Dynamics of entrapped air bubble during impact of high-velocity molten droplet on a solid substrate

2018 ◽  
Author(s):  
Digvijay Singh ◽  
Rajesh Kumar Shukla ◽  
Arvind Kumar
Keyword(s):  
High Velocity ◽  
Solid Substrate ◽  
Molten Droplet ◽  
Air Bubble ◽  
Entrapped Air

Modeling the impact, flattening and solidification of a molten droplet on a solid substrate during plasma spraying

2014 ◽  
Vol 317 ◽  
pp. 526-533 ◽  
Author(s):  
Y.Z. Zheng ◽  
Q. Li ◽  
Z.H. Zheng ◽  
J.F. Zhu ◽  
P.L. Cao
Keyword(s):  
Plasma Spraying ◽  
Solid Substrate ◽  
Molten Droplet ◽  
The Impact

Simulation of Air Entrapment by a Plunging Liquid Jet of Finite Length

Volume 1 ◽  
2004 ◽  
Author(s):  
Paul S. Krueger ◽  
Razvan Bidoae ◽  
Peter E. Raad
Keyword(s):  
Finite Length ◽  
Liquid Jet ◽  
Air Entrapment ◽  
Air Bubble ◽  
Pool Surface ◽  
Air Volume ◽  
Large Pool ◽  
Vorticity Generation ◽  
Simulation Results ◽  
Entrapped Air

The impingement of a finite length round water jet on a large pool of water was simulated numerically using a 3D Eulerian-Lagrangian Marker and Micro-Cell (ELMMC) method. The method allowed simulation of the initial impact of the jet on the pool surface, the deformation of the pool surface by the falling jet, and, under certain conditions, the entrapment of an air bubble as the pool closes in on the jet. The conditions considered were for ratios of jet length to radius (h/r) in the range of 4 to 25 and jet Froude number in the range of 16 to 74. The results agreed with previous experimental observations by Oguz et al. (J. Fluid Mech., 294, 1995) in terms of entrapped air volume and the possible geometries of entrapped bubbles (viz., toroidal or spheroidal). The simulation results also allowed for a detailed study of effects difficult to discern experimentally, such as vorticity generation and differences in entrapped air volume between toroidal and spheroidal bubbles.

scholarly journals High-speed X-ray imaging of a ball impacting on loose sand

2015 ◽  
Vol 777 ◽  
pp. 690-706 ◽  
Author(s):  
Tess Homan ◽  
Rob Mudde ◽  
Detlef Lohse ◽  
Devaraj van der Meer
Keyword(s):  
High Speed ◽  
Packing Fraction ◽  
Loose Sand ◽  
X Ray ◽  
Air Bubble ◽  
Cavity Collapse ◽  
X Ray Imaging ◽  
Custom Made ◽  
Set Up ◽  
Entrapped Air

When a ball is dropped in fine very loose sand, a splash and subsequently a jet are observed above the bed, followed by a granular eruption. To directly and quantitatively determine what happens inside the sand bed, high-speed X-ray tomography measurements are carried out in a custom-made set-up that allows for imaging of a large sand bed at atmospheric pressures. Herewith, we show that the jet originates from the pinch-off point created by the collapse of the air cavity formed behind the penetrating ball. Subsequently, we measure how the entrapped air bubble rises through the sand, and show that this is consistent with bubbles rising in continuously fluidized beds. Finally, we measure the packing fraction variation throughout the bed. From this we show that there is (i) a compressed area of sand in front of and next to the ball while the ball is moving down, (ii) a strongly compacted region at the pinch-off height after the cavity collapse and (iii) a relatively loosely packed centre in the wake of the rising bubble.

Impulsive Plunging Wave Breaking Downstream of a Bump in a Shallow Water Flume

2010 ◽  
Author(s):  
Bonguk Koo ◽  
Zhaoyuan Wang ◽  
Jianming Yang ◽  
Donghoon Kang ◽  
Frederick Stern
Keyword(s):  
Shallow Water ◽  
Wave Breaking ◽  
Breaking Wave ◽  
Maximum Height ◽  
Mean Flow ◽  
Fine Grid ◽  
Air Bubble ◽  
Jet Impact ◽  
Entrapped Air ◽  
Plunging Wave Breaking

The plunging wave-breaking process for impulsive flow over a bump in a shallow water flume is described using complementary experiments and simulations, which is relevant to ship hydrodynamics since it includes effect of wave-body interactions and wave breaking direction is opposite to the mean flow. Phase averaged measurements (relative to the time at which the maximum wave height is reached just before the first plunge) are conducted, including the overall flume flow and 2D PIV center-plane velocities and turbulence inside the plunging breaking wave and bottom pressures under the breaking wave. A total number of 226 individual plunging wave-breaking tests were conducted, which all followed a similar time line consisting of startup, steep wave formation, plunging wave, and chaotic wave breaking swept downstream time phases. The plunging wave breaking process consists of four repeated plunging events each with three [jet impact (plunge), oblique splash and vertical jet] sub-events, which were identified first using complementary CFD. Video images with red dye display the plunging wave breaking events and sub-events. The first and second plunges take longer than the last two plunges. Oblique splashes and vertical jets account for more time than plunging. The wave profile at maximum height, first plunge, bump and wave breaking vortex and entrapped air bubble trajectories, entrapped air bubble diameters, kinetic, potential, and total energy, and bottom pressures are analyzed. The simulations on four different grids qualitatively predict all four time phases, all four plunging events and their sub-events, and bottom pressure but with reduced velocity magnitudes and larger post-breaking water elevations. The medium grid results are presented and the fine grid simulations are in progress. Similarities and differences are discussed with the previous deep water or sloping beaches experimental and computational studies.

