeration coefficient which is a function of the landing number and includes a range between the lower and upper limits of the data. Also, by examining the amount of inlet air flow from the aeration tube for 24 different experiments, it was observed that this amount of air has a relative maximum at two points, the first maximum being related to low openings.

A compound open channel is composed of the main channel and flood plain. In experiments with compound open channel conducted to ensure that the flow is uniform and fully developed, it is necessary to study the distribution of discharge in the main channel and flood plains. The purpose of the present study is to investigate the effects of channel inlet condition on flow uniformity by considering distribution of discharge in channels with length to flood plain width ratio lower than 35 (needed for fully developed flow condition) by analyzing the flow field and turbulence parameters. For this purpose, particle image velocimetry method has been used in a rectangular compound open channel. To provide correct measurement of secondary velocities, using a non-intrusive method such as particle image velocimetry is completely essential. The results of this study show that in short compound channels with the same screen installed in the main channel and flood plain, there is significant mass transfer from the flood plain to the main channel until the end of the channel length. It was found that in this case, a considerable downfall occurs for the maximum velocity position in the main channel. However, with a supplementary screen installed in the flood plain, in addition to the typical screen, expected conditions are established similar to the fully developed compound channels. In this condition, the time-averaged streamwise velocities vary considerably in the flood plain along the spanwise direction. On the other hand, in short compound channels with the same screen installed in main channel and flood plain, the streamwise velocities do not change significantly along the flood plain width duo to the imperfect interaction of main channel and flood plain. These observations express that to provide correct distribution of discharge, a supplementary screen should be installed in the flood plain of the compound channel.

Flow structure around bridge pier is a very complicated phenomenon. Due to the special geometric and structural conditions in some cases, it is required that the piers be placed in pairs next to each other with special arrangements, which leads to a more complex flow structure around the piers. In this study, the variations of the flow velocity and turbulent kinetic energy around single and the twin bridge piers with a circular cross section is simulated using the Fluent model. The twin piers are placed in three configurations including tandem, side-by-side, and at inclined with the flow direction. The three-dimensional components of flow velocity, streamlines, and velocity contours have been investigated for both single and twin piers. By comparing the longitudinal velocity between measured and simulated conditions in two selected cross sections, the average error for the single tandem piers was 7.3% and 3.54%, respectively. Also, the longitudinal velocity in the tandem, side-by-side and inclined piers has decreased by 2.34% and 9.27% and increased by 87.8%, respectively, compared to the single pier conditions. In general, due to the minimum values of turbulent velocity and kinetic energy, the side-by-side model is recommended as the most appropriate arrangement of the piers with respect to the flow direction.

In this paper, the numerical method of heat transfer and fluid flow in the fuel cell of polymer membranes and cooling channels, with the parallel channel pattern and the use of liquid water in separate channels embedded in the bipolar plane, is investigated and the performance of four different field designs Gas flow and cooling, based on the absence of the need for an external thermal boundary condition, the temperature uniformity is simulated and compared using Ansys-Fluent software. The results showed that by increasing the Reynolds number of the cooling flow from 40 to 800, the pressure drop in the cooling flow channel path reaches from 40 to 640 Pascals. On the other hand, the Nusselt number of the cooling flow increases exponentially from 350 to about 700 by changing the Reynolds number from 40 to 400, and then it is fixed. The results also showed that the best cell performance was obtained at Reynolds number 60, because with increasing Reynolds number, the cooling flow and increasing pressure drop of the system’s noise power increases.

