Turbulent Wall Jet Research Articles

Spatiotemporal structure of flow field by a dielectric-barrier-discharge plasma actuator using phase-resolved particle image velocimetry

A typical dielectric-barrier-discharge plasma actuator (DBD-PA) operating in continuous mode generates a self-similar starting vortex followed by a quasi-steady wall jet. In the burst mode, it generates periodic vortices, leading to a spatially wider mean flow field. The characteristics of periodic vortices can be controlled by adjusting the duty cycle α and burst frequency fb of the actuation signal. In the present study, the flow field generated by the actuator in burst mode is studied for 50%≥α≤90%, and 10 Hz ≥fb≤90 Hz. The Reynolds number of mean flow based on the maximum induced velocity and jet half-width ranges from 171 to 524. High-speed laser-sheet visualization and time-resolved particle image velocimetry are used for flow field measurements. The flow field generated during burst mode operation shows the strong influence of the burst frequency. Periodic vortices with comparable size and convection speed of starting vortex are generated at low fb. Dipoles and small-scale vortices are formed at moderate fb similar to the behavior of a transitional wall jet. Kelvin–Helmholtz instability is observed at higher burst frequency. An ornamental vortex consisting of several small periodic vortices is formed at high values of fb during the starting period. Based on the temporal evolution of momentum, the flow field generated by the DBD-PA can be classified into (i) starting flow regime, (ii) transitional flow regime, and (iii) periodic flow regime. The self-similarity of the mean flow field generated by the DBD-PA is verified by comparing the mean velocity profile at multiple downstream locations with the self-similar solutions of laminar and turbulent wall jets. The entrainment coefficient of the mean flow field is similar to that of an axisymmetric turbulent wall jet. The bi-orthogonal analysis shows that both coherent mode energy content and the entropy are minimum (about 5% only) for the continuous mode actuation. For the burst mode actuation, both the coherent mode energy content and the entropy are higher in magnitude compared to that of continuous mode and decrease with increasing burst frequency. The vortices in the periodic flow regime are locked in with fb. The distance between subsequent vortices, λx and flow frequency, f follow a power-law relationship, λx=cf−n, where c is a constant and n can be approximated as 2/3.

Modulation of re-circulation zone behind a square obstruction by single inclined turbulent wall jet with varying angle of attack

The modulation of the re-circulation region is one of the primary interests of this numerical study. This study investigates the modulation of the re-circulation zone behind a square obstruction by a single inclined turbulent wall jet with varying angles of attack. The flow field is visualized using the post-processing system of the simulation software and the results have been analyzed. The experiments are carried out for different angles of attack of the wall jet and a range of high Reynolds numbers. The results show that the re-circulation zone is significantly affected by the angle of attack of the wall jet. The maximum length of the re-circulation zone decreased with increasing angle of attack. The wall jet angles of attack (AOA) also affect the strength and position of the vortex structures in the re-circulation zone. The results of this study provide insights into the use of inclined wall jets for controlling the flow field behind obstructions in engineering applications such as flow control and mixing enhancement. The numerical simulation is based on a two-phase volume of fluid (VOF) model with open channel boundary conditions. The standard k–ω SST turbulence model is applied to solve the Reynolds averaged equation.

Modeling of scour hole characteristics under turbulent wall jets using machine learning

The novelty of the present study is to investigate the parameters that depict the scour hole characteristics caused by turbulent wall jets and develop new mathematical relationships for them. Four significant parameters i.e., depth of scouring, location of scour depth, height of the dune and location of dune crest are identified to represent a complete phenomenon of scour hole formation. From the gamma test, densimetric Froude number, apron length, tailwater level, and median sediment size are found to be the key parameters that affect these four dependent parameters. Utilizing the previous data sets, Multi Regression Analysis (linear and non-linear) has been performed to establish the relationships between the dependent parameters and influencing independent parameters. Further, artificial neural network-particle swarm optimisation (ANN-PSO) and gene expression programming (GEP) based models are developed using the available data. In addition, results obtained from these models are compared with proposed regression equations and the best models are identified employing statistical performance parameters. The performance of the ANN-PSO model (RMSE = 1.512, R2 = 0.605), (RMSE = 6.644, R2 = 0.681), (RMSE = 6.386, R2 = 0.727) and (RMSE = 1.754, R2 = 0.636) for predicting four significant parameters are more satisfactory than that of regression and other soft computing techniques. Overall, by analysing all the statistical parameters, uncertainty analysis and reliability index, ANN-PSO model shows good accuracy and predicts well as compared to other presented models.

