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  • Flow field  (1)
  • Haemodynamics  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 25 (1987), S. 12-17 
    ISSN: 1741-0444
    Keywords: Arteries ; Atherosclerosis ; Bifucations ; Branches ; Haemodynamics ; Marker and cell ; Trunk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Atherosclerosis is known to be localised in arterial bends, bifurcations and branches. The exact mechanism is not known but it appears that the process starts due to haemodynamic changes. In general, the distribution arteries have relatively symmetrical bifurcations with varying angles and branch trunk area ratios. Several previously studied flow related characteristics were dependent on Reynolds number, angle of bifurcation and area ratios. The time dependence nature of the flow was not included in the above investigations. The equations of continuity and motion for two dimensional, time dependent flow of a homogenous, incompressible fluid through a horizontal, bifurcating rigid channel were therefore solved. The numerical method chosen to solve this problem was the marker and cell (MAC) method, which enabled the two velocity components and the pressure to be obtained directly. According to this system the flow field was divided into cells rather than points according to a prescribed scheme. It was found that a high shear stress zone developed at the daughter’s medial wall while at the lateral wall the fluid tends to follow the pressure gradient and the flow was reversed for part of the cycle. In addition, a high pressure zone which could attain values of twice the input pressure was found on the medial wall.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 38 (2000), S. 93-97 
    ISSN: 1741-0444
    Keywords: Mechanical heart valves ; Flow field ; Cavitation ; Vortices ; Navier-Stokes equations ; CFD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Cavitation in mechanical heart valves is traditionally attributed to the hammer effect and to squeeze and clearance flow occurring at the moment of valve closure. In the present study, an additional factor is considered—the contribution of vortex flow. Using a computational fluid dynamics analysis of a 2D model of a tilting disk mitral valve, we demonstrate that vortices may form in the vicinity of the inflow side of the valve. These vortices roll up from shear layers emanating from the valve tips during regurgitation. A significant decrease in the pressure at the centre of the vortices is found. The contribution of the vortex to the total pressure drop at the instant of closure is of the order of 70 mmHg. Adding this figure to the other pressure drop sources that reach 670 mmHg, it might be that this is the deciding factor that causes the drop in blood pressure below vapour pressure. The total pressure drop near the upper tip (750 mmHg) is larger than near the lower tip (670 mmHg), indicating a preferential location for cavitation inception, in agreement with existing experimental findings.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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