Flow-3D Numerical Model Research Articles

Numerical modeling of the two-dimensional free and impinging jets with solid and erosion bed using FLOW-3D

ABSTRACT This study simulates the flow properties of a plane-layered jet in free and impinging jets on a horizontal surface using Flow-3D and validates them with previous research and experimental data. The flow characteristics, such as velocity and shear stress distribution, are compared with theoretical relationships. The simulations vary the outlet velocities for the free jet and the surface types and slip conditions for the impinging jet. The results show that the free jet flow follows the self-similar theory, except for a faster decay of numerical velocities at the end of the jet’s path. The results also reveal a virtual origin (λ) before the nozzle outlet, ranging from 7.6 to 8.4 mm. The impinging jet results match the experimental wall shear stress distribution diagram, with the peak at y/H = 0.14. The transverse velocity profiles and the wall shear stress distribution of the impinging jet are influenced by the slip condition and the surface type, but the difference between smooth and granular surfaces is less than 3%. This study offers valuable insights into the behaviour of free and impinging jets on a horizontal surface and shows the effectiveness of the Flow-3D numerical model.

Selection of cross sections for solitary wave transmission efficient for submeged vertical porous breakwater using Flow-3D model

Climate change is causing progressively severe coastal erosion, especially in beaches and tourist areas. Vertical porous breakwaters were chosen to protect the beaches for their effectiveness in reducing waves and preventing erosion. However, submerged vertical porous breakwaters must be applied due to the characteristics of beaches that do not allow shielding. Thus, the width of the porous breakwaters should be increased, incurring construction costs. This study proposes cross-sections of submerged vertical porous breakwaters that have the same width and determines the selected cross-section in those sections that effectively meets the wave height reduction. The Flow-3D numerical model with porous structures and solitary wave boundary conditions was used to simulate 72 scenarios of the interactions between solitary waves and submerged vertical porous breakwaters. The selected cross-section is a parallel configuration, where the distance between the two breakwaters is twice the width of the first breakwater. Dimensionless graph systems defining parallel breakwater parameters according to incoming solitary waves were established.

Hydraulic Performance of Howell–Bunger and Butterfly Valves Used for Bottom Outlet in Large Dams under Flood Hazards

Floods control equipment in large dams is one of the most important requirements in hydraulic structures. Howell–Bunger valves and butterfly valves are two of these types of flow controls that are commonly used in bottom outlet dams. The optimal longitudinal distance (L) between the two Howell–Bunger and butterfly valves is such that the turbulence of the outlet flow from the butterfly valve should be dissipated before entering the outlet valve. Subsequently, the flow passing through the butterfly valves must have a fully developed flow state before reaching the Howell–Bunger valve. Therefore, the purpose of this study was to evaluate the optimal longitudinal distance between the Howell–Bunger and butterfly valves. For this purpose, different longitudinal distances were investigated using the Flow-3D numerical model. The ideal longitudinal distance obtained from the numerical model in the physical model was considered and tested. Based on the numerical study, the parameters of flow patterns, velocity profiles and vectors, turbulence kinetic energy, and formation of flow vorticity were investigated as criteria to determine the appropriate longitudinal distance. In addition, the most appropriate distance between the butterfly valve and the Howell–Bunger valve was determined, and the physical model was evaluated based on the optimal distance extracted from the numerical simulation. A comparison of the results from the numerical and the laboratory models showed that the minimum distance required in Howell–Bunger valves and butterfly valves should be equal to four times the diameter of the pipe (L=4D) so as not to adversely affect the performance of the bottom outlet system.

