Pulsating Flow in a Channel With a Backward-Facing Step

1997 ◽  
Vol 50 (11S) ◽  
pp. S232-S236
Author(s):  
Alvaro Valencia
Keyword(s):  
Vortex Breakdown ◽  
Separation Zone ◽  
Pulsating Flow ◽  
Steady Flows ◽  
Reattachment Length ◽  
Flow Conditions ◽  
Backward Facing Step ◽  
Primary Vortex ◽  
Inlet Flow ◽  
Inlet Velocity

The incompressible laminar flow in a channel with a backward-facing step is studied for steady cases and for pulsating inlet flow conditions. For steady flows, the influrnce of the inlet velocity profile, the height of the step, and the Reynolds number on the reattachment length is investigated. A parabolic entrance profile was used for pulsating flow. It was found with amplitude of oscillation of one by Re = 100 that the primary vortex breakdown through one pulsatile cycle and the wall shear stress in the separation zone varied markedly with pulsating inlet flow.

Numerical Simulation of Pulsating Flow over Blood Vessel Robot

2012 ◽  
Vol 591-593 ◽  
pp. 1734-1738
Author(s):  
Chun Yan Huang ◽  
Fan Jiang
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Blood Flow ◽  
Blood Vessel ◽  
Surface Pressure ◽  
Blood Parameters ◽  
Pulsating Flow ◽  
Inlet Velocity ◽  
Blood Density

In order to study the influence of pulsating blood flow to robot and blood vessel, UDF programming of the inlet velocity is defined as the boundary condition, and the model simulate the turbulent blood flow. Moreover, in this situation, this paper analyzes the influence caused by blood parameters for the biggest surface pressure on robot. The results are showed that the variation of pressure and velocity is different on different position at 0.08s and 0.27s, and the surface pressure of the robot become greater by the increase of blood density or viscosity.

scholarly journals Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1663 ◽  
Author(s):  
Lei Jiang ◽  
Mingjun Diao ◽  
Haomiao Sun ◽  
Yu Ren
Keyword(s):  
Numerical Simulations ◽  
Discharge Coefficient ◽  
Separation Zone ◽  
Turbulence Models ◽  
Numerical Results ◽  
Upstream Face ◽  
Flow Conditions ◽  
Flow Features ◽  
The Mean ◽  
Absolute Percent Error

The objective of this study was to evaluate the effect of the upstream angle on flow over a trapezoidal broad-crested weir based on numerical simulations using the open-source toolbox OpenFOAM. Eight trapezoidal broad-crested weir configurations with different upstream face angles (θ = 10°, 15°, 22.5°, 30°, 45°, 60°, 75°, 90°) were investigated under free-flow conditions. The volume-of-fluid (VOF) method and two turbulence models (the standard k-ε model and the SST k-w model) were employed in the numerical simulations. The numerical results were compared with the experimental results obtained from published papers. The root mean square error (RMSE) and the mean absolute percent error (MAPE) were used to evaluate the accuracy of the numerical results. The statistical results show that RMSE and MAPE values of the standard k-ε model are 0.35–0.67% and 0.50–1.48%, respectively; the RMSE and MAPE values of the SST k-w model are 0.25–0.66% and 0.55–1.41%, respectively. Additionally, the effects of the upstream face angle on the flow features, including the discharge coefficient and the flow separation zone, were also discussed in the present study.

scholarly journals Investigation of Flows in Rectangular Diffusers With Inlet Flow Distortion

1982 ◽  
Author(s):  
M. M. Al-Mudhafar ◽  
M. Ilyas ◽  
F. S. Bhinder
Keyword(s):  
Experimental Study ◽  
Velocity Profiles ◽  
Pressure Recovery ◽  
Two Dimensional ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Velocity ◽  
Inlet Distortion ◽  
Mach Numbers ◽  
Inlet Flow Distortion

The results of an experimental study on the influence of severely distorted velocity profiles on the performance of a straight two-dimensional diffuser are reported. The data cover entry Mach numbers ranging from 0.1 to 0.6 and several inlet distortion levels. The pressure recovery progressively deteriorates as the inlet velocity is distorted.

Radial Turbine Rotor Response to Pulsating Inlet Flows

2013 ◽  
Vol 136 (7) ◽  
Author(s):  
Teng Cao ◽  
Liping Xu ◽  
Mingyang Yang ◽  
Ricardo F. Martinez-Botas
Keyword(s):  
Numerical Method ◽  
Time Lag ◽  
Turbine Rotor ◽  
Pulsating Flow ◽  
Navier Stokes ◽  
Transient Effects ◽  
Flow Conditions ◽  
Radial Turbine ◽  
Reduced Frequency ◽  
Integrated Performance

The performance of automotive turbocharger turbines has long been realized to be quite different under pulsating flow conditions compared to that under the equivalent steady and quasi-steady conditions on which the conventional design concept is based. However, the mechanisms of this phenomenon are still intensively investigated nowadays. This paper presents an investigation of the response of a stand-alone rotor to inlet pulsating flow conditions by using a validated unsteady Reynolds-averaged Navier–Stokes solver (URANS). The effects of the frequency, the amplitude, and the temporal gradient of pulse waves on the instantaneous and cycle integrated performance of a radial turbine rotor in isolation were studied, decoupled from the upstream turbine volute. A numerical method was used to help gain the physical understanding of these effects. A validation of the numerical method against the experiments on a full configuration of the turbine was performed prior to the numerical tool being used in the investigation. The rotor was then taken out to be studied in isolation. The results show that the turbine rotor alone can be treated as a quasi-steady device only in terms of cycle integrated performance; however, instantaneously, the rotor behaves unsteadily, which increasingly deviates from the quasi-steady performance as the local reduced frequency of the pulsating wave is increased. This deviation is dominated by the effect of quasi-steady time lag; at higher local reduced frequency, the transient effects also become significant. Based on this study, an interpretation and a model of estimating the quasi-steady time lag have been proposed; a criterion for unsteadiness based on the temporal local reduced frequency concept is developed, which reduces to the Λ criterion proposed in the published literature when cycle averaged. This in turn emphasizes the importance of the pressure wave gradient in time.

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