Base pressure fluctuations on levitated freestream-aligned circular cylinder

Abstract

Base pressure fluctuations associated with the large-scale wake structures behind a freestream-aligned circular cylinder and aerodynamic force fluctuations related to them are experimentally investigated in the wind tunnel tests. Measurements at ReD=6.97×104 and 1.04×105 were conducted using pressure-sensitive paint (PSP) and a magnetic suspension and balance system (MSBS) for creating a supportless condition. The obtained pressure fields were mainly analyzed by a modal decomposition combining azimuthal Fourier decomposition and proper orthogonal decomposition (POD). The pressure fluctuations caused by large-scale vortex shedding were observed from the results of frequency analysis for mode coefficients. The states of the fluctuations were classified into three patterns, which are anticlockwise/clockwise circular and flapping patterns. These patterns have been observed in the previous studies for velocity fluctuations in the wake of a freestream-aligned circular cylinder. The conditional sampling analysis revealed that the trend in the amplitude of the pressure fluctuations is different by the state, and the flapping pattern causes a large pressure difference across the cylinder axis. Furthermore, the relationship between the antisymmetric pressure fluctuations and lift fluctuations, which act in the lateral direction of the cylinder, is confirmed.

Effect of ribs in a suddenly expanded flow at sonic Mach number

“…Nozzle investigation in terms of design always found a critical study when it is used for supersonic flow control [ 13 ]. Base pressure in sudden expansion ducts is one of the foremost problems in creating drag inside the duct of the nozzle, and therefore, control of base pressure is essential [ 14 , 15 ]. Performed a simulation and experiment in their study of ribs' role in controlling base pressure by Ambareren et al [ 16 ].…”