The flow field of a laboratory-simulated tornado was studied by means of 2-D ParticleImage Velocimetry or PIV technique with the purpose of investigating the effects of roughness onthe near-ground tornado-like vortex structure and its velocity distribution. The results show the flowregime transition from multi-celled vortices over the smooth surface at a higher swirl ratio to singleordual-celled vortices with roughness. Significant difference in velocities and turbulencecharacteristics is observed as a result of increasing ground roughness. This work is part of a projectthat seeks better understanding of the near-ground flow field and resulting wind-induced loads onstructures in a tornado.
原来道理是这样,“研究发现粗糙表面的钛种植体与骨组织的结合面积及结合强度均大于光滑表面的钛种植体,而且体外细胞培养也显示成骨细胞更易于粘附到粗糙的表面。与光滑表面相比,粗糙度 R a<50 μ m的表面能显著降低种植体—骨组织界面的炎症反应程度,减少软组织包绕层的厚度。亚微米及纳米结构可以引导细胞粘附和定向迁移生长,有利于形成良好的种植体周骨性结合”,所以种植体的表面形貌是影响骨整合的重要因素之一。