High-speed visualization and PIV measurements of cavitating flows around a semi-circular leading-edge flat plate and NACA0015 hydrofoil

2014 ◽  
Vol 60 ◽  
pp. 119-134 ◽  
Author(s):  
A.Yu. Kravtsova ◽  
D.M. Markovich ◽  
K.S. Pervunin ◽  
M.V. Timoshevskiy ◽  
K. Hanjalić
Keyword(s):  
Flat Plate ◽  
High Speed ◽  
Leading Edge ◽  
Cavitating Flows ◽  
Piv Measurements

High-speed laminar flow past a fin–body junction

2013 ◽  
Vol 737 ◽  
pp. 19-55 ◽  
Author(s):  
O. R. Tutty ◽  
G. T. Roberts ◽  
P. H. Schuricht
Keyword(s):  
Laminar Flow ◽  
Flat Plate ◽  
High Speed ◽  
Leading Edge ◽  
Limited Range ◽  
Interaction Region ◽  
Liquid Crystal Thermography ◽  
Heating Effects ◽  
Oil Flow ◽  
Free Stream Mach Number

AbstractInterference heating effects generated by a blunt fin-type protuberance on a flat plate exposed to a hypersonic flow have been investigated experimentally and numerically. Experiments and simulations were carried out at a free-stream Mach number of 6.7 under laminar flow conditions. The surface heating on the plate was measured experimentally using liquid-crystal thermography, which provided quantitative data with high spatial resolution. Complementary surface oil flow and schlieren experiments were also carried out to gain a better understanding of the interference flow field. The effects of fin leading-edge diameter on the heating distribution on the flat plate surface were explored. The results of the experiments and simulations agree well and reveal a highly complex interaction region which extends over seven diameters upstream of the fin. Within the interaction region surrounding the fin, heating enhancements up to ten times the undisturbed flat plate value were estimated from the experimental data. However, the liquid crystals have a limited range, and the numerical simulations indicated localized peak heating many times this value both on the plate and the fin itself.

Simulation of blunt-fin-induced shock-wave and turbulent boundary-layer interaction

1985 ◽  
Vol 154 ◽  
pp. 163-185 ◽  
Author(s):  
Ching-Mao Hung ◽  
Pieter G. Buning
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Flat Plate ◽  
High Speed ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Layer Interaction ◽  
Boundary Layer Interaction

The Reynolds-averaged Navier–Stokes equations are solved numerically for supersonic flow over a blunt fin mounted on a flat plate. The fin shock causes the boundary layer to separate, which results in a complicated, three-dimensional shock-wave and boundary-layer interaction. The computed results are in good agreement with the mean static pressure measured on the fin and the flat plate. The main features, such as peak pressure on the fin leading edge and a double peak on the plate, are predicted well. The role of the horseshoe vortex is discussed. This vortex leads to the development of high-speed flow and, hence, low-pressure regions on the fin and the plate. Different thicknesses of the incoming boundary layer have been studied. Varying the thicknesses by an order of magnitude shows that the size of the horseshoe vortex and, therefore, the spatial extent of the interaction are dominated by inviscid flow and only weakly dependent on the Reynolds number. Coloured graphics are used to show details of the interaction flow field.

High-speed imaging of cavitation regimes on a round-leading-edge flat plate and NACA0015 hydrofoil

2013 ◽  
Vol 16 (3) ◽  
pp. 181-184 ◽  
Author(s):  
A. Yu. Kravtsova ◽  
D. M. Markovich ◽  
K. S. Pervunin ◽  
M. V. Timoshevskiy ◽  
K. Hanjalić
Keyword(s):  
Flat Plate ◽  
High Speed ◽  
Leading Edge ◽  
High Speed Imaging

scholarly journals Observations of shock waves in cloud cavitation

1998 ◽  
Vol 355 ◽  
pp. 255-283 ◽  
Author(s):  
G. E. REISMAN ◽  
Y.-C. WANG ◽  
C. E. BRENNEN
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
High Speed ◽  
Leading Edge ◽  
Wave Structure ◽  
Cavitating Flows ◽  
Cloud Cavitation ◽  
Radiated Noise ◽  
Wave Dynamics ◽  
New Perspective

