Oliver Khan

Welcome back. This week, I hope to continue our break from the regular hydrodynamic stability program and share a project I worked on last fall. This work involved water channel dye visualization experiments to reveal the locations of flow separation and reattachment on the cambered NACA 65(1)-412 airfoil at transitional Reynolds numbers Re ∈ [104, 105]. These experiments fit … [Read more...] about Water Channel Dye Visualization Experiments – Fall 2023

Welcome back. In this blog, I was hoping to take a short break from hydrodynamic stability, and share an old essay I have written about computing finite-time Lyapunov exponent (FTLE) fields to analyze Lagrangian coherent structures (LCSs):  My project was to develop numerical integration code that could compute particle trajectories in unsteady flows. While previous … [Read more...] about Computing Finite-Time Lyapunov Exponent Fields around Airfoils

Welcome back. In today’s blog post, we will continue our discussion of hydrodynamic stability by discussing resolvent analysis, which is complementary to classical linear stability analysis. While linear stability analysis looks at the growth of small perturbations to an unforced base flow, resolvent analysis finds maximum gain input-output structures in a flow field that … [Read more...] about Hydrodynamic Stability: Resolvent Analysis

Welcome back. Last week, we derived the Orr-Sommerfeld equation, which governs the evolution of small disturbances in 2D parallel shear flows. This equation was cast as an eigenvalue problem, L𝜑 = c𝜑, that determined stream function amplitudes, 𝜑, and their associated complex wave speeds, c, that characterized the behavior of small perturbations. The governing Orr-Sommerfeld … [Read more...] about Hydrodynamic Stability: Non-Normality and Transient Energy Growth