• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.31-40
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• 2001

Low-order panel methods are being used to design marine propellers. Since the potential value over each panel for these methods is assumed to be a constant, the accuracy of prediction is known to be limited. Therefore, a higher order boundary element method(HOBEM) has been studied to enhance the accuracy of prediction. In this paper, a HOBEM representing the body boundary surfaces and physical quantities by a 9-node Lagrangian shape function is employed to analyse the flow around marine propellers in steady potential flow. First, the numerical results for a circular wing with thickness variations are compared with Jordan's linear solution. Then, the computational results of two propellers(DTRC 4119 & DTRC 4842 propeller) are compared with the experimental and numerical results published. The pressure distribution on the surface of the propeller is also compared with experimental data.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.1
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• pp.14-25
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• 2012

Recently, the application and installation of the pod propeller to the cruise ship is dramatically increased. It is because pod propulsion system allows a lot of flexibility in design of the internal arrangement of a ship. To reflect this trend, many researches have conducted to use the pod propeller for the roll stabilization of a ship. In the paper, a roll stabilization controller is designed by using fins and pod propellers as the control actuators for cruise ships. Two kinds of control algorithms are adopted for the roll control system; LQR (Linear Quadratic Regulator) algorithm and frequency-weighted LQR algorithm. Through the numerical simulation, the effect of the turning rate of the pod propeller on the roll control system is analyzed. Analysis of the simulation results indicated that the turning rate of the pod propellers is one of the important parameters which give the significant effects on the roll stabilization.

• Structural Engineering and Mechanics
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• v.30 no.1
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• pp.1-20
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• 2008

The dynamic characteristics of the passive, semi-active, and active tuned-liquidcolumn dampers (or TLCDs) are studied in this paper. The design of the latter two are based on the first one. A water-head difference (or simply named as water head in this paper) of a passive TLCD is pre-set to form the so-called semi-active one in this paper. The pre-set of water head is released at a proper time instant during an earthquake excitation in order to enhance the vibration reduction of a structure. Two propellers are installed along a shaft inside and at the center of a passive TLCD to form an active one. These two propellers are driven by a servo-motor controlled by a computer to provide the control force. The seismic responses of a five-story shear building with a passive, semiactive, and active TLCDs are computed for demonstration and discussion. The responses of this building with a tuned mass damper (or TMD) are also included for comparison. The small-scale shaking-table experiments of a pendulum-like system with a passive or active TLCD to harmonic and seismic excitations are conducted for verification.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.546-558
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• 2013

The research performed in this paper was carried out to investigate the numerical analysis of the sheet cavitation on marine propeller. The method is boundary element method (BEM). Using the Green's theorem, the velocity potential is expressed as an integral equation on the surface of the propeller by hyperboloid-shaped elements. Employing the boundary conditions, the potential is determined via solving the resulting system of equations. For the case study, a DTMB4119 propeller is analyzed with and without cavitating conditions. The pressure distribution and hydrodynamic performance curves of the propellers as well as cavity thickness obtained by numerical method are calculated and compared by the experimental results. Specifically in this article cavitation changes are investigate in both the radial and chord direction. Thus, cross flow variation has been studied in the formation and growth of sheet cavitation. According to the data obtained it can be seen that there is a better agreement and less error between the numerical results gained from the present method and Fluent results than Hong Sun method. This confirms the accurate estimation of the detachment point and the cavity change in radial direction.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.194-199
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• 2003

Developed m this research is a production information system for marie propellers. The paper deals with surface modeling and tool path generation modules of the system. Since the input point data may have some errors, the data is examined using the 2nd divided difference. The point data is interpolated to a $G^2$ chord-length spline surface with some end-conditions. The effects of the various end-conditions on the interpolated surface are discussed in the paper. The tool paths for blade, fillet, and boss of the propeller are generated. Some illustrative examples from an industry are presented.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.98-106
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• 2007

