Experimental study of the flow field in patient specific lower airways

In this study Particle Image Velocimetry (PIV) is used to visualize and measure airflow in the lower airways. Using Rapid Prototyping Manufacturing (RPM) technology, a hydraulic in vitro model was developed and constructed. Preliminary 2D PIV measurements compared successfully to Computational Fluid Dynamics (CFD) results

A Novel Hydraulic Thick-walled Phantom for the Assessment of Left Ventricular Function

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In Vitro Flow Modelling for Mitral Valve Leakage Quantification

In this study particle image velocimetry (PIV) is used to measure and visualise the blood flow through a leaking mitral heart valve. The results are compared with the results from Doppler echocardiography and computational fluid dynamics (CFD). Using CAD, five-axis milling and Rapid Prototyping Machining (RPM) technology, a hydraulic in vitro flow model was developed and constructed which is compatible with flow investigation with 2D normal speed PIV and 2D Doppler echocardiography. The same CAD model was used to conduct the CFD analysis. PIV results compared successfully with Doppler echo and CFD results, both in the upstream converging region and downstream the turbulent regurgitated jet zone. These results are expected to improve the assessment of mitral valve regurgitation severity with Doppler echocardiography in clinical practice

Functional imaging on patient-specific lower airways using Computational Fluid Dynamics

Adding functional information to anatomical CT-data by means of Computational Fluid Dynamics (CFD) is a non-invasive method for analyzing patient-specific respiratory dynamics. As CFD is based on numerical models, validation is required to obtain reliable results. For this purpose, 2D PIV measurements are performed and compared to the CFD data

A fast strong coupling algorithm for the partitioned fluid–structure interaction simulation of BMHVs

The numerical simulation of Bileaflet Mechanical Heart Valves (BMHVs) has gained strong interest in the last years, as a design and optimisation tool. In this paper, a strong coupling algorithm for the partitioned fluidstructure interaction simulation of a BMHV is presented. The convergence of the coupling iterations between the flow solver and the leaflet motion solver is accelerated by using the Jacobian with the derivatives of the pressure and viscous moments acting on the leaflets with respect to the leaflet accelerations. This Jacobian is numerically calculated from the coupling iterations. An error analysis is done to derive a criterion for the selection of useable coupling iterations. The algorithm is successfully tested for two 3D cases of a BMHV and a comparison is made with existing coupling schemes. It is observed that the developed coupling scheme outperforms these existing schemes in needed coupling iterations per time step and CPU time

Application of a strong FSI coupling scheme for the numerical simulation of bileaflet mechanical heart valve dynamics: study of wall shear stress on the valve leaflets

One of the major challenges in the design of Bileaflet Mechanical Heart Valves (BMHVs) is reduction of the blood damage generated by non-physiological blood flow. Numerical simulations provide relevant insights into the (fluid) dynamics of the BMHV and are used for design optimisation. In this paper, a strong coupling algorithm for the partitioned Fluid-Structure Interaction (FSI) simulation of a BMHV is presented. The convergence of the coupling iterations between the flow solver and the leaflet motion solver is accelerated by using a numerically calculated Jacobian with the derivatives of the pressure and viscous moments acting on the leaflets with respect to the leaflet accelerations. The developed algorithm is used to simulate the dynamics of a 3D BMHV in three different geometries, allowing an analysis of the solution process. Moreover, the leaflet kinematics and the general flow field are discussed, with special focus on the shear stresses on the valve leaflets

The influence of the upstream boundary condition in the numerical simulation of the opening of an aortic BMHV

In this paper, the influence of the upstream boundary condition for the numerical simulation of an aortic Bileaflet Mechanical Heart Valve (BMHV) is studied. Two types of upstream boundary conditions are discussed and evaluated. First, an inflow velocity profile is imposed at the inlet of the valve. Secondly, a geometrical boundary condition is used, which implies that the flow rate is governed by the geometrical contraction of the left-ventricle (LV). Both boundary conditions are used to simulate a 3D case with the same BMHV. The change in time of the LV volume is calculated such that the flow rate through the valve is identical in both cases. The dynamics of the BMHV are modelled using fluid-structure interaction (FSI) and only the opening phase of the valve is simulated. The simulations show that although the results for the two cases are similar, differences occur in the leaflet movement. In particular, when using the velocity profile, the leaflets impact the blocking mechanism at their open position with a 25% larger angular velocity. Therefore, when one wants to simulate the dynamics of such an impact, the upstream boundary condition needs to be chosen carefully