scholarly journals Partially Averaged Navier-Stokes: A (k-ω)/(k-ε) Bridging Model

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 129
Author(s):  
Abdelkader Frendi ◽  
Christopher Harrison
Keyword(s):  
Experimental Data ◽  
Circular Cylinder ◽  
Reynolds Stress ◽  
Shear Flows ◽  
Navier Stokes ◽  
Benchmark Problems ◽  
New Model ◽  
Bridging Model ◽  
Simulation Results ◽  
Rigid Walls

A new Partially Averaged Navier-Stokes (PANS) bridging model is derived from existing (k−ω) and (k−ε) PANS formulations. The model behaves like the PANS (k−ω) model near rigid walls and like the PANS (k−ε) model away from walls. The new model is tested using well-known benchmark problems; a backward-facing step representing wall-bounded flows, and a circular cylinder representing free shear flows. Our results are compared to existing experimental data and previous simulation results using PANS (k−ω) and PANS (k−ε). The comparisons show our model to be superior at predicting velocity profiles in both flows. In addition, Reynolds stress predictions are also shown to improve.

scholarly journals Reynolds Stress Perturbation for Epistemic Uncertainty Quantification of RANS Models Implemented in OpenFOAM

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 113 ◽  
Author(s):  
Luis F. Cremades Rey ◽  
Denis F. Hinz ◽  
Mahdi Abkar
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Reynolds Stress ◽  
Epistemic Uncertainty ◽  
Turbulent Viscosity ◽  
Navier Stokes ◽  
Simulation Data ◽  
Direct Numerical Simulation Data ◽  
Engineering Problems ◽  
Rans Models

Reynolds-averaged Navier-Stokes (RANS) models are widely used for the simulation of engineering problems. The turbulent-viscosity hypothesis is a central assumption to achieve closures in this class of models. This assumption introduces structural or so-called epistemic uncertainty. Estimating that epistemic uncertainty is a promising approach towards improving the reliability of RANS simulations. In this study, we adopt a methodology to estimate the epistemic uncertainty by perturbing the Reynolds stress tensor. We focus on the perturbation of the turbulent kinetic energy and the eigenvalues separately. We first implement this methodology in the open source package OpenFOAM. Then, we apply this framework to the backward-facing step benchmark case and compare the results with the unperturbed RANS model, available direct numerical simulation data and available experimental data. It is shown that the perturbation of both parameters successfully estimate the region bounding the most accurate results.

Numerical Investigation on Primary Atomization of the Fuel Spray in Diesel Engines

2012 ◽  
Vol 516-517 ◽  
pp. 634-637
Author(s):  
Zhi Xia He ◽  
Li Li Tian ◽  
Ju Yan Liu
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Investigation ◽  
Diesel Engines ◽  
Fuel Spray ◽  
New Model ◽  
Turbulence Flow ◽  
Primary Breakup ◽  
Simulation Results ◽  
Breakup Model

In addition to the aerodynamic effects, turbulence and cavitation play an important role on the primary atomization. Different spray breakup models were analysized and evaluated though simulation of spray with them and then a new model of coupling the nozzle cavitating and turbulence flow to the spray primary breakup was put forward. The numerical simulation results with all these different spray primary breakup models were comparied with the experimental data and then the new model were proved to be much better. The study may effectively help establish the accurate spray breakup model.

Study on New Model of Tension Process in Continuous Rolling

2010 ◽  
Vol 654-656 ◽  
pp. 226-229 ◽  
Author(s):  
Shen Bai Zheng ◽  
Jin Hong Ma ◽  
Zeng Feng Li
Keyword(s):  
Experimental Data ◽  
Continuous Rolling ◽  
New Model ◽  
Speed Difference ◽  
Simulation Results ◽  
Tension Peak ◽  
In The Beginning

It is proved that a tension peak occurred in the beginning of tension process between two stands by the continuous rolling test. Based on the speed difference, motor rigidity and coefficient of forward and backward slip, the steady equation of the kinematical mechanics is built. The simulation results of the tension formula accorded with the experimental data. The calculation of shock peak provides an important reference for the technology of continuous rolling.

