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前言碳端头材料,即石墨和碳/碳复合材料在高空/层流条件下会升华,形成一种为每种材料的组成和制造/加工方法所特有的表面微粗糙度分布。有代表性的表面粗糙度单元高度至少有一个量级的差别,因此只能用统计方法来表示。在再入期间形成的表面微粗糙度单元在层流边界层内会产生扰动。随着高度的下降,雷诺数就增大,因而最终可以获得能使粗糙度引起的扰动扩大的端头流场条件,即转捩开始。边界层转变为紊流使得加热率更严重,烧蚀率增大,端头外形改变得更迅速,并且在转捩的下游形成一种宏粗糙度的表面图象(即条纹组
Preface Carbon end materials, graphite and carbon / carbon composites, sublimate under high-altitude / laminar flow to form a surface micro-roughness profile that is unique to each material’s composition and manufacturing / processing method. Representative surface roughness units differ in height by at least one order of magnitude and can therefore only be represented statistically. Surface micro-roughness elements formed during reentry can cause perturbations within the laminar boundary layer. As the altitude decreases, the Reynolds number increases, and eventually the tip flow field condition that causes the roughness-induced disturbance to increase is obtained, ie, the transition starts. The transition from the boundary layer to the turbulent flow makes the heating rate more severe, the ablation rate increases, the tip profile changes more rapidly, and a macro-rough surface image is formed downstream of the transition