Calculation of Velocity Profiles in Drag-Reducing Flows

1976 ◽  
Vol 98 (3) ◽  
pp. 563-566 ◽  
Author(s):  
W. G. Tiederman ◽  
M. M. Reischman
Keyword(s):  
Pressure Drop ◽  
Excellent Agreement ◽  
Flow Rate ◽  
Eddy Diffusivity ◽  
Velocity Profiles ◽  
Calculation Procedure ◽  
Mean Velocity ◽  
Drop Flow

A calculation procedure for predicting mean velocity profiles in drag-reducing flows is presented. The procedure is based upon the eddy diffusivity model of Cess and it requires only pressure drop, flow rate and geometry information. The predictions show excellent agreement with experimentally measured profiles in both Newtonian and drag-reducing flows.

Fractal Orifices for Flowmetering

2012 ◽  
Author(s):  
Franck C. G. A. Nicolleau ◽  
Stephen B. M. Beck ◽  
Andrzej F. Nowakowski
Keyword(s):  
Wind Tunnel ◽  
Flow Rate ◽  
Velocity Profiles ◽  
Symmetric Design ◽  
Flow Properties ◽  
Mean Velocity ◽  
Fractal Pattern ◽  
The Mean

In this article we study the return to axi-symmetry for a flow generated after fractal plates in a circular wind tunnel. We consider two sets of plates: one orifice-like and one perforated-like. The mean velocity profiles are presented at different distances from the plate and we study the convergence of a flow rate based on these profiles. The return to axi-symmetry depends on how far was the original plate from an axi-symmetric design. It also depends on the level of iteration of the fractal pattern. In line with results for other flow properties [1, 2] It seems that there is not much to be gained by manufacturing fractal plates with more than three iteration levels.

scholarly journals Assessment of Different Pressure Drop-Flow Rate Equations in a Pressurized Porous Media Filter for Irrigation Systems

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2179
Author(s):  
Jonathan Graciano-Uribe ◽  
Toni Pujol ◽  
Jaume Puig-Bargués ◽  
Miquel Duran-Ros ◽  
Gerard Arbat ◽  
...  
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Silica Sand ◽  
Rate Equations ◽  
Uncertainty Range ◽  
Head Losses ◽  
Computational Fluid Dynamics Cfd ◽  
Drop Flow

The small open area available at the slots of underdrains in pressurized granular bed filters for drip irrigation implies: (1) the existence of a region with non-uniform flow, and (2) local values of modified particle Reynolds number >500. These flow conditions may disagree with those accepted as valid for common pressure drop-flow rate correlations proposed for packed beds. Here, we carried out detailed computational fluid dynamics (CFD) simulations of a laboratory filter to analyze the results obtained with five different equations of head losses in porous media: (1) Ergun, (2) Darcy-Forchheimer, (3) Darcy, (4) Kozeny-Carman and (5) power function. Simulations were compared with experimental data at different superficial velocities obtained from previous studies. Results for two silica sand media indicated that all equations predicted total filter pressure drop values within the experimental uncertainty range when superficial velocities <38.3 m h−1. At higher flow rates, Ergun equation approximated the best to the observed results for silica sand media, being the expression recommended. A simple analytical model of the pressure drop along flow streamlines that matched CFD simulation results was developed.

Fluid Dynamics of a Partially Collapsible Stenosis in a Flow Model of the Coronary Circulation

1996 ◽  
Vol 118 (4) ◽  
pp. 489-497 ◽  
Author(s):  
Maria Siebes ◽  
Charles S. Campbell ◽  
David Z. D’Argenio
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Coronary Circulation ◽  
Intraluminal Pressure ◽  
Dimensional Changes ◽  
Area Reduction ◽  
Stenosis Severity ◽  
Flexible Wall ◽  
Drop Flow

The influence of passive vasomotion on the pressure drop-flow (ΔP-Q) characteristics of a partially compliant stenosis was studied in an in vitro model of the coronary circulation. Twelve stenosis models of different severities (50 to 90 percent area reduction) and degrees of flexible wall (0 to 1/2 of the wall circumference) were inserted into thin-walled latex tubing and pressure and flow data were collected during simulated cardiac cycles. In general, the pressure drop increased with increasing fraction of flexible wall for a given flow rate and stenosis severity. The magnitude of this effect was directly dependent upon the underlying stenosis severity. The diastolic ΔP-Q relationship of severe, compliant models exhibited features of partial collapse with an increase in pressure drop at a decreasing flow rate. It is concluded that passive vasomotion of a normal wall segment at an eccentric stenosis in response to periodic changes in intraluminal pressure causes dimensional changes in the residual lumen area which can strongly affect the hemodynamic characteristics of the stenosis during the cardiac cycle. This mechanism may have important implications for the onset of plaque fracture and the prediction of the functional significance of a coronary stenosis based on quantitative angiogram analysis.

A Constitutive Equation for Extensional-Thickening Fluids Flowing Through Porous Media

2002 ◽  
Author(s):  
Paulo R. Souza Mendes ◽  
Moˆnica F. Naccache
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Constitutive Equation ◽  
Flow Rate ◽  
Pore Channel ◽  
Pressure Gradients ◽  
Rate Relationship ◽  
Liquid Behavior ◽  
The One ◽  
Drop Flow

A constitutive relation between the pressure gradient and the seepage velocity has been developed that carries information about the liquid behavior on extension. The relation was developed in two steps. Firstly the pressure drop/flow rate relationship for an ideal pore channel was obtained. Then a capillaric model theory was applied to obtain the sought-for constitutive equation. The proposed relation was validated comparing pressure drop/flow rate results with experimental data obtained in a geometry similar to the one used in the theoretical model. Also, some comparisons with experimental data for a M1 Boger fluid flowing in a model porous medium were performed. The results showed that the proposed relation has good predictions capabilities in a representative range of pressure gradients.

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