• Bulletin of the Society of Naval Architects of Korea
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• v.16 no.3
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• pp.9-19
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• 1979

A method of improving rudder effectiveness by applying a rotating cylinder to a rudder(so called "rotating-cylinder rudder") has been experimentally studied. Also, the improvements in ship's maneuvering characteristics with its application has been analytically evaluated. It has been shown that this improvement is significant.

• Steel and Composite Structures
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• v.51 no.2
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• pp.139-151
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• 2024

In this research, a semi-analytical solution is presented for computing mechanical displacements and thermal stresses in rotating thick cylindrical pressure vessels made of functionally graded material (FGM). The modulus of elasticity, linear thermal expansion coefficient, and density of the cylinder are assumed to change along the axial direction as a power-law function. It is also assumed that Poisson's ratio and thermal conductivity are constant. This cylinder was subjected to non-uniform internal pressure and thermal loading. Thermal loading varies in two directions. The governing equations are derived by the first-order shear deformation theory (FSDT). Using the multilayer method, a functionally graded (FG) cylinder with variable thickness is divided into n homogenous disks, and n sets of differential equations are obtained. Applying the boundary conditions and continuity conditions between the layers, the solution of this set of equations is obtained. To the best of the researchers' knowledge, in the literature, there is no study carried out bi-directional thermoelastic analysis of clamped-clamped rotating FGM thick-walled cylindrical pressure vessels under variable pressure in the longitudinal direction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.1
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• pp.13-19
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• 1995

An experimental investigation has been made for flow in a circular cylinder with a rotating bottom disk. Flow system considered in this paper is a characteristic model of interior flows of an electric washing machine. Flows in a tub of an electric washing machine are driven by a rotating bottom disk called a pulsator. The simple and characteristic model was composed of a circular cylinder with impulsively rotating endwall disk and a viscous fluid in it. Rotational motion of the pulsator is periodic and alternative in rotation direction. The flow field in the interior region is governed by a horizontal boundary layer forms on the impulsively rotating disk. Experimental approach was accomplished by adopting an image processing technique for velocity measurements. Comprehensive details of the flow structure are presented. Also a meridional circulation is obtained by tracking image particles suspended in the fluid. Flow structure and data are successfully procured for this complex rotating flow field.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.695-701
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• 2001

While a rotating inner cylinder executes a periodic translational motion in concentric annulus, the vibration of the rotating inner cylinder is induced by fluid-dynamic forces acting on the cylinder. In the previous study related to journal bearing, the unsteady viscous flow in the annulus and the fluid-dynamic forces were evaluated based on a numerical approach. Considering the dynamic-characteristics of unsteady viscous flow, an approximate analytical method has been developed for estimating added mass, viscous damping and fluid-stiffness coefficients. For the study of flow-induced vibrations and related instabilities, it is of interest to separate the coefficients from the fluid-dynamic forces. The added-mass and viscous damping coefficients for very narrow annular configurations, as journal bearing. can be approximated by considering the gap ratio to the radius of inner cylinder, while the fluid-stiffness coefficient is related to the Reynolds number, the oscillatory Reynolds number and the gap ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.481-486
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• 2011

It is important to predict the behavior of a liquid film around a rotating cylinder in the film coating process of the steel industry. When the cylinder rotates, the behavior of the liquid film on the rotating cylinder surface is influenced by the cylinder diameter, the rotation speed, the gravitational force, and the fluid properties. These parameters determine the liquid film thickness and the rise of the film on the cylinder surface. In the present study, the two-phase interfacial flow of the liquid film on the rotating cylinder were numerically investigated by using a VOF method. For various rotation speeds, cylinder diameters and fluid viscosities, the behavior of liquid film on the rotating cylinder were predicted. Thicker film around the rotating cylinder was observed with an increase in the rotation speed, cylinder diameter, and fluid viscosity. The present results for the film thickness agreed well with available experimental and analytical results.