Experimental investigation of the structure of plane turbulent wall jets. Part 1. Spectral analysis

Plane turbulent wall jets are traditionally considered to be composed of a turbulent boundary layer (TBL) topped by a half-free jet. However, certain peculiar features, such as counter-gradient momentum flux occurring below velocity maximum in experiments and numerical simulations, suggest a different structure of turbulence therein. Here, we hypothesize that turbulence in wall jets has two distinct structural modes, wall mode scaling on wall variables and free-jet mode scaling on jet variables. To investigate this hypothesis, experimental data from our wall jet facility are acquired using single hot-wire anemometry and two-dimensional particle image velocimetry at three nozzle Reynolds numbers 10 244, 15 742 and 21 228. Particle image velocimetry measurements with four side-by-side cameras capture the longest field of view studied so far in wall jets. Direct spatial spectra of these fields reveal modal spectral contributions to variances of velocity fluctuations, Reynolds shear stress, shear force, turbulence production, velocity fluctuation triple products and turbulent transport. The free-jet mode has wavelengths scaling on the jet length scale ${z_{T}}$ , and contains two dominant submodes with wavelengths $5{z_{T}}$ and $2.5{z_{T}}$ . The region of flow above the velocity maximum shows the presence of the outer jet mode whereas the region below it shows robust bimodal behaviour attributed to both wall and inner jet modes. Counter-gradient momentum flux is effected by the outer jet mode intruding into the region below velocity maximum. These findings support the hypothesis of wall and free-jet structural modes, and indicate that the region below velocity maximum could be much complex than a conventional TBL.

Advancements in predicting scour depth induced by turbulent wall jets: A comparative analysis of mathematical formulations and machine learning models

This study examines the scour depth induced by turbulent wall jets and proposes novel mathematical formulations to predict the depth of scouring. Through a comprehensive gamma test, key parameters influencing the scour depth are identified, including the apron length, densimetric Froude number, median sediment size, tailwater level, Reynolds number, and Froude number of the jet. Regression analysis is subsequently conducted to establish relationships between the dependent parameter and the aforementioned independent variables. A comparative analysis is then undertaken between the measured scour depths and those predicted by existing equations from previous studies. Furthermore, predictive models leveraging the support vector machine, artificial neural network with particle swarm optimization, M5 tree algorithm, gene expression programming, and adaptive neuro-fuzzy inference system (ANFIS) are developed using the collected data. Statistical metrics are employed to evaluate the performance of each model and the regression equation. The effectiveness of each model in predicting scour depth is demonstrated. Notably, ANFIS yields a coefficient of determination of 0.809 and a root mean square error (RMSE) of 1.585. Multi-nonlinear regression analysis exhibits a coefficient of determination of 0.752 and an RMSE of 0.421, while the M5 tree achieves a coefficient of determination of 0.739 and an RMSE of 1.874, demonstrating superior performance compared to other machine learning techniques and regression equations employed in this study.

Thermal analysis of a turbulent wall jet over an adiabatic wavy surface

The impact of wavy wall amplitude on the turbulent characteristics of a wall jet has been investigated experimentally, where the wavy wall is given an adiabatic condition. In the experimental study, the mean and turbulent velocity are measured using a constant temperature anemometer manufactured by Dantec Dynamics. For temperature measurement over the wall and within the flow domain, the FLIR camera and k-type thermocouple are used, respectively. For the current study, uniformly heated at △T0 = (T0 − T∞) = 30 ± 1.2 0C with a Reynolds number of 15,000 is utilized to flow over a sinusoidal wavy wall (y = A*sin (ωx)), where “A = Amplitude ⁄ a” is the amplitude normalised by the nozzle height “a". The nozzle height is 20 mm and to maintain the Reynolds number 15,000 at the inlet, velocity is set at 10.95 ± 0.36 m ⁄ s. The amplitude of the wavy wall is varied between 0.2 and 0.6 and the results are compared to those of the plane wall jet. The current problem is also numerically solved using the k − ε RNG and k − ω SST models. Based on the results, it is concluded that the k − ε RNG model predicts the wavy wall results quite well. It is also discovered that the thermal self-similar profile deviates from the Gaussian curve at the crest of the wavy wall. The influence of the wavy surface on the thermal characteristics of the turbulent wall jet is more pronounced in the near flow field. It is observed that the bottom wall temperature, fluctuating temperature and turbulent heat flux decrease with the increase in amplitude. This indicates that for the higher amplitude, the turbulence increases, which increases the intermixing of jet fluid with the colder ambient fluid. The present results can be used as a benchmark for validating numerical models working in this area.

