Andre Weiner, Richard Semaan
TU Braunschweig, Institute of Fluid Mechanics
Slice of local Mach number $Ma$; $Re_\infty=10^7$, $Ma_\infty=0.75$, $\alpha=4^\circ$.
Unsteady flow and interaction phenomena at high speed stall conditions
Improved understanding and prediction of flight envelop via:
Modal decomp. = spatial structures + temp. behavior
Common issues/questions in DMD analyses:
$\rightarrow$ (partial) answers in this presentation
Simulation approach in a nutshell:
Various views of the computational mesh.
Degrees of freedom in DMD analysis:
DMD as a five-step analysis - part I.
DMD as a five-step analysis - part II.
opt. TDMD, int. $\rightarrow$ total least-squares DMD with optimal amplitudes and integral mode selection.
Test 0: variance of state vector norms
Test 1: rank sensitivity of buffet frequency
Assumption: top mode = buffet mode
Test 2: sensitivity to the sampling rate
Test 3: rank sensitivity of the full spectrum
Temporal mean, std., and probe locations.
PSD based on speed at probe locations.
DMD spectrum obtained from slice data.
Characteristic DMD modes: shock motion and vortex shedding/acoustic waves.
Mode with vortex shedding and acoustic waves.
Comparable modes and spectra for volume, slice, and surface data.