Velocity Fluctuations at the Walls of a Packed Bed of Spheres for Medium Re-Numbers

1987 ◽  
Vol 109 (3) ◽  
pp. 242-247 ◽  
Author(s):  
R. H. Bahnen ◽  
C. G. Stojanoff
Keyword(s):  
Velocity Component ◽  
Laser Doppler Velocimetry ◽  
Convex Surface ◽  
Packed Bed ◽  
Experimental Results ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Cylindrical Container ◽  
Velocity Fluctuations ◽  
Different Diameters

A packed bed which is uniformly filled with equally large spheres is subjected to transpiration flow. The velocity component perpendicular to its surface was measured by means of Laser-Doppler-Velocimetry. Special attention is paid to the velocity fluctuations occurring at the wall of the cylindrical container and at the convex surface of rods of different diameters inserted in the bed center. The Re-numbers were between 800 and 1500. The experimental results are compared with results obtained from the literature.

scholarly journals Laser doppler velocimetry and confined flows

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 825-836
Author(s):  
Jelena Ilic ◽  
Slavica Ristic ◽  
Milesa Sreckovic
Keyword(s):  
Velocity Component ◽  
Laser Doppler Velocimetry ◽  
Focal Length ◽  
Cylindrical Tube ◽  
Laser Doppler ◽  
Doppler Velocimetry ◽  
Focal Length Lens ◽  
Cylindrical Tubes ◽  
Set Up ◽  
Confined Flows

Finding the mode, in which two component laser Doppler velocimetry can be applied to flows confined in cylindrical tubes or vessels, was the aim of this study. We have identified principle issues that influence the propagation of laser beams in laser Doppler velocimetry system, applied to flow confined in cylindrical tube. Among them, the most important are influences of fluid and wall refractive indices, wall thickness and internal radius ratio and beam intersection angle. In analysis of the degrees of these influences, we have applied mathematical model, based on geometrical optics. The separation of measurement volumes, that measure different velocity components, has been recognized as the main drawback. To overcome this, we propose a lens with dual focal length ? primary focal length for the measurement of one velocity component and secondary focal length for the measurement of the other velocity component. We present here the procedure for calculating the optimal value of secondary focal length, depending on experimental set-up parameters. The mathematical simulation of the application of the dual focal length lens, for chosen cases presented here, confirmed the accuracy of the proposed procedure.

scholarly journals Investigation of Internal Flow in Centrifugal Pump Diffuser using Laser Doppler Velocimetry (LDV) and Computational Fluid Dynamics

2021 ◽  
Vol 1909 (1) ◽  
pp. 012075
Author(s):  
Daisuke Sugiyama ◽  
Asuma Ichinose ◽  
Tomoki Takeda ◽  
Kazuyoshi Miyagawa ◽  
Hideyo Negishi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Centrifugal Pump ◽  
Laser Doppler Velocimetry ◽  
Internal Flow ◽  
Laser Doppler ◽  
Doppler Velocimetry

scholarly journals Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

2001 ◽  
Vol 7 (3) ◽  
pp. 173-181
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen
Keyword(s):  
Flow Rate ◽  
Turbulence Intensity ◽  
Laser Doppler Velocimetry ◽  
Reverse Flow ◽  
Flow Region ◽  
Design Flow ◽  
Laser Doppler ◽  
Centrifugal Fan ◽  
Doppler Velocimetry ◽  
Flow Rates

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Sign in / Sign up

Export Citation Format

Share Document