Experimental and Numerical Analysis of a Streamwise Vortex Downstream of a Delta Wing

Abstract

The present paper analyzes the vortical flow downstream of a delta wing. The delta wing is designed to generate a vortex that resembles the vortex of a nacelle strake. The experimental results of stereoscopic particle image velocimetry measurements performed at different positions downstream of the delta wing display the streamwise development of the vortex. Details of the postprocessing of the measurement data and a quantification of the uncertainties are presented. The evaluation of the mean axial and tangential velocity components and Reynolds stresses provides insights to the vortex characteristics and their development in the streamwise direction. In addition, results of numerical simulations with the DLR TAU-code applying the Menter-Shear Stress Transport (SST) eddy viscosity model and the Speziale-Sarkar-Gatski/Launder-Reece-Rodi (SSG/LRR)- Reynolds stress model show the ability of the turbulence models to capture the vortex development. The experimental results indicate a preservation of the vortex strength and structure downstream of the delta wing. The Menter-SST model does not predict this preservation; rather it computes a rapid decay of vortex strength and an increase in vortex size. In contrast, the results of the SSG/LRR- model are in good agreement with the experiments concerning the mean flow development. However, both turbulence models underpredict the turbulence in the vortex core.