Dynamic Simulation Analysis Of Water Recycling Of A Flying Wing UAV

In order to reduce the cost of experimental research on flight water landing,the simulation analysis method has become a trend.In this paper,the nonlinear transient dynamics analysis software MSC.Dytran is used to simulate the impact of the structure flying into the water.Firstly,the simulation and experiment of the same size model for the water entering process of the simple projectile structure were carried out.Different mesh size and water size have an impact on the simulation results.1)Small mesh size means the increase in the number of mesh grid and calculation time.To ensure the accuracy and computational efficiency in the same time,the mesh size should be selected slightly less than the critical size.2)The boundary effect makes the shock wave reflect from the water boundary,which would influence the simulation accuracy.As a result,the water size should be slightly larger than the critical size.Comparing with experiment under the same conditions,it shows that the simulation error can be controlled within 20%,which reflects the superiority and feasibility of simulation.After finite element modeling of the water recycling system,various conditions were designed considering different roll angle,yaw angle,wind direction and landing speed.Also,Euler waves were built to model different sea conditions.There are some simulation results which provide reference and guidance to the construction design of UAV in water recycling.1)The maximum overload in the structure starts instantly when touching the water.2)In zero state,the maximum load decreases with increasing the pitch angle at the same the vertical speed while the maximum vertical velocity decreases with overload at the constant pitch angle.3)The maximum overload on the UAV belly is relatively low while extremely high on the wing tip.4)The greater the pitching angle,the greater the depth of water entry.In addition,a GUI panel is designed in order to simplify the simulation process,which integrates pre-processing,simulation and post-processing into an interface.Finally,the simulation results of the UAV are optimized.A response surface based on RBF with appropriate design of experiments is constructed.Multi-objective optimization of the UAV key parts(including the head,belly and tail,right wing tip)is designed with the UAV's pitching angle and vertical velocity as design variables.Using the genetic algorithm toolbox carried out in MATLAB for optimization calculation,we get the optimal solution.