In the recent years, due to the hydropower plants environmental problems, hydrokinetic turbine usages has been increased. Using such turbines in rivers modify natural flow-field. In previous studies, impacts of turbine on the flow-field just only in rectangular open-channel is studied. In this work, the effects of hydrokinetic turbine in a straight compound channel has been numerically studied using Fluent extension of Ansys 16. To simulate the turbine rotation, Moving Reference Frame (MRF) method has been implemented. Results showed that due to the turbine presence, natural flow structure and pressure distribution has been drastically changed. Indeed, instead of compound channel secondary currents, a strong secondary flow from the right back to left bank (where the turbine installed) is formed. Also results show that a wake region behind the turbine and regions with high velocity around turbine can be notified. In low velocity inlet, the flow field is intact and natural condition is preserved, while high inlet velocity causes drastic changes. Therefore, it can be concluded that in this situation, considering low effects of turbine presence in flow structure the inlet velocity should be low, while in this condition, the efficiency due to the low velocity would be not be impressive.

Rubber dams are flexible cylindrical structures, attached to a rigid base, and are inflated with air and/or water. Most of the rubber dams are permanently inflated, however, they have the advantages of deflating and being flat, when they are not needed, and then inflated in a short period of time when they are required. Large deformation of the membrane due to the internal and external loads, makes the governing equations of such problem to be non-linear and complicated. In the present study, three-dimensional behavior of the rubber dams with respect to the boundary conditions of dam and flow was simulated numerically. Dam geometry and flow hydraulics were modeled, using ANSYS software, CFX and transient structural in workbench environment, simultaneously. Flow hydraulic characteristics and deformation of the dam are obtained, considering fluid-structure interaction. Water free-surface was obtained, applying two-phase air-water flow interface. SST turbulence model in CFX was employed for modelling the separation of flow, downstream of the inflatable dams. Due to the flexibility of the structure, large deformation theory was used in the transient structural solution. Consequently, different features of the flow field, including flow streamlines, velocity and pressure profiles are obtained and compared with those of the rigid circular-crested weirs. Results indicated that the flow hydraulic characteristics over the equilibrium shape of the rubber dams is analogous to those of the rigid circular-crested weirs.

Prediction of flow field in compound channel is an important task for hydraulic researches because of the three dimensional nature of the flow. In compound channels with prismatic floodplains, the main feature consists of the interaction effect between the fast moving flow in the main channel and the slow moving flow on the floodplains. This difference creates a high shear layer at the interface between the main channel and floodplains, leading to the generation of the large scale vortices with vertical axes, as well as the helical secondary with longitudinal axes, as shown by Sellin [1], Tominaga and Nezu [2], Ikeda [3], Bousmar [4] and Rezaei [5].

Spur dike is one of the river training structures that is considered to deviate the river from critical and erodible areas and the flow from the sides and towards the central axis. As a result of flow is developing a circular area with high turbulence around the spur dike. The hydraulic process results development of the scour hole on the upstream of the spur dike and settlement of sediment in the downstream and sides of the river. While scouring in spur dike structures results a serious threat to the river so it is needed to be researches in this field. This paper describes triplex repellent shielded spur dikes (directed to the upstream) with a distance of 3.5 times of the effective length of the spur dike in the outer bank of the channel. The first spur dike is located at 30 degree from the start of bend. The experimental channel is a 90º channel with rectangular section. The radius of curvature to the channel width is 2, which is classified as a sharp bend. Materials used are sands with uniform grains and its mean diameter is 1.28mm and its standard deviation coefficient is 1.3 and the relative density of sediment is 2.35. The results of flow field on flat bed and a scouring experiment are presented. Discharge was 25 l/s and All scour tests were done in 24 hours and in the moving threshold conditions (U/Uc =0.98) and clear water condition. Flow field is recorded using the Vectrino II velocimeter that can profile water in a 3cm column. It was found that in the levels upstream of the first spur dike in an adjacent to bed, stream lines are deviated to the inner bank. While in the middle levels, flow lines upstream of the spur dike is almost parallel to the channel walls and approached the spur dike, resulting deviation in the separation zone. In the scouring experiment it was obvious that at the beginning of the experiment, thus creating the down flow upstream of the spur dikes scouring initiates near the wing of each spur dike and it develops by the horse shoe vortex. But with the time sediment had been washed from upstream of the first spur dike, and moved to the foot of the spur dike until it reaches upstream of the former to the latter. Then scour hole upstream of the second spur dike starts to form. Results showed that the amount of scour upstream of second spur dike is 33 % and upstream of third spur dike is 81 % the maximum amount of scour that occurs upstream of the first spur dike. Mechanism causing scour and flows occurring within this range detailed in this paper.

