Flow features resulting from shock wave impact on a cylindrical cavity

2007 ◽  
Vol 580 ◽  
pp. 481-493 ◽  
Author(s):  
BERIC W. SKEWS ◽  
HARALD KLEINE
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Shear Layers ◽  
Complex Flow ◽  
Wave Impact ◽  
Time Resolved ◽  
Additional Information ◽  
Flow Features ◽  
Time Resolved Imaging ◽  
The Impact

The complex flow features that arise from the impact of a shock wave on a concave cavity are determined by means of high-speed video photography. Besides additional information on features that have previously been encountered in specific studies, such as those relating to shock wave reflection from a cylindrical wall and those associated with shock wave focusing, a number of new features become apparent when the interaction is studied over longer times using time-resolved imaging. The most notable of these new features occurs when two strong shear layers meet that have been generated earlier in the motion. Two jets can be formed, one facing forward and the other backward, with the first one folding back on itself. The shear layers themselves develop a Kelvin–Helmholtz instability which can be triggered by interaction with weak shear layers developed earlier in the motion. Movies are available with the online version of the paper.

scholarly journals Time-resolved imaging of a compressible air disc under a drop impacting on a solid surface

2015 ◽  
Vol 780 ◽  
pp. 636-648 ◽  
Author(s):  
E. Q. Li ◽  
S. T. Thoroddsen
Keyword(s):  
Solid Surface ◽  
High Speed ◽  
Theoretical Models ◽  
Adiabatic Compression ◽  
Time Resolved ◽  
Time Resolved Imaging ◽  
Rapid Deceleration ◽  
Drop Impacts ◽  
The Impact ◽  
Surface Minima

When a drop impacts on a solid surface, its rapid deceleration is cushioned by a thin layer of air, which leads to the entrapment of a bubble under its centre. For large impact velocities the lubrication pressure in this air layer becomes large enough to compress the air. Herein we use high-speed interferometry, with 200 ns time-resolution, to directly observe the thickness evolution of the air layer during the entire bubble entrapment process. The initial disc radius and thickness shows excellent agreement with available theoretical models, based on adiabatic compression. For the largest impact velocities the air is compressed by as much as a factor of 14. Immediately following the contact, the air disc shows rapid vertical expansion. The radial speed of the surface minima just before contact, can reach 50 times the impact velocity of the drop.

Mechanics of the influx phase in the jet regurgitant mode of a powered resonance tube

2019 ◽  
Vol 18 (2-3) ◽  
pp. 279-298 ◽  
Author(s):  
Bhavraj Thethy ◽  
David Tairych ◽  
Daniel Edgington-Mitchell
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Fluid Velocity ◽  
Velocity Variation ◽  
Shock Strength ◽  
Velocity Change ◽  
Resonator Length ◽  
Time Resolved ◽  
Reflected Waves ◽  
Shock Position

Time-resolved visualisation of shock wave motion within a powered resonant tube (PRT) is presented for the regurgitant mode of operation. Shock position and velocity are measured as functions of both time and space from ultra-high-speed schlieren visualisations. The shock wave velocity is seen to vary across the resonator length for both the incident and reflected waves. Three mechanisms are explored as explanations for the variation in velocity: change in local fluid velocity, variation in shock strength and variations in local temperature. For the incident wave, local fluid velocity and shock strength are extracted from the data and both are demonstrated to contribute to the observed variation, with a non-trivial remainder likely explained by variation in temperature.

High Speed Liquid Impact Onto Wetted Solid Surfaces

1994 ◽  
Vol 116 (2) ◽  
pp. 345-348 ◽  
Author(s):  
H. H. Shi ◽  
J. E. Field ◽  
C. S. J. Pickles
Keyword(s):  
Shock Wave ◽  
Liquid Layer ◽  
Solid Surface ◽  
High Speed ◽  
Shear Failure ◽  
Soda Lime ◽  
Liquid Jet ◽  
Soda Lime Glass ◽  
The Impact

The mechanics of impact by a high-speed liquid jet onto a solid surface covered by a liquid layer is described. After the liquid jet contacts the liquid layer, a shock wave is generated, which moves toward the solid surface. The shock wave is followed by the liquid jet penetrating through the layer. The influence of the liquid layer on the side jetting and stress waves is studied. Damage sites on soda-lime glass, PMMA (polymethylmethacrylate) and aluminium show the role of shear failure and cracking and provide evidence for analyzing the impact pressure on the wetted solids and the spatial pressure distribution. The liquid layer reduces the high edge impact pressures, which occur on dry targets. On wetted targets, the pressure is distributed more uniformly. Despite the cushioning effect of liquid layers, in some cases, a liquid can enhance material damage during impact due to penetration and stressing of surface cracks.

High-speed time-resolved color schlieren visualization of shock wave phenomena

Shock Waves ◽  
2005 ◽  
Vol 14 (5-6) ◽  
pp. 333-341 ◽  
Author(s):  
H. Kleine ◽  
K. Hiraki ◽  
H. Maruyama ◽  
T. Hayashida ◽  
J. Yonai ◽  
...  
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Time Resolved ◽  
Schlieren Visualization ◽  
Wave Phenomena

scholarly journals A Study of the Complex Flow Features Behind a Diffracted Shock Wave on a Convex Curved Wall

2015 ◽  
Vol 8 (4) ◽  
pp. 667-672
Author(s):  
adam muritala ◽  
B. W. Skews ◽  
craig law ◽  
◽  
◽  
...  
Keyword(s):  
Shock Wave ◽  
Complex Flow ◽  
Flow Features

