Aero-Optical Effects of Vortical Instabilities in Hypersonic Boundary Layers
Abstract
The performance of image-based sensors aboard hypersonic vehicles can be severely deteriorated by aero-optical distortions caused by compressible flows over the sensor aperture. While the aero-optical effects of canonical turbulent boundary layers on a flat plate has been extensively studied and are well understood, considerably less is known about aero-optical effects caused by transitional vortical structures, related to various instability mechanisms in boundary layers in three-dimensional flows. We propose to perform a joint experimental and numerical investigation of the aero-optical and fluidic environment of these vortical structures on the surface of a ``slab delta test model, which resembles a nose of notional hypersonic vehicle. The objective of the research is to quantify the aero-optical distortions due to instability-related vortical structures at various stages of their development. The results will be used to provide much-needed models and guidelines, sought after by industry and national labs, for designing effective imaging and tracking systems with acceptable aero-optical distortions for a variety of hypersonic vehicles. For the proposed experimental research, we will design and manufacture a model that will engender various stages of vortical instability structures, from incipient disturbance growth to full turbulence, depending on the angle of attack and Reynolds number. We will primarily study the naturally-developed structures over the smooth model. Limited studies with discrete roughness arrays will be used to input and amplify instabilities of a fixed, known spatial wavenumber. We will conduct extensive parametric studies of the spatio-temporally-resolved wavefronts using a high-speed Shack-Hartmann sensor, Digital Holography wavefront sensor, and Schlieren technique. These measurements will be complemented with other measurements of the aerothermodynamic environment using a surface-mounted fast-response pressure sensors and time-resolved IR thermography. To augment the measurement data and provide guidance/insight into optimizing the experiments, different simulations will be carried out in parallel with the experiments. These simulations will guide the design of experiments to identify relevant conditions to study. The experiments will provide comparison and validation data to the simulation approach. After validating the simulation approach with the experimental data that is low-enthalpy, the simulations will be used to study aero-optical effects in high-speed and high-enthalpy flows relevant to hypersonic flight. This will include the impact of high-temperature flows (e.g., thermal and chemical nonequilibrium) on aero-optical effects. We will use the collected experimental and simulation database to quantify the spatial and temporal characteristics of the aero-optical distortions and related flow properties of the vortical instabilities, both natural and perturbed by discrete surface roughness, in boundary layers at hypersonic speeds, using various cross-correlation, spectral, and modal analyses. More importantly, we will use this database to update existing and develop new models capable of predicting the overall time-averaged levels of the associated aero-optical distortions for different flow regimes.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 01, 2023
- Source ID
- W911NF2310369
Entities
People
- Stanislav Gordeyev
Organizations
- Army Contracting Command
- United States Army
- University of Notre Dame