Calculation of Vortex Shedding From a Circular Cylinder in Uniform and Shear Flows

2005 ◽  
Author(s):  
Branislav Basara
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Shear Flows ◽  
Reynolds Stress Model ◽  
Computational Approach ◽  
Navier Stokes ◽  
Exact Form ◽  
Simple Modification ◽  
Numerical Investigations ◽  
First Results

The present paper deals with numerical investigations of vortex shedding from a circular cylinder in uniform and shear flows. The computational approach is based on solving the complete Transient Reynolds-Averaged Navier-Stokes (TRANS) equations. The ζ-f model proposed recently by Hanjalic et al. (2004) is used for comparison with the recent computations of Basara et al. (2003) who used the Reynolds-stress model (RSM) developed by Speziale et al. (1991) and the hybrid EVM/RSM turbulence model developed by Basara and Jakirlic (2003). The recent study of the same flows (Basara, Jakirlic and Alajbegovic (2003)) showed that the wall treatment has an important role in correct predictions of forces acting on a cylinder. In this work, a new compound wall treatment (CWT) of Popovac and Hanjalic (2005) was used. A simple modification to the treatment of the dissipation rate of the original CWT is proposed. Furthermore, a new νt - k - ζ - f model is modeled on the basis of an exact form derived from the ζ-f model and the first results are given here. Calculations with the ζ-f model employed as a low-Re number model are performed and the results are compared with those obtained with the same model in conjunction with CWT.

scholarly journals A Fully Discrete SIPG Method for Solving Two Classes of Vortex Dominated Flows

2020 ◽  
Author(s):  
Lunji Song
Keyword(s):  
Circular Cylinder ◽  
Dynamical Behavior ◽  
Navier Stokes ◽  
Benchmark Problems ◽  
Navier Stokes Equation ◽  
Driven Cavity ◽  
Fully Discrete ◽  
Space Discretization ◽  
Cylinder Flow ◽  
Incompressible Navier Stokes Equation

To simulate incompressible Navier–Stokes equation, a temporal splitting scheme in time and high-order symmetric interior penalty Galerkin (SIPG) method in space discretization are employed, while the local Lax-Friedrichs flux is applied in the discretization of the nonlinear term. Under a constraint of the Courant–Friedrichs–Lewy (CFL) condition, two benchmark problems in 2D are simulated by the fully discrete SIPG method. One is a lid-driven cavity flow and the other is a circular cylinder flow. For the former, we compute velocity field, pressure contour and vorticity contour. In the latter, while the von Kármán vortex street appears with Reynolds number 50≤Re≤400, we simulate different dynamical behavior of circular cylinder flows, and numerically estimate the Strouhal numbers comparable to the existing experimental results. The calculations on vortex dominated flows are carried out to investigate the potential application of the SIPG method.

scholarly journals Effects of the Duct Angle and Propeller Location on the Hydrodynamic Characteristics of the Ducted Propeller

2018 ◽  
Vol 11 (22) ◽  
pp. 41
Author(s):  
Mehdi Chamanara ◽  
Hassan Ghassemi ◽  
Manouchehr Fadavie ◽  
Mohammad Aref Ghassemi
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Numerical Results ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Stress Model ◽  
Ducted Propeller ◽  
Rans Method

In the present study, the effect of the duct angle and propeller location on the hydrodynamic characteristics of the ducted propeller using Reynolds-Averaged Navier Stokes (RANS) method is reported. A Kaplan type propeller is selected with a 19A duct. The ducted propeller is analyzed by three turbulence models including the k-ε standard, k-ω SST and Reynolds stress model (RSM). The numerical results are compared with experimental data. The effects of the duct angle and the location of the propeller inside the propeller are presented and discussed.

