研究目的
To measure the configuration of the incident shockwave/side-wall boundary layer interaction using numerical (CFD) and experimental (BOS, SSLC and Schlieren) technologies, which are applied in a quasi-two-dimensional model, focusing on tests of the width of the Mach stem.
研究成果
BOS can accurately capture the internal flow structure with results consistent to within 7% error compared to CFD and other methods. The 3D reconstruction of the incident oblique shock, particularly the width of the Mach stem, was successful, demonstrating BOS's potential for flow field measurements. Optimal optical rotation angles (e.g., 20°) minimize errors, and the technique is simple and sensitive for such applications.
研究不足
The BOS technique may have reduced resolution and accuracy due to aerodynamic optical effects when optical paths are too long, and errors can increase if rotation angles are not optimized. The method requires careful calibration and is sensitive to background pattern quality and setup parameters.
1：Experimental Design and Method Selection:
The study uses background-oriented schlieren (BOS) technique for quantitative measurement of density gradients in a hypersonic flow field, with comparisons to CFD simulations, shear-sensitive liquid crystal (SSLC), and high-speed schlieren methods. The BOS setup involves multiple light paths rotated at angles (10°, 20°, 30°) to reconstruct 3D structures.
2：Sample Selection and Data Sources:
A M2.7 nozzle model with a ramp in a hypersonic wind tunnel is used, with flow conditions including Mach number 2.7, total temperature 290 K, upstream pressure 600 kPa, and downstream pressure 102.38 kPa.
3：7 nozzle model with a ramp in a hypersonic wind tunnel is used, with flow conditions including Mach number 7, total temperature 290 K, upstream pressure 600 kPa, and downstream pressure 38 kPa.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a Canon EOS series camera (resolution 4752x3168 pixels, aperture 1.4, focus 85 mm), white LED lamp (200 W), background pattern plate (A4 size with random spots), and a wind tunnel model made of aluminum alloy and optical glass.
4：4, focus 85 mm), white LED lamp (200 W), background pattern plate (A4 size with random spots), and a wind tunnel model made of aluminum alloy and optical glass.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The BOS setup involves placing a background plate at specific distances (e.g., 270 mm from flow center), capturing reference and test state images with the camera, and using cross-correlation algorithms (PIVlab) to calculate displacements and derive density gradients. Tests are conducted at different optical rotation angles to measure the width of the Mach stem.
5：Data Analysis Methods:
Data is analyzed using cross-correlation for displacement calculation, Gladstone-Dale relation for density derivation, and comparisons with CFD results for validation. Statistical errors are computed, and 3D reconstruction is performed based on geometric relations.
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