Characterizing the Effect of Sinusoidal Wall Amplitude on Turbulent Wall Jet Flow Parameters

Abstract The influence of wavy wall amplitude on the turbulent wall jet flow parameters has been investigated experimentally. For the present study, a sinusoidal wavy wall (y=A* sin(ωx)) has been used where “A=Amp/a” is the amplitude, which is normalized by the nozzle height “a.” The amplitude of the wavy wall is varied as 0.2, 0.4, and 0.6, and the results are compared with the results of plane wall jet. The constant temperature anemometer (CTA) has been used for the measurement of flow by using a transverse mechanism. The results for the mean velocity profile, turbulent intensity, and power spectral density are plotted at the crest and trough separately for more clear discussions. From the velocity profile, it is noticed that the formation of self-similar profile is delayed as the amplitude increases from 0.2 to 0.6, which means flow takes longer time to develop. There is an increase in the local maximum streamwise velocity Umax at crests for increasing amplitude. At the first crest, the rise in Umax is maximum, i.e., Umax is increased by 26%, 37%, and 60% for the amplitudes 0.2, 0.4, and 0.6, respectively, with respect to the plane wall case. In the near flow field, the turbulent intensity also becomes larger for the higher amplitude, which shows higher intermixing of fluid within the jet. This paper also produces the benchmark results which can be used for the validation of the numerical model dealing with the turbulent wall jet flowing over a wavy surface.

Heat transfer augmentation by plate motion in a wall jet flow over a heated plate: A conjugate heat transfer technique

The present study is an initiation to investigate the effect of plate movement on heat transfer characteristics in the solid plate and the fluid domain due to the turbulent wall jet flow over the plate in a quiescent surrounding. A conjugate technique is used to carry out the heat transfer solution that involves conduction in solid and convection in fluid coupled at the interface surface. The plate is heated continuously with a constant flux at its lower surface. A low-Reynolds number k − ε turbulence model developed by Yang and Shih (YS) is applied to simulate the turbulent flow. The parameters considered for the present study are the plate-jet velocity ratio ( 0 − 2 ) , the plate thickness ratio ( 0.5 − 1.5 ) , the conduction ratio ( 500 − 2000 ) , and the Reynolds number ( 7700 − 25 , 000 ) . The temperature distribution diagrams for various plate velocities, the interface temperature profile, and the averaged Nusselt number show a higher cooling rate at high plate-jet velocity ratios. The effect of plate thickness and conductivity ratios is visible in the temperature distribution diagrams. A better heat transfer is achieved at a higher Reynolds number, evident from the averaged and local Nusselt number distribution. A correlation is developed for average Nusselt number with the Reynolds number and plate-jet velocity ratios as the varying parameters.

Numerical investigation on conjugate behavior of heat transfer and its augmentation in a turbulent wall-jet flow on a heated plate in motion

The present research involves a computational investigation by adopting a conjugate technique in a turbulent wall jet flow on a moving plate heated isothermally at the bottom. The low-Reynolds-number YS model is adopted for the simulation to predict the thermal and fluid behavior in the near wall regime. The wall jet enters a quiescent environment of Prandtl number of 7 at a constant Reynolds number of Re = 15000 at the inlet. The thermal parameters considered for observing the thermal behavior are solid-fluid conduction ratio ( K ) , plate-jet thickness ratio ( S ) , and plate to jet velocity ratio ( U p ) . The temperature distributions in the plate domain, temperature at the solid-fluid interface, local Nusselt number, and average Nusselt number provided evidence of the effects of plate movement in the present cases. The plate motion strongly influences the distribution of the local and the averaged Nusselt number along with the temperature at the interface. The average Nusselt number calculated suggests that plate motion is crucial in enhancing heat transfer rate.

