Journal of Fluids and Structures 91 (2019) 102760 Contents lists available at ScienceDirect Journal of Fluids and Structures journal homepage: www.elsevier.com/locate/jfs Numerical investigation of hydroelastic water-entry impact dynamics of AUVs Yao Shi a,b,c ,∗ , Guang Pan a,b , Solomon C. Yim c , Guoxin Yan a,b , Dong Zhang a,b a School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, PR China b Key Laboratory of Unmanned Underwater Vehicle, Northwestern Polytechnical University, Xi’an 710072, PR China c School of Civil and Construction Engineering, Oregon State University, Corvallis, OR, 97331, United States of America article info Article history: Received 14 February 2019 Received in revised form 3 August 2019 Accepted 30 September 2019 Available online xxxx Keywords: Elastic AUV Hydroelastic effect Water entry Impact characteristics abstract In contrast to rigid body autonomous underwater vehicle (AUV) models, elastic AUV models will exhibit hydrodynamic effects due to elastic deformation of the shell during water entry, influencing their load-response characteristics. In this paper, the predictive capability of the selected simulation method is first verified by comparing the simulation results with test data acquired from experiments conducted in a drop-test tank. Then, the effects of the head shape parameters, shell thickness and water-entry state, such as the water-entry velocity and angle, on the acceleration, pressure, stress and structural deformation of an elastic AUV during water-entry impact are investigated. By comparing the characteristics of rigid and elastic bodies, the influence of the hydroelastic effect is revealed. The research results can provide guidance on the design of airborne vehicles and transmedia vehicles. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction With the great demand for marine exploration, autonomous underwater vehicles (AUVs) have become a popular international research topic because of their wide activity range, deep diving depth, complex structures and low cost. There are a number of methods for launching AUVs from their carrier into the ocean. For example, AUVs can be launched from submarine torpedo launchers and ships, fixed-wing aircrafts, helicopters or rocket-assisted flights. When dropped from the air, an AUV will sustain a tremendous impact load during the water-entry process. The shell will undergo an impact-induced structural dynamic response, causing elastic or elastic–plastic deformation of the shell structure, possibly leading to fracture and buckling damage. The impact load may affect the trajectory of the vehicle, resulting in problems, such as whipping, diving and uncontrolled trajectory. Therefore, accurate predictions of hydrodynamic forces acting on the AUV shell and the associated responses are crucial in the design of AUV structures. Most published works considered only fluid and rigid body motion coupling when dealing with the impact phe- nomenon of objects entering water from the air (Soliman et al., 1976; Yettou et al., 2006; Yang and Qiu, 2012; Challa et al., 2014; Wang and Soares, 2014; Erfanian et al., 2015; Facci et al., 2018). However, the outer structure of an AUV body is a flexible shell that will deform elastically under the action of the surrounding flow field. This elastic deformation will also affect the characteristics of the fluid flow field, resulting in coupled fluid–structure interaction, i.e., the changed flow field characteristics immediately alter the pressure acting on the shell and produce a hydroelastic effect. Generally, a quasi-static method is applied for structural response predictions if the hydroelastic effects are insubstantial. However, ∗ Corresponding author. E-mail address: shiyao@nwpu.edu.cn (Y. Shi). https://doi.org/10.1016/j.jfluidstructs.2019.102760 0889-9746/© 2019 Elsevier Ltd. All rights reserved.