Numerically Simulate Aero-force&heat Of Aerocraft Based On N-S Equation

Flow solver is considered as one of the most important parts inaerodynamic shape optimization design system. Accuracy, stability andefficiency of flow solver will affect optimization quality and efficiencysignificantly. With the development of CFD, the pressure distribution ofthe flow field can be predicted accurately provided that proper numericalschemes and grid systems are employed. However, CFD still faces manychallenges, such as estimating heat flux, analyzing transonic and unsteadyflows, developing turbulence models, to name a few. In full considerationof these complex flow problem internal mechanism, we take the RANSequations solver as the flow solver, and take these flow phenomena intoprogram design, numerical calculation, resulting in an accurate andefficient CFD results.Main works of this thesis could be summarized as follows:First of all, an overview of the development of CFD and the necessityof applying CFD is done. The classic spatial discretization schemes,turbulence models and aerodynamic heating calculating methodsdeveloped by the scholars are analyzed systematically and classified.Then, structural viscous grids are generated with Ansys ICEM CFDtools, multiple grid generating technology is used, the quality of grid isensured. AUSM+、 Central、 Roe and Van Leer schemes are usedrespectively to discretize the Navier-Stokes equations based on these grids.Five-stage Runge-Kutta and LU-SGS time stepping scheme are also usedto solve N-S equations. Convergence acceleration techniques such as implicit residual smoothing and multigrid technology are used.As follows, the flow around NACA0012foil, ONERA M6wing areanalyzed. Spatial discretization schemes and turbulence models arecompared and analzed from the view of accuracy, stability and efficiency.The effect that different schemes act on lift-drag characteristic, pressuredistributing, flowfield configuration, computational efficiency, dissipationand convergence characteristic of these schemes are also investigated.Results show that Roe scheme has advantages such as low dissipation,excellent shock capture ability. S-A model has good properties in partialseparation flow.For another, a solution is developed which calculates laminar andturbulent heating rates on arbitrary blunt-nosed three dimensional bodies inhypersonic flows. By comparison with experimental data for a blunted15half-angle cone and a bent-nose biconic, the method is found to yieldreasonably accurate laminar heating rates for these cases, improves thecalculational accuracy than using some engineering codes. Results showthat Roe schemes and B-L model is a reasonable choice to predict heatingrates. The grid effect is crucial in stagnation heat flux simulation whileinsignificant in axial distribution of heating flux.