Full-Field Dependence on Inlet Modeling of Non-Isothermal Turbulent Jets Using Validated Large Eddy Simulations

Abstract

Inlet conditions for a turbulent jet are known to affect the near field behavior but eventually lose their significance downstream. Metrics of importance are often derived from mean and fluctuating velocity components, but little has been done to explore inlet effects on transport of a scalar quantity (e.g., temperature). This paper aims to provide fundamental understanding in this regard and employs large eddy simulations (LES) of a nonisothermal round turbulent jet (Reynolds number of 16,000) with geometry and boundary conditions mimicked after a well-known experimental study. The jet inlet is first modeled with a standard Blasius profile and next by performing a simulation of the upstream flow modeled with either detached eddy simulations (DES) or LES for the second and third approaches, respectively. Only the model employing LES for both upstream nozzle and downstream jet is found to completely capture the root-mean-square (RMS) temperature behavior, namely, a distinct hump when normalized by the local mean centerline temperature at roughly five diameters downstream. Regarding the far field conditions, all three inlet conditions converge for the centerline values, but the radial distributions still portray non-negligible differences. Not surprisingly, the complete LES modeling approach agrees the best with experimental data for mean and RMS distributions, suggesting that the inlet condition plays a vital role in both the near and far field of the jet. The current effort is the very first LES study to successfully capture flow physics for a nonisothermal round turbulent jet in near and far field locations.

A Turbulent Inflow Generation Method for the LES of High Re Flow by Scaling Low Re Flow Data

“…Large eddy simulation (LES) is one of the most promising computational fluid dynamics (CFD) models to solve fluid flow problems, and it is now widely applied to simulate jet flows [1]. It is important to set turbulent inflows that are as realistic as possible for the LES of jet flows, since turbulent inflows that are not realistic enough greatly increase the calculation error, as proved by Salkhordeh and Kimber [2]. For high Re jet flows, the computational cost of turbulent inflow generation is a problem.…”