| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 92 === The diffraction of planer shock waves over a wedge has been investigated in this study by the conservation element and solution element method. We found that the CE/SE method has high numerical accuracy and low numerical dispersion. The method is very convenient to obtain the transient solution so as to comprehend the shock diffraction. We also compare this simulation result with experiment which has been studied by Glass in 1987 and the shock structure is almost identical to what we obtained except the viscous effect.
In this simulation, we quantified the vorticity and circulation. The shear layer caused by the velocity difference can be clearly understood with the help of the voricity contour. Furthermore, we study the interaction among the shear layer, main vortex and secondary reflected shock which is the diffracted shock interacting with the backward flat surface. We also found that with the increase of the incident shock’s Mach number, the interaction between contact surface and slipstream will be stronger. And the flow structure after the shock diffraction is more complicated if increasing the Mach number of the incident shock.
In this study, the results show that the circulation is influenced by both the secondary reflected shock and the wedge angle. The circulation increases as the backward wedge angle increases. The secondary reflected shock interacts with the contact surface first and then with the main vortex. This causes the secondary shock break into two parts and makes the flow structure more complicated.
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