scholarly journals Jet formation from bubbles near a solid boundary in a compressible liquid: Numerical study of distance dependence

2020 ◽  
Vol 5 (9) ◽  
Author(s):  
Christiane Lechner ◽  
Werner Lauterborn ◽  
Max Koch ◽  
Robert Mettin
Keyword(s):  
Numerical Study ◽  
Compressible Liquid ◽  
Solid Boundary ◽  
Jet Formation ◽  
Distance Dependence

Numerical study of jet flow generated by impact on weakly compressible liquid

2006 ◽  
Vol 18 (3) ◽  
pp. 032108 ◽  
Author(s):  
Alexander A. Korobkin ◽  
Alessandro Iafrati
Keyword(s):  
Numerical Study ◽  
Jet Flow ◽  
Compressible Liquid ◽  
Weakly Compressible

Tracer trajectories and displacement due to a micro-swimmer near a surface

2015 ◽  
Vol 773 ◽  
pp. 498-519 ◽  
Author(s):  
A. J. T. M. Mathijssen ◽  
D. O. Pushkin ◽  
J. M. Yeomans
Keyword(s):  
Particle Transport ◽  
Numerical Study ◽  
Tracer Particle ◽  
Persistence Length ◽  
Theoretical Work ◽  
Solid Boundary ◽  
Tracer Transport ◽  
Tracer Particles ◽  
Recent Theoretical Work ◽  
Run And Tumble

We study tracer particle transport due to flows created by a self-propelled micro-swimmer, such as a swimming bacterium, alga or a microscopic artificial swimmer. Recent theoretical work has shown that as a swimmer moves in the fluid bulk along an infinite straight path, tracer particles far from its path perform closed loops, whereas those close to the swimmer are entrained by its motion. However, in biologically and technologically important cases tracer transport is significantly altered for swimmers that move in a run-and-tumble fashion with a finite persistence length, and/or in the presence of a free surface or a solid boundary. Here we present a systematic analytical and numerical study exploring the resultant regimes and their crossovers. Our focus is on describing qualitative features of the tracer particle transport and developing quantitative tools for its analysis. Our work is a step towards understanding the ecological effects of flows created by swimming organisms, such as enhanced fluid mixing and biofilm formation.

Effect of Axis Ratio on Fluid Flow Around an Elliptic Cylinder—A Numerical Study

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
S. Kalyana Raman ◽  
K. Arul Prakash ◽  
S. Vengadesan
Keyword(s):  
Fluid Flow ◽  
Drag Coefficient ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Numerical Study ◽  
Elliptic Cylinder ◽  
Solid Boundary ◽  
Axis Ratio ◽  
Moderate Reynolds Number ◽  
Wake Formation

The bluff body simulations over canonical forms like circular and square cylinders are very well studied and the correlations for bulk parameters like mean drag coefficient and Strouhal numbers for the same are reported widely. In the case of elliptic cylinder, the literature is very sparse, especially for moderate Reynolds number (Re). Hence, in this work, a detailed study about fluid flow characteristics over an elliptic cylinder placed in a free stream is performed. Simulations are carried out for different Re ranging from 50 to 500 with axis ratio (AR) varied between 0.1 to 1.0 in steps of 0.1. Immersed boundary method is used for the solid boundary condition implementation which avoids the grid generation for each AR and a single Cartesian grid is used for all the simulations. The effect of AR for various Reynolds numbers is also focused on using the in-house code. The influence of AR is phenomenal for all the Re and the values of wake length, drag coefficient, and Strouhal number decrease with decreasing AR for a particular Re. The critical ARs, for vortex shedding and wake formation, are identified for various Re. Detailed correlations for wake length, critical ARs for vortex shedding and wake formation, mean drag coefficient and Strouhal number, in terms of AR, are reported in this work.

