This research adopts a shock tube 16 meters long and with a 9 cm bore to create a supersonic, high-temperature, and high-pressure flowfield to observe the gasification and ignition of HTPB solid fuel under different environments. Also, full-scale 3D numerical simulation is executed to enhance the comprehension of this complex phenomenon. The CFD (Computational Fluid Dynamics) code is based on the control volume method and the pre-conditioning method for solving the Navier-Stokes equations to simulate the compressible and incompressible coupling problem. In the tests, a HTPB slab is placed in the windowed-test section. Various test conditions generate different supersonic Mach numbers and environmental temperatures. In addition, the incident angles of the HTPB slab were changed relative to the incoming shock wave. Results show that as the Mach number around the slab section exceeded 1.25, the flowfield temperature achieved 1100 K, which is higher than the HTPB gasification temperature (930 K ∼ 1090 K). Then, gasification occurred and a short-period ignition could be observed. In particular, when the slab angle was 7 • , the phenomenon became more visible. This is due to the flow field temperature increase when the slab angle was at 7 • .

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Regurgitation in the heart diastolic phase represents a critical flow condition associated with many heart valve design considerations. The finite volume method, the Low-Reynolds-Number k-ω turbulent model and sliding mesh model are employed to solve and compare the complex flow field and the torque in each case. The end results expected from a cardiovascular CFD analysis are not limited only to the flowfield investigations. More importantly, it needs an evaluation criterion to judge if the design is acceptable as considered from a broader blood cell damage or activation perspective. In this study, blood cell damage index developed based on stress-time empirical rule and Lagrangian particle tracking is introduced to assess the viscous and turbulence-induced stresses effect to the blood cells.

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In this study, a fully coupled fluid-structure interaction (FSI) software system for a pulsatile flow across a moving tilting-disc valve with clearance is developed. Unsteady pulsatile flow coupled with induced valve motion has been examined in details. State-of-the-art computational fluid dynamics (CFD) methods are adopted in the present flow solver development. To account for nonstationary valve motion, the meshes surrounding the valve are generated and updated in each time-marching step using hybrid grid method. A single-degree-of-freedom rotational valve model is integrated simultaneously with the CFD adaptive time-stepping. It is found in the present study that, on both side of the occluder, strong shedding vortices occur and persist in the valve closing phase. These closure vortices show great influence on the prediction of the regurgitate flow characteristics and the subsequent valve opening dynamics as well. Based on the present software system, the results obtained from quasi-steady simulations performed at various instants of interest with prescribed valve motion are critically evaluated to assess whether simplified flow and valve conditions may lead to erroneous conclusions.