ABSTRACT In this study, the resistance characteristics of the amphibious vehicle in the transitional stage are studied. A deformable track wheel is designed and its effect on the amphibious vehicle’s resistance is studied. The numerical calculation method based on the RANS solver and the towing test method is used to analyse the hydrodynamic performance of the amphibious vehicle. Based on the comparison of the vehicle model with no wheel, the influence of wheels on additional resistance at the groove fault is studied. The inclination angles of the front and rear deformation wheels are studied respectively. The influence and principle of the track wheel configuration on drag are analysed and expounded in terms of pressure distribution, water climbing and spray on the wheel grooves, and the hull attitude. Finally, an adjustment strategy of the deformable configuration wheel in the transition stage is proposed.

Drag reduction design and research of high-speed amphibious vehicle’s deformable track wheels

The Star-CCM+ simulation software has been used to model a number of benchmark free surface flow cases, including the two dimensional submerged NACA 0012 foil, the surface piercing NACA 0024 foil, and the well investigated KCS vessel. The findings from the foil benchmark cases have permitted substantial improvement in the accuracy and convergence of the results for the KCS vessel when compared to preliminary studies undertaken as part of the master's project. It has been observed that a minimum set of temporal and spatial resolutions are required to yield an acceptable numerical solution, and guidelines to ensure that these requirements are met have been formulated, including modification of the default Star-CCM+ solver parameters for supposedly steady state free surface flows. Time step independent solutions for all of the cases investigated have been found, however the mesh resolution requirements to obtain this independence vary significantly, and some practical limitations regarding mesh size in the ship case precludes taking the most demanding requirements found and using them as a general recommendation. Some additional work, focusing on investigation of additional ship cases, has been proposed with the objective of clarifying guidelines for creating a time step independent mesh for ship flow problems. In general, a modelling approach has been identified using the Star-CCM+ software which yields a satisfactory result for a ship resistance prediction and a good starting point for further investigation of the nominal wake scaling problem.

Numerical Investigation of Free Surface Flows

A review on drag reduction technology: Focusing on amphibious vehicles

The influence of the walking mechanism on the resistance characteristics of a high-speed wheeled amphibious unmanned platform is studied and analyzed by considering its structure parameters and speed. Firstly, the walking mechanism system of the amphibious unmanned platform is optimally designed and its simulation model is established. Secondly, a realizable SST k-ω turbulence model and a CFD numerical model built by overset mesh technique are used to obtain a reliable numerical method. Then, the vehicle with retractable wheels is selected for simulation and the effect of wheel flip angle on the hydrodynamic performance is analyzed. Finally, the simulation result shows that: The numerical method has high accuracy and can better realize the simulation of vehicle motion and resistance prediction on water. The influence of the wheels on the water resistance is more significant. And the sinkage and trim value decrease gradually with wheel flipping, but when the hull was in the planing regime, the hull sink and rise increased with the wheel flipping. 

Optimization and Design of Walking Mechanism System for Amphibious Unmanned Platform

Abstract. In order to reduce the resistance and increase speed for
a high-speed wheeled amphibious vehicle, a wheel-retracting mechanism was
applied to a walking mechanism and the influence was researched. Firstly, to
obtain a reliable numerical method, a realizable shear stress transport (SST) k-ω turbulence
model and computational fluid dynamic (CFD) model built by an overset mesh technique was used and compared
with the corresponding model tests. Secondly, the effect of the wheels' flip
angle on resistance, heave and pitch was investigated. Then, the wheel well
was optimized by numerical simulation. Finally, the results showed that the
influence of the wheels on resistance was more significant, and the larger
the wheels' flip angle was, the more significant the resistance reduction
would be. An optimized wheel well was beneficial to resistance reduction.
Furthermore, the running attitude became steadier, thereby decreasing the
heave and pitch.


Influence of a walking mechanism on the hydrodynamic performance of a high-speed wheeled amphibious vehicle

Speed on water is a key indicator of amphibious vehicles. However, due to the inherent non-streamlined configuration, when reaching a certain velocity, the resistance acting on the vehicle hull is ...

Investigation on trim control of semi-planing amphibious cargo truck using experimental and numerical approaches:

Combining the structural features of cam engines and opposed engines, a kind of opposed cam piston engine is designed, in which a kind of variable sine curves family applied to the cam working surface. Based on the structure of this engine, a thermodynamic zero-dimensional model of the working cycle was established, and the accuracy of it was verified by the numerical simulation model utilizing the engine simulation software AVL BOOST. Based on the zero-dimensional model, the changes in the pressure, temperature, and quality of the working fluid in the cylinder under different cam profiles were calculated, and on this basis, the engine’s thermal efficiency, mechanical efficiency, overall machine efficiency, and power per liter were solved. Compared with common civil vehicle engines, OCPE has higher power per liter and has better economic performance and power performance.

Chengliang Sun

Papers

Investigation on trim control of semi-planing amphibious cargo truck using experimental and numerical approaches:

Simulation analysis and performance optimization of the combustion process of the opposed cam piston engine