Improvement of Rankine Panel Method for Seakeeping Prediction of a Ship in Low Frequency Region

Abstract

Rankine panel methods have been studied for solving 3D seakeeping problems of a ship with forward speed and oscillatory motions. Nevertheless, there is a drawback in the numerical method for satisfying the radiation condition of outgoing waves at low frequencies, because the waves generated ahead of a ship reflect from the outward computational boundary and smear the flow around the ship. The so-called panel shift technique has been adopted in the frequency-domain Rankine panel method, which is effective when the generated waves propagate downstream of a ship. In this paper, in addition to this conventional panel shift method, Rayleigh’s artificial friction is introduced in the free-surface boundary condition to suppress longer wave components in a computational region apart from the ship. With this practical new method, it is shown that there is no prominent wave reflection from the side and/or upstream computational boundaries even in the range of low frequencies. As a consequence, the unsteady pressure, hydrodynamic forces, wave-induced ship motions, added resistance are computed with reasonable accuracy even in following waves and in good agreement with measured results in the experiment using a bulk carrier model which is also conducted for the present study.

Temperature interference in improved FBG pressure sensor for towing tank test

“…The superiority of ver. 7 was confirmed through this test, as will be described later, so the same investigation was conducted on the RIOS bulk carrier model, for which much data have been accumulated [4,6,26].…”

“…The value of C f is given so that the slope is equal to that of the Pressure [N/m 2 ] Fig. 4 An example of calibration outputs from an FBG pressure sensor hydrostatic pressure g z ( : density of water, g: gravitational acceleration, z : sinkage), which is illustrated by the red line in Fig. 4.…”

“…On the other hand, local physical quantities are integrands or components for the global physical quantities, such as the wave field around an oscillating ship and the pressure on the ship hull. To estimate these quantities more accurately, various theoretical calculation schemes have been developed as alternatives to the strip methods [1,2] (e.g., [3][4][5][6]). Recently, with the development of computer technologies, computed results of seakeeping performance have been produced with Computational Fluid Dynamics (CFD) (e.g., [7][8][9][10]).…”

Resonant waves in the gap between two advancing barges

“…Other categories of radiation condition applicable to low forward speed problem have been proposed and validated recently. Yasuda et al [16] introduced Rayleigh's artificial friction in the boundary condition to suppress longer wave components in a computational region apart from the ship. Their simulation results showed that wave reflection from upstream boundary was very limited and good agreement with measured results was obtained as a result.…”