This paper describes an investigation of the dynamics and acoustics of cloud cavitation, the structures which are often formed by the periodic breakup and collapse of a sheet or vortex cavity. This form of cavitation frequently causes severe noise and damage, though the precise mechanism responsible for the enhancement of these adverse effects is not fully understood. In this paper, we investigate the large impulsive surface pressures generated by this type of cavitation and correlate these with the images from high-speed motion pictures. This reveals that several types of propagating structures (shock waves) are formed in a collapsing cloud and dictate the dynamics and acoustics of collapse. One type of shock wave structure is associated with the coherent collapse of a well-defined and separate cloud when it is convected into a region of higher pressure. This type of global structure causes the largest impulsive pressures and radiated noise. But two other types of structure, termed ‘crescent-shaped regions’ and ‘leading-edge structures’ occur during the less-coherent collapse of clouds. These local events are smaller and therefore produce less radiated noise but the interior pressure pulse magnitudes are almost as large as those produced by the global events.The ubiquity and severity of these propagating shock wave structures provides a new perspective on the mechanisms reponsible for noise and damage in cavitating flows involving clouds of bubbles. It would appear that shock wave dynamics rather than the collapse dynamics of single bubbles determine the damage and noise in many cavitating flows.

Experimental study of heat transfer in the boundary layer of a flat plate with the impact of weak shock waves on the leading edge

2020 ◽  
Author(s):  
V. L. Kocharin ◽  
A. A. Yatskikh ◽  
D. S. Prishchepova ◽  
A. V. Panina ◽  
Yu. G. Yermolaev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Experimental Study ◽  
Shock Waves ◽  
Flat Plate ◽  
Leading Edge ◽  
Weak Shock ◽  
The Impact

Steady longitudinal vortices in supersonic turbulent separated flows

2011 ◽  
Vol 672 ◽  
pp. 451-476 ◽  
Author(s):  
ERICH SCHÜLEIN ◽  
VICTOR M. TROFIMOV
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Roughness Element ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Leading Edge ◽  
Separated Flows ◽  
Vortex Generators ◽  
Longitudinal Vortices ◽  
Oil Flow

Large-scale longitudinal vortices in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces are investigated in this paper. Oil-flow visualization and infrared thermography techniques were applied in the wind tunnel tests at Mach numbers 3 and 5 to investigate the nominally 2-D ramp flow at deflection angles of 20°, 25° and 30°. The surface contour anomalies have been artificially simulated by very thin strips (vortex generators) of different shapes and thicknesses attached to the model surface. It is shown that the introduced streamwise vortical disturbances survive over very large downstream distances of the order of 104 vortex-generator heights in turbulent supersonic flows without pressure gradients. It is demonstrated that each vortex pair induced in the reattachment region of the ramp is definitely a child of a vortex pair, which was generated originally, for instance, by the small roughness element near the leading edge. The dependence of the spacing and intensity of the observed longitudinal vortices on the introduced disturbances (thickness and spanwise size of vortex generators) and on the flow parameters (Reynolds numbers, boundary-layer thickness, compression corner angles, etc.) has been shown experimentally.

Aerodynamic Measurements on the Interaction of Secondary Jets and Separation Bubble

2012 ◽  
Author(s):  
A. Samson ◽  
S. Sarkar
Keyword(s):  
Flat Plate ◽  
Large Scale ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Leading Edge ◽  
Bubble Interactions ◽  
Separated Shear Layer ◽  
Bubble Length ◽  
Flow Visualizations ◽  
Turbulence Generation

The dynamics of separation bubble under the influence of continuous jets ejected near the semi-circular leading edge of a flat plate is presented. Two different streamwise injection angles 30° and 60° and velocity ratios 0.5 and 1 for Re = 25000 and 55000 (based on the leading-edge diameter) are considered here. The flow visualizations illustrating jet and separated layer interactions have been carried out with PIV. The objective of this study is to understand the mutual interactions of separation bubble and the injected jets. It is observed that flow separates at the blending point of semi-circular arc and flat plate. The separated shear layer is laminar up to 20% of separation length after which perturbations are amplified and grows in the second-half of the bubble leading to breakdown and reattachment. Blowing has significantly affected the bubble length and thus, turbulence generation. Instantaneous flow visualizations supports the unsteadiness and development of three-dimensional motions leading to formation of Kelvin-Helmholtz rolls and shedding of large-scale vortices due to jet and bubble interactions. In turn, it has been seen that both the spanwise and streamwise dilution of injected air is highly influenced by the separation bubble.

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