High-speed Planing Hull Research Articles

Investigating the Effects of Cargo Weight and its Distribution on the Dynamic Performance of a High-Speed Planing Hull

The aim of this article is to evaluate the effects of cargo relative weight and its distribution along the boat’s length in addition to the relative water wavelength on the dynamic performance of a high-speed planing hull. Here, the dynamic performance is measured by the intensity of the boat’s heave and pitch motions. The Zarnick’s strip theory, which divides the vessel’s hull into equal lateral sections, is used to study the applied forces on the vessel, and a MATLAB code is provided based on it. It is demonstrated that increasing the cargo weight and its distribution result in more heave and pitch, and the maximum amount of them are observed in the wave with a length of about 5 times the length of the boat. In addition, the interactive effects of cargo weight and its distribution on the heave and pitch motions are affected by the relative wavelength. Therefore, the more centralized cargo distribution is preferred to increase the dynamic performance of a heavy planing boat with cargo weights more than 50% of the boat’s weight, while moving in short waves (λ⁄L<4); and for light cargo weight, less than 50% of the boat’s weight, the favorite cargo distribution is broad. When the boat sails in long waves, the desired distribution is reversed.

Moving air-water interface on no-slip solid walls for high-speed planing hulls

ABSTRACT In this study, the classical ‘moving-contact-line’ problem associated with the no-slip boundary condition (BC) is examined, with a particular focus on large-scale, high Reynolds number turbulent ship flows. Numerical ventilation is one of the main issues reported for the computational prediction of the high-speed small planing craft using the Volume-of-Fluid (VOF) method. A numerical strategy is presented to resolve this issue with a wave blanking distance defined and used when solving the VOF equations, which is chosen based on the y + values and the velocity profiles in the boundary layer. A series of numerical tests are conducted using a slamming plate and a stepped high-speed planing hull. The numerical experiments show that if the blanking distance is y + < 30 (inside the buffer and viscous sublayers), the air-water interface on the wall will be unstable and numerical ventilation will occur. For the blanking distance y + > 30 (outside the buffer layer), the air-water contact line is smooth and air entrainment can be avoided. It is suggested that the blank distance needs to satisfy 30.0 < y + < 200.0 in consideration of accuracy and stability, and a value of y + ∼ 100.0 can be used in practice.

A revisited verification and validation analysis for URANS simulation of planing hulls in calm water

Verification and Validation (V&V) is the foremost analysis which is carried out for evaluation of the accuracy level and dependability of computational fluid dynamic (CFD) simulations. The present study investigates the V&V of CFD models in predicting the dynamic trim and hull resistance of high-speed planing hulls with an aim to provide a deeper understanding of V&V analysis in this specific field of application. Two different planing hulls, namely the C05 stepped hull and the C1 interceptor hull, are analyzed with four different grids and time-steps using two mesh motion techniques, namely overset and morphing approach. The discretization (grid) and time-step uncertainties for each CFD simulation are estimated using the least squares method. The results indicate that the overset mesh approach performs better than the morphing grid method in terms of numerical uncertainty and validation achieved for both hulls. The error of both techniques in the prediction of resistance and trim angle of the boat shows an acceptable range of accuracy. The findings provide valuable insights for simulation-based designing and optimizing high-speed planing hulls, specifically by identifying the optimal mesh technique, cell number, and time-step for accurate prediction of wetted surface shape, ventilation formation, running attitude, and resistance.

Comparative study of experimental and CFD results for stepped planing hulls

In recent years, research has been conducted on reducing resistance by adding steps on the bottom of high-speed craft. The most significant issue in the design of multi-stepped planing craft is the selection of an appropriate step configuration, i.e., step geometry, location, and height. This requires a general knowledge of the hydrodynamic behavior of each step configuration. Although the towing tank test is an effective method to predict accurately the hydrodynamic behavior of stepped planing boats, there are restrictions in studying some details. In this study, a Computational Fluid Dynamic (CFD) method is used to investigate the hydrodynamic behavior of a stepped planing hull with eight different step configurations in detail. Comparison of the results of trim angle, resistance, sinkage, wetted surface, and ventilation length of swept-stepped planing hulls for different step configurations at various Froude numbers shows that a maximum average resistance reduction occurs at 1.9 <FrB < 4.0 with the step height of 2.73% BTC located at 48.46% L from the transom. There is also a lower resistance associated with a step height of 0.91% BTC at 48.35% L distance from the transom at FrB > 4. These results can be used to improve high-speed planing hull performances by utilizing an appropriate step configuration.

