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1.
ASAIO J ; 58(1): 32-9, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22210649

RESUMO

An aqueous Xanthan gum solution (XGS) was used as blood analog fluid to explore the influence of fluid viscoelasticity on the performance of an axial blood pump model. For comparison, a 39 wt% Newtonian aqueous glycerin solution (GS), the common fluid in blood pump tests, was also used as a working fluid. The experimental results showed that a higher head curve was obtained using XGS in the pump than using GS. The heads of the XGS that were computed using the viscoelastic turbulence model agreed well with the measured data. In contrast, the standard k-ε turbulence model failed to provide satisfactory predictions for the XGS. The computational results revealed that in most parts of the pump model flow fields, the Reynolds shear stress values and turbulent dissipation rates of the XGS were all lower than those of the GS. The hemolysis index of the pump model using the XGS was calculated to be only one-third of that using the GS.


Assuntos
Velocidade do Fluxo Sanguíneo , Modelos Cardiovasculares , Circulação Assistida , Simulação por Computador , Elasticidade , Desenho de Equipamento , Glicerol/química , Coração Auxiliar , Humanos , Cinética , Modelos Teóricos , Reologia , Estresse Mecânico , Viscosidade
2.
Artif Organs ; 36(4): 429-33, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21995643

RESUMO

The head curves of a 1.5:1 new axial blood pump model were measured using five working fluids at five rotational speeds. The working fluids were water, a 39wt% aqueous glycerin solution (GS), and three aqueous xanthan gum solutions (XGSs) with different concentrations. The flow velocities and shear stresses in the mechanical clearance between the casing and rotor were investigated using a laser Doppler velocimeter and hot-film sensor. At every rotational speed, the experiment in which viscous GS was used in the pump model showed a head curve lower than that obtained using water, whereas the head obtained using viscoelastic XGS was higher than that generated using water. A maximum difference of 65.8% between the heads measured in the 0.06% XGS and GS experiments was detected. The higher head produced by the XGS may have originated from the drag-reduction effect of XGS viscoelasticity. The measurements showed that a reverse washout flow at a velocity of 0.05-0.11m/s occurs in the clearance. This reverse washout flow is crucial to preventing flow stagnation and accompanying thrombus formation. The wall shear stress and the Taylor number of the rotating Couette-like flow in the clearance both indicated that it is a turbulent flow.


Assuntos
Coração Auxiliar , Hidrodinâmica , Humanos , Polissacarídeos Bacterianos/química , Desenho de Prótese , Reologia , Estresse Mecânico , Viscosidade
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