Compressibility Effects on Leading-Edge Dynamic Stall Criteria at High Reynolds Number

TL;DR

This paper investigates the effectiveness of leading-edge stall criteria in high Reynolds number flows with moderate compressibility, revealing their limitations at higher Mach numbers due to shock interactions.

Contribution

It evaluates existing stall criteria in compressible flows and highlights the need for their modification under strong shock interaction conditions.

Findings

Criteria predict stall onset at lower Mach numbers.

Shock interactions can cause early vortex formation.

Predictive accuracy decreases at higher Mach numbers.

Abstract

This study examines the applicability of two leading-edge dynamic stall criteria, namely, the maximum magnitudes of the leading-edge suction parameter (LESP) and the boundary enstrophy flux (BEF), in a moderately compressible flow regime. While previously shown to predict stall onset ahead of dynamic stall vortex (DSV) formation in incompressible and mildly compressible regimes, these criteria are assessed here at a Reynolds number of $1 \times 10^6$ and freestream Mach numbers between 0.3 and 0.5. Unsteady RANS simulations indicate that DSV formation occurs in close temporal proximity to the attainment of the stall criteria. However, at the highest Mach number considered, stronger shock interaction effects with the shear layer leads to DSV formation prior to the criteria being reached, reducing their predictive accuracy. These findings suggest that while the criteria remain effective at lower Mach numbers, their definitions require modification in compressible regimes where strong shock interactions significantly influence the stall process.