CFD Study on Hydrodynamic Performances of a Planing Hull

The scope of the present study is to investigate the effects of various geometrical hull features, such as tunnels, spray rails and whiskers on the hydrodynamic performance of a high-speed planing hull. The criteria being tested to emphasize the boat performance are the total drag, sinkage and trim angle. In addition, the decomposition of the resistance into viscous and wave-making resistance are taken into consideration. The study starts with a validation test against experimental data in order to accentuate the capability of the Computational Fluid Dynamics CFD simulation to accurately predict the total drag and trim angle of the initial form. This is later followed by a verification study based on the Richardson Extrapolation method with a grid- and time-step-convergence test in order to predict the numerical errors during the simulation. After establishing the simulation parameters regarding the proper grid size and time step, the comparative study takes place for five hull shapes and two whisker configurations while the boat is sailing at eight different speeds. The assessment of the hydrodynamic flow parameters is evaluated compared to the initial form in order to investigate the influence of the geometry change on the hydrodynamic performances of the boat. Validation of the numerical results showed the reliability of the CFD simulation to accurately predict the drag and trim angle of the boat, while the comparative study revealed that the total drag can be reduced by up to 9%, especially at higher speeds.

CFD based prediction on hydrodynamic effects of Interceptor and flap combination on planing hull

It has been a continuous effort for long years by high-speed vessel designers to achieve its optimal hydrodynamic performance. Few studies were made on the impact of interceptor and flap combination on high speed hulls in recent years. Interceptors are blades which extend vertically downwards at the transom of the vessel and a flap is attached to its end. The installation of interceptor near the vessel transom a change in pressure distribution around the hull and more significantly observed at the transom. The present study investigates on the hydrodynamic quality of 20deg deadrise high-speed planing hull mounted with interceptor-flap combination using computational fluid dynamics (CFD). Planing hull model was analyzedusing CFD based Finite Volume method with dynamic mesh. The height of the interceptor and angle of flap plays an important role on the efficiency of the vessel. Experiments were carried out in the towing tank at Indian Institute of Technology Madras for the planing hull and CFD studies were extended with interceptor-flap. The validation studies serve to authenticate the use of the interceptor on the basis of comparison with simulations using model tests. The pressure variation that is caused due to integrated interceptor-flap has an effect on the resistance of the vessel which further showed better control of trim. The numerical study on planing hull with interceptor-flap showed an increased waterline length which leads to reduced Froude number. The hydrodynamically improved underwater form was observed leading to resistance reduction of upto 25% on the vessel and significant reduction of trim upto 57% at the design speed.

Experimental measurement of the nearfield longitudinal wake profiles of a high-speed prismatic planing hull

ABSTRACT This study details an extensive investigation into the nearfield longitudinal wake profiles of a high-speed planing hull. Developing understanding this flow is benaficial to the designers of stepped hulls in determining how the forebody’s wake intersects with the afterbody. As no experimental data was available, a novel small-scale model-testing programme was undertaken, measuring Centreline (CL) and Quarter Beam (QB) nearfield longitudinal wake profiles, as well as the forces. The nearfield wake profile was found to exhibit trends in agreement with the findings of studies investigating the mid and far-field wake. The results of this experimental work are provided in full as validation data. Savitsky’s Wake Equations and the Linear Wake Assumption are then assessed to determine the level of confidence with which they may be used to model this flow. Savitsky’s Wake Equations displayed a surprising level of accuracy whereas the Linear Wake Assumption was invalid for the conditions investigated.

