Variation of measured particle velocity distributions with distance from a finite‐size plasma

1979 ◽  
Vol 50 (4) ◽  
pp. 2684-2688 ◽  
Author(s):  
C. P. DeNeef ◽  
A. J. Theiss
Keyword(s):  
Particle Velocity ◽  
Finite Size ◽  
Measured Particle

THE ACOUSTICAL FIELD NEAR A CIRCULAR TRANSDUCER

1952 ◽  
Vol 30 (2) ◽  
pp. 119-122 ◽  
Author(s):  
E. W. Guptill ◽  
A. D. MacDonald
Keyword(s):  
Approximate Solution ◽  
Plane Wave ◽  
Wave Velocity ◽  
Particle Velocity ◽  
Near Field ◽  
Measured Particle

An approximate solution for the near field of a circular transducer is given. The results indicate that, if a similar transducer is used as a receiver, the measured particle velocity is equal to 1 + (2.70/(ka)2) times the plane wave velocity, where ka is the number of wave lengths in the perimeter of the transducer.

Sedimentation and sediment flow in settling tanks with inclined walls

1995 ◽  
Vol 290 ◽  
pp. 39-66 ◽  
Author(s):  
B. Kapoor ◽  
A. Acrivos
Keyword(s):  
Layer Thickness ◽  
Particle Velocity ◽  
Slip Velocity ◽  
Laser Doppler Anemometry ◽  
Finite Size ◽  
Velocity Profiles ◽  
Spherical Particles ◽  
Sediment Layer ◽  
Inclined Plate ◽  
Theoretical Predictions

The flow of a sediment layer that forms on an inclined plate as a consequence of the steady sedimentation of spherical particles was investigated theoretically as well as experimentally. The theoretical analysis was based on the model proposed by Nir & Acrivos (1990), modified to include shear-induced diffusion due to gradients in the shear stress as well as a slip velocity along the wall due to the finite size of the particles. The resulting set of partial differential equations, which is amenable to a similarity-type solution both near the leading edge as well as far downstream, was solved numerically using a finite difference scheme thereby yielding theoretical predictions for the particle concentration and velocity profiles, plus the local sediment layer thickness, all along the plate. In addition, a new experimental technique based on laser Doppler anemometry was developed and was used to measure the particle velocity profiles in the highly concentrated sediment layer as well as the corresponding slip coefficient which relates the slip velocity to the velocity gradient adjacent to a wall. The thickness profile of the sediment layer was also measured experimentally by means of video imaging. It was found that the experimental results thus obtained for the particle velocity profile and for the local sediment layer thickness were in very good agreement with the corresponding theoretical predictions especially considering that the latter did not make use of any adjustable parameters.

scholarly journals Sedimentation of a dilute suspension of rigid spheres at intermediate Galileo numbers: the effect of clustering upon the particle motion

2014 ◽  
Vol 752 ◽  
pp. 310-348 ◽  
Author(s):  
Markus Uhlmann ◽  
Todor Doychev
Keyword(s):  
Particle Velocity ◽  
Settling Velocity ◽  
Fluid Velocity ◽  
Voronoi Tessellation ◽  
Density Ratio ◽  
Fluid Motion ◽  
Finite Size ◽  
Vertical Motion ◽  
Average Particle ◽  
Rigid Spheres

AbstractDirect numerical simulation of the gravity-induced settling of finite-size particles in triply periodic domains has been performed under dilute conditions. For a single solid-to-fluid-density ratio of 1.5 we have considered two values of the Galileo number corresponding to steady vertical motion ($\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mathit{Ga}=121$) and to steady oblique motion ($\mathit{Ga}=178$) in the case of one isolated sphere. For the multiparticle system we observe strong particle clustering only in the latter case. The geometry and time scales related to clustering are determined from Voronoï tessellation and particle-conditioned averaging. As a consequence of clustering, the average particle settling velocity is increased by 12 % as compared with the value of an isolated sphere; such a collective effect is not observed in the non-clustering case. By defining a local (instantaneous) fluid velocity average in the vicinity of the finite-size particles it is shown that the observed enhancement of the settling velocity is due to the fact that the downward fluid motion (with respect to the global average) which is induced in the cluster regions is preferentially sampled by the particles. It is further observed that the variance of the particle velocity is strongly enhanced in the clustering case. With the aid of a decomposition of the particle velocity it is shown that this increase is due to enhanced fluid velocity fluctuations (due to clustering) in the vicinity of the particles. Finally, we discuss a possible explanation for the observation of a critical Galileo number marking the onset of clustering under dilute conditions.

The partial realization theory of finite size two-dimensional arrays

1981 ◽  
Vol 64 (10) ◽  
pp. 1-8
Author(s):  
Tsuyoshi Matsuo ◽  
Yasumichi Hasegawa ◽  
Yoshikuni Okada
Keyword(s):  
Finite Size ◽  
Two Dimensional ◽  
Realization Theory
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