Abstract
A numerical technique to simulate the hydrodynamic behavior of ducted propellers attached to an underwater vehicle traveling under the mutually interacting flow fields of the vehicle and the propellers is proposed; the hydrodynamic performance of the propellers and the hydrodynamic loading on the main body of the vehicle when it is in different kinds of motion is investigated numerically. In the research, 3D geometric models of the duct, propeller, and main body of the vehicle are first constructed according to their geometrical features. A computational fluid dynamics (CFD) technique based on the hybrid algorithm of dynamic mesh-nested sliding mesh is applied to solve the Navier–Stokes equations that govern the fluid motion around the duct, propeller, and main body of the vehicle when it is in motion. These equations are solved numerically with the CFD code Fluent. With the proposed numerical simulation technique, the hydrodynamic characteristics of the thrusts generated by the ducted propellers and the loading on the main body in the vehicle system under the mutually interacting flow fields are observed. The results of our numerical simulation indicate that the hybrid algorithm of dynamic mesh-nested sliding mesh can simulate multiple degrees of freedom of motion in underwater vehicle systems. In different motion states, the main body exerts a significant influence on the investigated flow fields; during the vehicle motions, negative wakes are formed on both sides of the main body, which lead to a decrease in the thrusts generated by the propellers on both sides. The thrust of the middle propeller is greater than that of the normal single one because of the obstructing effect in the tunnel caused by the main body.
Highlights
Introduction published maps and institutional affilThe underwater robot, known as a remotely operated vehicle, is a working robot
To validate the effectiveness of the hybrid algorithm of dynamic mesh-nested sliding mesh that was used in the analysis of the underwater vehicle system, existing experimental data on the representative ducted propeller of type Ka 4-70/19A [15] were taken as a reference
Comparing the hydrodynamic characteristics of two-dimensional circular motion (Figure 16) with those of three-dimensional circular motion (Figure 20), we found that the motion parameters of multiple dimensions had a significant effect on the thrust characteristics of the propeller control mechanism of the underwater robot system
Summary
The fluid in the research was assumed to be incompressible viscous fluid. The equations governing the fluid motions around the duct, propeller, and underwater vehicle in an unsteady motion are given as follows: Continuity equation:. A standard RNG k-ε turbulence model was applied to describe turbulence within the flow field; the turbulence equations are as follows:. In these equations, Gk represents the generation of turbulence kinetic energy due to the mean velocity gradients, calculated as described in Modeling Turbulent Production in the k-ε Models. Gb is the generation of turbulence kinetic energy due to buoyancy, calculated as described in Effects of Buoyancy on Turbulence in the k-ε models. YM represents the contribution of the fluctuating dilatation in compressible turbulence to the overall dissipation rate, calculated as described in Effects of Compressibility on Turbulence in the k-ε models.
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