Turbulent Flow Using a Modified V2f Turbulence Model

2004 ◽  
Author(s):  
Hanif Montazeri ◽  
Siamak Kazemzadeh Hannani ◽  
Bijan Farhanieh
Keyword(s):  
Boundary Condition ◽  
Turbulence Model ◽  
Flow Problem ◽  
Two Dimensional ◽  
Convergence Problem ◽  
New Model ◽  
Step Flow ◽  
Wall Boundary Condition ◽  
Proposed Model ◽  
Accuracy Of Results

An improved version of the V2f turbulence model has been examined in this paper. The objective was to overcome the convergence problem encountered in the original V2f model. The convergence problem is due to the commonly-used wall boundary condition, which therefore has been modified in the proposed model. To test the soundness of the new model, several two-dimensional cases such as Poiseuille flow, channel flow, and backward-step flow has been analyzed and the results are compared with the standard k-ε model, DNS, and in case of the backward flow problem, also with the original V2f model. Based on the comparison, the new model presents a promising approach both with respect to convergence as well as the accuracy of results.

On the Grid Sensitivity of the Wall Boundary Condition of the k-ω Turbulence Model

2004 ◽  
Vol 126 (6) ◽  
pp. 900-910 ◽  
Author(s):  
L. Ec¸a ◽  
M. Hoekstra
Keyword(s):  
Boundary Condition ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Solid Wall ◽  
Turbulence Models ◽  
Numerical Implementation ◽  
Two Dimensional ◽  
Grid Refinement ◽  
Wall Boundary Condition ◽  
Order Of Magnitude

This paper presents a study on the k-ω turbulence model with regard to the numerical implementation of the ω boundary condition at a solid wall, where ω tends to infinity. Three different implementations are tested in the calculation of a simple two-dimensional turbulent flow over a flat plate. Grid refinement studies in grids with different near-wall grid line spacings are performed to assess the numerical uncertainty of the predicted drag coefficient CD. The results are compared with the predictions of several alternative algebraic, one-equation, and two-equation eddy-viscosity turbulence models. For the same level of grid refinement, the estimated uncertainty of CD obtained with the k-ω model is one order of magnitude larger than for all the other models.

scholarly journals Prediction of Heat and Mass Transfer in a Rotating Ribbed Coolant Passage With a 180 Degree Turn

1998 ◽  
Author(s):  
David L. Rigby
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Boundary Condition ◽  
Turbulence Model ◽  
Heat Mass Transfer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Wall Boundary Condition ◽  
Wall Boundary

Numerical results are presented for flow in a rotating internal passage with a 180 degree turn and ribbed walls. Reynolds numbers ranging from 5200 to 7900, and Rotation numbers of 0.0 and 0.24 were considered. The straight sections of the channel have a square cross section, with square ribs spaced one hydraulic diameter (D) apart on two opposite sides. The ribs have a height of 0.1D and are not staggered from one side to the other. The full three dimensional Reynolds Averaged Navier-Stokes equations are solved combined with the Wilcox k-ω turbulence model. By solving an additional equation for mass transfer, it is possible to isolate the effect of buoyancy in the presence of rotation. That is, heat transfer induced buoyancy effects can be eliminated as in naphthalene sublimation experiments. Heat transfer, mass transfer and flow field results are presented with favorable agreement with available experimental data. It is shown that numerically predicting the reattachment between ribs is essential to achieving an accurate prediction of heat/mass transfer. For the low Reynolds numbers considered, the standard turbulence model did not produce reattachment between ribs. By modifying the wall boundary condition on ω, the turbulent specific dissipation rate, much better agreement with the flow structure and heat/mass transfer was achieved. It is beyond the scope of the present work to make a general recommendation on the ω wall boundary condition. However, the present results suggest that the ω boundary condition should take into account the proximity to abrupt changes in geometry.

On the Wall Boundary Condition for Computing Turbulent Heat Transfer With K–ω Models

2000 ◽  
Author(s):  
J. Bredberg ◽  
S.-H. Peng ◽  
L. Davidson
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Reynolds Number ◽  
Channel Flow ◽  
Turbulence Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Wall Function ◽  
Wall Boundary Condition ◽  
Wall Boundary

Abstract A new wall boundary condition for the standard Wilcox’s k–ω model (1988) is proposed. The model combines a wall function and a low-Reynolds number approach, and a function that smoothly blends the two formulations, enabling the model to be used independently of the location of the first interior computational node. The model is calibrated using DNS-data for a channel flow and applied to a heat transfer prediction for a flow in a rib-roughened channel (Reb = 100 000). The results obtained with the new model are improved for various mesh sizes and are asymptotically identical with those of the standard k–ω turbulence model.

