Abstract

The impact of the choice of inlet boundary condition treatment on the fluid flow is studied in this work. The correct representation of the turbulence at the inlet to the domain is essential for the accuracy of Large Eddy Simulation. The inappro- priate specification of the inlet velocity has significant effect on the downstream flow pattern. The case of backward-facing step was used as a test case. Three different approaches of the inlet boundary conditions were studied: uniform velocity profile, mean velocity profile of the fully developed channel flow and velocity obtained from mapping velocity from plane positioned behind the inlet back to the inlet. The results of the simulations were compared with experimental results. It has shown, that using uniform velocity profile on inlet and even prescribing turbulent mean velocity profile without proper representation of turbulence fluctuations leads to unrealistic results.

Highlights

  • In the simulation of turbulent flow, the most important factor seems to be proper choice of turbulence model that will provide good representation of the flow

  • Description of mean velocity profile and other turbulence variables obtained from analytical solution or from experiments can be regarded as sufficient for the RANS simulations

  • Are described results obtained by various approaches to the inlet boundary condition

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Summary

INTRODUCTION

In the simulation of turbulent flow, the most important factor seems to be proper choice of turbulence model that will provide good representation of the flow Another issue of great importance is specification of boundary conditions, especially inlet boundary condition. Klein et al [4] proposed digital signal processing procedure to remedy lack of large- scale dominance in the inflow data generated by the random method.

GOVERNING EQUATIONS
DESCRIPTION OF THE TEST CASE
INLET BOUNDARY CONDITION
RESULTS
CONCLUSIONS
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