Visualization of Pressure Field in Turbulent Wake Between Two Bluff Bodies

2003 ◽  
Author(s):  
Norihiko Tokai
Keyword(s):  
Pressure Field ◽  
Normal Component ◽  
Turbulent Wake ◽  
Turbulence Structure ◽  
Bluff Bodies ◽  
Velocity Data ◽  
Rectangular Cylinder ◽  
Piv Measurement ◽  
Instantaneous Pressure ◽  
Velocity Pressure

An experimental method to visualize the instantaneous pressure field in turbulent flow has been proposed. Numerical solution of the discrete Poisson equation for pressure was sought, where the instantaneous velocity data was supplied by PIV measurement. The validity of the method was assessed by referring to available DNS data for wake of a rectangular cylinder. The method was applied to evaluate the instantaneous pressure distribution in the region between two columns set in tandem in uniform flow. It is shown that the correlation between fluctuating velocity and pressure gradient plays an important role in determining the turbulence structure in the wake, which is indicated by the fact that the normal component of Reynolds stress in front of the column set in the wake of another is extremely large where the velocity-pressure correlation overtakes the production rate.

717 Instantaneous pressure field evaluation based on the PIV measurement

2000 ◽  
Vol 2000.6 (0) ◽  
pp. 183-184
Author(s):  
Teruaki HONBO ◽  
Shinnosuke OBI ◽  
Shigeaki MASUDA
Keyword(s):  
Pressure Field ◽  
Field Evaluation ◽  
Piv Measurement ◽  
Instantaneous Pressure

scholarly journals Reconstruction of the 3D pressure field and energy dissipation of a Taylor droplet from a $$\upmu$$PIV measurement

2021 ◽  
Vol 62 (4) ◽  
Author(s):  
Ulrich Mießner ◽  
Thorben Helmers ◽  
Ralph Lindken ◽  
Jerry Westerweel
Keyword(s):  
Energy Dissipation ◽  
Pressure Gradient ◽  
Pressure Field ◽  
Estimation Method ◽  
Dissipated Energy ◽  
Spatial Integration ◽  
Mean Flow ◽  
Bypass Flow ◽  
Taylor Flow ◽  
Piv Measurement

Abstract In this study, we reconstruct the 3D pressure field and derive the 3D contributions of the energy dissipation from a 3D3C velocity field measurement of Taylor droplets moving in a horizontal microchannel ($$\rm Ca_c=0.0050$$ Ca c = 0.0050 , $$\rm Re_c=0.0519$$ Re c = 0.0519 , $$\rm Bo=0.0043$$ Bo = 0.0043 , $$\lambda =\tfrac{\eta _{d}}{\eta _{c}}=2.625$$ λ = η d η c = 2.625 ). We divide the pressure field in a wall-proximate part and a core-flow to describe the phenomenology. At the wall, the pressure decreases expectedly in downstream direction. In contrast, we find a reversed pressure gradient in the core of the flow that drives the bypass flow of continuous phase through the corners (gutters) and causes the Taylor droplet’s relative velocity between the faster droplet flow and the slower mean flow. Based on the pressure field, we quantify the driving pressure gradient of the bypass flow and verify a simple estimation method: the geometry of the gutter entrances delivers a Laplace pressure difference. As a direct measure for the viscous dissipation, we calculate the 3D distribution of work done on the flow elements, that is necessary to maintain the stationarity of the Taylor flow. The spatial integration of this distribution provides the overall dissipated energy and allows to identify and quantify different contributions from the individual fluid phases, from the wall-proximate layer and from the flow redirection due to presence of the droplet interface. For the first time, we provide deep insight into the 3D pressure field and the distribution of the energy dissipation in the Taylor flow based on experimentally acquired 3D3C velocity data. We provide the 3D pressure field of and the 3D distribution of work as supplementary material to enable a benchmark for CFD and numerical simulations. Graphical abstract

The diastolic flow velocity-pressure gradient relation and dpv50 to assess the hemodynamic significance of coronary stenoses

2006 ◽  
Vol 291 (6) ◽  
pp. H2630-H2635 ◽  
Author(s):  
Koen M. J. Marques ◽  
Machiel J. van Eenige ◽  
Hugo J. Spruijt ◽  
Nico Westerhof ◽  
Jos Twisk ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flow Velocity ◽  
Stress Testing ◽  
Coronary Vessels ◽  
Velocity Data ◽  
Severe Stenosis ◽  
Coronary Pressure ◽  
Coronary Stenoses ◽  
Sensitivity Specificity ◽  
Velocity Pressure

