| Micro Vortex Generators and SBLI |
| Rapid improvements in computational resources and advances in DNS/LES techniques have led improved flow modeling. In particular, DNS/LES have been used to investigate complex flow interactions such as those between a shock and a turbulent boundary layer. These studies with homogeneous and shear turbulence have dealt primarily with a mean one- or two-dimensional incoming flow and have revealed the evolution of the turbulent field under rapid rates of strain. At the same time, there have been recent developments in using micro vortex generators for passive control of shock/boundary-layer interactions, involving both experiment and computations. The precise mechanisms as to how they function at high speeds remains the subject of debate. Studies indicate that micro vortex generators modify the inner structure of the boundary layer to make the layer more resistant to separation, such as when a strong shock impinges on it. Some investigators suggest that the trailing vortices provide the mixing with the freestream to energize the boundary layer. However, apparently no experimental or computational results have been obtained to support this suggestion. A practical advantage of micro vortex generators is their small size which results in less drag than their conventional counterparts. |
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| This project is a joint effort between the Math (Prof. Liu) and MAE departments (Prof. Lu). One of the experimental efforts with this project has been to study the interaction of micro vortex generators with ramps and a cylinder with surface flow visualization. New methods have been developed to generate quantitative data for each test. A few pictures and videos appear below (about Mach 2.5 flow speed) with some of the experimental setups and results. |
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| Surface flow visualization over a 5 degree ramp. |
The 5 degree ramp with micro vortex generators. |
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| Surface flow visualization over a 25 degree ramp with test section unstart. |
The 25 degree ramp with micro vortex generators. |
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| Surface flow visualization past a cylinder. |
The cylinder with micro vortex generators. |
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| Video of surface flow visualization over a 5 degree ramp. |
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| Video of surface flow visualization over a 25 degree ramp with wind tunnel unstart. |
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| Video of surface flow visualization over a cylinder. |
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| The Math department work has generated a recent news article that can be found at the TACC website. Our research objectives for this project are detailed below: |
- Understand the performance of micro vortex generators in a rapidly evolving, 3D shock/boundary-layer interaction
- Develop high-order LES schemes for three-dimensional, rapidly distorted turbulent flows
- Validate LES schemes against mean and unsteady data
- Understand the effect of rapid cross-stream accelerations on the flowfield unsteadiness downstream of a three-dimensional shock/boundary layer interaction
- Elucidate the mean and unsteady flow physics through time- and frequency-domain analysis
- Investigate the interactions between shock-induced pressure gradients, flow unsteadiness and flow separation features
- Study the relation between flow unsteadiness, intermittent incoming boundary layer velocity profile fullness, and the existence of incoming boundary-layer streaks
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