Analysis of flight-measured boundary-layer stability and transition data

Abstract

The paper concentrates on the computational analysis of both the Tollmien-Schlichting and crossflow-type instabilities using the results of a boundary-layer transition flight experiment on a smooth swept test surface. In addition, the effect of nonadiabatic wall conditions is analyzed using the measured surface temperature distribution on the boundary-layer development and stability growth. The computational methods utilized in analyzing the boundary-layer stability characteristics are discussed: one approach analyzes the Tollmien-Schlichting and crossflow instabilities independently with maximum Tollmien-Schlichting n-factors near nine and maximum crossflow n-factors near six at transition onset for separate cases, while the second approach analyzes the instabilities for maximum growth regardless of the type. As much as a 27-percent increase in n-factor is found at transition onset due to an increased Tollmien-Schlichting instability.