scholarly journals Early-time free-surface flow driven by a deforming boundary

2015 ◽  
Vol 767 ◽  
pp. 811-841 ◽  
Author(s):  
C. Frederik Brasz ◽  
Craig B. Arnold ◽  
Howard A. Stone ◽  
John R. Lister
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Liquid Layer ◽  
Early Time ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Solid Boundary ◽  
Jet Formation ◽  
Domain Perturbation ◽  
Quiescent Liquid

AbstractWhen a solid boundary deforms rapidly into a quiescent liquid layer, a flow is induced that can lead to jet formation. An asymptotic analytical solution is presented for this flow, driven by a solid boundary deforming with dimensionless vertical velocity $V_{b}(x,t)={\it\epsilon}(1+\cos x)\,f(t)$, where the amplitude ${\it\epsilon}$ is small relative to the wavelength and the time dependence $f(t)$ approaches 0 for large $t$. Initially, the flow is directed outwards from the crest of the deformation and slows with the slowing of the boundary motion. A domain-perturbation method is used to reveal that, when the boundary stops moving, nonlinear interactions with the free surface leave a remnant momentum directed back towards the crest, and this momentum can be a precursor to jet formation. This scenario arises in a laser-induced printing technique in which an expanding blister imparts momentum into a liquid film to form a jet. The analysis provides insight into the physics underlying the interaction between the deforming boundary and free surface, in particular, the dependence of the remnant flow on the thickness of the liquid layer and the deformation amplitude and wavelength. Numerical simulations are used to show the range of validity of the analytical results, and the domain-perturbation solution is extended to an axisymmetric domain with a Gaussian boundary deformation to compare with previous numerical simulations of blister-actuated laser-induced forward transfer.

Critical microjets in collapsing cavities

1995 ◽  
Vol 290 ◽  
pp. 183-201 ◽  
Author(s):  
Michael S. Longuet-Higgins ◽  
Hasan Oguz
Keyword(s):  
Flow Field ◽  
Spherical Harmonic ◽  
Velocity Potential ◽  
Initial Conditions ◽  
Numerical Study ◽  
Critical Flow ◽  
Jet Formation ◽  
Initial Flow ◽  
The Family ◽  
Self Similar

Inward microjets are commonly observed in collapsing cavities, but here we show that jets with exceptionally high velocities and accelerations occur in certain critical flows dividing jet formation from bubble pinch-off. An example of the phenomenon occurs in the family of flows which evolve from a certain class of initial conditions: the initial flow field is that due to a moving point sink within the cavity.A numerical study of the critical flow shows that in the neighbourhood of microjet formation the flow is self-similar. The local accelerations, velocities and distances scale as tβ-2, tβ-1 and tβ respectively, where β = 0.575. The velocity potential is approximately a spherical harmonic of degree ¼.

A Criterion for the Formation of Micro Synthetic Jets

2004 ◽  
Author(s):  
V. Timchenko ◽  
J. Reizes ◽  
E. Leonardi ◽  
G. de Vahl Davis
Keyword(s):  
Numerical Study ◽  
Reynolds Numbers ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Frequency Range ◽  
Jet Formation ◽  
Synthetic Jet Actuator ◽  
Computational Data ◽  
Flow Device ◽  
New Criterion

A synthetic jet actuator is a zero net mass flow device, which under appropriate conditions generates a continuous jet always directed away from the orifice. Because of limited experimental and computational data on micro-sized jets, there is a need for a criterion to determine the onset of the sustained jet regime. A numerical study of axisymmetric micro synthetic jets for a frequency range from 250 to 50,000 Hz, orifice diameters range from 20 to 200 μm, and Reynolds numbers from 6.5 to 35 has been performed in order to identify a general jet formation criterion. The parametric study has allowed us to develop a new criterion for the onset of micro synthetic jets with Stokes numbers less than 7.

scholarly journals Numerical study of coronal plasma jet formation

2021 ◽  
Vol 28 (1) ◽  
pp. 012901
Author(s):  
J. Latham ◽  
E. V. Belova ◽  
M. Yamada
Keyword(s):  
Numerical Study ◽  
Plasma Jet ◽  
Coronal Plasma ◽  
Jet Formation
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