Hypersonic Wind-Tunnel Measurements of Boundary-Layer Pressure Fluctuations

TLDR

Hypersonic vehicles experience high boundary‑layer pressure fluctuations during atmospheric reentry. The study measured surface pressure fluctuations on a 7‑sharp cone in two wind tunnels to better understand and predict hypersonic boundary‑layer pressure fluctuations. Measurements were performed on a 7‑sharp cone in Sandia’s Hypersonic Wind Tunnel and Purdue’s Mach‑6 Quiet Tunnel, and the transition location was predicted using Pate’s correlation based on tunnel noise parameters. Fluctuations under laminar boundary layers reflected tunnel noise levels, were an order of magnitude lower under quiet flow, increased during transition, and turbulent fluctuations were lower than transitional ones; second‑mode waves grew, saturated, and broke down near the transition peak.

Abstract

During atmospheric reentry, hypersonic vehicles are subjected to high levels of boundarylayer pressure ∞uctuations. To improve understanding and prediction of these ∞uctuations, measurements of surface pressure ∞uctuations on a 7 ‐ sharp cone were conducted in Sandia’s Hypersonic Wind Tunnel under noisy ∞ow and in Purdue University’s Boeing/AFOSR Mach-6 Quiet Tunnel under noisy and quiet ∞ow. Fluctuations under laminar boundary layers re∞ected tunnel noise levels. Laminar boundary-layer measurements under quiet ∞ow were an order of magnitude lower than under noisy ∞ow. Transition on the model only occurred under noisy ∞ow, and ∞uctuations peaked during transition. The transition location, marked by the peak, was predicted using tunnel noise parameters (Pate’s correlation). Turbulent boundary-layer ∞uctuations were lower than transitional ∞uctuations and also re∞ected tunnel noise levels. Measurements of second-mode waves showed the waves started to grow under a laminar boundary layer, saturated, and then broke down near the peak in transitional pressure ∞uctuations.