Pipelines are used to transport products mainly in the oil and gas industry. For effective operation, the pipelines must be pigged in periods of time. For a suitable performance, pigs should move at a constant velocity. It seems that the study of fluid flow around a moving pig, the pig dynamics and also, estimation of the pig movement variables is essential to control pig velocity. In this research, fluid flow around moving pig in pipeline is simulated by ANSYS CFX. At first, the force on static pig in pipeline for the different bypasses was obtained and compared with the previous study and the good agreement has been observed. Then,for mesh movement around moving pig in pipeline the remeshing method in the dynamic mesh technique was used. up and downstream distribution of pig and also velocity, acceleration and position of pig in different time are obtianed. Therefore, the Navier-Stokes equations for uncompressible viscous fluid flow are solved. The k-εturbulence model is used to simulate turbulence. In the study of pig movement through the pipe, the result showed that at first, the fluid force on pig is high and as time goes on, is reduced becouse the relative velocity between the pig and fluid flow is decreased and become equal to external force (friction force) so the net force on pig get zero. Thus, the pig acceleration is approaching to zero and the pig velocity is being constant. Also as pig goes forward the velocity and pressure through the pipe decrease because of pig acceleration reduction. So that the fluid condition becomes permanent. In the study of effect of pig on fluid velocity through the pipe, it is obvious that the most effect is on fluid velocity in pig output and in the long distance from the pig the it’s changes is low.

Velocity in a main channel is much higher than the floodplain in compound channels. This leads to the transfer of momentum between the main channel water and that of the floodplain. The relative “pull” and “drag” of the flow between faster and slower moving sections of a compound channel، complicates the momentum transfer between them. This momentum transfer also causes a secondary flow in compound channels. Considerable research on physical models for the behavior of the compound channels with different widths of the main channel and floodplain have been done by Shiono and Knight [1]، and Myers and Lines [2]. These researches help to understand the complex pattern of flow and boundary shear stress that has a significant role in momentum transfer between main channel and floodplain. Extensive studies have been for combination parameters of flow field in curved channels with compound channels as well as done in a sinusoidal compound channels. Toebs andsooky Studies in this direction can be pointed out [3]. In addition to compound channel، another locations that the secondary flow has an important effect on behavior of flow filed are in the channels and rivers bends. Some of flow characteristics such as secondary flow power and vortices power can assist to better understanding of flow filed in bends. Despite of expanded using of these characteristics in bends، they haven’t used in compound channel too much. In this research، the flow filed was simulated using different turbulence models and verified by experimental data in prismatic compound channel. Then the secondary flow power and vortices power of secondary flow in compound channel were computed.

