Spade Rudder Research Articles

MARIN rudder mathematical model

This paper presents the mathematical model used in MARIN’s time domain software to describe the hydrodynamic loads excited by a rudder. The paper provides a detailed description of the mathematical model and its theory, along with highlighting the novel features that have been added to extend the model to four quadrants operations. Furthermore, the paper compares the mathematical model with experiments, showcasing the model’s capabilities and shortcomings. For this comparison, a spade rudder behind the KRISO Container Ship with and without a propeller upstream has been used as a case study to illustrate how the model performs in practice.

Investigations of Hydrodynamic Force Generated on the Rotating Cylinder Implemented as a Bow Rudder on a Large-Scale Ship Model

This paper presents experimental studies of the force generated on the rotating cylinder implemented as a bow rudder on a large-scale ship model. The research focused on the maneuverability of the unit equipped with a rotating cylinder (RC) in the front part of the model and its future use as a steering device on small draft river barges. The study presented in this paper is a continuation of the research carried out using the small physical model of a river push train in 1:20 geometric scale equipped with two bow RCs and open water tests of separated rotating cylinders carried out in a flume tank. The experimental test setup with RC installed on the model in 1:24 geometric scale allowed to compare the parameters of standard maneuvers performed with the use of RC and without it. The proposed method based on the measurement of the ship model trajectory during maneuvers allowed to compare the hydrodynamic steering force generated by RC with the steering force generated by the conventional stern spade rudder. The results of the experiments compared with empirical models show a similar trend. RC dynamics was tested for rotational speeds up to 570 RPM (revolutions per minute) and ship model velocity up to 1 m/s. The rotating cylinder generated velocity field is presented and phenomena influencing the generated hydrodynamic force are discussed.

WHY YACHT RUDDERS BREAK

For most sailing yachts, losing a rudder is probably the most catastrophic structural failure other than losing the keel. Rudder failure happens with distressing regularity. This paper examines the hypothesis that the underlying reason is design failure. There are many qualitative decisions to be taken in the design calculation process. Example calculations are presented which show that the maximum rudder force generated in steady state conditions is easily underestimated. For a typical spade rudder of a typical modern production sailing yacht, the normal rudder force should be calculated using a boat speed of at least 125% hull speed, and a force coefficient of at least 1.3. Care must be taken in selecting an appropriate value for the allowable stress of the material used for the stock.

Why Yacht Rudders Break

For most sailing yachts, losing a rudder is probably the most catastrophic structural failure other than losing the keel. Rudder failure happens with distressing regularity. This paper examines the hypothesis that the underlying reason is design failure. There are many qualitative decisions to be taken in the design calculation process. Example calculations are presented which show that the maximum rudder force generated in steady state conditions is easily underestimated. For a typical spade rudder of a typical modern production sailing yacht, the normal rudder force should be calculated using a boat speed of at least 125% hull speed, and a force coefficient of at least 1.3. Care must be taken in selecting an appropriate value for the allowable stress of the material used for the stock.

Modelling a spade rudder as a hollow two-way tapered Kirchhoff’s plate : free dry and wet vibration study with numerical verification

A semi-analytical approach to free dry and wet vibration of a trapezoidal, 2-way tapered, pivoted hollow spade rudder is presented. The rudder is modeled as a hollow Kirchhoff’s plate, with a NACA0018 profile chord section. The rudder pivot is modeled as a combination of a translational spring and a rotational spring. The span-wise and chord-wise non-uniform beam vibration is first analyzed by the Rayleigh-Ritz method, to establish the non-uniform beam modeshapes, which act as admissible functions to the Galerkin’s method for plate vibration. Eigenvalue analysis generates the plate natural frequencies and the plate modeshapes. Alternately, uniform beam modeshapes themselves are used as admissible functions into the Galerkin’s method. Frequencies are analyzed for various pivot positions, taper ratios, and NACA sections. For the wet vibration, constant strength source distribution technique is used to generate the added mass of a 2D aerofoil. Also, 3D panel method is used to generate the modal added masses, and hence the wet natural frequencies. The added mass coefficient is generated for various aerofoil fineness ratios, pivot fixities, taper ratios, aspect ratios.

