渦格子揚力面モデルによる調和伴流中のプロペラ非定常特性解析

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The theoretical calculation of hydrodynamic characteristics of a marine propeller has been remarkably developed by the aid of high speed computers with large memory capacity. It is already useful for practical applications to the design problems on the steady characteristics. But the unsteady characteristics have not necessarily been solved enough. The authors have analyzed some fundamental unsteady problems on the fluctuating thrust and torque of a propeller in the typical harmonic wakes, the pattern modes of which are given by the function cos nθ, where n one to eight, employing the mathematical model of the harmonic-oscillating vortex lattices lifting-surface. The numerical results of this calculation present some interesting facts, such as existence of amplification effect of thrust and torque fluctuations in the certain modes of wake pattern cos 2θ, cos 3θ and cos 4θ, and their progressive phase due to striking influence of the time derivative term of circulations of vortices. On the contrary, the outflow of shed vortices from the trailing edge has effect to reduce the amplitude and to give a lag of the phase. It is pointed out that the non-linear effect of a non-uniform wake field brings about the higher efficiency of propeller than in open water and another fluctuations of thrust and torque of double blade frequency. The results are compared with other theoretical calculations of Koyama's method and a quasi-steady way. The performance tests of three model peopellers of 3, 4, and 5 blades were carried out behind the mesh-screens to generate harmonic wakes. The data of experiments were analyzed to be compared with calculations. The agreement of them is to be satisfied when errors in experiments and analyses are considered.
社団法人日本船舶海洋工学会の論文

渦格子揚力面モデルによる調和伴流中のプロペラ非定常特性解析

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