Spur dikes are the training structures that may be used for river bank erosion protections. These structures may increase the navigation depth. The spur dike creates stable pool for aquatic habitat. Most of the previous researches focused on scour hole dimensions and the flowfield around the emerged spur dikes. As the spur dikes may be submerged during the floods، in this paper، the flowfield around a submerged T-shape spur dike was investigated using Vecterino apparatus. The experiment was conducted in a channel with 8m length، 60cm width and 80 cm depth at TarbiatModares University (Tehran- Iran). The parameters that were investigated in this paper includes، mean velocities، turbulence parameters and streamlines. The results of this study indicate that the high velocity region of the flow elongates to the far distance of downstream in the upper layers. There is a recirculating flow downstream of spur dike. Due to the effect of the spur dike overflow، the downstream recirculating flow، rotates in the opposite direction as compare to the emerged spur dike. The recirculating flow elongates to the far distance of downstream as compare to the submerged trapezoidal spur dike. Turbulence parameters analyzed in this research include normal Reynolds stress، bed shear stresses، the probability of each process and triple correlations. Maximum normal Reynolds stresses were observed at the upstream tip of the spur dike. In addition، the maximum shear stress was observed at the same region. The high stress region around the spur dikes showed a shear layer region around the spur dikes. Analysis of the probability of the turbulent bursting events in streamwise direction shows that ejection and sweep events are the most probable events in the upstream section of the spur dikes. In the streamwise direction، the interaction events are the most probable process near the upstream tip of the spur dike، while ejection and sweep events in the widthwise direction are the most probable events near the upstream tip of the spur dike. In the downstream recirculation zone of the spur dike، the probability of the events approximately are the same in the streamwise direction and interaction events are the most probable events in widthwise directions. Triple correlations presented useful information about the turbulent bursting process. The triple correlation analysis in widthwise direction showed that the ejection is the strongest event in shear layer region. Triple correlation analysis in the streamwise direction، showed that ejection was the strongest event in the upstream of the spur dike and in the region between near channel wall and spur dike wing. This causes sediment transport in streamwise direction as suspended load. The interaction events are the strongest events in the downstream recirculation zone، hence the sediments were deposited in this region.

Submerged vanes are small flow training structures، designed to modify the near bed flow pattern and redistribution of flow and sediment transport whit in channel cross section. The vanes generating secondary circulation in the flow. The flow field around lateral intake located in the outer bank of channel bends and the interaction between this flow field and secondary flow due to submerged vanes in completely three dimensional and complex. The purpose of this paper is determination of appropriate location of the one submerged vane with respect to the downstream and upstream edge of the lateral intake in a U shape channel bend and choice the best angle of vane for reduce the sediment entry to the lateral intake. In this order we use the Fluent software to numerical simulation of 3D flow pattern around the one vane that locating in front of downstream edge of a lateral intake in a U shape channel bend. The results of numerical were verified with the existing experimental data. Comparison of the predicted x velocity and y velocity field with laboratory measurements indicates that the model capture experimental trend with reasonable accuracy. Computations are performed using Reynolds Stress Model. After model verification، the effect of different position of the vane with respect to downstream of intake (the first، middle and end point of vane is in front of downstream edge of intake) and upstream edge of intake (the first، middle and end point of vane is in front of upstream edge) and effect of different angle of vane (15، 17، 20، 25، 30 degree) on flow pattern and shear stress pattern of bed is considered. The appropriate position and angle of the vane has been selected by effect of the vane on area of high shear stress zone and area of low velocity contour around the vane and reduction of dimension of saddle point near the downstream edge of lateral intake and situation of stream line around the vane and in front of the intake at the bottom of the channel. The results show the best position of vane with respect to downstream edge of lateral intake is the case that the first point of vane is in front of downstream edge of intake and the best position of vane with respect to upstream edge of intake is the case that the end point of vane is in front of upstream edge of intake. Also the results show that the appropriate value for angle of attack of the vane at downstream edge of intake (the first point of vane is in front of downstream edge of intake) is about 20-25 degree and optimum value for angle of attack of the vane at upstream edge of intake (the end point of vane is in front of upstream edge of intake) is about 17-20 degree.

With respect to special conditions apply to the gas turbine, its blades are affected by many different factors such as, hot corrosion, oxidation, wear, impact of external particles, and etc. and are destroyed. Due to the reduction of their working life time, the turbine efficiency reduces and ultimately the heavy costs of periodic repairs are needed, and also new replacements of their blades are unavoidable. The aim of this study is investigation of the effects of corrosion and blade damage on flow field and gas turbine performance, by numerical simulation. In this research, a two stage turbine is modeled in the form of three dimensional and the results are validated with experimental data. To analyze of the behavior of entire flow, conservation of mass, momentum, and energy equations are solved. The numerical simulation of the turbine is done with ANSYS CFX software. Then the increased rotors tip clearance effects with decreasing thickness due to corrosion in both nozzles and blade leading edge and trailing edge were separately studied on turbine flow field and its performance in five actual different pressure ratios. The results showed that the most important factor in reducing the efficiency of gas turbine is due to rotor tip clearance increasing. Also corrosion of the blade edge respect to the trailing edge damage is a little more affected on reducing efficiency and increasing loss coefficients.

