Research on the water-entry attitude of a submersible aircraft

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.

Conceptualising a Hybrid Flying and Diving Craft

“…Such trade-offs are worth exploring to improve underwater endurance. Chinese research has also explored dynamic and CFD modelling for direct entry approaches [7,8] and more recently, a dynamic water exit [13] to 'rapidly exit from water with a wide range of pitch angles', for better survivability in bad sea states. We explored structural forces with a conventional surface landing and found them to be the highest design case and a major driver of structural weight estimates.…”

“…The conceptual design has been socialised and confirmed at technical conferences from each core discipline, including subsea [1], defence technology [2], computational fluid dynamics [3], and telecommunications [4]. There was some limited research literature on 2 of 22 hybrid uncrewed aerial vehicles that encouraged the beginning of this research work, such as a 2015 comprehensive survey [5], 2016 research into a power system [6], water entry analyses in 2016 [7] and 2017 [8], a design based upon computational fluid dynamics in 2017 [9], and some testing and characterisation in 2018 [10].…”

Simulation and experimental research on trans-media vehicle water-entry motion characteristics at low speed

“…In order to simply the problem, by the theoretical calculation, and based on the suitable assumption, the fluid force can be separated as two kinds of force to be obtained. One force is in the ideal state which has no viscousness, and the other force is the fluid force with the viscousness [ 23 ].…”

Motion Characteristics After Ricochet: An Experimental Investigation

“…Of these, the water-entry crossing is the key stage for the AWTMV to achieve a smooth transition from the air into water. However, the forces on the AWTMV dramatically change due to the change in the medium from air to water, which may cause the failure of the water-entry crossing and harm the subsequent mission the of AWTMV [4].…”