Surface Pressure Fluctuations Produced by Attached and Separated Supersonic Boundary Layers

Surface Pressure Fluctuations Produced by Attached and Separated Supersonic Boundary Layers
Author: Alan L. Kistler
Publisher:
Total Pages: 26
Release: 1963
Genre: Aerodynamics, Supersonic
ISBN:

Measurements were obtained of the pressure fluctuations on a solid surface immersed in a supersonic stream for Mach numbers up to 5.0. The pressures resulting from both the attached and separated turbulent boundary layers were investigated. The results for the attached layer show that the root mean square value of the pressure fluctuation is proportional to the mean shear stress at the wall with a proportionality constant that is only weakly dependent on Mach number. The convection velocity characterizing the space-time correlations of pressure on the wall decreases with increasing Mach number, as does the ratio of the scale of the pressure fluctuations to the geometrical boundary layer thickness. The pressures associated with the separated flow produced by a forward facing step were significantly larger than the pressures produced by an attached boundary layer. The data can be interpreted as showing that the pressure fluctuations originate from two distinct causes, fluctuations due to changes in geometry of the separated region and fluctuations due to the disturbed motion within the separation bubble. (Author).

DNS of Hypersonic Turbulent Boundary Layers

DNS of Hypersonic Turbulent Boundary Layers
Author: Junji Huang
Publisher:
Total Pages: 0
Release: 2022
Genre: Turbulence
ISBN:

Understanding the physics of the pressure fluctuations induced by high-speed turbulent boundary layers (TBLs) is of major practical importance. The fluctuating pressure on aerodynamic surfaces of flight vehicles determines the vibrational loading of the vehicles and often leads to damaging effects as fatigue and flutter. The freestream pressure fluctuations radiated from the tunnel-wall TBLs are responsible for the genesis of freestream acoustic noise in conventional (i.e., noisy) supersonic and hypersonic wind tunnels. In this manuscript, wall and freestream pressure fluctuations induced by high-speed TBLs were characterized by direct numerical simulations (DNS). The DNS database covered a broad range of flow conditions (Mach number of $M_\infty = 2.5-14$, wall-to-recovery temperature ratio of $T_w/T_r = 0.18-1.0$, Reynolds number of $Re_\tau=450-1172$) and geometric configurations (flat plate, sharp circular cone, two dimensional channel, realistic wind-tunnel nozzle). The DNS overcame multiple experimental difficulties and provided access to wall and freestream pressure statistics that were difficulty to obtain otherwise, including the root-mean-square fluctuations and higher order moments (skewness and flatness) , probability density function , two-point correlation, convection speed, and coherence function. The study yielded useful insights into the physics of the boundary-layer-induced pressure field and provided critical assessment to reduced-order models such as the Corcos theory for modeling the wall pressure and the eddy-Mach-wave radiation theory for predicting the freestream acoustic pressure.