The onset of turbulence in physiological pulsatile flow in a straight tube

The frequency response of surface-mounted electrochemical mass transfer probes used to deduce wall shear rates has been investigated experimentally for the case of fully developed laminar pulsatile flow in a straight tube. Generally good agreement is found with the asymptotic results obtained by Lighthill’s methods. The significance of the results with regard to the investigation of models of pulsatile flows of physiological interest is discussed. It is concluded that the frequency-dependent phase and amplitude corrections required to obtain accurate wall shear measurements are of such magnitudes as to render impractical the use of electrochemical probes to determine wall shear rates in these flows.

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Visualization of velocity profile in pulsatile flow through straight tube using laser-induced fluorescence method.

JOURNAL OF THE FLOW VISUALIZATION SOCIETY OF JAPAN ◽

10.3154/jvs1981.8.353 ◽

1988 ◽

Vol 8 (30) ◽

pp. 353-356

Author(s):

S. Sakaguchi ◽

K. Ohba ◽

A. Sakurai

Keyword(s):

Velocity Profile ◽

Pulsatile Flow ◽

Laser Induced Fluorescence ◽

Fluorescence Method ◽

Straight Tube ◽

Flow Through

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Pulsatile Flow Into a 45-Degree Tube Bifurcation

10.1115/imece2001/fed-24947 ◽

2001 ◽

Author(s):

M. Tadjfar ◽

R. Himeno

Keyword(s):

Pulsatile Flow ◽

Coming Out ◽

Stokes Equations ◽

Reverse Flow ◽

Periodic Flow ◽

Straight Tube ◽

Tube Flow ◽

Forward Flow ◽

Flow Part ◽

Mother Tube

Abstract In this study, we use numerical simulation to investigate the pulsatile flow into a 45°-tube bifurcation. There is a well-known analytical solution for the pulsatile flow in a straight pipe. However, to study the pulsatile flow into a branched pipe only numerical solution or experimental techniques are available. The unsteady, three-dimensional, incompressible Navier-Stokes equations are solved using a finite volume solver. A time periodic flow is established. As compared to the straight tube flow case, it is found that the introduction of bifurcation changes the periodic flow structure upstream and downstream of the bifurcation. The periodic flow in the forward flow and the reverse flow part of the cycle are very different. The forward flow part of the cycle is a problem of splitting the mother tube flow into the two daughter tubes. The reverse flow part of the cycle is the problem of two jets coming out of the daughter tubes mixing in the mother tube chamber.

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Unsteady Entrance Flow Development in a Straight Tube

Journal of Biomechanical Engineering ◽

10.1115/1.2895742 ◽

1994 ◽

Vol 116 (3) ◽

pp. 355-360 ◽

Cited By ~ 39

Author(s):

Xiaoyi He ◽

David N. Ku

Keyword(s):

Pulsatile Flow ◽

Arterial System ◽

Length Variation ◽

Straight Tube ◽

Phase Lag ◽

Entrance Length ◽

Flow Waveform ◽

Mean Flow ◽

Inlet Flow ◽

Entrance Flow

The entrance conditions for pulsatile flow are important in the understanding blood flow out of the heart and in developing regions at branches. The pulsatile entrance flow was solved using a spectral element simulation of the full unsteady Navier- Stokes equations. A mean Reynolds number of 200 and a range of Womersley parameters from 1.8 to 12.5 was used for a sinusoidal inlet flow waveform 1+sin (ωt). Variations in the entrance length were observed during the pulsatile cycle. The amplitude of the entrance length variation decreased with an increase in the Womersley parameter. The phase lag between the entrance length and the inlet flow waveform increased for Womersley parameter α up to 5.0 and decreased for α larger than 5.0. For low α, the maximum entrance length during pulsatile flow was approximately the same as the steady entrance length for the peak flow. For high α, the pulsatile entrance length was more uniform during the cycle and tended to the entrance length for the mean flow. The wall shear rate reached its far downstream value after only about half of the entrance length and also exhibited a dependence on α. The results quantify the entrance conditions typically encountered in studies of the arterial system.

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Flush-Mounted Hot Film Anemometer Accuracy in Pulsatile Flow

Journal of Biomechanical Engineering ◽

10.1115/1.3138607 ◽

1986 ◽

Vol 108 (3) ◽

pp. 228-231 ◽

Cited By ~ 7

Author(s):

S. Nandy ◽

J. M. Tarbell

Keyword(s):

Shear Stress ◽

Wall Shear Stress ◽

Pulsatile Flow ◽

Straight Tube ◽

Average Deviation ◽

Pulsatile Flows ◽

Measured Flow ◽

Wall Shear ◽

Hot Film ◽

Low Shear

The accuracy of a flush-mounted hot film anemometer probe for wall shear stress measurements in physiological pulsatile flows was evaluated in fully developed pulsatile flow in a rigid straight tube. Measured wall shear stress waveform based on steady flow anemometer probe calibrations were compared to theoretical wall shear stress waveforms based on well-established theory and measured flow rate waveforms. The measured and theoretical waveforms were in close agreement during systole (average deviation of 14 percent at peak systole). As expected, agreement was poor during diastole because of flow reversal and diminished frequency response at low shear rate.

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