Investigation of Flow Behavior of Turbulent Wall-Jet in the Viscous Shear Regime With Moving Wall Condition

AbstractThis work involves studying the effects of plate motion on the turbulent flow behavior of a wall jet stream flowing over a flat plate moving at a constant velocity in a quiescent atmosphere. A modified low-Reynolds-number turbulence model developed by Yang and Shih (YS model) is used to perform the numerical investigation. The YS model involves applying integration to a wall technique to capture the flow and heat transfer phenomenon in the near-wall region. The Reynolds number is taken as 15,000 and Prandtl number of the fluid as 7. The plate motion effect on the flow behavior is observed for the various velocity ratios Up =0−2. The velocity vector diagrams and the local velocity profiles at various axial locations are plotted to analyze the flow pattern variation with the plate velocity. Based on the investigation of velocity profiles, nearly self-similar velocity profiles are noticed for Up=0, 0.5, and 2 whereas for Up=1.0 and 1.5, the velocity profiles display similarity near the wall but diverge away from the wall. The turbulent kinetic energy (TKE) (k) and its dissipation rate (ε) within the viscous shear regime are predicted for moving plate conditions. The dissipation rate appears to be higher for higher velocity ratios. Overall, the plate motion significantly influences the flow field.

Effects of Secondary Current on the Local Erosion Induced by Circular Turbulent Wall Jets in Cross Flow

This paper presents the results of a series of laboratory experiments, by placing a turbulent wall jet in the upstream and downstream of a 90° channel bend, to investigate the effects of secondary flow on formation of local sediment erosion and deposition. The effects of jet and current flow intensities on the erosion pattern were characterized by the jet’s Reynolds number, Re, channel Froude number, Fr, and the ratio of water depth to nozzle diameter, h/do. The geometrical characteristics of local erosion such as jet trajectory, maximum scour depth, ds, and maximum mound height, hm, were measured. The area and volume of scours and mounds were calculated from measurements, and the results were correlated with the controlling parameters. Experimental observations indicated the existence of distinct scour patterns due to variations of channel Froude number. Two additional scour holes were identified due to the effect of stream interactions and formation of vortex regions immediately downstream of sediment mound. It was found that both channel and jet flows contributed to trajectory of the jet and the footprint of erosion. A threshold Froude number of Fr=0.091 was identified at which the current and jet flow were in equilibrium. The results showed that for a constant value of Fr, all scour parameters increased with increasing Reynolds number. However, Re did not have any effects on the jet’s deflection. Comparing the erosion profiles in the upstream and downstream bend indicated that the secondary current and turbulent redistribution altered the erosion and mound formation in the downstream of the bend in relatively high Reynolds (i.e., Re≥23,000), high channel Froude numbers (i.e., Fr>0.091) and high jet submergence (i.e., h/do>10.53).

Flow Structure of a Three-Dimensional Turbulent Wall Jet

A numerical simulation is conducted to study the flow of a three-dimensional incompressible wall jet. The study is aimed to determine the flow structure and to compare the propagation mechanisms of turbulent and laminar wall jets. The numerical solution of the Navier–Stokes equations in the turbulent case is obtained using the wall-resolved large eddy simulation. The simulation results are compared with experimental data.

Comparison of Turbulence Models in Simulation of Plane Jet Flow

Plane turbulent jets are widely used in a variety of applications. Such as jets in drying processes, air curtains for room conditioning, heating, mixing, ventilating applications etc., therefore, jet flow is a very important research topic in both experimental and analytical research.
 Depending upon the position and forces acts on the jet, jets are broadly classified as turbulent free jet and turbulent wall jet. The studies conducted herein provide the comparison between various turbulence model present Computational Fluid Dynamics(CFD). Numerical approaches were used in the present investigation. CFD technique helped to understand better the hydrodynamics of the jet flow and correlate the numerical result.
 Among the all turbulence model studied, the k-ε turbulence model performed the best. Performance of k-ω model was found to be somewhat superior to Spalart-Allmaras and Reynolds stress model.

Effect of armor layer on the local scour formation induced by a deeply submerged circular wall jet in confined channels

A series of laboratory experiments was conducted in a confined channel to study the effect of armor layer on the scour formation induced by a deeply submerged circular turbulent wall jet. A wide range of particle sizes was utilized to form an armor layer and the local erosion downstream of a circular wall jet was measured. The time evolution of scour dimensions was recorded and the scour profiles of the mixed bed were compared with the scour profiles of a relatively uniform sand bed with the same average particle size. Three regimes were identified as the initial stage (Regime I), the quasi-steady state (Regime II), and the steady state (Regime III). The characteristic lengths of the scour showed rapid growth at the early stage of scour development and the growth rate decreased until the scour reached the steady-state condition. The effect of armor layer on scour dimensions was pronounced, which significantly reduced the maximum scour depth due to formation of an armor layer. The characteristic parameters affecting the maximum scour depth and width were identified and empirical correlations were introduced for the prediction of scour dimensions. The scour profiles in the mixed bed showed two consecutive scour depths. It was found that the area occupied by the armor layer increased by increasing the Froude number of the jet.

