Sergey A. Smirnov

Numerical simulations of nonlinear thermally stratified spin-up in a circular cylinder

We present a numerical study of incremental spin-up of a thermally stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface. This investigation reveals a feasibility for transition from an axisymmetric initial circulation to nonaxisymmetric flow patterns, and it is motivated by the desire to compare the spin-up for Dirichlet and Neumann thermal boundary conditions. The numerical simulations demonstrate that the destabilizing mechanism is not purely baroclinic but that vertical and horizontal shears may contribute to the instability. By characterizing the azimuthal instabilities without introducing any simplification, we were able to assess to what extent an insulating boundary condition changes the time-dependent emergence of the instability. Our results agree with previous experimental data and provide a framework for understanding the role played by the baroclinic vorticity in the development of instabilities in thermally stratified incremental spin-up flows

Numerical Study on Diastolic Left Ventricular Hemodynamics Using Motion Models of Mitral Valve With/Without Edge-to-Edge Repair

Edge-to-edge repair (ETER) is a newly developed technique to correct such mitral valve (MV) malfunctions as regurgitation [1,2]. This technique changes MV geometric configuration by suturing the anterior and posterior leaflets at central or commissural edges, and consequently alters MV and left ventricle (LV) dynamics. For instance, stress in the MV elevated due to ETER may cause leaflets tearing near suture. Little has been known about shear stress on the MV and LV walls under MV ETER conditions, where high shear stress might cause platelet activation or hemolysis [3]. When ETER is done at the central leaflet edges, it generates two MV orifices, leads to two deflected jets, and completely changes vortices in the LV. ETER also reduces the orifice area, and increases jet velocity and transmitral pressure [1,2,4]. Flow patterns in the LV and ETER effects on the LV and MV functions have not been understood well.Copyright