Published papers

This paper reports an experimental study on application of pendulum theory to determine the possibility of overturning of a rectangular hull model. The model was not a hull of a self-propelling ship but was a pontoon used as a non-self-navigating work vessel.

In this study, we propose the righting moment rate (Rr) as a new stability index for rectangular hulls; the hulls of such a shape have both a lower height and larger width than ships, and they are used for work vessels without a propulsion unit. In naval architecture and marine engineering, the metacentric height (GM) is one of the most basic stability indexes.

This study experimentally investigated heat transfer and flow characteristics under natural convection in a closed rectangular chamber filled with HFE-7100 fluid, employing megasonic waves.

We examined wave phenomena pertinent to water in a rotating, laterally oscillating cylindrical container. In particular, we measured the time-dependent dynamic water pressure and pressure change by fast Fourier transform analysis. The swirling of water in the container had three frequency components; the frequency responses of each frequency component are reported herein. When swirling occurs in a rotating cylindrical container, it was found that the wave rotating in the same direction as the rotation of the cylindrical container and the wave rotating in the opposite direction to the cylindrical container exist at the same time.

We investigated characteristics of water sloshing in a rotating, laterally oscillating, cylindrical container both theoretically and experimentally. In our experiment, the time-dependent dynamic pressure of the water on the wall rather than the free-surface displacement of the water was measured, and the experimental parameters are the lateral forcing frequency, the rotation frequency of the cylindrical container, and the water depth. We also conducted a theoretical analysis to understand the experimental results. The swirling of water in the container had some frequency components; the frequency responses of each frequency component are examined herein.

We have investigated the free-surface fluctuations of liquid in a rotating, laterally oscillating, cylindrical vessel. We measured the time-dependent fluid-dynamic pressure instead of the free surface luctuations. From an FFT analysis of the dynamic pressure, we obtained two significant frequencies. They are associated, respectively, with waves that rotate in the same direction, and in the opposite direction, relative to the rotation of the vessel. We also examined these results using linearized wave theory.

極性流体の各種の定常流れを理論解析し，寸法効果パラメータ，極性効果パラメータの諸量が流れ場に及ぼす影響を調べた。

多孔質円管内の助走区間領域における過渡流れを理論的に調べ，しみ出し・しみ込み速度が速度分布の発達過程に及ぼす影響を明らかにした。

末端に圧力タンクが設置された直線テーパ管内の圧力波動の伝播の様子を実験を行って明らかにし，理論解析結果と比較検討し，理論解析の有効性を明らかにした。

磁性流体の構成方程式を新たに提案し，それを円管内の流れ場解析に用いた。そして，従来明確で無かった流れ場の様子を明らかにした。

A phenomenological treatment is given for the steady ferrofluid flows in annular pipes in the presence of uniform external magnetic fields. It is found that the apparent viscosity of a dilute colloidal suspension of ferromagnetic particles is a marked function of both the magnitude and direction of an externally applied magnetic field. The experimental fact shown by McTague (1969) that the additional viscosity is greater by a factor of 2 for the field parallel to the flow than with it perpendicular is theoretically explained. Analytical expressions of the distributions of velocity and angular velocity of the ferrofluid in annular pipes are derived under the influence of the external field. The induced magnetization calculated here to first order is skewsymmetric with respect to the plane through the center line of the pipe and perpendicular to the applied magnetic field.

だ円柱が突然加速運動を開始した場合のだ円柱まわりの流れ場を差分法によって数値解析し，だ円柱の抗力係数，揚力係数が時間経過と共にどのように変化するかを調べた。

The early stage of the flows due to uniformly accelerated flat plate, elliptic and circular cylinders from rest in incompressible viscous fluids are numerically studied by the finite difference method. The time dependence of streamlines and equi-vorticity lines are shown in the flow patterns. The Dufort-Frankel technique is used for solving the vorticity transport equation and the finite Fourier transport equation and the finite Fourier transform for solving the stream function, which is applied to the analysis of a block tridiagonal matrix equation. The main conclusions are as follows ; (1) The Fourier series method is more than ten times faster than the SOR method. (2) Numerical experiments obtained here have very good agreements with real experiments for flat plates and circular cylinders. (3) The length of vortex pairs behind an uniformly accelerated elliptic cylinder at the attack angle 90° is obtained as a resultant of numerical experiments. (4) The growing process of the secondary vortexes behind a circular cylinder is revealed at Reynolds number 731.

