中文摘要：

以填充氦气的平流层浮空器为应用背景,对非均匀复杂热边界条件下大尺寸椭球形封闭腔内低压气体的自然对流热特性与动力学特性进行了数值模拟。以Fluent软件为基础,采用用户自定义函数（UDF）自编程技术引入外部非均匀的对流-辐射耦合热边界条件,考虑了低压气体密度对压力、温度的依赖关系。分析了不同条件下腔壁与内部气体温度、对流换热特性以及流场、压力、质心变化等动力学特性,通过数据分析,获得了腔内自然对流的局部对流换热系数关联式。研究结果表明,在平流层环境下,外部非均匀热边界条件及其变化对封闭腔内低压气体的自然对流热特性与动力学特性影响很大。

英文摘要：

Aiming at the application of stratospheric aerostats filled with gas helium,the natural convection of a low pressure gas inside a huge ellipsoidal enclosure is simulated numerically.The natural convection is induced by the combined thermal conditions of the airflow and radiative heat transfer outside the wall of the enclosure.Using the user-define feture（UDF）,the combined thermal conditions are introduced into the numerical simulation by the Fluent,and the dependence of gas density on its pressure and temperature is considered.Thermal and dynamic characteristics are analyzed,such as the temperature field,the heat transfer coefficient distribution as well as the velocity field,the pressure field and the centroid.A correlation is presented for the local heat transfer coefficient by analyzing the numerical results.The investigation demonstrates that the varying non-uniform thermal conditions of stratospheric surroundings exert significant influences on both the thermal and dynamic characteristics of the natural convection of a low pressure gas inside an enclosure.