scholarly journals Unstructured Grid Solutions for Incompressible Laminar Flow over a Circular Cylinder Using a Particular Finite Volume-Finite Element Method

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Mahdi Yousefifard ◽  
Parviz Ghadimi ◽  
Rahim Zamanian
Keyword(s):  
Laminar Flow ◽  
Circular Cylinder ◽  
High Performance ◽  
Unstructured Grid ◽  
Unstructured Grids ◽  
Control Volume ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Benchmark Problems ◽  
Navier Stokes Equation

A numerical modeling of a 2D Navier-Stokes equation by a particular vertex centered control volume framework on an unstructured grid is presented in this paper. Triangular elements are applied with an effective high performance fully coupled algorithm, to simulate incompressible laminar flow over a circular cylinder. The cell face velocities in the discretization of the continuity and momentum equations are calculated by a combined linear and momentum interpolation scheme, respectively, and their performances are compared. Flow analyses have been conducted based on various Reynolds numbers up to 200 for the steady and unsteady flows using structured and unstructured grids. The robustness and accuracy of the scheme in the unstructured mesh are proved using the benchmark problems of incompressible laminar flow over a circular cylinder at low and medium Reynolds numbers. Results have been compared with the structured grid results, both cases with equal cell numbers and same strategy for the mesh refinement. Current results display good agreement with the experimental values. Overall, it is shown that, using the suggested method for the current problem, unstructured grids are highly competitive with the structured grids.

scholarly journals Numerical Study of Natural Supercavitation Influenced by Rheological Properties of Turbulent Drag-Reducing Additives

2014 ◽  
Vol 6 ◽  
pp. 275316 ◽  
Author(s):  
Chen-Xing Jiang ◽  
Feng-Chen Li
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Study ◽  
Cavitation Number ◽  
Navier Stokes ◽  
Multiphase Model ◽  
Turbulent Vortex ◽  
Turbulent Drag ◽  
Simulation Results ◽  
Overall Resistance

Natural supercavitations in water and turbulent drag-reducing solution were numerically simulated using unsteady Reynolds averaged Navier-Stokes (RANS) scheme with mixture-multiphase model. The Cross viscosity equation was adopted to represent the fluid property of aqueous solution of drag-reducing additives. The characteristics of natural supercavity configuration and overall resistance of the navigating body were presented, respectively. The numerical simulation results indicated that, at the same cavitation number, the length and diameter of supercavity in drag-reducing solution are larger than those in water, and the drag coefficient of navigating body in solution is smaller than that in water; the surface tension plays an important role in incepting and maintaining the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitation, drag reduction, and decrease of turbulent vortex structures. Numerical simulation results are consistent with the available experimental data.

Turbulence simulations of flow past a circular cylinder based on a nonlinear partially averaged Navier–Stokes (PANS) method

2015 ◽  
Vol 29 (25) ◽  
pp. 1550143 ◽  
Author(s):  
Haiyan Bie ◽  
Jintao Liu ◽  
Zongrui Hao ◽  
Yulin Wu
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
High Reynolds Number ◽  
Navier Stokes ◽  
Normal Velocity ◽  
Turbulence Flow ◽  
Flow Past ◽  
Energy Formula ◽  
Simulation Results ◽  
High Reynolds

A nonlinear partially averaged Navier–Stokes (PANS) method based on RNG [Formula: see text]–[Formula: see text] turbulence model is evaluated by a moderately high Reynolds number turbulence flow past a circular cylinder. The ratios of unresolved-to-total kinetic energy [Formula: see text] and unresolved-to-total dissipation [Formula: see text] for PANS method are sensitive to the simulation result. Simulation results based on different [Formula: see text] are compared with the experimental data. The quantities including mean streamline velocity, mean normal velocity, streamlines, etc. are analyzed. The computational result is reasonable when [Formula: see text] is less than 0.6. The PANS method can be used in the simulation of high Reynolds number turbulence flow.

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