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The work is focused on numerical simulations of roughness induced transition for hypersonic flow on a flat plate wall mounted roughness element. Numerical simulations are compared to experimental results in order to resemble the physics highlighted in the tests. In particular, stress has been placed on the detection of the vortices in the wake behind the roughness element and on the onset of transition.

A computational method is introduced to infer statistical information on boundarylayer perturbations upstream of laminar-turbulent transition in a supersonic boundary layer. The method uses the intermittency function as a basis, which specifies the amount of time a flow is turbulent at a given streamwise location. The methods yields a joint probability density function for amplitude and frequency of boundary-layer perturbations upstream of transition. It relies on linear stability theory to link the probability density function with the intermittency. In order to infer parameters governing the function, we perform a statistical inverse analysis using the Markov chain Monte Carlo method. The approach is applied to a synthetic test case and to experimental data.

Laminar to turbulent transition in supersonic boundary layer is numerically investigated by combining linear stability theory and Uncertainty Quantification. Linear stability theory is used to determine the N −factor for the e N transition prediction method for a Mach 6 flat plate test case. Transition onset location is determined by using the N −factor experimentally obtained in the facility where the test was carried out. Uncertainty quantification is used to compute the probability of transition within the intermittency region downstream of the transition onset. The stochastic approach allows to model the transition region as in the experimental cases since a gradual passage from the laminar to the turbulent flow is obtained. The probability of transition resembles the shape of the skin friction or the heat flux distribution generally observed in the experiments within the transition region. Here we focus on the transition zone rather than on the onset location.

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