The acceleration of solid particles subjected to cavitation nucleation

2008 ◽  
Vol 610 ◽  
pp. 157-182 ◽  
Author(s):  
BRAM M. BORKENT ◽  
MANISH ARORA ◽  
CLAUS-DIETER OHL ◽  
NICO DE JONG ◽  
MICHEL VERSLUIS ◽  
...  
Keyword(s):  
High Speed ◽  
Pressure Pulse ◽  
Particle System ◽  
Volume Growth ◽  
Solid Particles ◽  
Spherical Particles ◽  
High Speed Photography ◽  
Neck Formation ◽  
Cavitation Inception ◽  
Nucleation Sites

The cavity–particle dynamics at cavitation inception on the surface of spherical particles suspended in water and exposed to a strong tensile stress wave is experimentally studied with high-speed photography. Particles, which serve as nucleation sites for cavitation bubbles, are set into a fast translatory motion during the explosive growth of the cavity. They reach velocities of ~40 ms−1 and even higher. When the volume growth of the cavity slows down, the particle detaches from the cavity through a process of neck-breaking, and the particle is shot away. The experimental observations are simulated with (i) a spherical cavity model and (ii) with an axisymmetric boundary element method (BEM). The input for both models is a pressure pulse, which is obtained from the observed radial cavity dynamics during an individual experiment. The model then allows us to calculate the resulting particle trajectory. The cavity shapes obtained from the BEM calculations compare well with the photographs until neck formation occurs. In several cases we observed inception at two or more locations on a single particle. Moreover, after collapse of the primary cavity, a second inception was often observed. Finally, an example is presented to demonstrate the potential application of the cavity–particle system as a particle cannon, e.g. in the context of drug delivery into tissue.

Use of a liquid shock tube as a device for the study of material deformation under impulsive loading conditions

2004 ◽  
Vol 218 (1) ◽  
pp. 39-51 ◽  
Author(s):  
B W Skews ◽  
O E Kosing ◽  
R J Hattingh
Keyword(s):  
Shock Tube ◽  
Deformation Process ◽  
High Speed ◽  
Pressure Pulse ◽  
Applied Pressure ◽  
Impulsive Loading ◽  
High Speed Photography ◽  
Material Deformation ◽  
Metal Plates ◽  
Versatile Tool

The deformation of metal plates and tubes achievable through the use of liquid shock waves generated in a shock tube is studied, with reference to both free-forming and forming the metal into dies, as well as to imprinting detailed features. The process is highly controllable, in terms of the magnitude and duration of the applied pressure pulse. A projectile is fired into a liquid column producing a high-pressure liquid shock wave which impinges on the testpiece. Different projectile materials, driving pressures and impact velocities are used to alter the energy and impulse transmitted. A particular attraction of its use in a laboratory is the application of high-speed photography to the deformation process. Illustration of the application of the facility to slamming studies and to fracture of brittle materials is included. It is concluded that the techniques employed offer a useful and versatile tool for many studies of material deformation.

Interaction and Wall Corrections for the Slow Motion of Two Fluid or Solid Particles Parallel to the Axis of a Circular Cylinder through a Viscous Fluid

1980 ◽  
Vol 22 (5) ◽  
pp. 243-249 ◽  
Author(s):  
T. Greenstein
Keyword(s):  
Circular Cylinder ◽  
Solid Particle ◽  
Particle System ◽  
Slow Motion ◽  
Solid Particles ◽  
Spherical Particles ◽  
Cylinder Wall ◽  
Characteristic Distance ◽  
Direction Parallel ◽  
Drag Forces

Numerical values are provided which enable the drag force on the reference spherical fluid or solid particle, and the torque on the reference spherical solid particle, to be computed for the particular case when two spherical particles move in a direction parallel to their line of centres parallel to the axis of a circular cylinder. Results for this motion are also expressed in terms of the ratio of drag forces experienced by (1) the particle of arbitrary shape in a bounded, two particle system, and the particle in an unbounded, two particle system, and (2) the particle in a bounded, two particle system, and the particle moving alone with the same speed and orientation in the same, but unbounded, fluid. The computation furnishes the interaction and wall corrections correctly to the first-order in the ratios of characteristic particle dimension to characteristic distance of the particle from both another particle and from the cylinder wall. The axisymmetric problem was extended to the more general case where the two particles may be placed eccentrically within the cylinder and the torque was also computed. Furthermore, the two particles may be fluid droplets as well as solid particles.