Spatiotemporally-Resolved Dynamics of Dispersing Ferrofluid Aggregates

2008 ◽  
Author(s):  
Alicia M. Williams ◽  
Pavlos P. Vlachos
Keyword(s):  
Internal Flow ◽  
Bulk Flow ◽  
Experimental Techniques ◽  
Recirculation Region ◽  
Complex Flow ◽  
Time Resolved ◽  
Square Channel ◽  
Spatiotemporal Behavior ◽  
Pulsatile Flows ◽  
The Impact

Ferrohydrodynamics research has been approached predominantly from either numerical or basic experimental techniques. However, to date, these experimental techniques have been limited to ultrasonic point measurements or shadowgraphs due to the opacity of the ferrofluids. As a result, the complete dynamics of many ferrohydrodynamics flows have remained unexplored. In this work, Time Resolved Digital Particle Image Velocimetry (TRDPIV) is employed to fully resolve the dynamic interaction of ferrofluid aggregates with bulk nonmagnetic fluids. This topic is hydrodynamically rich, where shearing between the aggregate and bulk flow develop into the Kelvin-Helmholtz instability. Ferrofluid aggregates are mixed with fluorescent particles in order to enable visualization of the internal flow structure of the aggregate and generate quantitative velocity measurements. The TRDPIV measurements are made in a 15 mm square channel where ferrofluid retained by a 0.5 Tesla permanent magnet is studied as it disperses. The effects of both steady and pulsatile flows are quantified, as are the impact of varying the magnetic field gradients. In both steady and pulsatile flows, a recirculation region is observed within the ferrofluid, driven by the shear layer between the bulk flow and aggregate interface. The interaction of the aggregate with the flow is also governed by the aggregate height relative to that of the test section. Higher, larger aggregates are less stable, and therefore, more likely to be dispersed by the bulk flow. As the aggregate diminishes in size, it is both more stable and is less subject to shearing forces from the flow. Flow pulsatility enriches the dynamics of the flow and generates complex flow structures resulting from interaction between the aggregate and bulk flow. This work is the first to explore the rich spatiotemporal behavior of dispersing ferrofluid aggregates interacting with steady and unsteady bulk flows.

Numerical study of a planar shock interacting with a cylindrical water column embedded with an air cavity

2017 ◽  
Vol 825 ◽  
pp. 825-852 ◽  
Author(s):  
Gaoming Xiang ◽  
Bing Wang
Keyword(s):  
Shock Wave ◽  
Water Column ◽  
Numerical Study ◽  
Incident Shock ◽  
Weno Scheme ◽  
Geometrical Parameters ◽  
Wave Impact ◽  
Planar Shock ◽  
Mach Numbers ◽  
The Impact

This paper performs a numerical study on the interaction of a planar shock wave with a water column embedded with/without a cavity of different sizes at high Weber numbers. The conservative-type Euler and non-conservative scalar two-equations representing the transportation of two-phase properties consist of the diffusion interface capture models. The numerical fluxes are computed by the Godunov-type Harten-Lax–van Leer contact Riemann solver coupled with an incremental fifth-order weighted essentially non-oscillatory (WENO) scheme. A third-order total variation diminishing (TVD) Runge–Kutta scheme is used to advance the solution in time. The morphology and dynamical characteristics are analysed qualitatively and quantitatively to demonstrate the breakup mechanism of the water column and formation of transverse jets under different incident shock intensities and embedded-cavity sizes. The jet tip velocities are extracted by analysing the interface evolution. The liquid column is prone to aerodynamic breakup with the formation of micro-mist at later stages instead of liquid evaporation because of the weakly heating effects of the surrounding air. It is numerically confirmed that the liquid-phase pressure will drop below the saturated vapour pressure, and the low pressure can be sustained for a certain time because of the focusing of the expansion wave, which accounts for the cavitation inside the liquid water column. The geometrical parameters of the deformed water column are identified, showing that the centreline width decreases but the transverse height increases nonlinearly with time. The deformation rates are nonlinearly correlated under different Mach numbers. The first transverse jet is found for a water column with an embedded cavity, whereas the water hammer shock and second jet do not occur under the impact of low intensity incident shock waves. The $x$-velocity component recorded at the rear stagnation point can remain unchanged for a comparable time after a declined evolution, which indicates that the downstream wall of the shocked water ring somehow moves uniformly. It can be explained that the acceleration of the downstream wall is balanced by the trailing shedding vortex, and this effect is more evident under higher Mach numbers. The increased enstrophy, mainly generated at the interface, demonstrates the competition of the baroclinic effects of the shock wave impact over dilatation.

Rayleigh-Taylor Instability of a Shock Accelerated Gas Water Interface

2001 ◽  
Author(s):  
Xiao-Liang Wang ◽  
Motoyuki Itoh
Keyword(s):  
Shock Wave ◽  
High Speed ◽  
Taylor Instability ◽  
Gravitational Acceleration ◽  
Water Interface ◽  
Wave Impact ◽  
Growth Coefficient ◽  
Video Images ◽  
Rayleigh Taylor Instability ◽  
Interfacial Plane

Abstract Rayleigh-Taylor instability at a gas-water interface has been investigated experimentally. Such instability was produced by accelerating a water column down a vertical circular tube employing shock wave impact. Accelerations from 50 to 100 times gravitational acceleration with fluid depths from 125 to 250 mm were studied. The resulting instability from small amplitude random perturbations was recorded and later analyzed using high-speed video images. Cavity formation was observed in the middle of the gas-water interface soon after the shock wave impact; bubbles and spikes then developed across the rest of the interfacial plane. Measurements of the growth coefficient of the bubbles and spikes show that they are nearly constant over different runs.

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