Direct numerical simulation of hypersonic transition induced by an isolated cylindrical roughness element

Hypersonic boundary layer transition induced by an isolated cylindrical roughness element is investigated using direct numerical simulation method based on a finite volume formulation.To simulate the transition procedure by resolving the generation and evolvement of small-scale coherent structures,and capture the shock wave at the same time,high-order minimum dispersion and controllable dissipation scheme is validated and then applied.The results are compared with the available measurements in the quiet wind tunnel,such as the dominated frequency and root mean square of pressure.The computational dominated frequency of 19.23 k Hz is very close to the experimental one,21 k Hz.Also,the disturbances of the roughness are mostly generated by the"jet"just before the roughness,and then they travel and develop downstream with the shear layer and vortex shedding.The transition is mainly dominated by the instabilities of both the horseshoe vortex and the shear layer.