High temperatures and different properties of entering gas into the turbine of a gas turbine cycle can decrease its performance. Considering the complexity of the flow distribution inside the turbine، three-dimensional analysis to find out the flow and temperature field in the turbine stages is very important. As time passing the increasing of the roughness of blades is unavoidable. The aim of this paper is investigation of the blades roughness effects on flow field and efficiency of gas turbine with numerical calculations. In this research، a two-stage turbine is modeled in the form of three-dimensional and the results are validated with experimental data. Then the effects of blades roughness on flow field and performance of turbine in five pressure ratios is investigated. Also، in order to determine the role of stators and rotors in decreasing the turbine efficiency، in a special roughness، the first and second stators and then corresponding rotors have separately been examined and then this phenomenon affected on blades simultaneously. Results showed that the efficiency drop by applying all together on the turbine stage is approximately equal to summation of efficiency drops by applying separately.

A s‌e‌r‌i‌e‌s o‌f w‌i‌n‌d t‌u‌n‌n‌e‌l t‌e‌s‌t‌s w‌e‌r‌e c‌o‌n‌d‌u‌c‌t‌e‌d t‌o e‌x‌a‌m‌i‌n‌e t‌h‌e f‌l‌o‌w f‌i‌e‌l‌d o‌v‌e‌r s‌w‌e‌p‌t w‌i‌n‌g‌s a‌t s‌u‌b‌s‌o‌n‌i‌c s‌p‌e‌e‌d u‌n‌d‌e‌r v‌a‌r‌i‌o‌u‌s c‌o‌n‌d‌i‌t‌i‌o‌n‌s. F‌o‌r t‌h‌i‌s p‌u‌r‌p‌o‌s‌e, t‌h‌r‌e‌e m‌o‌d‌e‌l‌s w‌i‌t‌h s‌w‌e‌e‌p a‌n‌g‌l‌e‌s o‌f 23, 33 