Color Doppler Velocity Measurements Compared with Laser Doppler Anemometry Under Pulsatile Flow Conditions

1999 ◽  
Vol 27 (4) ◽  
pp. 255-266 ◽  
Author(s):  
C. J. Weigand ◽  
D. W. Liepsch
Keyword(s):  
Pulsatile Flow ◽  
Laser Doppler Anemometry ◽  
Color Doppler ◽  
Laser Doppler ◽  
Doppler Velocity ◽  
Flow Conditions ◽  
Velocity Measurements

Instantaneous diastolic transmitral pressure differences from color Doppler M mode echocardiography

1996 ◽  
Vol 271 (4) ◽  
pp. H1267-H1276 ◽  
Author(s):  
N. L. Greenberg ◽  
P. M. Vandervoort ◽  
J. D. Thomas
Keyword(s):  
Pressure Difference ◽  
Continuous Wave ◽  
Color Doppler ◽  
Digital Processing ◽  
Left Ventricular ◽  
Filling Pressure ◽  
Diastolic Filling ◽  
Doppler Velocity ◽  
Inertial Forces ◽  
Velocity Measurements

Pulsed and continuous wave Doppler velocity measurements are routinely used in clinical practice to assess severity of stenotic and regurgitant valves or to estimate intracavitary pressures. However, this method only evaluates the convective component of the pressure gradient (based on the velocity measurements) and neglects the contribution of inertial forces that can be important, in particular for flow across nonstenotic valves. Digital processing of color Doppler ultrasound data was used to noninvasively estimate both the convective and inertial components of the transmitral pressure difference. Simultaneous pressure and velocity measurements were obtained in six anesthetized open-chest dogs. The instantaneous diastolic transmitral pressure difference is computed from the M mode spatiotemporal velocity distribution using the unsteady flow form of the Bernoulli equation. The inclusion of the inertial forces ([delta PI]max = 0.90 +/- 0.30 mmHg) in the noninvasive pressure difference calculation significantly increased the correlation with catheter-based measurement (r = 0.15 +/- 0.23 vs. 0.85 +/- 0.08; P < 0.0001) and also allowed an accurate approximation of the peak early filling pressure difference ([delta PC+I]max = 0.95[delta Pcath]max + 0.07, r = 0.92, P < 0.001, error: epsilon C+I ([delta PC+I]max-[delta Pcath]max) = 0.01 +/- 0.24 mmHg, N = 90]. Noninvasive estimation of left ventricular filling pressure differences using this technique will improve the understanding of diastolic filling and function of the heart.

scholarly journals Laser-Doppler measurements on a round turbulent jet in dilute polymer solutions

1973 ◽  
Vol 60 (4) ◽  
pp. 721-731 ◽  
Author(s):  
Steven J. Barker
Keyword(s):  
Polymer Solutions ◽  
Initial Conditions ◽  
Laser Doppler ◽  
Turbulent Jet ◽  
Laser Doppler Velocimeter ◽  
Doppler Velocity ◽  
Velocity Measurements ◽  
Convergent Nozzle ◽  
Round Jets ◽  
Dilute Polymer Solutions

A laser-Doppler velocimeter suitable for the measurement of mean and fluctuating flow velocities in water is described. Results of a study using this system in an axisymmetric turbulent jet of water and dilute polymer solutions are given. The laser-Doppler technique is better suited for such measurements than either Pitot tubes or heat-transfer gauges because the Doppler velocity measurements are independent of the physical properties of the fluid. Previous velocity measurements in polymer jets have suffered from the effects of the additives upon the sensors.Turbulent round jets with Reynolds numbers between 5000 and 50000 were studied. For a jet issuing from a convergent nozzle the additives were found to have no effect upon the mean axial velocity or turbulence intensity at any point in the jet. However, for a jet issuing from a long length of circular pipe, the additives reduced the centre-line velocity and increased the turbulence level in the early part of the jet. Thus the principal effect of a polymer additive upon the jet appears to result from its effect upon the initial conditions.

Highly spatially resolving laser Doppler velocity measurements of the tip clearance flow inside a hard disk drive model

2010 ◽  
Vol 50 (3) ◽  
pp. 573-586 ◽  
Author(s):  
Katsuaki Shirai ◽  
Yusuke Yaguchi ◽  
Lars Büttner ◽  
Jürgen Czarske ◽  
Shinnosuke Obi
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Tip Clearance ◽  
Laser Doppler ◽  
Doppler Velocity ◽  
Velocity Measurements ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Drive Model
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