Effects of Divergence Shape on the Characteristics of Hydraulic Jump in Stilling Basins Using Numerical Simulation and Neural Networks

Measures such as sudden cross-sectional divergence is among the factors affecting the characteristics of hydraulic jump. If for any reason it is not possible or cost-effective to provide the depth required for the hydraulic jump, then gradual or sudden flow cross-sectional divergence can be a good way to reduce the depth required for the jump. In this research, using the neural network and FLOW-3D numerical model, a three-dimensional (3D) model for fluid simulation, the effect of sudden divergence stilling basin on characteristics was simulated. The results of the neural network are very close to the physical model. The study revealed that 3D simulation using Flow-3D software could simulate a hydraulic jump with an average error of 2.41%. The efficiency of stilling basins divergent was calculated to be 71%, which is higher than the classic stilling basins with an efficiency of 53.3%. Depth after jumping in divergent stilling basins modeled at 27.8 and 41.4 l/s was found to be 12 and 25% less than classic basins, respectively. Compared to the classical mode in the divergent stilling basins parabolic, gradual, and sudden, the decrease in jump length was found to be 25.9%, 27.5%, and 31.8%, respectively. The results showed that the sudden divergent stilling basin has the best performance in terms of hydraulic parameters.

Effect of Lateral Spacing of Structures on Tsunami-Induced Scour

April Le Quéré, P.; Nistor, I., and Mohammadian, M., 2021. Effect of lateral spacing of structures on tsunami-induced scour. Journal of Coastal Research, 37(4), 813–826. Coconut Creek (Florida), ISSN 0749-0208.Tsunamis are a devastating force, as seen by the extreme tsunamis that struck the Indian and Pacific Oceans over the past two decades: the 2004 Indian Ocean Tsunami, the 2010 Chile Tsunami, and the 2011 Tohoku Japan Tsunami. In those events, flood-induced scouring was found to be an important phenomenon that often led to infrastructure damage. Past research has focused on scouring around single columns and other isolated horizontal structures to attempt to understand the complex processes characterizing this phenomenon. However, given that coastal cities often comprise complex arrangements of multiple structures, often crammed, tsunami inundation flow often finds concentrated paths in between such structures; these flow concentrations increase the resulting scouring. This research is an attempt to inform the scientific community on the potential of augmented scour attributable to flow concentration that is due to the lateral spacing of structures and to compare it with nonconcentrated flow-induced scour. The authors employed the FLOW-3D numerical model for this study. This model was first calibrated using a physical model experiment performed in the dam break flume of the University of Ottawa, Canada. Results from this study demonstrate that flow concentration due to the lateral spacing of structures leads to greater scouring than for the case of an isolated structure and that the magnitude of the scour, for most cases studied, was larger than what is prescribed by the latest building codes.

An experimental and numerical model for performance evaluation of the new galley design filter bucket for storm networks

Storm networks are a major item of civil infrastructure and a significant element of community life. One of the most significant problems facing storm networks is the blockage of pipes, frequently caused by sediments in the sewage system. This study was undertaken to offer a performance evaluation of a new design of gravel filter bucket for storm networks that offers the separation of sediments at different intensities of rainfall and street slopes based on the development of an experimental model. Stormwater with different sediment loads was simulated and samples of filtrate examined with regard to removal efficiency for these particles. A flow-3D numerical model was also developed to investigate the removal efficiency of the gravel filter. The predicted removal efficiency was then validated using experimental data. Assuming proper model validation, numerical models of this type can yield evaluation data with respect to filter removal efficiency for other dimensions and particle sizes of sediment. The results in this case indicated that the efficiency of the gravel filter increased with increases in slope, intensity, and duration. The gravel filter efficiency was 61% at a low intensity of rainfall and 90% at a high intensity of rainfall, while the results also showed 88% and 63% efficiency for the maximum and minimum diameter sediments, respectively. In terms of validation, the numerical model was compared with a statistical equation to calculate the filter efficiency (Ef ), with the use of an SPSS model to estimate the R2 value, which was 0.88.