Forced wet flexural dynamics of spade rudder in propeller slipstream: semi-analytical approach of pivoted FFFF plate

A semi-analytical approach of forced vibration of a trapezoidal, two-way tapered, hollow model spade rudder, is presented. The pivoted rudder is in the propeller slipstream; which causes harmonic hydrodynamic load. The excitation frequency of propeller-induced vibration (PIV) equals the propeller blade passing frequency. The rudder operates at a Reynolds’s number of the order of 108. It has a span of 1 m, root chord of 0.6 m, and tip chord of 0.5 m. It is considered as a hollow Free–Free–Free–Free Kirchhoff’s plate, with the chord section as an NACA0018 profile. The dry vibration is analyzed by the energy-based Galerkin’s method, using closed-form admissible functions in the two perpendicular directions. 3D constant-strength panel method is used to generate the modal added masses, and hence the wet natural frequencies. The drag and the lift coefficient of the rudder, at various angles of attack, are estimated to find the spatial distribution of the total PIV-causing normal force. The mean flow velocity about the rudder is the velocity of advance behind the propeller. The fluid velocity past the aerofoil section depends on the profile thickness and the angle of attack, thereby influencing the local lift. The hydrodynamic pressure varies parabolically along the span. The effect of the wake developed by the propeller, the stern shape, and the rudder angle on the hydrodynamic loading on rudder is included to express the transverse time-varying loading. The wet, forced vibration of the Kirchhoff’s plate is analyzed in MATLAB. The maximum bending stress and twisting sheer at the rudder stock is calculated for various angles of attack.

프로펠러 회전류에서 작동하는 방향타의 받음각 특성 연구

This study aims at numerically investigating the angle of attack characteristics of the rudder behind a rotating propeller. The rotating propeller of 5 blades and the full spade rudder are placed in the numerical water tunnel with a uniform flow condition to consider propeller-rudder interaction. The turbulence closure model is employed to simulate the three-dimensional unsteady incompressible viscous turbulent flow around the propeller and the rudder. The present numerical method are well verified by comparing with the experimental results. In order to identify the dependence of the angle of attack of the rudder on the rudder angle, a wide range of rudder angles is considered. The present study carried out the quantitative and qualitative analysis of the angle of attack in terms of the pressure distribution, streamlines and the evaluation of the flow incidence, resulting in that the angle of attack increases as we move from the root and the tip to the center of the rudder, regardless of the rudder angle. The distribution of the angle-of-attack along the span is strongly affected by rotating propeller flow and rudder angle. Consequently, the distribution of the angle-of-attack of the oncoming flow against the rudder leading edge plays a role in determination of rudder performance.

콴다효과를 이용한 전 가동 타의 양력성능 개선에 관한 연구

The shape of a conventional full spade rudder has been modified to implement the Coanda effect and consequential changes in the flow characteristics are carefully examined to show the significant enhancement in the lift performance. A preliminary numerical study has been done to identify the optimum configuration of the modified rudder sections. For the purpose, chord wise locations of the jet slit and the radii of the trailing edge were varied in several ways and the changes in the lift characteristics have been observed at the various angles of attack, particularly focusing on the usefulness of the Coanda effect upon delaying the stall or increase in the circulation. Making the most use of the results so attained, full spade rudder of a VLCC has been reformed to realize the Coanda effect. A series of model experiments and numerical simulations are performed to confirm the effectiveness of the Coanda effect in improving the performance of the modified rudder. It is found that considerable enhancement in the lift performance of the rudder is plausible at any rudder angle if an optimum jet momentum is provided.

