Interfacial Instability of an Oscillating Shear Layer

1986 ◽  
Vol 108 (1) ◽  
pp. 89-92 ◽  
Author(s):  
C. K. Shyh ◽  
B. R. Munson
Keyword(s):  
Viscous Fluid ◽  
Rigid Body ◽  
Shear Layer ◽  
Fluid Layer ◽  
Interfacial Instability ◽  
Shear Layer Instability ◽  
Stability Results

The oscillating interface between a very viscous fluid layer (which oscillates as a nearly rigid body with the bounding container) and a relatively inviscid layer becomes unstable under certain conditions. The dimensionless experimental stability results are correlated by a modified form of the classical Kelvin-Helmholtz shear layer instability result.

On shock-induced light-fluid-layer evolution

2021 ◽  
Vol 933 ◽  
Author(s):  
Yu Liang ◽  
Xisheng Luo
Keyword(s):  
Layer Thickness ◽  
Coupling Effect ◽  
Fluid Layer ◽  
Nonlinear Models ◽  
Interfacial Instability ◽  
Dimensional Theory ◽  
One Dimensional ◽  
Helium Gas ◽  
Wave Patterns ◽  
Thickness Variations

Shock-induced light-fluid-layer evolution is firstly investigated experimentally and theoretically. Specifically, three quasi-one-dimensional helium gas layers with different layer thicknesses are generated to study the wave patterns and interface motions. Six quasi-two-dimensional helium gas layers with diverse layer thicknesses and amplitude combinations are created to explore the Richtmyer–Meshkov instability of a light-fluid layer. Due to the multiple reflected shocks reverberating inside a light-fluid layer, the speeds of the two interfaces gradually converge, and the layer thickness saturates eventually. A general one-dimensional theory is adopted to describe the two interfaces’ motions and the layer thickness variations. It is found that, for the first interface, the end time of its phase reversal determines the influence of the reflected shocks on it. However, the reverberated shocks indeed lead to the second interface being more unstable. When the two interfaces are initially in phase, and the initial fluid layer is very thin, the two interfaces’ spike heads collide and stabilise the two interfaces. Linear and nonlinear models are successfully adopted by considering the interface-coupling effect and the reverberated shocks to predict the two interfaces’ perturbation growths in all regimes. The interfacial instability of a light-fluid layer is quantitatively compared with that of a heavy-fluid layer. It is concluded that the kind of waves reverberating inside a fluid layer significantly affects the fluid-layer evolution.

scholarly journals Instability patterns between counter-rotating disks

2003 ◽  
Vol 10 (3) ◽  
pp. 281-288 ◽  
Author(s):  
F. Moisy ◽  
T. Pasutto ◽  
M. Rabaud
Keyword(s):  
Aspect Ratio ◽  
Shear Layer ◽  
Particle Image ◽  
Shear Layer Instability ◽  
Free Shear Layer ◽  
Rotating Disks ◽  
Height Ratio ◽  
Aspect Ratios ◽  
Image Velocimetry ◽  
Local Reynolds Number

Abstract. The instability patterns in the flow between counter-rotating disks (radius to height ratio R/h from 3.8 to 20.9) are investigated experimentally by means of visualization and Particle Image Velocimetry. We restrict ourselves to the situation where the boundary layers remain stable, focusing on the shear layer instability that occurs only in the counter-rotating regime. The associated pattern is a combination of a circular chain of vortices, as observed by Lopez et al. (2002) at low aspect ratio, surrounded by a set of spiral arms, first described by Gauthier et al. (2002) in the case of high aspect ratio. Stability curve and critical modes are measured for the whole range of aspect ratios. From the measurement of a local Reynolds number based on the shear layer thickness, evidence is given that a free shear layer instability, with only weak curvature effect, is responsible for the observed patterns. Accordingly, the number of vortices is shown to scale as the shear layer radius, which results from the competition between the centrifugal effects of each disk.

On the Vibration Damping of a Plate by Means of a Viscous Fluid Layer

1987 ◽  
Vol 109 (2) ◽  
pp. 178-184 ◽  
Author(s):  
K. Uno Ingard ◽  
Adnan Akay
Keyword(s):  
Viscous Fluid ◽  
Frequency Response ◽  
Flow Resistance ◽  
Acoustic Radiation ◽  
Fluid Layer ◽  
Vibration Damping ◽  
Plate Motion ◽  
Flexible Plate ◽  
Dependent Flow ◽  
Rigid Plane

Vibration damping of a plate by means of a fluid layer is investigated. First, the frequency-dependent flow resistance of a fluid layer is explained with a simple illustration of the damping mechanism. Then, the vibration response of a plate is examined when it is backed by a rigid plane or another flexible plate with a fluid layer constricted in-between. Effects of the plate motion and acoustic radiation on the damping mechanism are also considered. The numerical results are presented in terms of frequency response of the plates.

Mitigating Blockage Effects on Flow Over a Circular Cylinder in an Adaptive-Wall Wind Tunnel

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Michael Bishop ◽  
Serhiy Yarusevych
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Shear Layer ◽  
Cylinder Surface ◽  
Blockage Ratio ◽  
Shear Layer Instability ◽  
Frequency Increase ◽  
Pressure Distributions ◽  
Instability Frequency

The effect of wall streamlining on flow development over a circular cylinder was investigated experimentally in an adaptive-wall wind tunnel. Experiments were carried out for a Reynolds number of 57,000 and three blockage ratios of 5%, 8%, and 17%. Three test section wall configurations were investigated, namely, geometrically straight walls (GSW), aerodynamically straight walls (ASW), and streamlined walls (SLW). The results show that solid blockage effects are evident in cylinder surface pressure distributions for the GSW and ASW configurations, manifested by an increased peak suction and base suction. Upon streamlining the walls, pressure distributions for each blockage ratio investigated closely match distributions expected for low blockage ratios. Wake blockage limits wake growth in the GSW configuration at 7.75 and 15 diameters downstream of the cylinder for blockages of 17% and 8%, respectively. This adverse effect can be rectified by streamlining the walls, with the resulting wake width development matching that expected for low blockage ratios. Wake vortex shedding frequency and shear layer instability frequency increase in the GSW and ASW configurations with increasing blockage ratio. The observed invariance of the near wake width with wall configuration suggests that the frequency increase is caused by the increased velocity due to solid blockage effects. For all the blockage ratios investigated, this increase is rectified in the SLW configuration, with the resulting Strouhal numbers of about 0.19 matching that expected for low blockage ratios at the corresponding Reynolds number. Blockage effects on the shear layer instability frequency are also successfully mitigated by streamlining the walls.

Sign in / Sign up

Export Citation Format

Share Document