Thermal-Motion-Deformation Coupling Analysis Of High-altitude Balloon During Ascent

With the inherent features of easy to launch,long duration and low cost,high-altitude balloon is treated as the ideal near-space platform.Since high altitude balloon is a large inflatable structure,it’s thermal characteristics,motion and shape may be easily affected by the external atmospheric environment during ascent.Therefore,in order to ensure the safety,it is of great significance to study the ascent process of high-altitude balloon.this paper studies the thermal-dynamic characteristics and shape deformation of the high-altitude balloon during ascent.The work is as follows:Firstly,the external atmospheric environment and thermal factors that affecting the highaltitude balloon during the lift-off process were introduced in detail.The mathematical models of solar radiation,long-wave radiation and convective heat transfer were established.The thermal model of the balloon which considering the transparence of the envelope was proposed.The overall force analysis of the balloon and the force balance of the envelope element during ascent were analyzed in detail.Based on which,the motion equation and the shape structure equation were established respectively.Secondly,based on the motion equation and the shape structure model to write a calculation program.The two-dimensional shape deformation and stress distribution of the balloon during ascent were simulated and analyzed.The effects of material absorption,load and launch time on the shape deformation and stress distribution of the high-altitude balloon were analyzed.Then,the aerodynamic simulation on the high-altitude balloon was carried out by simulation software.during ascent.The effect of dynamic pressure on the shape structure of the balloon was analyzed.Combining of the balloon shape,ascent speed and altitude obtained before,the drag forces of the balloon during ascent were calculated.Based on the drag forces,the drag coefficient equation of the balloon during ascent was fitted.The drag coefficient obtained can be used to correct the ascent speed and shape deformation of the sphere’s ascent process.Finally,the three-dimensional shape deformation of the high-altitude balloon during ascent was simulated in detail by introducing static pressure distribution,dynamic pressure distribution and wrinkle generation.Comparing the three-dimensional shape with the actual observation,it shows that the three-dimensional simulation which considering wrinkle is much more coincident with the real situations.Comparing the two-dimensional shape with the threedimensional shape parameters,it is known that the generation of the wrinkle of the envelope may cause variation in the height of the sphere and the maximum cross-sectional radius.Based on the above analysis,it is shown that using the heat-fluid-solid coupling simulation method,together with the dynamic pressure distribution,wrinkle generation and drag coefficient,the thermal characteristics and the shape deformation of the high-altitude balloon during ascent can be accurately simulated and analyzed.