Grey area in Embedded WMLES on a transonic nacelle-aircraft configuration

TL;DR

This study applies a hybrid RANS-LES simulation technique to a transonic aircraft-nacelle configuration, validating the method and demonstrating its capabilities and limitations in capturing shock-induced separation and turbulent boundary layers.

Contribution

It introduces a hybrid RANS-LES approach with a synthetic turbulence generator for aircraft nacelle flow simulation, highlighting its strengths and limitations in transonic conditions.

Findings

Successful simulation of turbulent boundary layer development

Identification of the adaption region limitations for shock buffet

Validation of the mesh and method for aircraft configurations

Abstract

A scale resolving hybrid RANS-LES technique is applied to an aircraft-nacelle configuration under transonic flow conditions using the unstructured, compressible TAU solver. Therefore, a wall modelled LES methodology is locally applied to the nacelle lower surface in order to examine shock induced separation. In this context a synthetic turbulence generator (STG) is used to shorten the adaption region at the RANS-LES interface. Prior to the actual examinations, fundamental features of the simulation technique are validated by simulations of decaying isotropic turbulence as well as a flat plate flow. For the aircraft-nacelle configuration at a Reynolds number of 3.3 million a sophisticated mesh with 420 million points was designed which refines 32 % of the outer casing surface of the nacelle. The results show a development of a well resolved turbulent boundary layer with a broad spectrum of turbulent scales which demonstrates the applicability of the mesh and method for aircraft configurations. Furthermore, the necessity of a low dissipation low dispersion scheme is demonstrated. However, the distinct adaption region downstream of the STG limits the employment of the method in case of shock buffet for the given flow conditions.