scholarly journals Experimental Study on the Relationship Between Cavitation and Lift Fluctuations of S-Shaped Hydrofoil

2021 ◽  
Vol 9 ◽  
Author(s):  
Haiyu Liu ◽  
Pengcheng Lin ◽  
Fangping Tang ◽  
Ye Chen ◽  
Wenpeng Zhang ◽  
...  
Keyword(s):  
High Speed ◽  
Developmental Process ◽  
Angle Of Attack ◽  
Cavitation Number ◽  
High Speed Photography ◽  
Cloud Cavitation ◽  
Cavitation Inception ◽  
Sheet Cavitation ◽  
Hydraulic Machinery ◽  
Stall Angle

In order to study the energy loss of bi-directional hydraulic machinery under cavitation conditions, this paper uses high-speed photography combined with six-axis force and torque sensors to collect cavitating flow images and lift signals of S-shaped hydrofoils simultaneously in a cavitation tunnel. The experimental results show that the stall angle of attack of the S-shaped hydrofoil is at ±12° and that the lift characteristics are almost symmetrical about +1°. Choosing α = +6° and α = −4° with almost equal average lift for comparison, it was found that both cavitation inception and cloud cavitation inception were earlier at α = −4° than at α = +6°, and that the cavitation length at α = −4° grew significantly faster than at α = +6°. When α = +6°, the cavity around the S-shaped hydrofoil undergoes a typical cavitation stage as the cavitation number decreases: from incipient cavitation to sheet cavitation to cloud cavitation. However, when α = −4°, as the cavitation number decreases, the cavitation phase goes through a developmental process from incipient cavitation to sheet cavitation to cloud cavitation to sheet cavitation to cloud cavitation, mainly because the shape of the S-shaped hydrofoil at the negative angle of attack affects the flow of the cavity tails, which is not sufficient to form re-entrant jets that cuts off the sheet cavitation. The formation mechanism of cloud cavitation at the two different angles of attack (α = +6°、−4°) is the same, both being due to the movement of the re-entrant jet leading to the unstable shedding of sheet cavity. The fast Fourier analysis reveals that the fluctuations of the lift signals under cloud cavitation are significantly higher than those under non-cavitation, and the main frequencies of the lift signals under cloud cavitation were all twice the frequency of the cloud cavitation shedding.

scholarly journals DEM-CFD Simulation and Experiments on the Flow Characteristics of Particles in Vortex Pumps

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2444
Author(s):  
Xiongfa Gao ◽  
Weidong Shi ◽  
Ya Shi ◽  
Hao Chang ◽  
Ting Zhao
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Cfd Simulation ◽  
Flow Characteristics ◽  
Solid Particles ◽  
Experimental Results ◽  
High Speed Photography ◽  
Inlet Section ◽  
Impeller Blade ◽  
Vortex Pump

Due to their outstanding anti-clogging ability, vortex pumps have been gradually promoted and applied in recent years. However, when transporting sewage containing solids, they will still encounter problems such as partial clogging, overwork wear, etc., therefore, it is particularly important to master the flow characteristics of solid particles in the vortex pump. In this paper, the Discrete Element Model-Computational Fluid Dynamics (DEM-CFD) coupled calculation method is introduced into the numerical simulation of vortex pumps and particles with diameters of 1, 2 and 3 mm and concentrations of 1% and 5%, were subjected to numerical simulation and study of the flow characteristics of the particles, then rapeseed was used to represent solid particles in tests. It was obvious that the CFD results were in good agreement with the experimental results, whereby the high speed photography experimental results of the pump inlet section show that the experimental results are consistent with the numerical simulation results. The results show that there are three typical movement tracks of solid particles in the vortex pump: in Track A particles flow through the impeller and enter the volute by the through flow, in Track B particles go directly into the volute through the lateral cavity under the influence of circulation flow and in Track C the particles enter the impeller from the front cover end area of the impeller blade inlet and then into the volute through the back half area of blade. It can be found that the particles are mainly distributed at the back of the volute.