To evaluate the hemodynamic impact of coronary stenoses, the fractional (FFR) or coronary flow velocity reserve (CFVR) usually is measured. The combined measurement of instantaneous flow velocity and pressure gradient (v-dp relation) is rarely used in humans. We derived from the v-dp relation a new index, dpv50 (pressure gradient at flow velocity of 50 cm/s), and compared the diagnostic performance of dpv50, CFVR, and FFR. Before coronary angiography was performed, patients underwent noninvasive stress testing. In all coronary vessels with an intermediate or severe stenosis, the flow velocity, aortic, and distal coronary pressure were measured simultaneously with a Doppler and pressure guidewire after induction of hyperemia. After regression analysis of all middiastolic flow velocity and pressure gradient data, the dpv50 was calculated. With the use of the results of noninvasive stress testing, the dpv50 cutoff value was established at 22.4 mmHg. In 77 patients, 124 coronary vessels with a mean 39% (SD 19) diameter stenosis were analyzed. In 43 stenoses, ischemia was detected. We found a sensitivity, specificity, and accuracy of 56%, 86%, and 76% for CFVR; 77%, 99%, and 91% for FFR; and 95%, 95%, and 95% for dpv50. To establish that dpv50 is not dependent on maximal hyperemia, dpv50 was recalculated after omission of the highest quartile of flow velocity data, showing a difference of 3%. We found that dpv50 provided the highest sensitivity and accuracy compared with FFR and CFVR in the assessment of coronary stenoses. In contrast to CFVR and FFR, assessment of dpv50 is not dependent on maximal hyperemia.

Turbulent Wake of Rectangular Cylinder Near Plane Wall and Free Surface

AIAA Journal ◽  
2008 ◽  
Vol 46 (1) ◽  
pp. 104-117 ◽  
Author(s):  
M. Agelinchaab ◽  
J. M. Tsikata ◽  
M. F. Tachie ◽  
K. K. Adane
Keyword(s):  
Free Surface ◽  
Turbulent Wake ◽  
Plane Wall ◽  
Rectangular Cylinder

scholarly journals Instantaneous fluid force acting on a circular cylinder control by a small rod

2018 ◽  
Vol 180 ◽  
pp. 02110
Author(s):  
Takayuki Tsutsui
Keyword(s):  
Flow Control ◽  
Bluff Body ◽  
Pressure Field ◽  
Control Methods ◽  
Fluid Force ◽  
Separated Shear Layer ◽  
Instantaneous Pressure ◽  
Flow Visualizations ◽  
Bluff Body Flow ◽  
Layer Control

Two unique bluff body flow control methods using a small rod have been proposed in previous studies. The first is the forced reattachment method, which is a type of separated shear layer control. This method reduces drag and generates a lift. The second is the front rod method, which involves the placement of a small rod upstream of the bluff body to control the incoming flow and reduce drag. This paper describes the features of the instantaneous fluid force achieved using these flow control methods. These methods were experimentally applied to a cylinder, and the instantaneous pressure field and the flow visualizations of these methods are presented. When the forced reattachment method was applied, a lift force was generated, and the vibration was less than that in the case of the front rod method. When the front rod method was applied, the drag force was reduced by over 50% in comparison with those in the uncontrolled case and the case with the forced reattachment method.

scholarly journals Evaluation of Pressure Field around a Sauare Cylinder from PIV Measurement

2009 ◽  
Vol 29-1 (1) ◽  
pp. 199-199
Author(s):  
Masayoshi OKAMIYA ◽  
Takayuki YAMAGATA ◽  
Nobuyuki FUJISAWA ◽  
Toshiyuki HAYASE
Keyword(s):  
Pressure Field ◽  
Piv Measurement

M1007 Evaluation of Pressure Field based on PIV Measurement in a Channel Flow with Square Cylinder

2015 ◽  
Vol 2015.90 (0) ◽  
pp. 396
Author(s):  
Takahiro KAMIWAKI ◽  
Keita IJIRO ◽  
Mamoru SENDA ◽  
Kyoji INAOKA
Keyword(s):  
Channel Flow ◽  
Pressure Field ◽  
Square Cylinder ◽  
Piv Measurement
Sign in / Sign up

Export Citation Format

Share Document