Control of Upswept Afterbody Vortices Using Continuous and Pulsed Blowing

TY - JOUR

T1 - Control of Upswept Afterbody Vortices Using Continuous and Pulsed Blowing

AU - Jackson, Richard

AU - Wang, Zhijin

AU - Gursul, Ismet

PY - 2019/10/14

Y1 - 2019/10/14

N2 - An experimental study was performed in a water tunnel to evaluate the effects of continuous and pulsed blowing jets on the counter-rotating vortices generated by the afterbody of a slanted base cylinder. Drag reductions from continuous blowing through circular jets were found to vary significantly with direction and location, and approached 7% when blowing outboard from upstream locations on the upswept face. However, for all circular jets tested, the external power required was larger than the power saved due to the drag reduction. Jet vortices restricted shear layer development, leading to smaller afterbody vortex cores further from the surface. A high aspect ratio jet flap, ejecting nearly parallel to the freestream, achieved drag reductions close to 9%, equating to the net energy savings of almost 3% for the best case. Jet vortices shortened the shear layer, resulting in vortices with reduced circulation, which were displaced away from the upswept face. Pulsing the jet flap resulted in improved drag reductions and energy savings (up to around 6%) compared to the equivalent continuous blowing case at the same time-averaged jet momentum coefficient. Pulsed blowing caused an increase in vortex separation and meandering, while the circulation was reduced by up to 10% of that for continuous blowing.

AB - An experimental study was performed in a water tunnel to evaluate the effects of continuous and pulsed blowing jets on the counter-rotating vortices generated by the afterbody of a slanted base cylinder. Drag reductions from continuous blowing through circular jets were found to vary significantly with direction and location, and approached 7% when blowing outboard from upstream locations on the upswept face. However, for all circular jets tested, the external power required was larger than the power saved due to the drag reduction. Jet vortices restricted shear layer development, leading to smaller afterbody vortex cores further from the surface. A high aspect ratio jet flap, ejecting nearly parallel to the freestream, achieved drag reductions close to 9%, equating to the net energy savings of almost 3% for the best case. Jet vortices shortened the shear layer, resulting in vortices with reduced circulation, which were displaced away from the upswept face. Pulsing the jet flap resulted in improved drag reductions and energy savings (up to around 6%) compared to the equivalent continuous blowing case at the same time-averaged jet momentum coefficient. Pulsed blowing caused an increase in vortex separation and meandering, while the circulation was reduced by up to 10% of that for continuous blowing.

M3 - Article

JO - AIAA Journal of Aircraft

JF - AIAA Journal of Aircraft

SN - 0021-8669

ER -