Modelling of natural and bypass transition in aerodynamics

Abstract

Abstract. Most of transition models are proposed for modelling of the bypass transition common in the internal aerodynamics especially in turbomachinery where free stream turbulence is the dominant parameter affecting the transition onset. Free-stream turbulence level in the external aerodynamics is usually noticeably lower and so the natural transition often occurs in flows around airfoils. The transition model with the algebraic equation for the intermittency coefficient proposed originally by Straka and PĜíhoda [3] for the bypass transition was modified for modelling of the transition at low free-stream turbulence. The modification is carried out using experimental data of Schubauer and Skramstad [18]. Further, the three-equation k-k L -Z model proposed by Walters and Cokljat [10] was used for the modelling of the transition at low free-stream turbulence. Both models were tested by means of the incompressible flow around airfoils at moderate and very low free-stream turbulence.

Comparison of Two Transition Models Modified for Low Free-Stream Turbulence

“…The value A = 215 was determined according to results of Schubauer and Skramstad [6] and is in accordance with most experimental data. The detailed description of the modified model is given by Fürst et al [7].…”