• Journal of Ocean Engineering and Technology
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• v.23 no.4
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• pp.47-51
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• 2009

Thrust is one of the important performance characteristics of an AUV. At the design stage, the resistance of an AUV at its maximum speed is estimated and then the thrust system is designed, including the propeller diameter, propeller rpm, driving system, and required power. However, it is not possible to be certain that the thrust system has been correctly designed until the AUV is launched and its speed is measured. If data from a propeller open-water test is available, the thrust and torque of the propeller at a certain speed can be estimated. In addition, if the motor's torque characteristics are available, the maximum speed saturated by the induced propeller torque can be estimated. In this paper, an easy technique for estimating the maximum speed of an AUV will be shown, even in a case where additional resistance is gained from appendages not considered at the design stage. Furthermore, the thrust performance changes by adjusting the diameter of the propeller can be easily investigated.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.141-146
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• 2011

This study numerically carried out the propeller open water test(POW) by solving Navier-Stokes equations governing the three-dimensional unsteady incompressible viscous flow with the turbulence closure model of the ${\kappa}-{\omega}$ SST model. Numerical simulations are performed at various range of advance ratios. Corresponding to Reynolds numbers of $5.89{\times}105{\sim}6.47{\times}105$ based on free stream velocity and the chord length at 0.7 propeller radius. The present results give a good agreement with those of the experiment. The propeller induced vortical structures have been analyzed by visualizing the resultant vorticity. As the advance ratio increases, the magnitude and length of the resultant vorticity decrease significantly. As the main focus of present study, the numerical model to present the ($r-{\theta}$) plane-averaged resultant vorticity along the streamwise direction for various advance ratios has been suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.150-155
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• 2019

Cavitation refers to a phenomenon in which empty spaces occur in a fluid due to changes in pressure and a velocity. When a liquid moves at a high speed, the pressure drops below the vapor pressure, and vapor bubbles are generated in the liquid. This study used CFD to analyze the flow of fluid machinery used in marine and offshore plants. The goals are to ensure the validity of the analysis method for marine propellers in an open water test, to increase the forward ratio, and to use FLUENT to understand the flow pattern due to cavitation. A three-dimensional analysis was performed and compared with experimental data from MOERI. The efficiency was highest at advance ratios of 0.7 - 0.8. Thrust was generated due to the difference between the pressure surface and the suction surface, and it was estimated that bubbles would be generated in the vicinity of the back side surface rather than the face side of the propeller, resulting in more cavitation. The cavitation decreased sharply as the advance ratio increased. The thrust and torque coefficients were comparable to those of the MOERI experimental data except at the advance ratio of 1, which showed a difference of less than 5%. Therefore, it was confirmed that CFD can evaluate an open water propeller test.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.3
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• pp.158-166
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• 2021

In this paper, a numerical analysis technique using a body force model is investigated to estimate the available net thrust of multi-pod-driven ice-breaking vessels under bollard pull and overload conditions. To employ the body force model in present flow simulations, drag and thrust components acting on the pod unit are calculated by using Propeller Open Water (POW) test data. The available net thrusts according to the direction of operation are evaluated in both bollard pull and overload conditions under deep water. The simulation results are compared with the model test data. The available net thrusts, calculated by the present analysis for ahead operating modes at 3~6 knots which are typical speeds of the target vessel in arctic field, are agreed well with the model test results. It is also found that the present result for astern operating mode appears approximately 6 % larger than the model test result. In addition, the available net thrusts are calculated under the both operating conditions accompanied by shallow water effects, and the main cause of the difference is studied. Based on the result of the present study, it is confirmed that the body force model can be applied to the performance evaluation of multi-pod propulsion system and the main engine selection in early design stage of the vessel.