High-speed Planing Hull Research Articles

Composite bottom panel slamming of a fast planing hull via tightly coupled fluid-structure interaction simulations and sea trials

The paper presents partitioned tightly coupled fluid-structure interaction (FSI) simulations for composite panel slamming of a high-speed planing hull, including comparison with full-scale experiments. Panels with different layout/stiffness are investigated. Computational fluid dynamics (CFD) is performed using the URANS code CFDShip-Iowa. Computational structural dynamics (CSD) uses modal expansion by ANSYS finite elements. One- and two-way tightly coupled FSI is performed. The complexity of sea-trial conditions is reduced by statistical/frequency analysis, allowing for a simplified representation by one regular wave. Simulations provide details of slamming, including correlation of re-entering pressure peaks with motions and strain peaks. Numerical/modeling issues are discussed. Expected value and associated uncertainty of experimental pressure/strain peak and duration are used for validation. The difference of panels’ dynamics is well predicted. Validation errors and uncertainties (average 25% and 14%) are quite large. Nevertheless, errors always fall within one standard deviation of experimental-data individual readings. Results are promising especially if compared to earlier slamming studies for regular/irregular waves in controlled towing tank tests, which show average error and validation uncertainty of 25% and 10%. The current study lays the groundwork for research on high-fidelity CFD/CSD FSI of real-world geometry slamming and ultimately multidisciplinary design optimization of structural and hull-form parameters.

A Numerical Study on Dynamic Instability Motion Control of Wave-Piercing High-Speed Planing Craft in Calm Water using Side Appendages

In this research, we have calculated characteristics of wave-piercing high-speed planing hull, by using a RANS solver and overset grid method, for comparing with experimental measurements of that and simulating with several appendages, since the computed results of commercial CFD code look reasonable for the prediction of the performances of planing hulls on calm water in planing conditions. As a result, it is confirmed that the dynamic instability phenomena in pitch and heave motions (porpoising) occurred after a certain FnV, and effectively suppressed using some of appendages, especially the 0.5L spray rail is suppressed to 24-55 % in the pitch motion and 33-55 % in the heave motion. In spray phenomenon, 1L hard chine suppress spray effectively and it is effective to set the angle of appendages to be less than 0° in order to suppress wave.

A nonlinear mathematical model for coupled heave, pitch, and roll motions of a high-speed planing hull

A mathematical method is presented for time-domain simulation of coupled heave, pitch, and roll motions of a planing hull. This method is introduced by using 2D+t theory and employs potential field related to hydrodynamic impact of an asymmetric wedge with roll speed to solve four relations for the involved added masses in the motion. Momentum variation of the derived added mass terms is used to compute 2D normal force and roll moment. Two-dimensional hydrostatic moment and moment due to hydrodynamic forces are taken into consideration and time derivative of the wetted half-beam is determined by using the roll speed. Three-dimensional forces are computed by integrating the 2D forces over the length of the boat and new added mass terms are derived for the coupled heave, pitch, and roll motions. Ultimately, a nonlinear system of equations for the motion is presented by putting the forces together. Validity of the proposed method is assessed using an extensive set of test cases, which are conducted in four steps. Predicting coupled heave and pitch motions without roll motion, dynamic response of a 2D wedge due to asymmetric impact, computing the hydrodynamic coefficients in coupled heave and roll motions, and predicting roll motion of a planing boat due to a forced pitch motion are involved in the validation steps, respectively. Results of the first three steps are compared against experimental results, while the results of the last step are compared against the results of previously published simulations. Favorable agreement has been displayed between the obtained results and the available data in all of these steps. Finally, the proposed method is used to investigate the effects of the roll motion on the heave and pitch motions of planing hulls. Based on the obtained results, amplitudes of the heave and pitch motions exhibit an increase when the boat is free of roll which is due to an increase in the exciting force, accelerations, and reduction of heave and pitch added masses in this situation.

파랑관통형 고속활주선 선형개발에 관한 연구

A new wave-piercing-type high-speed planing boat without a chin e was developed, and its basic performance was investigated in a model test, including the resistance, trim, and sinkage. The maximum speed of the developed ship was 35 knots. The hull form was developed by combining a VSV (very slender vessel) and TH (transonic hull), which have large deadrise angles at the bow. The main dimensions were estimated by a statistical approach using actual ship data. The effect of a side fin attached at the stern near the water line was investigated from a resistance point of view. It was found that the developed hull form showed the possibility of a new concept for a high-speed planing hull without a chine, and the side fin played an important role in increasing the resistance performance by controlling the trim and sinkage in the high-speed range.