Numerical study of energy dissipation and block barriers in stepped spillways

Abstract In this research, the accuracy of the Flow-3D numerical model in the flow simulation in a stepped spillway was probed using data obtained from the physical model. In addition, the effects of block barriers on the energy dissipation rate were investigated. To adopt a proper turbulent model, Renormalization Group k-ε, RNG k-ε, and standard k-ε models were employed. Then, the Flow-3D was run in five discharges for nine spillways with the ratios of block length to step length (Lb/l) and block height to step height (Hb/h) as 0.3, 0.4, and 0.5. The results indicated that both turbulent models had almost similar outcomes though the run time of the RNG k-ε model was shorter. The blocks with a shorter length in low ratios of Hb/h and the lengthier blocks in high ratios of Hb/h undergo more relative energy dissipation relative to the no-block situation. For Hb/h = 0.3 and Lb/l equal to 0.3, 0.4, and 0.5, the relative energy dissipation climbed on average as 8.5, 6.5, and 4.5% respectively, compared with the no-block case. The most influence exerted on relative energy dissipation was obtained via the blocks with Hb/h = Lb/l equal to 0.3 and 0.5 with respective increases of 8.6 and 8.4%.

Discharge coefficient in the combined weir-gate structure

The present study investigated the flow discharge coefficient (Cdt) in the combined rectangular broad crested weir-gate structure. To this end, the effect of the following dimensionless parameters on the Cdt were investigated: the width ratio of the central weir to the width of the total structure (B/Bo), the height ratio of the central weir to the height of the central weir floor (Z/P), the ratio of the gate width to the width of the total structure (b/Bo), the ratio of the gate opening height to the height of the central weir floor (d/P), and the ratio of the head on central weir to the total head behind the structure (h1/H). The Flow-3D numerical model, artificial intelligence models such as linear multilayer perceptron (MLP), Canfis network (CNN), recurrent network (RNN), modular neural network (MNN), and regression equation, were used to estimate the Cdt. The results indicated that increasing d/P and b/Bo ratios led to a decline in this coefficient. In the case of h1/H ≤ 0.4, an increase in B/Bo ratio resulted in decreasing the turbulence intensity and Cdt while the impact of enhancing the size of B/Bo was not significant if h1/H > 0.4. Besides, increasing Z/P ratio caused an increase in resistance against the flow and thus a decline in Cdt. Further, the results of artificial intelligence models and regression equation demonstrated that the MNN model with an RMSE and R2 of 0.03 and 0.97, respectively, could have an accurate estimate of the Cdt values.

Experimental and numerical modeling of the simultaneous effect of sluice gate and bump on hydraulic jump

Sluice gate has always been used due to their ease of construction, control water level and measure flow discharge. Numerous studies have been carried out on sluice gates. On the other hand, estimating the discharge of flow below sluice gates is a major problem in many water engineering issues. The flow may become supercritical while passing the sluice gate. A bump can be used on the channel bed after the sluice gate in order to accelerate the formation of hydraulic jump phenomenon which converts supercritical flow to subcritical flow, therefore damages and undesirable effects caused by high water pressure in the supercritical flow can be prevented. In this paper, the simultaneous effects of sluice gate and bump in a channel on the formation of the hydraulic jump have been investigated. For this purpose, this phenomenon is modeled in hydraulic laboratory, then, it is simulated by FLOW3D numerical model. The desired conditions are carried out for four different locations of the bump with two different flow rates for each. Also, each experiment conducted on two types of positive and negative channel slope. Finally, a comparison is made between the fine and coarse mesh size on the numerical model to show the sensitivity of hydraulic jump simulation to meshing. The results indicate that as the location of the bump moves downstream of the channel for the positive slope of the channel, the location of the hydraulic jump formation goes downstream, and by decreasing the flow and giving negative slope to the channel, the location of occurrence of hydraulic Jump moves toward upstream of the channel. Also, comparison of different disturbance models indicates the superiority of LES disturbance model in showing jump disturbances compared to other models.

