Towards High-Reynolds-Number Quiet Flow in Hypersonic Wind Tunnels

Book excerpt: This grant was initially focused on developing high-Reynolds-number quiet 0-ow in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue. Reliable quiet 0-ow was achieved at freestream unit Reynolds numbers of more than 3 million per foot, beginning in Sept. 2006. The facility became the only operational hypersonic quiet tunnel, anywhere in the world. Tunnel noise was then shown to have a substantial effect on: (a) roughness-induced transition for the X-51A forebody and a slender cone, and (b) transition induced by stationary cross flow waves. Quiet-tunnel measurements were also made to aid estimates of transition for the DARPA FALCON HTV-2 program. Second-mode instability waves were measured on a slender cone using hot wires, fast pressure sensors, and ALTP heat-transfer gauges.