Simulation of Air\u2013Water Interface Effects for High-speed Planing Hull

High-speed planing crafts have successfully evolved through developments in the last several decades. Classical approaches such as inviscid potential flow–based methods and the empirically based Savitsky method provide general understanding for practical design. However, sometimes such analyses suffer inaccuracies since the air–water interface effects, especially in the transition phase, are not fully accounted for. Hence, understanding the behaviour at the transition speed is of fundamental importance for the designer. The fluid forces in planing hulls are dominated by phenomena such as flow separation at various discontinuities viz., knuckles, chines and transom, with resultant spray generation. In such cases, the application of potential theory at high speeds introduces limitations. This paper investigates the simulation of modelling of the pre-planing behaviour with a view to capturing the air–water interface effects, with validations through experiments to compare the drag, dynamic trim and wetted surface area. The paper also brings out the merits of gridding strategies to obtain reliable results especially with regard to spray generation due to the air–water interface effects. The verification and validation studies serve to authenticate the use of the multi-gridding strategies on the basis of comparisons with simulations using model tests. It emerges from the study that overset/chimera grids give better results compared with single unstructured hexahedral grids. Two overset methods are investigated to obtain reliable estimation of the dynamic trim and drag, and their ability to capture the spray resulting from the air–water interaction. The results demonstrate very close simulation of the actual flow kinematics at steady-speed conditions in terms of spray at the air–water interface, drag at the pre-planing and full planing range and dynamic trim angles.

Numerical Modelling of the Nearfield Longitudinal Wake Profiles of a High-Speed Prismatic Planing Hull

This study investigates the level of accuracy with which Computational Fluid Dynamics (CFD) is capable of modelling the nearfield longitudinal wake profiles of a high-speed planing hull. It also looks to establish how various set-ups influence the accuracy, with a specific emphasis on turbulence modelling. It analyses a hull over a broad range of conditions to provide detailed insight into the strengths and limitations of CFD, comparing the numerical results to the experimental results previously generated by the authors. A quantitative comparison is made for the centreline (CL) and quarterbeam (QB) longitudinal wake profile plots. Following this, a qualitative comparison is made between photos of the flow pattern from the experimental testing and free surface elevation plots from CFD. The study concluded that CFD is an accurate and robust method of modelling the nearfield longitudinal wake profiles of a high-speed planning hull.

Water takeoff performance calculation method for amphibious aircraft based on digital virtual flight

Owing to the strong coupling among the hydrodynamic forces, aerodynamic forces and motion of amphibious aircraft during the water takeoff process, the water takeoff performance is difficult to calculate accurately and quickly. Based on an analysis of the dynamics and kinematics characteristics of amphibious aircraft and the hydrodynamic theory of high-speed planing hulls, a suitable mathematical model is established for calculating the hydrodynamics of aircraft during water takeoff. A pilot model is designed to illustrate how pilots are affected by the lack of visual reference and the necessity to simultaneously control the pitch angle, flight velocity and other parameters during water takeoff. Combined with the aerodynamic model, engine thrust model and aircraft motion model, a digital virtual flight simulation model is developed for amphibious aircraft during water takeoff, and a calculation method for the water takeoff performance of amphibious aircraft is proposed based on digital virtual flight. Typical performance indicators, such as the liftoff time and liftoff distance, can be obtained via digital virtual flight calculations. A comparison of the measured flight test data and the calculation results shows that the calculation error is less than 10%, which verifies the correctness and accuracy of the proposed method. This method can be used for the preliminary evaluation of airworthiness compliance of amphibious aircraft design schemes, and the relevant calculation results can also provide a theoretical reference for the formulation of flight test plans for airworthiness certification.

Numerical investigation on the hydrodynamic performance of high-speed planing hull with transom interceptor

ABSTRACT The study presents numerical investigations on hydrodynamic quality of high-speed planing hull with spray rails and interceptor. Interceptors are blades which extend vertically downwards at the bottom near transom. The pressure distribution is the main cause for reduction in trim of the vessel. The interceptor has an effect on vessel resistance reduction which further result in more desirable trim control. The hull model was analysed with interceptor at different heights based on Finite Volume method using dynamic mesh. The two degrees-of-freedom considered is heave and pitch. The model tests are performed in the current towing tank facility available in the Department of Ocean Engineering, Indian Institute of Technology, Madras for the planing hull with and without interceptor in calm water. The height of interceptor plays an important role on the vessel performance. The study shows better trim reduction with consequent decrease in total resistance of vessel in planing regime.

Numerical roll damping prediction of a planing hull

ABSTRACT In this study, the roll damping coefficients of a high-speed planing hull are calculated numerically in order to show the effects of forward speed, roll amplitude and oscillation frequency. Forced roll simulations are carried out to calculate roll damping coefficients. The numerical study is performed at high forward speeds by using a commercial URANS (Unsteady Reynolds-averaged Navier–Stokes) solver. The uncertainty analysis of the numerical results is performed using the GCI (Grid Convergence Index) method in terms of grid spacing and time step size. The obtained numerical results are compared with existing experimental data and empirical methods. Results show that lift contribution is the major component of the roll damping at high speeds since the roll damping does not change considerably at different roll amplitudes and frequencies. It is also found that numerical calculations show better accuracy compared to the implemented empirical method.