• Journal of KSNVE
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• v.11 no.3
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• pp.428-436
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• 2001

The rotating inner cylinder executes a periodic translational motion in concentric annulus while the outer one is stationary. In the study of flow-induced vibrations and relaxed instabilities, it is of interest to evaluate the fluid-dynamic forces acting on the rotating inner cylinder. In the present work, the governing equations for the confined flow are expressed as Navier-Stokes equations, including the steady and unsteady terms. The fluid parameters for steady flow generated by the rotating cylinder are determined analytically while the unsteady ones by the oscillatory motion are evaluates by a numerical method based on the spectral collocation method. In order to validate the numerical approach, the numerical results are compared wish the analytical ones given by existing theories, for simple cases where the both approaches are applicable. Good agreement was found between the results. It is found the effects of the Reynolds number, defined by rotating velocity, on the fluid-dynamic forces are important for the case of relatively low oscillatory Reynolds number, defined by oscillatory frequency : j.e., in case of $Re_\omega\gg Re_S$.

• Steel and Composite Structures
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• v.22 no.5
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• pp.1193-1214
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• 2016

In this paper, the 3D stress state and inter-laminar stresses in a rotating thin laminated cylinder shell are studied. The thickness of the cylinder is supposed to be thin and it is made of laminated composite material and can have general layer stacking. The governing equations of the cylindrical shell are obtained by employing the Layerwise theory (LWT). The effect of rotation is considered as rotational body force which is induced due to the rotation of the cylinder about its axis. The Layerwise theory (LWT), is used to discrete the partial differential equations of the problem to ordinary ones, in terms of the displacements of the mathematical layers. By applying the Free boundary conditions the solution of the governing equations is completed and the stress state, the inter-laminar stresses, and the edge effect in the rotating cylindrical shells are investigated in the numerical results. To verify the results, LWT solution is compared with the results of the FEM solution and good agreements are achieved. The inter-laminar normal and shear stresses in rotating cylinder are studied and effects of layer stacking and angular velocity is investigated in the numerical results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1310-1321
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• 1994

Turbulent coherent structures in the intermediate wake of a stationary and rotating cylinder, spin rate S=0.7, situated in a uniform were experimentally investigated using a conditionalphase average technique. Measurements were carried out at a section of 8.5 diameters downstream form the center of cylinder and a Reynolds number of $Re=6.5{\times}10^{3}.$/TEX> The phase averaged velocity and velocity vector fields, contours of vorticity, turbulent intermittency function and velocity fluctuation energy are presented and discussed in relation to the large scale coherent structures by Karman vortices that shed periodically from the cylinder. Coherent wake structures of the rotating cylinder is almost identical with stationary cylinder, but the lateral displacement and shrinkage of turbulent wake region is occured by rotation. Rotation of the cylinder result in that the deflection of wake center to deceleration region(Y/D${\simeq}-0.3)$ and the decrease of mean velocity defect(10%), vorticity strength of large scale structures(19%), total velocity fluctuation energy(12%).

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.327-330
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• 2006

This paper represents the numerical analysis on effects of radius ratio in a concentric annulus with a rotating inner cylinder. The numerical model consisted of two cylinder which inner cylinder is rotating and outer cylinder is fix, and the axial direction is used the cyclic condition because of the length for axial direction is assumed infinite. The diameter of inner cylinder is assumed 86.8mm, the numerical parameters are angular velocity and radius ratio. Also, the whole walls of numerical model have no-slip and the working fluid is used water at $20^{\circ}C$. The numerical analysis is assumed the transient state to observe the flow variations by time and the 3-D cylindrical coordinate system. The calculation grid adopted a non-constant grid for dense arrangement near the wall side of cylinder, the standard $k-{\omega}$ high Reynolds number model to consider the effect of turbulence flow and wall, the fully implicit method for time term and the quick scheme for momentum equation. The numerical method is compared with the experimental results by Wereley and Lueptow, and the results are very good agreement. As the results, TVF isn't appeared when Re is small because of the initial flow instability is disappear by effect of the centrifugal force and viscosity. The vortex size is from 0.8 to 1.1 for TVF at various $\eta$, and the traveling distance for wavy vortex have the critical traveling distance for each case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.833-843
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• 2002

The present experimental and numerical investigations are performed for the characteristics of transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure losses and skin- friction coefficients have been measured for the fully developed flow of water and glycerine-water solution (44%) with the inner cylinder rotating at speed of 0∼600 nm, respectively. The transitional flow has been examined by the measurement of pressure losses to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients. The occurrence of transition has been checked by the gradient changes of pressure losses and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, it is gradually declined for turbulent flow regime.