Effect of frequency of the wavy wall on turbulent wall jet heat transfer characteristics

The thermal and hydraulic characteristics of a sinusoidal wavy wall are studied numerically to increase the heat transfer rate of the turbulent wall jet. To do so, the sinusoidal profile (y=A∗sin(ωNx)) is used for the wavy wall, where ωN=2πN/L is the frequency with suffix N denoting the number of cycles for the given length L and A is the amplitude. The amplitude “A” is varied from 0 to 0.8a and ωN is changed from ω4 to ω12, to find out the optimum amplitude and frequency for which the heat transfer rate is maximum. The low Reynolds number two equations RNG k−ϵ model is used for the detailed study and to understand the impact of a re-circulation zone on the heat transfer rate. The inlet velocity is uniform and equals to 10.95 m/s for all the cases to achieve the inlet Reynolds number 15000 for a 20 mm nozzle height. At the inlet, jet is heated to a temperature of 330 K and the wavy wall on which the jet flows is provided an isothermal condition with 300 K temperature. With these conditions, the results for streamwise maximum velocity decay, skin friction coefficient, re-circulation area and local Nusselt number have been compared for different amplitudes and frequencies of the wavy wall. From the results, it has been observed that with the increasing amplitude and frequency the Umax increases, the area of re-circulation zone increases and the thermal potential core decreases. For the wavy wall amplitude A = 0.8 and frequency ω12, the peak of Umax is 170% more than the plane wall jet, the area covered by re-circulation zone is 58.2% of the total area and the thermal potential core reduces to X=3.7 which is about 50% of the plane wall jet. The local Nusselt number also increases with the increasing amplitude and frequency in the near field, but in the far field it starts decreasing as the re-circulation effect dominates there. For the wavy wall, the maximum increase in heat transfer rate is 23.23% with respect to the plane wall case.

Effect of corrugated side-walls on plane turbulent wall jets in narrow channels

An experimental study is presented to investigate the effect of corrugated sidewalls on submerged wall jets in narrow channels. Experiments were performed in a flume 0.3 m wide, 0.5 m deep, and 13.5 m long. Jets issued under the gate with a fixed thickness of 2.5 cm and the tailwater depth was adjusted to 37.5 cm, giving a fixed tailwater depth ratio yt/bo = 15. Experiments were conducted for five slot Froude numbers 2, 3, 4. 5, and 6. The Reynolds number ranged between 24712 and 74136. Three sets of experiments of five runs each, were performed. In Set A, the experiments were performed with smooth sidewalls whereas in Sets B and C, two arrangements of corrugated sidewalls (with gaps and with no gaps) were used, respectively. Velocity profiles along the centerline of the flume, water surface profile and the eddy length were measured for each experiment. It was found that the corrugations with gaps caused the largest decay in the maximum velocity; however, the effect of the presence of the sidewall corrugations on the velocity decay diminishes with the Froude number. Furthermore, the corrugated sidewalls with no gaps were observed to induce more flow entrainment and therefore cause a steep increase in the jet discharge and momentum flux near the slot. However, the corrugated sidewalls with gaps induced more mixing and diffusion, farther downstream from the slot, and caused a faster decay in the jet discharge and momentum. The use of corrugated sidewalls is introduced in this study as an alternative technique, to corrugated beds, to be used for energy dissipation in narrow channels. The sidewall corrugations are easier to maintain as less debris/sediments are trapped in between the corrugations. In addition, if channel maintenance is required, the movement of the maintenance facilities on a smooth bed would be much easier than that on a corrugated bed. Moreover, the sidewall corrugations will not be damaged during the maintenance process.

Numerical study on mean flow characteristics for a combined turbulent wall and offset jets with a parallel co-flow

Combined turbulent wall and offset jets with and without the presence of a parallel co-flow stream are investigated using the k-ω turbulence model. We focus on the effects of co-flow velocity on the locations of various characteristic points formed owing to the interaction of wall and offset jets in the dual jet flow. The inlet Reynolds number is taken as 15,000 and the offset ratio is varied from 5 to 11. At low offset ratios, the co-flow velocity effect remains almost negligible. With the progressive increase in co-flow velocity, the characteristic points are gradually relocated towards the further downstream direction with a transverse movement away from the bottom wall whose effect is weakened with the increase in co-flow velocity. Furthermore, regression analysis shows power law and linear correlations of the longitudinal and transverse coordinates of characteristic points with the co-flow velocity and the offset ratio.

