Abstract
BackgroundThe water entry of a submersible aircraft, which is transient, highly coupled, and nonlinear, is complicated. After analyzing the mechanics of this process, the change rate of every variable is considered. A dynamic model is build and employed to study vehicle attitude and overturn phenomenon during water entry. Experiments are carried out and a method to organize experiment data is proposed. The accuracy of the method is confirmed by comparing the results of simulation of dynamic model and experiment under the same condition.ResultsBased on the analysis of the experiment and simulation, the initial attack angle and angular velocity largely influence the water entry of vehicle. Simulations of water entry with different initial and angular velocities are completed, followed by an analysis, and the motion law of vehicle is obtained. To solve the problem of vehicle stability and control during water entry, an approach is proposed by which the vehicle sails with a zero attack angle after entering water by controlling the initial angular velocity. With the dynamic model and optimization research algorithm, calculation is performed, and the optimal initial angular velocity of water-entry is obtained.ConclusionsThe outcome of simulations confirms that the effectiveness of the propose approach by which the initial water-entry angular velocity is controlled.
Highlights
The water entry of a submersible aircraft, which is transient, highly coupled, and nonlinear, is complicated
Recently, researchers began to focus on submersible aircrafts that fly and navigate underwater
To prevent the overturn phenomenon and effectively control the water entry of vehicle, the motion law and attitude control during water entry of submersible aircraft are studied in this work
Summary
The water entry of a submersible aircraft, which is transient, highly coupled, and nonlinear, is complicated. The computational fluid dynamics (CFD) method can be used to calculate the drag Fμx, lift Fμy, moment of force Mμz in a given speed, and the attack angle when the vehicle is full immersion. According to the calculation by CFD, a one-to-one correspondence exists between the viscous fluid dynamic coefficient and the changing relationship of the attack angle and speed.
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