Numerical investigation of the tunnel aperture on drag reduction in a high-speed tunneled planing hull

One of the methods for reducing drag is inducing a change in the shape of the body due to making longitudinal side tunnels on the hull body. In this method, the usual shape of a specific mono-hull is changed into tunneled one keeping the geometric parameters, including deadrise angle, keel line, beam width, and the hull length, constant. Various geometric parameters are effective on drag reduction of different sections of the tunnel while designing and manufacturing the hull. To obtain an optimum shape for the tunnel, this study has attempted the influence of the size of the tunnel aperture on hydrodynamic parameters of the hull. For this purpose and through considering the moving mesh, numerical simulation of the problem by means of finite volume method has been employed, using FLUENT commercial software. For turbulence modeling, k-e model, and for simulating the free surface, the volume of fluid two phase model has been used. In addition, remeshing and smoothing methods were employed for moving mesh. The presented results show that, forming a tunnel in the base hull could cause a reduction in the total drag in high-speed planing hulls and in the vessel draft over the whole range. Furthermore, in high Froude number, a reduction in the size of the tunnel aperture (up to a specific amount) could lead to a decrease in the total drag.

URANS studies of hydrodynamic performance and slamming loads on high-speed planing hulls in calm water and waves for deep and shallow conditions

URANS capability for hydrodynamic performance and slamming of high speed planing crafts are assessed, using metrics specified for naval applications. Wedge drop validation studies using two different solvers, one single-phase and the other two-phase, shows good agreement with experimental data for time history of pressure gauges. Planing hull validation studies are carried out using the historical benchmark experiments of Fridsma. Simulation conditions include calm water in deep and shallow conditions with fixed and free to sinkage and trim motions, as well as regular and irregular head waves in deep water free to heave and pitch motions. For simulations in calm deep water free to sinkage and trim, grid studies show that refined grid density on the hull, especially over the spray root area, chines, and transom stern are necessary for accurate solutions. Detailed verification and validation studies are carried out with satisfactory results since monotonic convergence and validation are achieved for most of the variables. Additional assessment metrics are studied including wave rise, hull pressure distribution, surface streamlines, existence of porpoising, and main spray trajectory. The results are compared with empirical expressions with reasonably good agreement except for main spray trajectory. Resolving the details of the spray flow is beyond the scope of the current work since finer grid resolution and/or more advanced free surface modeling is required. For simulations in calm deep water with fixed sinkage and trim, the assessment metrics include drag and lift forces, pitch moment, drag-lift ratio, and center of pressure. The results agree well with empirical expressions. For simulations in shallow water, similar studies are carried out and reasonable comparison results are obtained. Seakeeping simulations in regular head waves are carried out and validated with experimental data for response amplitudes and phases, with good agreement. Simulations in irregular head waves are carried out for two different weight configurations and validated against experiments for mean and amplitudes of resistance, heave, pitch, and acceleration. Slamming load analysis is carried out, where both emerging and re-entering slams are detected, although the current experimental data lack slamming pressures for validation. More recent research provides additional studies for calm water motions, slamming pressures, and spray flow trajectory that supports current results.

Toward numerical modeling of the stepped and non-stepped planing hull

Drag increases rapidly with speed in high-speed planing hull. During the last decades, many researchers have tried to reduce hull drag in order to achieve the highest speed. Based on these researches, several methods have been applied to reduce drag such as hull form optimization, marine coating, and planing equipments. One of the most efficient strategies is to use a step on the hull bottom that leads to significant wetted surface reduction, resulting in a considerable reduction in total drag. In the current study, the numerical method is used to investigate the influence of a step on the pressure distribution, hydrodynamics characteristics, and wake profile of a modern high-speed chine planing hull. The numerical results obtained show a good agreement in comparison with the experimental results.

High-speed planing hull drag reduction using tunnels

Forward speed is perhaps the most important parameter in the design of a planing hull. The speed strongly influences the drag and thus the energy supplied by the engine of the ship. Employment of an appropriate drag reduction strategy plays an important role in the design of these hulls. The flow around a Cougar high-speed planing hull was numerically simulated and the results were compared against experiments available in the literature. To reduce the total drag, two tunnels were introduced at the bottom section of the original Cougar hull. The weight and center of gravity of both hulls remained the same. An unstructured mesh was generated in the computational domain around the hull and a Re-Normalization Group K–ε formulation was used to model the turbulence. To capture the free-surface of the flow around the hull, the volume-of-fluid model was applied. The drag forces of both the original and modified Cougar hulls were obtained for various forward speeds, corresponding to the original hull length-based Froude numbers ranging from 1.00 to 5.62. The results show a 14% reduction in total drag for the modified hull at the forward speed of 60knot.

