Aerodynamic Numerical Simulation Analysis of Water–Air Two-Phase Flow in Trans-Medium Aircraft

Abstract

A trans-medium aircraft is a new concept aircraft that can both dive in the water and fly in the air. In this paper, a new type of water–air multi-medium span vehicle is designed based on the water entry and exit structure model of a multi-rotor UAV. Based on the designed structural model of the cross-media aircraft, the OpenFOAM open source numerical platform is used to analyze the single-medium aerodynamic characteristics and the multi-medium spanning flow analysis. The rotating flow characteristics of single-medium air rotor and underwater propeller are calculated by sliding mesh. In order to prevent the numerical divergence caused by the deformation of the grid movement, the overset grid method and the multiphase flow technology are used for the numerical simulation of the water entry and exit of the cross-medium aircraft. Through the above analysis, the flow field characteristics of the trans-medium vehicle in different media are verified, and the changes in the body load and attitude at different water entry angles are also obtained during the process of medium crossing.

Research of Slamming Load Characteristics during Trans-Media Aircraft Entry into Water

“…Since the UAV enters the water at a low velocity, it can be assumed that the water is an incompressible fluid and the heat energy generated during the movement is negligible [22]; the basic equations required for the calculation are as follows:…”

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.…”

“…Over the last two years, and concurrent with our LOSSEI research, there has been a spate of Chinese publications documenting the design and testing of HUAVs, starting with the design fabrication and characterisation of a HUAV in 2021 [11], followed by 2022 research into lifting principles [12], a numerical simulation of air-water transition [13], further design, fabrication, and experimentation [14], cross-domain control [15], and a miniature low-cost HUAV [16]. Such work confirms that some technologies have progressed for HUAVs sufficiently for us to recommend substantive proof-of-concept testing for this and other such hybrid vehicles.…”