A Lattice Boltzmann Method Based Numerical Scheme for Microchannel Flows

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
S. C. Fu ◽  
W. W. F. Leung ◽  
R. M. C. So
Keyword(s):  
Boundary Condition ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Numerical Scheme ◽  
Fluid Viscosity ◽  
Two Dimensional ◽  
Wall Boundary Condition ◽  
Wall Boundary ◽  
Microchannel Flows ◽  
Boltzmann Method

Conventional lattice Boltzmann method (LBM) is hyperbolic and can be solved locally, explicitly, and efficiently on parallel computers. The LBM has been applied to different types of complex flows with varying degrees of success, and with increased attention focusing on microscale flows now. Due to its small scale, microchannel flows exhibit many interesting phenomena that are not observed in their macroscale counterpart. It is known that the Navier–Stokes equations can still be used to treat microchannel flows if a slip-wall boundary condition is assumed. The setting of boundary conditions in the conventional LBM has been a difficult task, and reliable boundary setting methods are limited. This paper reports on the development of a finite difference LBM (FDLBM) based numerical scheme suitable for microchannel flows to solve the modeled Boltzmann equation using a splitting technique that allows convenient application of a slip-wall boundary condition. Moreover, the fluid viscosity is accounted for as an additional term in the equilibrium particle distribution function, which offers the ability to simulate both Newtonian and non-Newtonian fluids. A two-dimensional nine-velocity lattice model is developed for the numerical simulation. Validation of the FDLBM is carried out against microchannel and microtube flows, a driven cavity flow, and a two-dimensional sudden expansion flow. Excellent agreement is obtained between numerical calculations and analytical solutions of these flows.

Numerical Simulation of a Semi-Confined Slot Turbulent Impinging Jet

2011 ◽  
Vol 268-270 ◽  
pp. 345-350
Author(s):  
Ming Bo Wang ◽  
Rui He Wang ◽  
Xian Yong Liu
Keyword(s):  
Boundary Condition ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Constant Velocity ◽  
Turbulent Intensity ◽  
Two Dimensional ◽  
Confined Space ◽  
Wall Function ◽  
Plate Spacing ◽  
Better Than

A Realizable k-ε turbulence model in conjunction with a standard wall function has been applied to the prediction of a fully-developed two-dimensional jet impinging within a semi-confined space. A single geometry with a Reynolds number of 10,000 and a nozzle –to-plate spacing of eight diameters has been considered at different inlet boundary conditions. The numerical results, including the time-averaged velocities and the turbulent intensity, have been compared with the experimental data reported by Yoshida (ref 5). It is found that the trends in the axial velocity, the radial velocity and the turbulent intensity are fairly predicted. The fully-developed boundary condition is generally better than the constant velocity boundary condition. The differences between the numerical and experimental results can be attributed to the turbulence model and the treatment of the low Reynolds number zone near the wall.

Exploring a Three-Equation R–k–ε Turbulence Model

1996 ◽  
Vol 118 (4) ◽  
pp. 795-799 ◽  
Author(s):  
U. C. Goldberg
Keyword(s):  
Experimental Data ◽  
Boundary Condition ◽  
Reynolds Number ◽  
Time Scale ◽  
Eddy Viscosity ◽  
Current Approach ◽  
Wall Distance ◽  
Wall Boundary Condition ◽  
Proposed Model ◽  
Arbitrary Flow

A low Reynolds number extension of the k–ε model is proposed and evaluated. This version has the following attributes: (a) it does not involve wall distance or normal-to-wall directionality; (b) it enforces time scale realisability by preventing it from falling below the Kolmogorov (dissipative eddy) scale, (ν/ε)1/2; (c) it employs a simple wall boundary condition for ε. The current approach requires an additional transport equation for the undamped eddy viscosity, R, thus the resulting model is of the three-equation variety. Since wall distance is not used, the proposed model is applicable to arbitrary flow topologies. Predictions using this model are compared with experimental data of several flow cases, with encouraging results.

Temperature field evaluation of a two-dimensional partial heat flow problem through Green's Functions

2019 ◽  
Author(s):  
Guilherme Ramalho Costa ◽  
José Aguiar santos junior ◽  
José Ricardo Ferreira Oliveira ◽  
Jefferson Gomes do Nascimento ◽  
Gilmar Guimaraes
Keyword(s):  
Temperature Field ◽  
Heat Flow ◽  
Green's Functions ◽  
Flow Problem ◽  
Green’S Functions ◽  
Field Evaluation ◽  
Two Dimensional
Sign in / Sign up

Export Citation Format

Share Document