Design of high-speed planing hulls for the improvement of resistance and seakeeping performance

High-speed vessels require good resistance and seakeeping performance for safe operations in rough seas. The resistance and seakeeping performance of high-speed vessels varies significantly depending on their hull forms. In this study, three planing hulls that have almost the same displacement and principal dimension are designed and the hydrodynamic characteristics of those hulls are estimated by high-speed model tests. All model ships are deep-V type planing hulls. The bows of no.2 and no.3 model ships are designed to be advantageous for wave-piercing in rough water. No.2 and no.3 model ships have concave and straight forebody cross-sections, respectively. And length-to-beam ratios of no.2 and no.3 models are larger than that of no.1 model. In calm water tests, running attitude and resistance of model ships are measured at various speeds. And motion tests in regular waves are performed to measure the heave and pitch motion responses of the model ships. The required power of no.1 (VPS) model is smallest, but its vertical motion amplitudes in waves are the largest. No.2 (VWC) model shows the smallest motion amplitudes in waves, but needs the greatest power at high speed. The resistance and seakeeping performance of no.3 (VWS) model ship are the middle of three model ships, respectively. And in regular waves, no.1 model ship experiences 'fly over' phenomena around its resonant frequency. Vertical accelerations at specific locations such as F.P., center of gravity of model ships are measured at their resonant frequency. It is necessary to measure accelerations by accelerometers or other devices in model tests for the accurate prediction of vertical accelerations in real ships.

Design of high-speed planing hulls for the improvement of resistance and seakeeping performance

High-speed vessels require good resistance and seakeeping performance for safe operations in rough seas. The resistance and seakeeping performance of high-speed vessels varies significantly depending on their hull forms. In this study, three planing hulls that have almost the same displacement and principal dimension are designed and the hydrodynamic characteristics of those hulls are estimated by high-speed model tests. All model ships are deep-V type planing hulls. The bows of no.2 and no.3 model ships are designed to be advantageous for wave-piercing in rough water. No. 2 and no. 3 model ships have concave and straight forebody cross-sections, respectively. And length-to-beam ratios of no.2 and no.3 models are larger than that of no.1 model. In calm water tests, running attitude and resistance of model ships are measured at various speeds. And motion tests in regular waves are performed to measure the heave and pitch motion responses of the model ships. The required power of no.1 (VPS) model is smallest, but its vertical motion amplitudes in waves are the largest. No.2 (VWC) model shows the smallest motion amplitudes in waves, but needs the greatest power at high speed. The resistance and seakeeping performance of no.3 (VWS) model ship are the middle of three model ships, respectively. And in regular waves, no.1 model ship experiences ‘fly over’ phenomena around its resonant frequency. Vertical accelerations at specific locations such as F.P., center of gravity of model ships are measured at their resonant frequency. It is necessary to measure accelerations by accelerometers or other devices in model tests for the accurate prediction of vertical accelerations in real ships.

The Brief Introduction of High-Speed Trimaran Planing Hull and the Preliminary Study of the Longitudinal Stability

The character of lines and high-speed performance of trimaran planing hull is briefly introduced. By use of model experiments the law of longitudinal motion stability of the trimaran planing hull is studied. According to the combination of upper and lower speed limits at which the dolphin motion takes place at different displacements and the positions of gravity, these critical points from the experiments are linearly fitted by using MATLAB in order to obtain the limit curve. The veracity of the limit curve to evaluate the longitudinal stability is proved.

Inclusion of Whisker Spray Drag in Performance Prediction Method for High-Speed Planing Hulls

The planing hull performance prediction method published by Savitsky in the October 1964 issue of SNAME's Marine Technology included only the viscous drag and pressure drag components in the bottom area aft of the stagnation line. While discussing the existence of an additional component of viscous drag in the whisker spray region forward of the stagnation line, a method to quantify this drag component was not developed in Savitsky (1964). Earlier studies by Savitsky and Ross (1952) and Savitsky and Neidinger (1954) discuss the potential whisker spray drag component but do not present a complete analytical derivation of its magnitude nor verification of the results by comparison with experimental data. The present study fills this void by developing a method for quantifying the whisker spray contribution to total hull resistance as a function of deadrise angle, trim angle, and speed, and incorporating the results into the SNAME published hull performance prediction method. The analytical results are compared with data from model tests conducted at three separate towing tank facilities and show fairly good agreement with these data. It is shown that for high-speed planing hulls, the whisker spray drag component can be as much as 15% of the total drag. In addition, (1) procedures are provided for the proper location, size, and geometry of spray strips to deflect the whisker spray away from the hull bottom; (2) the aerodynamic drag of the hull cross-sectional area above the waterline is also quantified and included in the final performance prediction method; and (3) the equilibrium trim angle identified in the prediction program (for prismatic hull forms) is, for nonprismatic hulls, related to the trim angle of the v4 buttock line (relative to the level water surface) when measured at the forward edge of the mean wetted length.