Although much progress has already been made in solving problems in step responses of pressure in a linear tapered pipe, new developments are still needed before the two dimensional wave equation can be solved routinely. This paper describes one such development. A new method of solving one dimensional wave equation in linear tapered compound pipes with arbitrary cross-sections has been devised. Results which are obtained from this theory are compared with experiments in pipes with square cross-sections. And we obtained the following conclusions: (1) Damping coefficients in an arbitrary cross-section are defined and are expressed analytically for some representative cross-sections. (2) The viscous solution of wave equation obtained by Laplace transformation explains well distorted pressure histories in a linear tapered pipe with an arbitrary cross-section. (3) Pressure waves in a square cross-section include higher modes of frequency and damp rapidly more than ones in a circular cross-section. But fundamental characteristics as waves are independent of the cross-section of the pipe except for the small aspect ratio.

The flow normal to an infinite thin elliptic cylinder which is uniformly accelerated from rest in a direction perpendicular to its generating lines in a viscous fluid is considered. The Dufort-Frankel method for the vorticity transport equation is used for the numerical simulation of viscous incompressible flows, and a new finite Fourier transform method is introduced in order to handle the stream function equation for accurate and efficient calculation. A major part of the present paper is devoted to physical properties of the flow for the early stages of development of the wake behind the obstacle. A computer-aided flow visualization method is used to demonstrate the main features of the hydrodynamic field for the flow. The rest of this paper demonstrates the important unsteady forces such as time-dependent drag, lift and moment acting on the body immersed in a viscous fluid, and presents specific numerical results for various transition.

Two-dimensional flows of magnetic fluid between two parallel plates in the transverse and longitudinal magnetic fields are investigated experimentally. The increasing rate of resistance coefficient is obtained and discussed with respect to the magnetic field length and Reynolds number.

Propagation of waves on the surface of a magnetic fluid are investigated experimentally. It is found that the surface velocity of a magnetic fluid depends on intensity of a magnetic fie1d, frequency of a traveling magnetic field and depth of a magnetic fluid. Influences of these parameters on the propagation of waves are precisely examined. The surface velocity is proportional to intensity of a magnetic field. There exists the most suitable condition which gives the maximum surface velocity. This condition is closely connected with the frequency of a traveling magnetic field and the depth of a magnetic fluid. Theoretical investigation is also carried out in order to clarify the present phenomenon.

The GSMAC-FEM (Generalized Simplified Marker and Cell FEM) which is an extension of the SMAC-FDM is a stable and fast scheme for the incompressible viscous flow. The rotation form of the Navier-Stokes equation in which velocity and Bernoulli function are interpolated as a linear function and a constant function. This interpolation is simple and convenient in making the mesh system. On the contrary, the approximation which is mentioned above makes it difficult to analyze inlet-exit flow including the Neumann's boundary conditions. The present paper shows a modified GSMAC method which is available for high Reynolds flows with Neumann's boundary conditions (especially the pressure boundary).The modified scheme consists of an algorithm which satisfies the continuity equation much more than the previous GSMAC method.

A theoretical solution of a pulsatile flow in the entrance region of a porous pipe was derived by Oseen's approximation reported in the previous paper when the radial wall velocity was constant along the pipe axis. According to Hornbeck's investigation, radial wall velocity alters due to the difference between the inner and outer pressure of a porous pipe. In the present paper, we dealt with a pulsatile flow whose radial wall velocity varies exponentially along the pipe axis. Dynamic characteristics such as velocity, and pressure coefficient are precisely discussed on the boundary conditions for pulsatile injection and suction from the pipe wall.