Dynamic Simulation And Experimental Study On Tethered Balloon At Mooring Condition

Based on the wind tunnel test, dynamic characteristics of tethered balloon has been studied in this dissertation. As a part of domestic research on the large scale tethered balloon platform, and combining with the fact that few institutions research it in our nation, dynamic simulation of the model has been performed on the basis of the experimental results.As lack of the necessary researches on dynamic characteristics of tethered balloon, we choose it as an object of study. This paper did some research on it, the main work involves three parts as following:(1) Part of experimentCarrying out a wind tunnel test on the reduced-scale model, and compiling a data processing program, especially extracting the data using for dynamic simulation. The method used here is transforming body axial system into wind axial system by solving linear equations.(2) Part of modelingBuilding three-dimensional visualized model of each part of the tethered balloon, and carrying on the assembly. Giving out the calculating formula of moment of inertia for the rotation body and rotation plane. Testing and verifying the feasibility of the numerical method to get the geometrical parameters of the tethered balloon.(3) Part of dynamic simulationAfter finishing the modeling, it is necessary to define the joints and simplify the tether and the contact between the balloon and the air cushion. Then, carrying out dynamic simulation of two categories of the model.Several conclusions can be drawn from the research of this paper:(1) The result of wind tunnel test indicates that when the cathedral angle of tailplane decreases from 45°to 40°, the lift coefficient, drag coefficient and the lift-drag ratio increase , and the balloon can get a better longitudinal stability as well. The locations of windscreen have little influence on lift coefficient, but drag coefficient decreases when the location is in the front.(2) Pressure distribution measurement and silk-thread test show that there is no laminar separation in front and middle parts of the balloon, but vortex appears at the root of fins.(3) The result of dynamic simulation indicates that stability of the balloon will be worse with the increase of airflow speed. And when the airflow speed increases to 30 m/s, the air cushion must be added to prevent the tethered balloon platform being destroyed.(4) The data of simulation shows that both of the two different classes of air cushions can protect the balloon system. Comparing the cushion with an arc top to the cushion with a straight top, the former is more effective.