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25 pages, 11392 KiB

Open AccessArticle

Lift–Drag Performance of a New Unmanned Aerial Vehicle in Different Media and Ground Effect

by Wenhua Wang, Lijian Wang, Kedong Zhang and Yi Huang

J. Mar. Sci. Eng. 2024, 12(7), 1052; https://doi.org/10.3390/jmse12071052 - 22 Jun 2024

Cited by 1 | Viewed by 1590

Water–air trans-media unmanned vehicle is a kind of aircraft, which can freely fly in the air, sail in the water and pass through free surface. For trans-media aircrafts, the development process from air–surface to air–underwater and from submarine-launched drive to autonomous drive is investigated. By analyzing the characteristic of manta ray, flying fish and existing aircraft, this paper proposes a new water–air trans-media unmanned vehicle with flat dish-airfoil-shaped main body and telescopic NACA-type wing. Then the numerical method to calculate the lift and drag forces is established and validated by the results of classic NACA cases. On this basis, the flow field around the new vehicle is numerically simulated, and its lift–drag performances in different media (air and water) and ground effect are analyzed, comparing it with a model inspired by the Blackwing Unmanned Aerial Vehicle (UAV). The findings illustrate the superior performance of the new vehicle in terms of lift and drag forces, offering an innovative design framework for water–air trans-media UAV applications. Full article

(This article belongs to the Section Ocean Engineering)

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18 pages, 13672 KiB

Open AccessArticle

Numerical Analysis on Water-Exit Process of Submersible Aerial Vehicle under Different Launch Conditions

by Bing Liu, Xiaohan Chen, Enyi Li and Guigao Le

J. Mar. Sci. Eng. 2023, 11(4), 839; https://doi.org/10.3390/jmse11040839 - 15 Apr 2023

Cited by 6 | Viewed by 2345

Abstract

To study the influence of launch conditions and wave interference on the stability of submersible aerial vehicles at the water–air interface, a coupling model for water-exit motion of submersible aerial vehicles was established by using the RNG k-ε turbulence model and VOF method. The water-exit processes of submersible aerial vehicles under different initial inclination angles and velocities were numerically simulated and the effects of initial inclination angle and velocity on the water-exit motion of submersible aerial vehicles were obtained. Based on the response surface function theory, a mathematical model for the motion stability of submersible aerial vehicles at the water–air interface was established, so that the submersible aerial vehicle’s pitch angle and velocity at the end of vehicle’s water-exit process, corresponding to any initial inclination angle and velocity, can be solved. The deviation between the simulated calculation result and the established fitting function model result was 2.7%. The minimum water-exit velocity of submarine aerial vehicles should be greater than 10.8 m/s. The research provides technical support for the trans-media motion stability analysis and hydrodynamic performance design of the submersible aerial vehicle. Full article

(This article belongs to the Special Issue Advances in Marine Applications of Computational Fluid Dynamics)

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16 pages, 5933 KiB

Open AccessArticle

Numerical Investigation on Air Film Fusion of Pressure-Equalizing Exhaust around Shoulder Ventilation of Submarine-Launched Vehicle

by Yao Shi, Jinyi Ren, Shan Gao and Guang Pan

J. Mar. Sci. Eng. 2022, 10(1), 39; https://doi.org/10.3390/jmse10010039 - 31 Dec 2021

Cited by 17 | Viewed by 2438

Abstract

In order to study the influence of pressure-equalizing exhaust at the shoulder of a submarine-launched vehicle on the surface hydrodynamic characteristics, this paper establishes a numerical calculation method based on the VOF multiphase flow model, the standard RNG turbulence model and the overset mesh technology; the method compares the fusion characteristics of the air film at the shoulder of the underwater vehicle, as well as the distribution of surface pressure along the vehicle’s axial direction. The results show that the approximate isobaric zone derived from air film fusion can greatly improve the hydrodynamic characteristics of the vehicle, and the number of venting holes determines the circumferential fusion time of the air film. The greater the number of venting holes, the sooner circumferential fusion starts. Full article

(This article belongs to the Special Issue Computational Fluid Mechanics)

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17 pages, 8819 KiB

Open AccessArticle

Effect of NACA0012 Airfoil Pitching Oscillation on Flow Past a Cylinder

by Rong Han, Wei Liu, Xiao-Liang Yang and Xing-Hua Chang

Energies 2021, 14(17), 5582; https://doi.org/10.3390/en14175582 - 6 Sep 2021

Cited by 3 | Viewed by 3363

Abstract

The flow past a cylinder is a classical problem in flow physics. In a certain range of Reynolds number, there will be Karman vortex street phenomenon in the wake of a cylinder, which will greatly increase the pressure drag of the cylinder. By controlling the vortex shedding phenomenon, drag reduction of the cylinder could be effectively realized. In this paper, a NACA0012 airfoil with pitching oscillation is placed downstream of the cylinder. Based on the tight coupling method, kinematics equations and Navier–Stokes equations in the arbitrary Lagrangian–Eulerian form are solved. Firstly, the effect of airfoil oscillation period and the distance between airfoil leading edge and cylinder center (x/D) are studied respectively, especially considering the aspects of vortex shedding and drag reduction effect. Besides, the vortex interaction in the flow field around the airfoil and cylinder is analyzed in detail. It is found that the NACA0012 airfoil with pitching oscillation can change the period of vortex shedding. Moreover, it can also increase the drag reduction rate to as high as 50.5%, which presents a certain application prospect in the engineering drag reduction field, e.g., for launch vehicles, ship masts, submarine pipelines, etc. Full article

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12 pages, 828 KiB

Open AccessProceeding Paper

Multi-Objective Optimization Design of a 30 kW Electro-Hydrostatic Actuator

by Chi Zhang, Xu Han, Tatiana Minav and Yongling Fu

Proceedings 2020, 64(1), 5; https://doi.org/10.3390/IeCAT2020-08525 - 22 Nov 2020

Viewed by 1532

Abstract

Electro-hydrostatic actuators (EHAs) combine the advantages of electric and hydraulic actuation, and it results in a preferable solution for heavy load actuation. The required power level of the EHA is increasing because it is being introduced to large vehicles such as submarines and heavy launch vehicles. Thus, a 30 kW EHA is under development for launch vehicles, which simultaneously require high dynamic performance, light weight, high efficiency, etc. Therefore, a dedicated multi-objective optimization design method is proposed for the preliminary design of the 30 kW EHA. In this study, firstly, the design requirements were analyzed for the launch vehicle application, and the objectives and the constraints of the optimization design were defined for the 30 kW EHA. Secondly, dedicated models were developed for evaluating each objective or constraint, including weight, bandwidth, and efficiency. Thirdly, the multi-objective EHA optimization design was implemented based on the genetic algorithm. Lastly, the optimization design results were evaluated through simulation analysis, which demonstrated that the 30 kW EHA achieved more than 10 Hz bandwidth with under 72 kg weight while the efficiency was also optimized. Full article

(This article belongs to the Proceedings of The 1st International Electronic Conference on Actuator Technology: Materials, Devices and Applications)

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