Hypersonic Base Flow Characterization
Abstract
The proposed research will focus on advancing the understanding of base recirculation zones in hypersonic flows. Recent focus by the Air Force on endo-atmospheric hypersonic vehicles is a regime where base flow is a major contributor to total drag and heat transfer is high enough to be of concern over long periods of flight. We will investigate the breakdown of the shear layer that drives the dynamics of the separation process. Starting from the work by Lamb and Oberkompf, they identified the need for experimental studies to help better quantify developed correlations for base pressure and heat transfer rate. Purdue and Florida State University (FSU) will conduct experiments in their facilities that will enable a large range of Mach number and Reynolds number to be explored on streamlined shapes such as sphere-cone geometries. We will extend this analysis to non-axisymmetric bodies to better understand the influence of forebody vortices on the base region. Measurements will be conducted with and without boundary layer transition trips to simulate natural and forced transition. Boundary layer characteristics will be measured at the base shoulder using a multiprobe pressure rake to establish quantifiable inputs for Computational Fluid Dynamics (CFD) modeling. Particle Image Velocimetry (PIV) and Schlieren imaging will be used to characterize the recirculation region. Using a local Reynolds number reference frame in the shear layer, breakdown can be better quantified and help to develop a correlation that can bridge the gap between laminar and turbulent flow. FSU will also develop new Pressure/Temperature Sensitive Paint (PSP/TSP) techniques that will be targeted for measurement of base flow pressure and temperature. This will provide insight into the spatial distribution of pressure and provide better insight into base pressure field as compared to the previous work with point pressure measurements using individual pressure sensors. New PSP binders will be investigated to enable high temperature base flow environments at hypersonic speeds. This will culminate in a new PSP technique where the measurement will be conducted inside the model simulating a hypersonic flight test. CFD modeling will be conducted by University of Florida (UF) in coordination with experiments to be carried out at Purdue and FSU. Large Eddy Simulation (LES) methods will be incorporated to help explore the breakdown of the shear layer. Comparison between upstream laminar and turbulent boundary layers will be explored. To conduct turbulent boundary layer simulations, we will investigate a body force trip model that will replicate the transition process on a model. In addition, upstream disturbances will be modeled to simulate the behavior between a quiet and noisy flow operation of the Purdue BAM6QT and FSU Polysonic facilities. Data extraction techniques will be utilized to understand the spatial and temporal instabilities in the shear layer for both laminar and turbulent boundary layer states. Understanding the instabilities will be key to developing techniques for causing early transition of the base flow shear layer and reducing base drag contribution. Once these instabilities are identified, numerical simulations will be conducted to demonstrate the ability to influence the breakdown process.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 21, 2022
- Source ID
- FA95502110432XX0
Entities
People
- Ryan Gosse
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Florida