Effect of sidewall spacing on the temperature field of a three-dimensional heated turbulent wall jet

The effect of sidewalls on the temperature field of a three-dimensional heated turbulent wall jet is characterized by the temperature measurement inside the sidewall enclosure (SWE). The SWE is defined as the presence of sidewalls parallel to the vertical jet centerline plane on both the sides. The sidewalls are equally spaced from the vertical jet centerline plane, and the distance between the sidewall is termed as the width (W). Four different widths (W) 140 mm, 160 mm, 180 mm, and 200 mm SWE are considered at a Reynolds number of Re= 25,000. The temperature field decay rate is increased with an increase in the SWE width in the downstream locations after x/h= 35. The decay rate of the jet centerline temperature in 200 mm SWE is 4.6% higher than the 140 mm SWE. The lateral spread increases with a decrease in SWE width due to the accumulation of the thermal energy content in the lateral shear layers adjacent to the sidewalls. In the near field, thermal spread in the wall-normal direction increases with the increase in the SWE width, but in far-field locations (x/h= 30), the thermal spread increases with a decrease in the SWE width. The wall-normal thermal similarity is delayed with a decrease in the width of the SWE, and it is found at x/h= 25, 22, 19 and 15 for the 140 mm, 160 mm, 180 mm, and 200 mm SWEs, respectively. The temperature field shows the climbing effect over the sidewalls similar to the velocity field in the transverse plane (z−y). The spread of the temperature fields in the lateral direction increases with the increase in the width of the enclosure. The similarity of the temperature field gets distorted near the sidewall (λ=0.9, where λ=z/(W/2) and z= lateral location) due to thermal energy content in lateral shear layers. The one point temperature fluctuation shows the normal distribution of the probability density function along the jet centerline for all the cases of SWE. The probability density function is independent of the SWE width before the attachment (x/h≤ 10) of the flow stream at the sidewall, but after the attachment (x/h≥ 10) of the flow stream to the sidewalls, the probability density function deviated from the normal distribution curve. The skewness and flatness factors were also calculated based on the instantaneous temperature fluctuation inside the SWE.

CFD Investigation of Thermal Characteristics for a Dual Jet with a Parallel Co-flow.

A combined turbulent wall jet and offset jet (also known as the dual jet) with and without the presence of a parallel co-flow stream is studied. The standard k–ω turbulence model is used to predict the turbulent flow. The study focuses on the effects of the co-flow velocity (CFV) on the heat-transfer characteristics of the dual jet flow with the bottom wall maintained at a constant wall temperature. The CFV is varied up to 40% of the jet inlet velocity, and the height of the offset jet is varied from 5 to 11 times the jet width with the inlet Reynolds number taken as 15,000. The heat-transfer results reveal that the local Nusselt number (Nux) along the bottom wall exhibits a peak at the immediate downstream of the nozzle exit, followed by a continuous decay in the rest of the converging region before showing a small rise for a short streamwise distance in the merging region. Further downstream, in the combined region, Nux gradually decreases with the downstream distance. Except the merging region, no influence of co-flow is observed in the other two flow zones (converging and combined regions). In the merging region, for a given offset ratio (OR), Nux remains nearly constant for a certain axial distance, and it decreases as the CFV increases. As a result of the increase in the CFV, the average Nusselt number decreases, indicating a reduction in overall convective heat transfer for higher values of the CFV. A regression analysis among the average Nusselt number (), CFV, and OR results in a correlation function in the form of within the range OR = 5–11 and CFV = 0–40%.

Simulation of the flow field and scour evolution by turbulent wall jets under a sluice gate

This numerical study of scour process tested the skills of computational fluid dynamics in modeling the unsteady flow field during the scour development stage by two-dimensional turbulent wall jets under a sluice gate. The modeling was found to well describe the experimentally observed flow patterns, that is, the main jet diverged to a returning jet and a tail jet. The model also correctly predicts the evolution of the scour depth and length. We examined the self-similarity of the profiles of scour bed and overlying velocities throughout the entire scour development and equilibrium stages. We found self-preserved profiles of velocities and scour beds using local jet parameters. Four growth curves were compared in describing the temporal evolution of scour depth. Finally, non-dimensional scaling of the equilibrium maximal scour depth was investigated. We used the theory of wall jet, and suggested that a modified jet Froude number can be used to predict the equilibrium scour depth, which accounts for the attenuation of the jet velocities along the apron.