Four-dimensional particle tracking velocimetry measurements and detached eddy simulations of the turbulence structure and vortex breakdown and interactions of the David Taylor Model Basin 5415 sonar dome vortices

Four-dimensional particle tracking velocimetry measurements obtained at a 10° static drift condition were analyzed for the David Taylor Model Basin 5415 sonar dome vortices to assess the turbulence structure and vortex breakdown and interactions, and for the validation of scale-resolved computational fluid dynamics. The focus is on the strongest sonar dome vortex at x/L=0.12 (just downstream of the sonar dome). Brief discussion is provided for the interactions between the strong sonar dome vortex and the second-strongest sonar dome vortex. Macro-scale analysis showed elliptically shaped vortices and Gaussian and Bell distributions for the Q-criterion and vorticity of the strongest vortex. Micro-scale analysis used model spectra and micro-scale estimates, which were based on the macro-scales, as benchmarks (BMs) and were approximately half the size of the spatial resolution, indicating that sub-millimeter resolution is needed. The temporal and spatial autocorrelation functions were used to compute micro-scale results. The Taylor micro-scales were larger than their BMs and roughly 1.5 times the spatial resolution, indicating that the micro-scales are constrained by current resolution limitations. The temporal analysis resolved the energy-containing range and a significant portion of the inertial sub-range of the turbulence. The spatial analysis resolved a narrower band of the inertial sub-range. The Reynolds stress ellipsoid is oblate, suggesting that the principal axes are largely affected by the normal Reynolds stresses. The strongest vortex undergoes a spiral vortex breakdown/helical mode instability and visibly interacts with the second-strongest vortex. The analysis is supplemented by comparison with previous tomographic particle imagery velocimetry and detached eddy simulation results.