Performance assessment of OpenFOAM and FLOW-3D in the numerical modeling of a low Reynolds number hydraulic jump

The flow resistance of the existing modules in the bio-ecological drainage system (BIOECODS) is high and may lead to flood instead of its mitigation. As part of efforts to enhance the performance of the system, the river engineering and urban drainage research center (REDAC) module was developed. This study modelled the hydrodynamics of flow through this module using FLOW-3D and laboratory experiments for two cases of free flow without module (FFWM) and flow with a module (FWM) to understand and visualize the effects of the module. With less than 5% error between the numerical and experimental results, REDAC module altered the flow pattern and created resistance by increasing the Manning's roughness coefficient at the upstream, depth-averaged flow velocity (43.50 cm/s to about 46.50 cm/s) at the downstream and decreasing water depth (7.75-6.50 cm). These variations can be attributed to the complex nature of the module pattern with further increase across the porous openings. Therefore, the technique used herein can be applied to characterize the behavior of fluids in larger arrangments of modules and under different flow conditions without the need for expensive laboratory experiments.

Section: Theory and Governing Equationsmentioning

confidence: 99%

Section: Theory and Governing Equationsmentioning

confidence: 99%

Modelling of Flow Parameters through Subsurface Drainage Modules for Application in BIOECODS

Abdurrasheed

Yusof

Al‐Qadami

et al. 2019

“…Such a model is described in Hirt and Nichols [34]. Since its commercial release, FLOW-3D has been used in research, providing to engineers valuable insight into many physical flow processes [35][36][37][38].…”

Section: Model Descriptionmentioning

confidence: 99%

Computational Fluid Dynamics for Modeling Gravity Currents in the Presence of Oscillatory Ambient Flow

Stancanelli¹,

Musumeci²,

Foti³

2018

Gravity currents generated by lock release are studied in the case of initially quiescent ambient fluid and oscillating ambient fluid (regular surface waves). In particular, the dynamics of the density currents are investigated by means of CFD numerical simulations. The aim is to evaluate the influence of the ambient fluid velocity field on the observed mixing and turbulent processes. Results of two different turbulence closure models, namely the standard k − ε turbulence model and the LES model, are analyzed. Model predictions are validated through comparison with laboratory measurements. Results show that the k − ε model is able to catch the main current propagation parameters (e.g., front velocity at the different phases of the evolution of the current, gravity current depth, etc.), but that a LES model provides more realistic insights into the turbulent processes (e.g., formation of interfacial Kelvin-Helmholtz billows, vortex stretching and eventual break up into 3D turbulence). The ambient fluid velocity field strongly influences the dynamics of the gravity currents. In particular, the presence of an oscillatory motion induces a relative increase of mixing at the front (up to 25%) in proximity of the bottom layer, and further upstream, an increase of the mixing process (up to 60%) is observed due to the mass transport generated by waves. The observed mixing phenomena observed are also affected by the ratio between the gravity current velocity v f and the horizontal orbital velocity induced by waves u w , which has a stronger impact in the wave dominated regime (v f /u w < 1).

“…A possible explanation of this behaviour could reside in an underprediction of turbulent kinetic energy (or in an overprediction of it dissipation rate) by the k-ε model, which leads to a slightly lower turbulent diffusion downstream of the jump. A possible solution to these problems could be found in a careful tuning of the model parameters, or in the application of a different two-equation model, such as the RNG k-ε model, which has been successfully applied to the Eulerian numerical simulations of hydraulic jumps [22]. However, the obtained results showed that a good agreement with experiments could be already obtained by applying the simpler, mixing-length turbulence model and, therefore, all the remaining SPH simulations (tests T2 to T7) were performed with it.…”

Section: Test Turbulence Model η/σ Npmentioning

confidence: 99%

“…Numerical modelling of a hydraulic jump can be challenging for purely Eulerian or mixed Eulerian-Lagrangian techniques (see, for instance: [17][18][19][20][21][22]), because of the onset of oscillations, leading to the propagation of short breaking waves which can reduce the accuracy of free-surface capturing schemes [12]. On the other hand, meshless Lagrangian techniques appear in general to be more suitable to capture the complex and highly-unsteady free-surface patterns which characterize a hydraulic jump.…”

Section: Introductionmentioning

confidence: 99%

SPH Modelling of Hydraulic Jump Oscillations at an Abrupt Drop

Padova

Mossa

Sibilla

2017

This paper shows the results of the numerical modelling of the transition from supercritical to subcritical flow at an abrupt drop, which can be characterised by the occurrence of oscillatory flow conditions between two different jump types. Weakly-Compressible Smoothed Particle (WCSPH) model was employed and both an algebraic mixing-length model and a two-equation model were used to represent turbulent stresses. The purpose of this paper is to obtain through the SPH model a deeper understanding of the physical features of a flow, which is, in general, difficult to be reproduced numerically, owing to its unstable character. In particular, the experience already gained in SPH simulations of vorticity-dominated flows allows one to assess the fluctuations of hydrodynamic characteristics of the flow field, (e.g., free surface profile downstream of the jump, velocity, pressure and vorticity). Numerical results showed satisfactory agreement with measurements and most of the peculiar features of the flow were qualitatively and quantitatively reproduced.