Entrapped Gas and Vapor Formation Influence on Surge Pressure in Liquid Pipeline Systems

2016 ◽  
Author(s):  
David Cheng ◽  
Borith Seng
Keyword(s):  
Experimental Data ◽  
Single Phase ◽  
Air Bubble ◽  
Modeling Methods ◽  
Column Separation ◽  
Design Engineers ◽  
Pipeline Systems ◽  
Entrapped Air ◽  
Pipeline Design ◽  
Vapor Formation

Predicting the effects of entrapped gas or vapor formation on surge is very important in design and operation of liquid pipelines. This paper identified the scenarios in which entrapped air and vapor formation need to be considered in pipeline operation and design. Useful modeling methods utilizing common liquid pipeline transient hydraulics software are provided. Validation of the presented methods was completed using experimental data from published literature. Examples are presented in showing the implementation of the provided modeling methods on real pipeline design scenarios. Finally, advantages and limitations of the presented methods was discussed. The methods presented in this paper enable pipeline operators and design engineers to properly estimate the complicated surge issues such as the influence of air bubble venting and column separation and collapse using commonly available single phase hydraulics tools. The operators and engineers will benefit from the provided methods in finding and validating reliable surge mitigation solutions and creating pipeline design with higher integrity level. The paper also presents the limitation of the methods and continuous improvements that can be achieved in the future.

scholarly journals Observations of internal flow inside an evaporating nanofluid sessile droplet in the presence of an entrapped air bubble

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Dong Hwan Shin ◽  
Jeffrey S. Allen ◽  
Seong Hyuk Lee ◽  
Chang Kyoung Choi
Keyword(s):  
Internal Flow ◽  
Sessile Droplet ◽  
Air Bubble ◽  
Entrapped Air

Numerical Simulation of Molten Metal Droplet Impinging in Uniform Droplet Spray Rapid Prototyping

2011 ◽  
Vol 704-705 ◽  
pp. 680-684 ◽  
Author(s):  
Feng Liang Yin ◽  
Sheng Zhu ◽  
Jian Liu ◽  
Yuan Yuan Liang
Keyword(s):  
Numerical Simulation ◽  
Surface Tension ◽  
Rapid Prototyping ◽  
Solidification Process ◽  
Solid Substrate ◽  
The Body ◽  
Molten Droplet ◽  
Uniform Droplet Spray ◽  
Droplet Spray ◽  
Uniform Droplet

A two-dimensional mathematical model has been developed to simulate the impinging and solidification process of a single droplet onto substrate in uniform droplet spray rapid prototyping. Droplet free surface is tracked by volume-of-fluid (VOF) algorithm. The effect of surface tension on the droplet is taken into consideration by means of considering surface tension to be a component of the body force. The governing equations are solved using a finite volume formulation. The calculation results predicted the final shape of a molten droplet impacting onto a solid substrate, and revealed that the solidification process began at the leading edge with the spread process of droplet. The simulation results provide insight and information not easy available from experimental. Keywords: numerical simulation, droplet, rapid prototyping

Hybrid Extrusion Force-Velocity Control Using Freeze-Form Extrusion Fabrication for Functionally Graded Material Parts

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Bradley K. Deuser ◽  
Lie Tang ◽  
Robert G. Landers ◽  
Ming C. Leu ◽  
Greg E. Hilmas
Keyword(s):  
Hybrid Control ◽  
Three Dimensional ◽  
Extrusion Process ◽  
Solid Substrate ◽  
Functionally Graded ◽  
Subzero Temperature ◽  
Extrusion Force ◽  
Air Bubble ◽  
Graded Material ◽  
Force Velocity

Freeze-form extrusion fabrication (FEF) is an additive manufacturing (AM) process that uses an aqueous-based paste loaded with ceramic or metal powder to build complex, three-dimensional parts by extruding the material from a syringe onto a solid substrate in a subzero temperature environment. This paper describes the development of an intelligent control methodology for paste extrusion that utilizes a hybrid extrusion force-velocity controller. A plunger velocity controller was used to ensure a steady extrusion flow rate, and an extrusion force controller was developed to precisely regulate the starting and stopping of the extrusion process. Both controllers were coupled with a hybrid control scheme for extrusion-on-demand and air bubble release compensation. The plunger velocity controller successfully regulated the output material composition from two syringes, and the extrusion force controller precisely controlled the extrusion start and stop. Air bubble release compensation reduced the severity of extrusion gap defects and extrusion track thinning resulting from air bubble releases. Monolithic and functionally graded parts were fabricated to illustrate the functionality of the hybrid extrusion force-velocity controller.

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