• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.866-872
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• 2006

A numerical study on the propulsive characteristics of a biomimetic foil is done by developing an unsteady linearly-varying strength vortex method. A biomimetic foil is represented as a deforming foil with a tail fin. Present method is verified by comparing the simulated results with results using finite element and finite volume methods. A new boundary condition is imposed by considering the relative rotational velocity, which has not been included in the previous published literature. It is found that the undulation amplitude increases the thrust while maximum thickness is stepping down the thrust. It is also shown that there exists an optimal frequency for maximum thrust generation. It is believed that present results can be used in the investigation of the propulsive characteristics of the biomimetic deforming foil.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.1-8
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• 1996

A potential-based panel method has been developed for numerical computation of wave resistance on a hybrid hydrofoil. Hybrid hydrofoil is composed of a main body, two struts and two hydrofoils. The main body, which is assumed to be an axisymmetric body for the present analysis, is normally used to support displacement of a body with its buoyancy. Normal dipoles and the sources are distributed on the body(main body, struts, hydrofoils) and the sources are distributed on the free surface. Linearized free surface and the radiation conditions are satisfied using the fourth order finite difference operator and the semi-linear pressure Kutta condition is used for the numerical computation of the hydrofoils. Poisson type free surface condition has been used for the numerical computation and hyperboloidal panel method has been used for better numerical accuracy. To verify this numeric method, model tests are performed in circulation water channel. From the comparison of experimental results with numeric ones, the present method can be used as a useful tool for the design of high speed vessels.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.868-874
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• 2007

Noises from the helicopter rotor model are calculated numerically at various pitch angles. The aerodynamic data are calculated by using prescribed wake model and unsteady panel method. The distribution of aerodynamic loads on the blade surface are obtained from $0^{\circ}$ to $9^{\circ}$ pitch angles with equiangular increments of $1.5^{\circ}$. Although thickness noise is not related to the change of pitch angles, loading noise level increases about 3~4dBA every $1.5^{\circ}$ increment of pitch angle. The additive noise level shows sufficient value to perceive the loudness. From the result of directivity pattern the sound level at the lower region of the blade disc plane is higher than that of the upper region.