On the Lateral Motion of Bubbles Generated From Re-Entrant Cavities Located on Asymmetrically Structured Surfaces

2011 ◽  
Author(s):  
Naveenan Thiagarajan ◽  
Florian Kapsenberg ◽  
Vinod Narayanan ◽  
Sushil H. Bhavnani ◽  
Charles Ellis
Keyword(s):  
High Speed ◽  
High Speed Photography ◽  
Lateral Motion ◽  
Structured Surfaces ◽  
Tooth Structure ◽  
Nucleation Sites ◽  
Downstream Slope ◽  
Field Velocity ◽  
Novel Concept ◽  
Acting In Concert

This paper describes a novel concept of lateral motion of bubbles in pool boiling, which has the potential to be translated into a liquid propulsion system when used in a closed loop. The lateral motion of bubbles is achieved due to nucleation from cavities on an asymmetric saw-tooth profile created on a silicon surface. The surface modification involves etching a 3D sawtooth structure with a nominal angle of approximately 24° using gray-scale lithography. The downstream slope of each sawtooth structure features re-entrant cavity structures that act as controlled nucleation sites. The angle of the surface thus obtained causes a net imbalance of forces acting in concert on the flow field around the bubbles departing from the surface. The first part of the paper discusses the steps involved in fabricating such a heat sink with a saw-tooth structure augmented by re-entrant cavities. This is followed by description of the experimental facility used for studying the feasibility of the concept. High-speed photography in conjunction with bubble tracking is used to determine the bubble velocities. Results for a subcooled condition show substantial axial bubble velocities on the order of up to 68.5 cm/s near the cavities and a far-field velocity of up to 4 cm/s.

Holographic Interferometric Study of Heat Transfer Associated With a Single Vapor Bubble Sliding Along a Downward-Facing Heater Surface

2003 ◽  
Author(s):  
Sathish Manickam ◽  
Vijay Dhir
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Volume Growth ◽  
High Speed Photography ◽  
Heater Surface ◽  
Growth Data ◽  
Volumetric Growth ◽  
Experimental Conditions ◽  
Fringe Patterns

Heat transfer associated with a single vapor bubble sliding along a downward-facing heater surface was studied experimentally to understand the mechanisms contributing to heat transfer enhancement. Heater surface was made of polished silicon wafer of length 185 mm and width 49.5 mm. Saturated and subcooled performance fluid PF 5060 at atmospheric pressure was used as the test liquid. The heater surface was at 75° inclination to the vertical for the experiments reported here. Single vapor bubbles were generated at an artificially formed cavity at the bottom end of the heater surface. Holographic interferometry was used to obtain the temperature profile around the bubble as it slides along the heater surface near the top end of the heater plate. From the fringe patterns, the temperature gradient around the bubble interface was measured and heat transfer into or out of the bubble was computed. In addition to these experiments, the volumetric growth of the vapor bubble as it slides along the heater surface was obtained using direct high-speed photography for the same experimental conditions. Heat transfer from the wall was estimated utilizing inputs from both interferometry studies as well as the volume growth data. Results are given for a range of liquid subcoolings and wall superheats, and are compared with previously published works.

Crack divergence phenomena in tempered glass

2020 ◽  
Vol 13 (3) ◽  
pp. 115-129
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Optimal Design ◽  
High Speed ◽  
Glass Plate ◽  
Acute Angle ◽  
Divergence Angle ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Thick Glass

High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.

Experimental study of hydrodynamic effects in the inverse water hydrocarbon emulsions flow in microchannels

2016 ◽  
Vol 11 (1) ◽  
pp. 30-37 ◽  
Author(s):  
A.A. Rakhimov ◽  
A.T. Akhmetov
Keyword(s):  
High Speed ◽  
Petroleum Industry ◽  
Chemical Compounds ◽  
High Viscosity ◽  
Blocking Effect ◽  
High Speed Photography ◽  
Simple Chemical ◽  
Reported Study ◽  
Dynamic Blocking ◽  
Hydrodynamic Effects

The paper presents results of hydrodynamic and rheological studies of the inverse water hydrocarbon emulsions. The success of the application of invert emulsions in the petroleum industry due, along with the high viscosity of the emulsion, greatly exceeding the viscosity of the carrier phase, the dynamic blocking effect, which consists in the fact that the rate of flow of emulsions in capillary structures and cracks falls with time to 3-4 orders, despite the permanent pressure drop. The reported study shows an increase in viscosity with increasing concentration or dispersion of emulsion. The increase in dispersion of w/o emulsion leads to an acceleration of the onset of dynamic blocking. The use of microfluidic devices, is made by soft photolithography, along with high-speed photography (10,000 frames/s), allowed us to see in the blocking condition the deformation of the microdroplets of water in inverse emulsion prepared from simple chemical compounds.

Sign in / Sign up

Export Citation Format

Share Document