Lunch & Learn: Effect of Submergence on Transonic Flow Around a Hemisphere w/Dr. Scott Sherer, AFRL

Time: 11:45 am

Location:
China Garden Buffet
112 Woodman Dr.
Dayton, OH 45431

Lunch: You will be able to purchase the buffet


Abstract:
The effect of varying submergence on the transonic flow past canonical wall mounted hemispheres is investigated at a freestream Mach number M∞= 0.8 using delayed detached eddy simulations. Four submergence levels are considered, ranging from a full hemisphere (100% exposed) to a highly submerged case where the equator is well below the waterline (40% exposed). Analysis of the mean and unsteady features indicates that the shock foot and line of surface separation move downstream with submergence. However, the frequency associated with the streamwise motion of the shock remains consistent between the cases in terms of a suitably nondimensionalized Strouhal number SD ~ 0.26. Proper orthogonal decomposition is used to isolate and rank the different modes; as the hemisphere is submerged, there is an  evident change in prominence from the asymmetric “shifting” to the symmetric “breathing” mode. Dynamic mode decomposition was used to investigate the spectral content of these modes; the results show that the breathing mode collapses at a frequency of SD ~ 0.26 for all cases, while the shifting mode extends over a broad frequency range of SD between 0.13 and 0.21. Aero optic analysis shows that the distortion for the more submerged hemisphere cases is associated primarily with the breathing mode, while for the fully exposed hemisphere the shifting mode is dominant.

Biography
Dr Scott Sherer received his Ph D in Aeronautical and Astronautical Engineering from The Ohio State University in 2002 He is currently a Senior Aerospace Engineer in the Aerodynamic Technology Branch (AFRL/ His professional interests include computational aerodynamics, overset grid methods, high order methods and airborne kinetic and directed energy weapon integration He is an Associate Fellow of AIAA His personal interests include music, gardening and playing ice hockey.