This paper presents a statistical prediction procedure for the propeller racing of ships with twin screw propellers sailing in ocean waves. The propeller racing is one of the most important factors of seakeeping qualities in relation to the safety of main engine and shafting system. It is especially significant key word for designing the twin-screw-propeller-type ship in view of allowable maximum propeller diameter etc.. In former studies, the propeller racing generally means the situation (propeller exposed) in which the relative motion amplitude between ship hull and wave surface would exceed a depth of point in rotary disk propeller. Therefore, it seems that the magnitude of the amplitude and its exceeding frequency have been examined as a principal subject of study as usual. However, the time during which the amplitude exceeds a depth of point must be also one of most important factor affecting the trend of propeller racing. This paper proposes a simply practical method for estimating the time lasting of exposed propeller related to twin screw propeller racing in rough confused seas on the basis of the statistics. Then, it is confirmed that the practical method is useful and convenience for considering the propeller racing in the stage of the basic design.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.3
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• pp.8-17
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• 2002

In this paper, the computational analysis of open-water characteristics for three model propellers(P4119, P4842 and 3 podded propeller of KRISO) is done by using a viscous-flow method based on Reynolds-Averaged Navier-Stokes equations. The results are presented for open-water performances, blade-section pressures, and circumferentially-averaged velocity profiles for the all three propeller models. Overall close agreements with available experimental data are shown. However, some discrepancies are also found in the pressure near the leading edge of the propeller blade and the open-water performance of the podded propellers.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.2
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• pp.9-17
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• 1984

Laminar and turbulent boundary layers on a rotating sector and a helical blade are calculated by differential method. The estimation of three dimensional viscous flows provide quite useful informations for the design of propellers and turbo-machinery. A general method of calculation is presented in this paper. Calculated laminar boundary layer on a sector shows smooth development of flows from Blasius' solution at the leading edge to von Karman's solution of a rotating disk at the down-stream. Eddy viscosity model is adopted for the calculation of turbulent flows. Turbulent flows on a rotating blade show similar characters as laminar flows. But cross-flow angle of turbulent flows are reduced in comparison with laminar boundary layers. Effects of rotation make flow structures significantly different from two-dimensional flows. In the range of Reynolds number of model scale propellers, large portion of the blade are still in the transition region from laminar to turbulent flows. Therefore viscous flow pattern might be quite different on the blade of model propeller. The present method of calculation is to be useful for the research of scale effects, cavitation, and roughness effects of propeller blades.

• Journal of Ocean Engineering and Technology
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• v.28 no.3
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• pp.199-208
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• 2014

In this study, propeller open water characteristics ($K_P$, $K_T$ and ${\eta}_o$) were compared for three different ducted propellers using a Computational Fluid Dynamics (CFD) analysis, as well as an experimental test at a basin. The best shape of the duct was selected from the three types of specially designed ducts based on the CFD analysis results. The same propeller model (Kaplan type propeller) was used inside all three duct models, and the propeller open water characteristics were compared, predominantly at the design speed for an underwater vehicle. Finally, the results of the CFD test simulations for the selected duct case were verified by experimental open water tests in a towing tank.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1753-1764
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• 2006

A U-80 propeller and its modified version, U-75 propeller, are used for a micro air vehicle. The performance characteristics of a U-80 propeller and a U-75 propeller have not much known in the published literature. Thus, their aerodynamic characteristics are investigated using a lifting surface numerical method. The lifting surface method is validated by comparing computed results with measured data in a wind tunnel. From the computed results, it is found that the U-75 propeller produces larger thrust with higher efficiency than the U-80 propeller. To enhance the performance of these propellers, a new propeller is designed by following the sequential design procedures with the design parameters such as hub-tip ratio, maximum camber and its position, and chord length distribution along the radial direction. The performance of the designed propeller is shown to be improved much comparing with those of both the U-80 and U-75 propellers.