Boundary Layer Assessment of INTONATE Model

Abstract

During the wind tunnel tests of the DLR INTONATE project on a model of a short- and medium-haul aircraft, a detailed investigation of the boundary layer development was carried out on the model- cockpit and the cylindrical fuselage. For this study two different boundary layer rakes, one with 34mm height mounted over the cockpit Kulite sensors and another with 91mm height over the fuselage, were used to determine boundary layer thickness and boundary layer edge velocity (Ue). The objective behind these measurements is to implement empirical wall pressure spectra model, in which BL thickness and Ue are the main input parameters. Due to the sharp change in curvature of the cockpit, the flow gets decelerated on the windshield and hence resulting into unusual flow behaviour behind the windshield. This flow causes locally strange boundary layer profiles, where the velocity gradient suddenly increases at approximately 5mm above the surface for angle of attacks ranging from 2°-4°. Upon comparing the obtained test results with the CFD simulation of the cockpit model in the free field as well as inside the wind tunnel, the course of the boundary layer for most of the measured positions seems to be identical to that of the simulations.