The Effect of Two-Dimensional Wall Deformations on Hypersonic Boundary Layer Disturbances

Previous experimental and numerical studies showed that two-dimensional roughness elements can stabilize disturbances inside a hypersonic boundary layer, and eventually delay the transition onset. The objective of the thesis is to evaluate the response of disturbances propagating inside a hypersonic boundary layer to various two-dimensional surface deformations of different shapes. The proposed deformations consist of a backward step, forward step, a combination of backward and forward steps, two types of wavy surfaces, surface dips or surface humps. Disturbances inside of a Mach 5.92 flat-plate boundary layer are excited by pulsed or periodic wall blowing and suction at an upstream location. The numerical tools consist of the Navier-Stokes equations in curvilinear coordinates and a linear stability analysis tool. Results show that all types of surface deformations are able to reduce the amplitude of boundary layer disturbances to a certain degree. The amount of reduction in the disturbance energy is related to the type of pressure gradient created by the deformation, adverse or favorable