a‌n‌d 40 d‌e‌g‌r‌e‌e‌s w‌e‌r‌e u‌s‌e‌d. T‌o I‌n‌c‌r‌e‌a‌s‌e t‌h‌e R‌e‌y‌n‌o‌l‌d‌s n‌u‌m‌b‌e‌r, a‌l‌l m‌o‌d‌e‌l‌s w‌e‌r‌e e‌m‌p‌l‌o‌y‌e‌d a‌s s‌e‌m‌i s‌p‌a‌n w‌i‌n‌g t‌y‌p‌e‌s a‌n‌d t‌h‌e e‌f‌f‌e‌c‌t‌s e‌l‌i‌m‌i‌n‌a‌t‌e‌d b‌y i‌n‌s‌t‌a‌l‌l‌i‌n‌g t‌h‌e m‌o‌d‌e‌l‌s o‌n a f‌l‌a‌t p‌l‌a‌t‌e a‌t t‌h‌e‌i‌r r‌o‌o‌t‌s. T‌h‌e f‌l‌a‌t p‌l‌a‌t‌e w‌a‌s i‌n‌s‌t‌a‌l‌l‌e‌d i‌n t‌h‌e m‌i‌d‌d‌l‌e o‌f t‌h‌e t‌e‌s‌t s‌e‌c‌t‌i‌o‌n a‌t a d‌i‌s‌t‌a‌n‌c‌e f‌r‌o‌m t‌h‌e w‌a‌l‌l. T‌h‌e t‌e‌s‌t‌s w‌e‌r‌e p‌e‌r‌f‌o‌r‌m‌e‌d a‌t v‌a‌r‌i‌o‌u‌s R‌e‌y‌n‌o‌l‌d‌s n‌u‌m‌b‌e‌r‌s a‌n‌d a‌t v‌a‌r‌i‌o‌u‌s a‌n‌g‌l‌e‌s o‌f a‌t‌t‌a‌c‌k o‌n a‌l‌l s‌e‌m‌i-s‌p‌a‌n w‌i‌n‌g‌s, w‌h‌i‌c‌h h‌a‌d t‌h‌e s‌a‌m‌e a‌s‌p‌e‌c‌t r‌a‌t‌i‌o b‌u‌t d‌i‌f‌f‌e‌r‌e‌n‌t s‌w‌e‌e‌p a‌n‌g‌l‌e‌s. T‌h‌e r‌e‌s‌u‌l‌t‌s s‌h‌o‌w t‌h‌a‌t i‌n‌c‌r‌e‌a‌s‌i‌n‌g t‌h‌e s‌w‌e‌e‌p a‌n‌g‌l‌e c‌a‌u‌s‌e‌s a d‌e‌c‌r‌e‌a‌s‌e i‌n t‌h‌e v‌e‌l‌o‌c‌i‌t‌y o‌v‌e‌r t‌h‌e w‌i‌n‌g s‌u‌r‌f‌a‌c‌e. T‌h‌e p‌r‌e‌s‌s‌u‌r‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n o‌n t‌h‌e u‌p‌p‌e‌r s‌u‌r‌f‌a‌c‌e o‌f t‌h‌e w‌i‌n‌g s‌h‌o‌w‌s s‌o‌m‌e d‌i‌f‌f‌e‌r‌e‌n‌c‌e‌s w‌h‌e‌n c‌o‌m‌p‌a‌r‌e‌d t‌o t‌h‌e 2-D c‌a‌s‌e, d‌u‌e t‌o t‌h‌e e‌x‌i‌s‌t‌e‌n‌c‌e o‌f t‌h‌e c‌r‌o‌s‌s f‌l‌o‌w a‌n‌d w‌i‌n‌g t‌i‌p v‌o‌r‌t‌i‌c‌e‌s. A‌s t‌h‌e w‌i‌n‌g s‌w‌e‌e‌p a‌n‌g‌l‌e w‌a‌s v‌a‌r‌i‌e‌d, t‌h‌e d‌i‌f‌f‌e‌r‌e‌n‌c‌e‌s v‌a‌r‌i‌e‌d t‌o‌o. T‌h‌e r‌e‌s‌u‌l‌t‌s i‌n‌d‌i‌c‌a‌t‌e t‌h‌a‌t t‌h‌e w‌i‌n‌g t‌i‌p v‌o‌r‌t‌i‌c‌e‌s a‌m‌p‌l‌i‌f‌y t‌h‌e 3D e‌f‌f‌e‌c‌t‌s o‌f t‌h‌e f‌l‌o‌w. T‌h‌e p‌r‌e‌s‌s‌u‌r‌e r‌e‌d‌u‌c‌t‌i‌o‌n i‌n t‌h‌e v‌i‌c‌i‌n‌i‌t‌y o‌f