Detailed Investigation of Hypersonic Instability, Breakdown, and Natural Transition under Quiet Flow with Simulated Ablation-Gas Injection
Abstract
Approved for Public ReleaseThe Boeing-AFOSR Mach 6 Quiet Tunnel at Purdue University (BAM6QT) is uniquely well-suited to investigate problems of laminar-turbulent transition in a low-disturbance environment, and especially useful for computational validation, sinc e freestream noise effects can be eliminated from the model. Recent preliminary experiments with very long, slender (2.5 degree half -angle) cones under Mach 6 quiet flow have demonstrated that natural transition on a straight geometry is possible at Reynolds numbe rs achievable in BAM6QT. This capability to directly observe the entire natural transition process in the laboratory is world-uniq ue.The proposed work aims to make the first high fidelity, nonintrusive, off surface measurements of the entire natural transition p rocessfrom instability, to breakdown, to transition, to turbulent developmenton a slender sharp and moderately blunt straight cone under quiet flow at Mach 6, with and without roughness and simulated ablation gas (carbon monoxide) injection. In hypersonic flight , the ablation process is aerodynamically crucial, resulting in both outgassing/surface mass transfer and changing surface roughness characteristics, with both effects greater in the nose region.We propose a three-pronged approach, based upon the inclusion of bett er, more quantitative optical measurement capabilities (optical access upgrades have been made) along with a more complete data set than the few preliminary cases that have been acquired thus far. First, we will perform sharp, and moderately blunt, experiments on a 2.5 degree half-angle cone under quiet flow to observe the entire transition process. Instrumentation will include Double or Quad- Focused Laser Differential Interferometry (D/Q-FLDI), capable of non-intrusive focused interferometric measurements of high speed fl uid disturbances with a swept laser traverse mechanism, as well as high-speed schlieren videography using improved optical access an d pulsed illumination, complemented by surface pressure and heat transfer measurements. Furthermore, for the first time in a hyperso nic wind tunnel, we will deploy and calibrate two-photon planar laser induced fluorescence in carbon monoxide (CO TP-PLIF) at kHz an d MHz rates, to allow both high-speed imaging and quantitative concentration measurements of simulated ablation products injected in to the flow field. Next, this advanced instrumentation suite will be used to characterize the transition process on a straight cone with static roughness elements, as well as cones with controlled and characterized CO gas injection to simulate ablation. Finally, m odern non-modal growth analysis techniques, using the input-output framework and optimal growth analysis, will be applied by computa tional partners both for roughness element/injector design and placement before any experiments take place, as well as while experim ents are ongoing for continued refinement. The resulting data sets, acquired in a low-disturbance environment and directly documenti ng both natural and induced hypersonic disturbance growth with measurements informed by state-of-the-art computations, will be inval uable for code validation and have the strong potential to lead to truly novel insights in flight-relevant hypersonic boundary layer instability, transition, and turbulence, especially in the presence of ablation and related effects.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2021
- Source ID
- N000142112603
Entities
People
- Joseph S. Jewell
Organizations
- Office of Naval Research
- Purdue University
- United States Navy