Investigating changes in wave reflection coefficient and upward coefficients and wave force in lattice breaker using Flow 3D numerical model

Investigating changes in wave reflection coefficient and upward coefficients and wave force in lattice breaker using Flow 3D numerical model

Optimizing chute-flip bucket system based on meta-modelling approach

Optimal design of chute-flip bucket (CFB) system depends on various parameters, among which energy dissipation and cavitation prevention are the most important. This study develops a simulation-optimization model based on a calibrated Flow-3D numerical model, multi-layer perceptron artificial neural network (MLP-ANN), and genetic algorithm (GA) optimization approach for determining the optimal geometry of the CFB system. To alleviate the computational time burden of the Flow-3D numerical model, a MLP-ANN meta-model is developed based on some limited simulations of Flow-3D. The meta-model framework is then coupled with GA to provide an efficient design framework for the CFB system. The proposed framework is employed to design optimal geometry of the CFB system of the Jareh dam in Ahvaz, Iran. The results show that the obtained optimal design increases the cavitation index up to 30% and energy dissipation up to 32% compared to the old engineering design already in place.

Development of a Desalination System Driven by Low Energy Ocean Surface Waves

Verduzco-Zapata, M.G.; Olivos-Ortiz, A.; Linan-Cabello, M.; Ortega-Ortiz, C.; Galicia-Perez, M.; Matthews, C., and Cervantes-Rosas, O., 2018. Development of a Desalination System Driven by Low Energy Ocean Surface In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1321–1325. Coconut Creek (Florida), ISSN 0749-0208.As an effort to mitigate the water scarcity and to achieve a water security status in remote coastal communities with few or no hydraulic systems, or in places with compromised services due to natural disasters, a new semi-portable wave driven desalination device is being developed and tested using a state of the art numerical model. In this early stage of development, the main challenge is to further optimize mechanisms that allow to adjust to tidal and wave variations and to efficiently resist the stresses exerted by cycle motions. The solution is partially handled through the use of a taut-line mooring mechanism which allows the device to work at large range of wave conditions. This prototype consists of two subsystems: a point absorber WEC conformed by a single buoy, and a standard reverse osmosis (RO) system. When interacting with the incoming waves, the mooring line is pulled and pressurizes seawater enough to drive it through several filters including the RO membranes. The FLOW-3D numerical model was used to test the efficiency of the WEC subsystem under several sea states associated with low energy wave conditions. The displacements and motions of the WEC as well as the forces in its anchor line were calculated. The results suggest that it provides the necessary force to pressurize the seawater for the desalination process. Further testing is needed to improve the reliability and survivability of the system which in turn will help to scale the prototype in order to obtain greater quantities of freshwater and thus be competitive with other technologies.

Numerical study on the effect of the spur dikes on sedimentation pattern

Abstract The spur dikes are structures that usually used for flow diversion from erodible wall and they usually create a appropriate path for directing the flow, flood control, protection of external walls, and some other cases. Through modifying the hydraulic conditions and creation of smooth flow, spur dikes can decrease water erosion force and power of sediment transport. In this study, the channel and spur dike related to the Heltz Laboratory model have been simulated using Flow-3D numerical model. The RNG turbulence model has been applied for turbulence modeling. The turbulent flow field around inclined spur dike and the effect of such parameters as angle, hydraulic conditions and sedimentation pattern have been investigated. The results showed that increasing the angle of spur dike affects the length and width of sedimentation area. When angle of spur dike increases from 90 to 120 deg, the width and length of the sedimentation area will increase up to about 71 and 92 percent, respectively.

Numerical Modeling of Local Scour at the Junction of Open Channels in Flow3D Numerical Model

At the junction of channels, the two corresponding flows of the main and submain channels are diverted from their main alignment and the form and the flow properties change at the junction. Changes in water level profile and depth of flow, velocity distribution, stagnation zone, constriction of public channel, energy loss and also formation of hydraulic jump are among the most important hydraulic variables in this location. For accurate recognition of hydraulic properties of flow and local scour at the junction of channels, physical models are made and constructed. Setting up a physical model requires many conditions and high costs which sometimes are not justifiable, hence appropriate numerical models could be proposed for such options. In this research using Flow3D numerical model, the numerical modelling of the flow has been performed in 3D form utilizing the available laboratory information which is calibrated and validated and accuracy of the numerical modelling, and the corresponding relative error are determined. The calibration and validation of the numerical model results demonstrate that the maximum relative error of the numerical model when simulating for maximum values of scour depth at the flow junction is equal to 8.2%. Also using the numerical model it was found that with passage of time in numerical model, from .....