t‌h‌e w‌i‌n‌g t‌i‌p d‌e‌t‌e‌r‌i‌o‌r‌a‌t‌e‌s t‌h‌e p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e a‌t t‌h‌a‌t s‌e‌c‌t‌i‌o‌n, c‌o‌m‌p‌a‌r‌e‌d t‌o o‌t‌h‌e‌r s‌e‌c‌t‌i‌o‌n‌s o‌f t‌h‌e w‌i‌n‌g. T‌h‌i‌s p‌h‌e‌n‌o‌m‌e‌n‌o‌n w‌o‌u‌l‌d e‌v‌e‌n‌t‌u‌a‌l‌l‌y c‌a‌u‌s‌e s‌t‌a‌l‌l t‌o o‌c‌c‌u‌r a‌t t‌h‌i‌s s‌e‌c‌t‌i‌o‌n (w‌i‌n‌g t‌i‌p) s‌o‌o‌n‌e‌r t‌h‌a‌n a‌t o‌t‌h‌e‌r s‌e‌c‌t‌i‌o‌n‌s. T‌h‌e m‌a‌x‌i‌m‌u‌m p‌r‌e‌s‌s‌u‌r‌e d‌r‌o‌p n‌e‌a‌r t‌h‌e w‌i‌n‌g t‌i‌p r‌e‌m‌a‌i‌n‌s u‌n‌c‌h‌a‌n‌g‌e‌d w‌i‌t‌h c‌h‌a‌n‌g‌i‌n‌g t‌h‌e s‌w‌e‌e‌p a‌n‌g‌l‌e f‌o‌r z‌e‌r‌o a‌n‌g‌l‌e o‌f a‌t‌t‌a‌c‌k o‌n‌l‌y. B‌u‌t, f‌o‌r o‌t‌h‌e‌r a‌n‌g‌l‌e‌s o‌f a‌t‌t‌a‌c‌k, t‌h‌e s‌i‌t‌u‌a‌t‌i‌o‌n i‌s d‌i‌f‌f‌e‌r‌e‌n‌t. F‌o‌r t‌h‌e w‌i‌n‌g w‌i‌t‌h a s‌w‌e‌e‌p a‌n‌g‌l‌e o‌f 40 d‌e‌g‌r‌e‌e‌s, t‌h‌e s‌u‌r‌f‌a‌c‌e p‌r‌e‌s‌s‌u‌r‌e o‌f a‌l‌l s‌e‌c‌t‌i‌o‌n‌s d‌i‌f‌f‌e‌r‌s s‌i‌g‌n‌i‌f‌i‌c‌a‌n‌t‌l‌y a‌n‌d t‌h‌e m‌a‌x‌i‌m‌u‌m p‌r‌e‌s‌s‌u‌r‌e i‌s m‌u‌c‌h l‌o‌w‌e‌r t‌o‌o. H‌o‌w‌e‌v‌e‌r, n‌e‌a‌r t‌h‌e w‌i‌n‌g t‌i‌p, t‌h‌e d‌i‌f‌f‌e‌r‌e‌n‌c‌e‌s a‌r‌e n‌o‌t s‌i‌g‌n‌i‌f‌i‌c‌a‌n‌t. T‌h‌i‌s p‌h‌e‌n‌o‌m‌e‌n‌o‌n i‌s r‌e‌l‌a‌t‌e‌d t‌o t‌h‌e e‌f‌f‌e‌c‌t o‌f w‌i‌n‌g t‌i‌p v‌o‌r‌t‌i‌c‌e‌s t‌h‌a‌t a‌r‌e m‌o‌r‌e d‌o‌m‌i‌n‌a‌n‌t a‌t h‌i‌g‌h‌e‌r s‌w‌e‌e‌p a‌n‌g‌l‌e‌s. T‌h‌e t‌e‌s‌t r‌e‌s‌u‌l‌t‌s i‌n a‌l‌l t‌h‌r‌e‌e m‌o‌d‌e‌l‌s s‌h‌o‌w t‌h‌a‌t t‌h‌e p‌r‌e‌s‌s‌u‌r‌e c‌o‌e‌f‌f‌i‌c‌i‌e‌n‌t d‌e‌c‌r‌e‌a‌s‌e‌s w‌i‌t‌h i‌n‌c‌r‌e‌a‌s‌i‌n‌g R‌e‌y‌n‌o‌l‌d‌s, a‌n‌d t‌h‌i‌s p‌h‌e‌n‌o‌m‌e‌n‌o‌n i‌s m‌o‌s‌t p‌r‌o‌m‌i‌n‌e‌n‌t f‌o‌r t‌h‌e h‌i‌g‌h‌e‌s‌t s‌w‌e‌e‌p a‌n‌g‌l‌e o‌f 40 d‌e‌g‌r‌e‌e‌s.

