고속탄자 유동의 가시화 실험 및 비정렬격자 계산

다국어 초록 (Multilingual Abstract)

Exterior ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and an unstructured grid Navier-Stokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Reynolds-Averaged Navier-Stokes solution on unstructured grids. Osher's approximate Riemann solver is used to discretize the convection term. Higher-order spatial accuracy is obtained by MUSCL extension and van Albada type flux limiter is used to stabilize the numerical oscillation near the solution discontinuity. Accurate Galerkin method is used to discretize the viscous term. Explicit fourth-order Runge- Kutta method is used for the time-stepping, which simplifies the application of MUSCL extension. A two-layer k- ε turbulence model is used to simulate the turbulent wakes accurately. Axisymmetric flow and two-dimensional flow with an angle of attack have been computed. Grid-dependency is also checked by carrying out the computation with doubled meshes. 2-D calculation shows that effect of angle of attack on the flow field is negligible. Axi-symmetric results of the computation agrees well with the flow visualization. Primary oblique shock is represented within 2-3 meshes in numerical results, and the varicose mode of the vortex shedding is clearly captured in the turbulent wake region.<br/>