Dynamic Characteristics And Flow Field Analyses On A Rocket Sled-Drag Parachute System

In a drag parachute design project,there exists the obvious difference between the rocket sled test result and the design performance.In this thesis,the theoretical and numerical methods are used to study the dynamic characteristics and flow field characteristics of the rocket sled-drag parachute system.The reasons leading to the difference of the parachute performance are analyzed,and the correction theory and method to analyze the rocket seld test raw data are given.The results and conclusions are briefly described as follows:(1)The simulation results of the wind tunnel test and the raw data of the rocket sled test are analyzed respectively.The parachute performance parameters are obtained in the method for eliminating the wall effect of the wind tunnel test.Meanwhile,based on the raw data of the rocket sled test,the velocity and acceleration of the rocket sled are obtained by using the non-equidistant two order finite difference method.The relationship between the velocity,acceleration,force,time and other physical parameters is analyzed.(2)The flow field characteristics of the rocket sled as well as the aircraft are investigated by the method of the Reynolds-Averaged Navier-Stokes.Based on the experimental data and the data of aerodynamic force of the rocket sled obtained from numerical simulation,the method including friction analysis and calculation under unsteady state and high sliding velocity condition is established.Under the typical conditions of the rocket sled test(velocity from 60m/s to 90m/s),it exists a phenomenon of airflow downwash in the rocket sled wake.The influence of velocity on the flow field characteristics,the aerodynamic lift coefficient and drag coefficient of the rocket sled is slight.During landing,the velocity distribution and pressure distribution of the rocket sled wake has good similarity with the velocity distribution and pressure distribution of the aircraft wake with single vertical fin,respectively.Meanwhile,it is found that the relative sliding velocity is still the main factor influencing the friction factor,and the friction factor shows a decreasing trend with the increase of the relative sliding velocity.(3)The inflated shapes of the double cruciform parachutes under the wind tunnel test conditions,far field boundary conditions,and the rocket sled test conditions are simulated through the fluid-structure interaction solver based on the Mass Spring Damper(MSD).The flow field characteristics around the drag parachute system are discussed in detail.In addition,the fluid-structure interaction solver based on the Arbitrary Lagrange-Euler method is used for the simulation of the inflation process of the single and double drag parachutes under the far field conditions.The results show that under the wind tunnel test condition and far field boundary condition the inflated shapes of the parachute obtained from the MSD method and the ALE method are basically the same,and the drag coefficients for both single and double drag parachutes calculated by the RANS method show good agreement with the experimental data respectively.However,the parachute system is continuously influenced by the airflow downwash in the rocket sled wake flow.(4)The main reasons for the difference between the rocket sled test result and the design performance are analyzed,and the correction theory and method for the experimental data analysis is provided.It is found that the unsteady state and dynamic pressure loss are the main factors for the difference.The rocket sled-drag parachute system flow and drag parachute flow under far field boundary are compared.And the influences of the unsteady state and dynamic pressure loss on the drag parachute performance are quantitatively analyzed based on the simulation results and experimental data.Meanwhile,the correction calculation method for the drag parachute performance in the rocket sled test is established,which is applied to the data analysis of the rocket sled-drag parachute system,and the drag parachute performance can be better reflected by the calculation results.