Comparison between the Dynamic Behavior of the Non-stepped and Double-stepped Planing Hulls in Rough Water: A Numerical Study

Reducing vertical motions of high-speed planing hulls in rough water is one of the most important factors that help a boat to become more operable, and will benefit the structure of the boat and the crew on board. In the recent decade, stepped planing hulls have been investigated with emphasis on their better performance in calm water than that of nonstepped planing hulls. However, there are still doubts about their performance in rough water. In this study, we investigate this problem by providing numerical simulations for motions of a double-stepped and a non-stepped planing hull in a vertical plane when they encounter head waves. The problem will be solved using the finite volume method and volume of fluid method. To this end, a numerical computational fluid dynamics code (STARCCM1) has been used. Accuracy of the numerical simulations is evaluated by comparing their outcome with available experimental data. The dynamic response of the investigated hulls has been numerically modeled for two different wave lengths, one of which is smaller than the boat length and the other which is larger than the boat length. Using the numerical simulations, heave and pitch motions as well as vertical acceleration are found. It has been found that at wave lengths larger than the boat length, heave amplitude decreases by 10–40%when two steps are added to the bottom of a vessel. It has also been observed that pitch of a planing hull is reduced by 18–32% in the presence of the two steps on its bottom. Finally, it has been observed that for wave lengths larger than the boat length, the maximum vertical acceleration decreases by a gravitational acceleration of about .2–.7.

An experimental study on the stern bottom pressure distribution of a high-speed planing vessel with and without interceptors

In this study, the effects of hydrodynamic interceptors on a high-speed vessel were investigated to identify the operating principle based on experiments. Model tests were performed using a high-speed towing carriage. The resistance, trim and rise of Center of Gravity (CG) of the high-speed vessel were measured for various ship speeds and interceptor heights. As the interceptor height increased, the trim and rise of CG were reduced. In order to quantitatively analyze these phenomena, the pressure at the stern bottom was measured using tactile sensors. The reliability of the measured results from the tactile sensors was verified through repeat tests. The pressure on the stern bottom increased in proportion to the interceptor height, as the interceptor partially blocked the flow there. Then, the trim was reduced. However, as the ship speed increases, the pressure at the location close to the interceptor decreases when the interceptor height is small, leading to increased trim. Therefore, the interceptor height for running attitude control should be carefully determined considering multiple factors in the operating condition of the high-speed planing hull.

Dynamic response modeling of high-speed planing craft with enforced acceleration

An approach is investigated in this study for structural dynamic analysis of a high-speed planing hull, in which the pointwise acceleration data collected from sea trials are enforced as base excitation. The paper first performed the full boat analysis of an 11-meter high speed craft for a period of one wave impact selected from each of nine seakeeping runs. The sea trial acceleration data collected from 11 accelerometers placed close to the centerline and the keel are enforced as input, while those from 3 accelerometers placed around the pilot cabin are selected for validation. The substructure dynamic analysis of the isolated pilot cabin was then conducted and validated, in which 7 pointwise enforced accelerations are selected from the simulation output of the full boat dynamic analysis. The substructure dynamic analysis enables detailed investigation of local stress concentrations where critical equipment and personnel are located. The proposed approach can be extended to rigid-flexible body coupling analysis of a high-speed craft when it is running with large pitching and yawing motion.

하이브리드 방법을 사용한 고속 활주정의 내항성능평가 절차 개발

하이브리드 방법을 사용한 고속 활주정의 내항성능평가 절차 개발

전산유체계산을 통한 고속 활주선의 저항성능 및 유동분포 해석

전산유체계산을 통한 고속 활주선의 저항성능 및 유동분포 해석

A Review on the Performance Test of a High-Speed Planing Hull with 35 knot Speed by Appling the Streamlined Step of Hull Form

