An Investigation of Grid Resolution on Hypersonic Viscous Flow Simulation

The effects of grid resolution on hypersonic viscous flow simulations are investigated in detail. Previous studies have shown that grid plays an important role on the aerothermodynamic predictions for a hypersonic vehicle. We investigate flows over simplified geometry to analyze the behavior of grid resolution when the flow is solved using the Navier-Stokes equations. It shows that grid&nbsp;independent solutions can be achieved with fine meshes where the surface-based cell Reynolds number is in the order of 10. The reason for fine meshes is analyzed using wall functions derived using the boundary layer approximation. It is found that the truncated error of numerical schemes is increased dramatically when the flow approaches the surface, which explains the fact that near-surface cells should be much smaller than faraway cells to maintain the numerical error at a low level.&nbsp;</div

酚酞聚芳醚酮-双马来酰亚胺体系流变行为时间-温度依赖性

采用流变仪对酚酞聚芳醚酮(PEKC)-双马来酰亚胺(BMI)树脂体系的流变特性的时间和温度依赖性进行了研究,发现:BMI树脂凝胶点对频率有依赖性,而tanδ对频率无依赖性;PEKC-BMI复合树脂体系的黏度增大主要是由于BMI对PEKC的溶解与BMI的热固化。相比较110℃和130℃两种条件,在较高温度时复合树脂体系的黏度增大主要是热固化的影响;随注胶温度提高,复合体系的凝胶时间随PEKC含量的增加而快速缩短,在较高注胶温度下凝胶模量增大较慢,在较低注胶温度下凝胶时模量随PEKC含量的增加而提高较快;随着复合树脂体系中PEKC含量的增加,该体系的凝胶活化能由4.9kJ/mol增大到65.9kJ/mol,表明该体系的凝胶化作用对温度的敏感性增大