Hydrodynamics with complex boundary motions by non-inertial SPH method and its application in attitude-liquid-control coupled dynamics of a liquid-filled quadrotor UAV

Smoothed Particle Hydrodynamics (SPH) is a fully Lagrangian method that does not require the use of any mesh. Due to its advantages, SPH method is usually adopted to simulate flows with free surfaces. Based on traditional SPH, non-inertial SPH as a new method is proposed recently to deal with cases when the liquid is subjected to inertial force for the motion of reference frame. This study finds that the transport velocity of liquid particles has additional effects on the solution of momentum equation in Navier-Stokes equations. Comparisons and validations are conducted to quantificationally investigate this influence in this paper. Furthermore, the modified non-inertial SPH method is applied to simulate the attitude-liquid-control coupled dynamics of a liquid-filled quadrotor unmanned aerial vehicle (UAV). Parallelization technology and particle searching method based on KD-tree algorithm are used to speed up the simulation. Coupled model of the liquid-filled quadrotor is built firstly, and the liquid sloshing effect on the position & attitude of UAV and the control output of power system are then simulated and discussed. Results prove that the liquid sloshing will deteriorate the trajectory tracking performance, especially the tracking error and rotor output.