In this study, the effects of strength and direction of a magnetic field on lid-driven cavity flow in a wide range of magnetic field strength variations (0 to 10 Tesla) are studied. The governing equations, including conservative equations of momentum, continuity and magnetic field were solved numerically. Momentum and continuity were solved by the finite volume method, using SIMPLE algorithm where the finite difference method was used for solving of magnetic field equation. In this research, the effects of magnetic field on the velocity distribution, streamlines, and vortex flow shows that the vortices of the cavity shrink up to 0.01 Tesla, where the uniform and vertical magnetic field was applied from the bottom surface. For the magnetic field of 0.01 Tesla, the vortices disappear. Higher values of magnetic field create larger vortices.

A s e r i e s o f s u b s o n i c w i n d t u n n e l e x p e r i m e n t s w e r e c a r r i e d o u t t o i n v e s t i g a t e e f f e c t s o f t h e p r e s e n c e a n d p o s i t i o n s o f a c a n a r d o n t h e v e l o c i t y f i e l d o v e r a d e l t a w i n g. I n t h i s r e s e a r c h, f l o w f i e l d m e a s u r e m e n t s o n a o n e-m e t e r a l u m i n u m a l l o y m o d e l a r e p e r f o r m e d. I n o r d e r t o u n d e r s t a n d c a n a r d i n f l u e n c e, t h e c a n a r d w a s s e t a t t w o v e r t i c a l p o s i t i o n s, h i g h a n d m i d, w i t h r e s p e c t t o t h e w i n g l e v e l. F l o w f i e l d m e a s u r e m e n t s w e r e p e r f o r m e d t o s t u d y t h e m e c h a n i s m o f c a n a r d-w i n g v o r t e x i n t e r a c t i o n s. T h e d a t a s h o w t h a t c a n a r d v e r t i c a l p o s i t i o n s h a v e a s i g n i f i c a n t i n f l u e n c e o n t h e v o r t i c e s l o c a t i o n s, a s w e l l a s o n v o r t e x b r e a k d o w n. R e s u l t s o f t h e f l o w f i e l d m e a s u r e d b y a s p e c i f i c r a k e s h o w t h a t t h e w i n g l e a d i n g e d g e v o r t e x b e c o m e s s t r o n g e r b y i n c r e a s i n g T h e a n g l e o f a t t a c k. I n a d d i t i o n, t h e v e r t i c a l d i s t a n c e o f t h e v o r t e x, w i t h r e s p e c t t o t h e w i n g s u r f a c e, i n c r e a s e s, a n d t h e p o s i t i o n o f t h e v o r t e x b r e a k d o w n m o v e s u p s t r e a m. T h e p r e s s u r e l o s s i n d u c e d b y t h e c a n a r d v o r t e x o n t h e w i n g s u r f a c e m o v e s t h e w i n g v o r t e x t o w a r d t h e l e a d i n g e d g e. W h e n t h e t w o v o r t i c e s a r e p l a c e d a t a n a p p r o p r i a t e d i s t a n c e f r o m e a c h o t h e r, t h e i r m e r g i n g c a n l e a d t o a s u d d e n p r e s s u r e l o s s. I n t h e m i d c a n a r d c o n f i g u r a t i o n c a s e, b o t h c a n a r d a n d w i n g v o r t i c e s m e r g e a t x/c $s u c c$ 0.5, a n d, a s a r e s u l t o f t h i s p h e n o m e n o n, a b r u p t p r e s s u r e l o s s o c c u r s a n d a s t a b l e v o r t i c a l f l o w i s m a i n t a i n e d o n t h e w i n g. I t i s s h o w n t h a t l o w a l p h a c a n a r d d e f l e c t i o n s, w i t h r e s p e c t t o t h e w i n g o r f r e e s t r e a m, m a k e s s i g n i f i c a n t c h a n g e s t o t h e f l o w f i e l d o v e r t h e w i n g.