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Comparison between Doppler echocardiography and hot-film anemometry in measuring the turbulent shear stress downstream of artificial mitral valves： a methodological study

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Chinese Medical Journal 2013年第11期126卷 2174-2178页

作者： SUN Yi LI Rui-jie LI Gan-niu LI Bin WANG Yu MA Run-wei YANG Bai-hui LU Sen-lin ZHANG Gui-min Department of Cardiovascular Surgery First Affiliated Hospital of Kunming Medical University Kunming Yunnan 650031 China Department of Cardiology First Affiliated Hospital of Kunming Medical University Kunming Yunnan 650031 China College of Aerospace Engineering Nanjing University of Aeronauticsand Astronautics Nanjing Jiangsu 210016 China

Background turbulent shear stress （TSS） plays an important role in the research of fluid dynamics of heart valves. This study aimed to perform a quantitative study of TSS downstream of porcine artificial mitral valves in order to verify the correlation of hot-film anemometry （HFA） and Doppler echocardiography combined with computer-aided image analysis for the detection of TSS. Methods A porcine model of mitral valve replacement was established. HFA and Doppler ultrasound techniques were used to directly and indirectly measure TSS-relevant parameters of the artificial mitral valve following different mitral valve replacements： different approaches were used to reserve the subvalvular apparatus of the mitral valve. A correlation analysis was then carried out. Results There was a significant correlation between the HFA and Doppler ultrasound combined with computer-aided image analysis of the TSS at the same time and at the same site. No significant difference was found in the TSS measured by the two methods. Conclusions Compared with HFA, Doppler echocardiography combined with computer-aided image analysis is a safe, non-invasive, and real-time method that enables accurate and quantitative detection of TSS downstream in vivo, objectively reflecting the flow field downstream of the artificial mitral valve. Doppler ultrasound combined with computer- aided image analysis can be employed for quantitatively evaluating the downstream hemodynamic performance of the mitral valve.

关键词： porcine mitral valve replacement turbulent shear stress Doppler echocardiography hot-film anemometry

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VELOCITY AND SUSPENSION CONCENTRATION IN SEDIMENT-MIXED FLUID

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International Journal of Sediment Research 2002年第3期17卷 220-232页

作者： B.S.MAZUMDER,K.GHOSHAL Professor Physics and Applied Mathematics Unit Indian statistical Institute Calcutta-700 108 India. Project Fellow Flume Laboratory Physics and Applied Mathematics Unit Indian Statistical Institute Calcutta-700 108 India.

The present paper is focussed on the effects of viscous and turbulent shear stresses on both vertical velocity and concentration distributions in large suspension of sands. When the flow carries large amount of sediments in suspension, the properties of fluid mixture are changed in terms of modified viscosity, density and fall velocity, and hence the flow characteristics. Theoretical models have been developed for both velocity and concentration profiles, taking into account the viscous and turbulent shear stresses, which are the function of volumetric concentration. Comparison of theoretical models with experimental data reveals that (i) the modified velocity and concentration profiles agree well with the observed data for high suspension, (ii) the higher the sediment suspension, the smaller the von-Karman constant, and (iii) sediment diffusion coefficient is less than momentum diffusion coefficient for fine sands in suspension.

关键词： Sediment suspension Viscosity turbulent shear stress Hindered settling Velocity and concentration profiles

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