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Numerical study of effects of pulsatile amplitude for transitional turbulent pulsatile flow in pipes with ring-type constrictions

โœ Scribed by T.S. Lee; Z.D. Shi


Publisher
John Wiley and Sons
Year
1999
Tongue
English
Weight
218 KB
Volume
30
Category
Article
ISSN
0271-2091

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โœฆ Synopsis


The effects of pulsatile amplitude on sinusoidal transitional turbulent flows through a rigid pipe in the vicinity of a sharp-edged mechanical ring-type constriction have been studied numerically. Pulsatile flows were studied for transitional turbulent flow with Reynolds number (Re) of the order of 10 4 , Womersley number (Nw) of the order of 50 with a corresponding Strouhal number (St) of the order of 0.04. The pulsatile flow considered is a sinusoidal flow with dimensionless amplitudes varying from 0.0 to 1.0. Transitional laminar and turbulent flow characteristics in an alternative manner within the pulsatile flow fields were observed and studied numerically. The flow characteristics were studied through the pulsatile contours of streamlines, vorticity, shear stress and isobars. It was observed that fluid accelerations tend to suppress the development of flow disturbances. All the instantaneous maximum values of turbulent kinetic energy, turbulent viscosity, turbulent shear stress are smaller during the acceleration phase when compared with those during deceleration period. Various parametric equations within a pulsatile cycle have also been formulated through numerical experimentations with different pulsatile amplitudes. In the vicinity of constrictions, the empirical relationships were obtained for the instantaneous flow rate (Q), the pressure gradient (dp/dz), the pressure loss (P loss ), the maximum velocity (V max ), the maximum vorticity (n max ), the maximum wall vorticity (n w,max ), the maximum shear stress (~m ax ) and the maximum wall shear stress (~w ,max ). Elliptic relation was observed between flow rate and pressure gradient. Quadratic relations were observed between flow rate and the pressure loss, the maximum values of shear stress, wall shear stress, turbulent kinematic energy and the turbulent viscosity. Linear relationships exist between the instantaneous flow rate and the maximum values of vorticity, wall vorticity and velocity. The time-average axial pressure gradient and the time average pressure loss across the constriction were observed to increase linearly with the pulsatile amplitude.


๐Ÿ“œ SIMILAR VOLUMES


NUMERICAL STUDY OF EFFECTS OF PULSATILE
โœ T. S. Lee; T. W. Ng; Z. D. Shi ๐Ÿ“‚ Article ๐Ÿ“… 1997 ๐Ÿ› John Wiley and Sons ๐ŸŒ English โš– 345 KB ๐Ÿ‘ 1 views

The effects of pulsatile amplitude on sinusoidal laminar flows through a rigid pipe with sharp-edged ring-type constrictions have been studied numerically. The parameters considered are: mean Reynolds number (Re) of the order of 100; Strouhal number (St) in the range 010-3198; Womersley number (Nw)

Effects of Reynolds number on physiologi
โœ T.S. Lee; Z.D. Shi ๐Ÿ“‚ Article ๐Ÿ“… 1999 ๐Ÿ› John Wiley and Sons ๐ŸŒ English โš– 297 KB ๐Ÿ‘ 1 views

The effects of Reynolds number on the physiological-type of laminar pulsatile flow fields within the vicinity of mechanical ring-type constriction in small pipes were studied numerically. The parameters considered are: the Reynolds number (Re) in the range of 50 -1500; Strouhal number (St) in the ra