전가동타와 비대칭타의 유체동역학적 특성 및 속도성능

This article examines hydrodynamic characteristics and speed performances of a ship attached with a full spade and a twisted rudder based on a computational method. For this study, a 13,100 TEU container carrier is selected. The turbulent flows around a ship are analyzed by solving the Reynolds-averaged Navier-Stokes equation together with the application of Reynolds stress turbulence model. The computations are carried out at the conditions of rudder, bare hull, hull-rudder and hull-propeller-rudder. An asymmetric body-force propeller is applied. The speed performance is predicted by the model-ship performance analysis method of the revised ITTC'78 method. The hydrodynamic forces are compared in both rudder-open-water and self-propulsion conditions. The flow characteristics, the speed performance including propulsion factors and the rudder-cavitation performance are also compared. The model tests are conducted at a deep-water towing tank to validate the computational predictions. The computational predictions show that the twisted rudder is superior to the full spade rudder in the respect of the speed and the cavitation performances.

타의 종류에 따른 컨테이너선의 조종성능 특성 연구

Generally Horn-type rudders have been used for single propeller and single rudder system. The reason is that the rudder torques of Horn-type rudder are smaller than those of Spade rudder with same lift force. But it is found that the rudder cavitation occurs on a Horn-type rudder of fast container ship. In this paper the comparison results of Horn-type and Spade rudders are described. HPMM tests are carried out to compare the effects of two rudder types on the maneuverability of a ship. It is shown that the maneuvering performance of a ship equipped with Horn-type rudder is better than that equipped with Spade rudder by comparing the test results and maneuvering coefficients at scantling condition. The reason is that the movable part area of Horn-type rudder is about 14％ larger than that of Spade rudder with same total area. And the rudder torque of Spade rudder is greater than that of Horn rudder. At ballast condition, however, the effect of rudder type is negligible.

Directly coupled fluid structural model of a ship rudder behind a propeller

A computational method is presented that models fluid structural interaction problems for three-dimensional marine structures. Flow can be modelled with either potential or viscous incompressible flow. The structure deformation is modelled by a shell finite element formulation. The two fields are coupled by a domain decomposition approach that uses virtual surfaces to transfer information. A typical spade rudder has been modelled for steady-state three-dimensional problems in a free stream and in way of a propeller race. These computational models have been tested for mesh dependancy in both the fluid and structural domains as well as the virtual surface definition. The results show increased correlation to experimental data from uncoupled hydrodynamic modelling as well as detailed structural deformation. Of note is the variation in rudder stock bending moment from that utilised by classification society scantling rules.

Designing the best catamaran

The AHP is used to develop a sailboat called an MHM-Maran that combines the characteristics of a sloop with a catamaran. With one large and one small pontoon (connected by two poles made of titanium), a fin keel, spade rudder, and a never-before-seen sail (maranaker), it offers many performance benefits to the sailor and is being considered by a contemporary sailboat manufacturer.

Operational and Developmental Experience on the U.S. Navy Hydrofoil "High Point"

Developmental trials on the U.S. Navy's first hydrofoil ship have determined operational capabilities arid evaluated a number of problem areas. Takeoff speed is 27 knots at a gross weight of 262,000 Ib. At a cruise speed of 40 knots, 4400 lip are required with propellers turning at 1270 rpm. Accelerations in Sea State 4 of 0.35 g rms, while hullborne at 8 knots, are to be compared with 0.07 g rms while foilborne at full power speed. Ventilation of the forward foil and hull furrowing occurred 2 to 3 times/mm in the occasionally larger short-crested waves, thus indicating a need to lengthen the forward strut to give the craft increased capability in the higher seas. A turning radius of 3000 ft was reduced to 1100 ft by increasing the size of the spade rudder. An unstable cavity at the forward foil-strut juncture, causing a roughness in the ride at high speeds, will be corrected with a fillet pod around this juncture. The original neoprene coating on the foils and struts failed below the waterlirie because of adhesion difficulties. Salt water leaking into the transmission oil sumps was the principle reason for frequent dry dockings, thus limiting foilborrie operation to approximately 2200 miles, to date.