Designing Manhole in Water Transmission Lines Using Flow3D Numerical Model

Using cascades and drops existing in flow path has a history of 3000 years. Particularly, Roman engineers employed stepped spillways with the same idea in several countries; however, there are few information about the hydraulic performance of aqueducts. Most of these channels have flat long cross sections with low torsions (variable slope) such that they can encompass cascade and steep spillways or dopshaft. Given that there are few studies conducted on dropshafts, the present paper attempted to discuss about such structures in flow path and water transmission lines as well as introducing the existing principles and relations and present, the obtained results of designing though Flow3D. The obtained error percentage was about 20% which is acceptable for numerical studies.

Simulation of Flow Suspended Load in Weirs by Using Flow3D Model

Sharp-crested weir and side-channel weirs can be considered among the control and flow-measuring structures which are greatly applicable in channels, dam spillways and other hydraulic structures. Discharge coefficient in these two types of weirs is affected by the structural geometry and the hydraulics of the flow. Suspended load is one of the main factors which may affect the hydraulics of the flow and consequently modify the flow discharge coefficient. Using different geometrical and hydraulic conditions, the discharge coefficient relation in sharp-crested and side channel weirs for the case of suspended load can be extracted. Flow3D numerical model is capable of precisely simulation the flow containing suspended and bed load in the main channel. The discharge coefficient equation is deduced and presented based on the Froude number, by numerical iterations. The numerical results reveal that the discharge coefficient in the two cases of clear water and the flow containing suspended load are totally different. At the same hydraulic load, the discharge coefficient in the case of existing suspended load is greater than the case of clear water; In addition, the discharge coefficient is reduced by increasing the Froude number in all cases with different load concentrations.

SIMULATION OF LOCAL SCOUR CAUSED BY SUBMERGED HORIZONTAL JETS WITH FLOW-3D NUMERICAL MODEL

One of the most concerning issues for researchers is to predict the shape and dimensions of the scour pit nearhydraulic structures such as the base of bridges, weirs, valves and stilling basins due to both financial and humanhazards induced by destruction of the structure. As the scour issue has its own complexity in relation to themultiplicity of effecting factors on it, in this study therefore, the results of laboratory analysis of local scour due tosubmerged horizontal jets were compared with numerical simulation results from Flow-3D three-dimensional modelto test the potency of the numerical model. As a result, the model is proposed in place of the experimental modelwhich has its own drawbacks and high costs. In this study, we measure maximum scour depth in relative equilibriumin 2 states and 6 test modes with different valve openings and tail water depth per different discharges. Comparisonof the results indicates about 11% error for Flow-3D numerical model in relation to the experimental model which byconsidering the complexity of scour and deposition phenomena, is considered a good result.

EXPERIMENTAL AND NUMERICAL COMPARISION OF 3D DAM-BREAK FLOOD WAVE PROPAGATION

Dam-break flood wave is an irregular, time-dependent and rapidly varying free surface open channel flow and therefore, is one of the complex and difficult problems. The research for solving this problem is mainly directed at experimental and numerical studies due to the difficulties in collecting field data. Despite that, the experimental and numerical studies on 3-dimensional dam-break problem are limited in the literature. In this study, the propagation of expanding dam-break flood wave in the downstream direction is investigated using a vertical plate placed in front of a reservoir built in the laboratory. The propagation of the wave front was observed using high speed camera and obtained results were compared with FLOW-3D numerical model which uses 3D RANS equations. The results were in quite good agreement.