飞艇动导数与附加质量相互融合的方法

Fusing method for dynamic derivatives and added mass of airships

飞艇的动导数和附加质量分别表征其在有黏流和无旋无环流中所受非定常气动力/力矩。为了解决在飞艇建模中这两种气动系数的融合问题,分别研究了动导数和附加质量的成分划分问题以及同成分气动系数的融合方法。通过介绍能同时兼容有黏流和无旋无环流的气动力和力矩分析理论,得出同成分气动力/力矩融合时应当取有黏流中的结果并摒弃对应的无旋无环流结果。通过研究气动力/力矩与运动体当前运动参数的关联性,建立依据当前运动参数划分气动力/力矩或气动系数的方法。为了使两种流场中的气动系数分类方法相同,对飞艇的当前运动参数进行重构,使得气动系数在两种流场中均可按重构后运动参数明确划分和计算。根据研究结果,建立了一种动导数与附加质量的新融合方法,并讨论了它与现有文献方法的差异。通过算例分析不同融合方法对飞艇纵向扰动运动特性的影响,说明采用新融合方法的必要性。

Dynamic stability derivatives and added mass represent an airship’s aerodynamics in viscous flow and acyclic potential flow.To develop a method for fusing these two aerodynamic coefficients in airship modeling,the classification method for dynamic stability derivatives and added mass and the fusing method for same aerodynamic coefficient ingredient are studied.By introducing a unified theory for analyzing aerodynamics in incompressible flow,a conclusion is drawn that the viscous aerodynamics should be reserved and the corresponding results in acyclic potential flow should be abandoned in fusing the same ingredient of aerodynamics.By studying the relationship between aerodynamics and the present motion parameter of an airship,the classification method for aerodynamics and the aerodynamic coefficient is built.To keep the aerodynamic classification method same in the two flow fields,a new method for reconstructing the present motion parameters of airships is proposed so that the aerodynamic coefficients in the two flow fields can be both classified according to the new parameters,and each ingredient can be evaluated.Based on these studies,a new fusing method for dynamic stability derivatives and added mass is proposed and its difference with the present fusing method is discussed.A numerical example is presented to show the effect of different fusing methods on the dynamic characteristics of an airship’s longitudinal perturbation motion and illustrate the necessity for adopting this new fusing method.