ê³ ì† 주행시 ë§ˆì°°ì €í•­ì„ 감소시키기 위해 ì„ ì²´ì˜ ì„ ì €ë¶€ë¶„ì˜ 모양을 변화시키는 등 최근 ê´€ë ¨ 분야의 개발이 ì´ë£¨ì–´ì§€ê³ ìžˆëŠ” 바, 본 개발에서는 ê¸°í•˜í•™ì ìœ¼ë¡œ ê³ ì†í™œì£¼ì„ ì˜ ìŠ¤í  단면을 ìœ ì„ í˜•(streamlined type) 구조로 ì œìž‘í•´ 침수 í‘œë©´ì ì— 의한 ë§ˆì°°ì €í•­ì˜ 최소화를 ëª©ì ìœ¼ë¡œ 준비하였다, 본 개발의 ëª©ì ì€ ì–´ì— ì˜ ê°ì¢ ìœ„ê¸‰ìƒí™© 및 ì•ˆì „ì„±ì„ ê³ ë ¤í•œ ê³ ì†í™œì£¼ì„ ì˜ 구조설계를 기반으로 하여 ì–´ì— ì˜ 특수성 및 ìž‘ì— íŠ¹ì„±(어군 ì¶”ì  및 어획물 출하)을 ê³ ë ¤í•œ ìµœì ì„ í˜•ìœ¼ë¡œì„œ ìœ ì„ í˜• ë§ˆì°°ì €ê°í˜• ê³ ì†í™œì£¼ì„ ì„ ì œìž‘í•˜ëŠ”ë° ê·¸ 목표가 있으며, 이 ê³¼ì •ì—ì„œ ì œìž‘ëœ 성과물에 대한 성능평가를 수행하여 ì •ëŸ‰ì  목표치를 í™•ë³´í•˜ê³ ìž 함에 본 ê¸°ìˆ ê°œë°œ ë ¼ë¬¸ì˜ 소개 배경이 있다. 핵심용어: ìœ ì„ í˜• ìŠ¤í  ì„ í˜•, 성능시험, 연비, 연료소모량, 활주ì„

Performance of high-speed planing hulls accelerating from rest under the action of a surface piercing propeller and an outboard engine

In this paper, a mathematical model for performance prediction of a high-speed planing hull in forward acceleration motion has been developed. Three degrees of freedom have been considered for solving the problem. Utilizing previous empirical equations of displacement ships, motion of the vessel in displacement regime has been simulated. In order to model pre-planing and planing regimes, 2D + T theory has been used. Equations for prediction of performance of a surface piercing propeller (SPP) and an engine have been presented. Validity of the proposed method has been assessed by comparing its results against previous experimental data, and good agreement between experimental and mathematical results in prediction of performance of planing hulls has been seen. Motion of the vessel has been simulated under the action of a semi-submersible propeller and an outboard engine. Behavior of the vessel has been analyzed and the relationships between forces and moments with displacements, as well as pitch and heave rate have been described. It has shown how hydrodynamic force contributes as the beam Froude Number goes beyond 1.0, which results in increment of vertical position of the vessel. Also, it has been observed that, net pitching moment decreases from a positive value to a negative value in displacement regime, and then, by the appearance of hydrodynamic moment, net moment approaches zero and finally vanishes. The results also have indicated that a sudden jump occurs in thrust force vs. time curve, which is caused at critical advanced ratio. Beside this, it has been seen that, when propeller comes of water, a sharp increase in advanced ratio happens. Effects of surge motion have also been studied, which show that, maximum trim angle occurs at a larger beam Froude Number. It has also been observed that sinkage is larger in the presence of surge motion in pre-planing regime as extra hydrodynamic forces due to damping and added mass contributions in vertical direction occur. Finally, it has been observed that surge is accompanied with larger resistance which is resulted due to contribution of heave and pitch motions in surge direction, especially in pre-planing and planing regimes.

Study on Sea Trial Analysis of Wave Piercing High Speed Planing Boat

This study investigated the sea trial performance of a wave piercing high speed planing hull (WPH). The bow shape of the boat is sharp, and it has no chine or spray strip like a normal planing boat. The skeg is attached to the bottom of the boat in the longitudinal direction from the bow to the stern. The speed performance was analyzed as the speed dropped in a wave, and the seakeeping performance was compared with that of a planing boat with a similar velocity coefficient by measuring the vertical acceleration of the bow in the wave. The turning circle was compared with Lewandowski’s estimation for a planing boat. As a result of this study, it was confirmed that the velocity drop of the developed WPH was not large in a wave, and the vertical acceleration was greatly reduced compared with that of a normal planing boat. The turning circle was somewhat larger than the estimated results for a planing boat, but the overall tendency was the same.