Abstract: Laminar-turbulent transition in boundary-layer flows: Stability theory and Direct Numerical Simulations
Transition from laminar to turbulent flow is still one of the least understood topics in fluid dynamics. In this lecture, two key theoretical/numerical tools for investigating laminar-turbulent transition in boundary layers will be introduced, namely Linear Stability Theory (LST) and Direct Numerical Simulations (DNS). In our research in the Computational Fluid Dynamics Laboratory (CFDL) at the AME Department we are investigating stability and transition in boundary layers for a large range of flow speeds, from low speed (incompressible) all the way to hypersonic speeds (M>4). Fundamental aspects of the numerical methods employed for solving the unsteady Navier-Stokes equation for low-speed flows (incompressible, M=0) and compressible flows (M>0) will be discussed. Finally, typical results from Direct Numerical Simulations of boundary transition will be presented.