图书馆订购 Guest

ISSN Online: 2379-1748

ISBN Flash Drive: 978-1-56700-483-0

ISBN Online: 978-1-56700-482-3

4th Thermal and Fluids Engineering Conference
April, 14–17, 2019 , Las Vegas, NV, USA

RESOLUTION QUALITY INDICES FOR LARGE EDDY SIMULATION IN MODELLING A TURBULENT FREE JET

Get access (open in a dialog) pages 1835-1845
DOI: 10.1615/TFEC2019.tfl.027935

摘要

Resolution quality indices for large-eddy simulations (LES) are evaluated in modelling a turbulent free jet. For this purpose, based on the preliminary assumptions and understanding of flow physics, a trial mesh is generated. Turbulent length scales are calculated on this trial mesh, by carrying out a RANS simulation to predict a suitable mesh for the turbulent jet. From the Taylor micro-scales distribution on this trial mesh, LES mesh is generated with reasonably low number of cells. LES simulation is performed on this mesh using the dynamic Smagorinsky sub-gird scale (SGS) model. Using various LES indices for resolution quality (LES_IQ) such as that based on the resolved turbulent kinetic energy (LES_IQk), Kolmogorov length scales (LES_IQη) and effective viscosity (LES_IQν), verification of the grid resolution is carried out. Primary focus here is to find a suitable mesh for LES for the turbulent jet flow with a minimum number of trial mesh, using the guidelines available in literature. As the turbulence characteristics of a jet depend on its initial conditions, the flow field through a round convergent nozzle is first simulated using the elliptic blending Reynolds stress transport model to ensure the correct initial conditions, which are caused by the anisotropy of the flow inside the nozzle. Mean velocities and Reynolds stresses from the nozzle simulation are then used as inlet conditions for the LES simulation of the jet at a Reynolds number 28,000 based on the nozzle diameter of 10 mm and flow velocity of 2.8 m/s. All mesh quality indices used here reflect mesh's ability to resolve the flow appropriately. Further validation of the LES velocity field and turbulence parameters is established by comparison with particle image velocimetry (PIV) experiments.