고속어선의 운동성능 개선장치 개발에 관한 연구

In spite of many efforts, in the design of high speed fishing vessel the sea-keeping performance improvement without neglection of resistance-propulsion performance by hull form itself has its limitations. In this paper, the development of sea-keeping improving appendage pitching and trim improver for high speed planing hull on behalf of the hull form of fishing vessel has been introduced. The developed appendage verified its effectiveness in the full scale test and also has been proved the better resistance performance in the model test and full scale test.

부가물에 의한 고속어선의 성능개선 가능성에 관한 연구

TPI는 고속 활주선의 소음, 진동, 트림 및 핏칭운동을 감소시킨 것으로 실선 시운전에서 증명되었다. 또한 모형시험에서 저항성능도 미소하게나마 개선시킨 것으로 입증되었다 In the design of high speed fishing vessel, it's hull form has to be decided from a view point of resistance and propulsion performance without neglection of seakeeping characteristics. In spite of many efforts, the performance improvement by hull form itself has it's limitations, specially for high speed craft. In this paper, a study on the improvement of performance for high speed planing hull type fishing vessel has been introduced.

Asymmetric Vessel Impact and Planing Hydrodynamics

The paper proposes a two-dimensional theory for asymmetric impact problems of vessels with arbitrary geometry. The interaction of two body sides is incorporated into the hydrodynamic impact model. Following Vorus's (1996) flat-cylinder theory, two types of flow models are established for cases of small and large asymmetry. The distinguishing difference between the two types is whether the flow is attached or separates at the keel on the first instances of impact. General solutions for such nonlinear boundary value problems are determined by solving the singular integral equations, while free-vortex shedding (jet-spraying) is carried out through a time-marching procedure. Initial conditions are derived from basic solutions of flat-sided contours with constant impact velocity. The method of discrete vortices is then applied to the prediction of slamming loads (including both lifting force and restoring moment) on typical two-dimensional sections of vessels with flat or nearly flat bottoms. Calculated results of both flow types, i.e., small and large asymmetry, are presented for various hull contours with constant or variable impact velocity. This approach also provides the foundation for future work involving traverse dynamic stability analysis of high speed planing hulls

Computer Aided Resistance Prediction Of High Speed Planing Hull Forms

Planing crafts have been the traditional solution to high speed at sea. However, the limitations on high speed planing hull forms in a seaway have led to a tremendous amount of work currently being carried out on hydrofoils, catamarans and hybrid crafts. Despite these facts, the warship, commercial and pleasure markets still show demands for planing crafts and many new designs appear every year. The objective of this paper is to develop a computational procedure for predicting the total resistance of hard chine planing hull forms, prior to model testing. The computer prediction is later validated with existing experimental results.

Modern Nonlinear Dynamical Analysis of Vertical Plane Motion of Planing Hulls

When operating in a seaway, high-speed planing hulls exhibit strong nonlinearities. This paper investigates the vertical plane dynamic stability and response associated with such craft. Explicit expressions for the hydrodynamic forces are developed and modern methods of dynamical systems analysis are applied. An illustrative example is given in which the forced and unforced motions are examined. Parameter studies relating to the following topics are made: the onset of porpoising, the magnitude of motions while porpoising, and forced motions due to regular waves. It is found that while nonlinear effects can reduce the response over that predicted by linear theory, these same effects can also be responsible for sudden extreme behavior. The method described here is another tool that designers and operators can use to provide a more comfortable and safer vessel performance.

Gas Turbine Propulsion for High-Speed Small Craft

This paper presents the results of marine gas turbine propulsion studies related to small craft of the high-speed planing hull type. These include appraisal of craft performance requirements for both transportation and patrol mission profiles. A substantial increase in both service speed and craft productivity may be realized with gas turbine propulsion. A combined power system is analyzed for loiter/cruise/dash patrol missions, and the operational tradeoff flexibility that may be realized is illustrated. Comparisons of existing gas turbine engine types and their utilization in marine propulsion systems with pump-jets and propellers of both fixed-and controllable-pitch configurations are included. Marine gas turbine power system integration is discussed, with an example illustrating design considerations associated with a turbomarine power system that includes capability of an optional three-mode power-level operation. An appendix describes significant features of several gas turbine test craft.