High Frame Rate Ultrasound Particle Image Velocimetry for Estimating High Velocity Flow Patterns in the Left Ventricle

Echocardiographic determination of multi-component blood flow dynamics in the left ventricle remains a challenge. In this study we compare contrast enhanced, high frame rate (1000 fps) echo particle image velocimetry (ePIV) against optical particle image velocimetry (oPIV, gold standard), in a realistic left ventricular phantom. We find that ePIV compares well to oPIV, even for the high velocity inflow jet (normalized RMSE = 9 ±1%). Additionally, we perform the method of Proper Orthogonal Decomposition, to better qualify and quantify the differences between the two modalities. We show that ePIV and oPIV resolve very similar flow structures, especially for the lowest order mode with a cosine similarity index of 86%. The co

On the improved finite volume procedure for simulation of turbulent flows over real complex terrains

This article presents a new and substantially improved finite volume procedure for simulation of incompressible flows on non-orthogonal grids. Cell-centered least-squares gradients are obtained in a robust and highly accurate way. A new discretization of the diffusive terms is employed, which is based on extension of the original cell-face gradient interpolation and is more suitable for complex grid distortions. A flexible flux-limited interpolation of dependent variables on distorted computational grids is introduced. An efficient preconditioner for Krylov method solution of linear systems is proposed, which substantially improves the solution of Poisson equation for pressure correction. The pressure-correction algorithm is adapted for efficient convergence on highly complex grids using a sequence of non-orthogonal corrector solutions and its effect on iteration convergence is analyzed. The non-orthogonalities treated by current procedure are more accustomed to numerical grids generated from a real complex terrain elevation data. The main focus is on the simulation of atmospheric micro-scale flows pertinent to wind energy application