Planing Craft Research Articles

Monitoring and characterization of vibration and shock conditions aboard high-performance marine craft

The stochastic environmental conditions together with craft design and operational characteristics make it difficult to predict the vibration environments aboard high-performance marine craft, particularly the risk of impact acceleration events and the shock component of the exposure often being associated with structural failure and human injuries. The different timescales and the magnitudes involved complicate the real-time analysis of vibration and shock conditions aboard these craft. The article introduces a new measure, severity index, indicating the risk of severe impact acceleration, and proposes a method for real-time feedback on the severity of impact exposure together with accumulated vibration exposure. The method analyzes the immediate 60 s of vibration exposure history and computes the severity of impact exposure as for the present state based on severity index. The severity index probes the characteristic of the present acceleration stochastic process, that is, the risk of an upcoming heavy impact, and serves as an alert to the crew. The accumulated vibration exposure, important for mapping and logging the crew exposure, is determined by the ISO 2631:1997 vibration dose value. The severity due to the impact and accumulated vibration exposure is communicated to the crew every second as a color-coded indicator: green, yellow and red, representing low, medium and high, based on defined impact and dose limits. The severity index and feedback method are developed and validated by a data set of 27 three-hour simulations of a planning craft in irregular waves and verified for its feasibility in real-world applications by full-scale acceleration data recorded aboard high-speed planing craft in operation.

Performance Prediction of Two-Stepped Planing Hulls Using Morphing Mesh Approach

Change in body shape characteristics is one of the ways to reduce the resistance and thereby increasing the speed of planing hulls. Creating the transverse steps is one of these variations. The main reason to use the steps in high-speed planing craft is that the wetted surface of the vessel is divided into small parts with higher width-length ratio in high velocities and in this situation, the generated lift force is more efficient. In this article, by performing a three-dimensional numerical solution, motion characteristics of a two-stepped planing hull with transverse steps in calm water have been examined. For this purpose, the vessel is free to trim and sinkage, and by using the morphing mesh approach, the numerical simulation continued until the equilibrium condition of the two-stepped planing hull is satisfied. Resistance, lift, trim angle, and wetted surface in various velocities have been computed and compared against existing experimental data. Analysis of considered two-stepped hull in calm water shows that the numerical solution for resistance, trim, and lift are relatively precise in comparison to model test data. Furthermore, various hull characteristics such as wetted length of keel, chine wetted length, spray angle and, ventilation length have been investigated. 1. Introduction In recent years, naval architectures have proposed significant modifications in planing hulls' design by creating steps, tunnel, and other geometric features. By considering these geometric variations, the hull wetted surface and, consequently, its resistance have been reduced and planing hulls velocity can be increased. In this regard, the step is one of the main hull's modifications which can lead to resistance reduction. Generally, lift of stepped planing hulls is distributed over the forward, middle, and stern plane of the hull (Fig. 1), and therefore, its ride quality will also be improved. Moreover, planing hulls with various step configurations have been used in high-speed craft since 1910, and various types of step with different shapes and arrangements have been used in planing hulls.

Statistical Analysis of Wedge Effect on the Seakeeping of a Planing Hull in Irregular Waves at the Onset of the Planing Region

In the current paper, different experiments are conducted on a high speed planing craft in irregular waves, with and without a wedge. Performance and seakeeping aspects of these planing hulls in the form of trim, rise-up, and resistance in regular waves and heave, pitch, bow, and center of gravity (CG) acceleration in irregular waves are extracted in time series. Irregular waves represent sea state 3 with 12cm height and peak period of 1.66. A model length of 2.63m and 1:5 scale is considered and all data for irregular waves are scaled, as well. The deadrise angle is constant and is taken to be 24 degrees. The targeted experimental tests are conducted for four longitudinal Froude numbers of 1.0, 1.18, 1.37, and 1.57, which are all in the planing regime. The results are analyzed for the mean height of wave, significant wave height, RMS, and spectrum. The comprehensive study of wedges' effects is also presented which indicates that a wedge can decrease the motions and accelerations, exceedingly. Ultimately, the obtained results are compared against those by Fridsma (1971) and Soletic (2010) and it is demonstrated that motions and accelerations are indeed reduced.

Experimental Study of the Wedge Effects on the Performance of a Hard-chine Planing Craft in Calm Water

In this paper, effects of a wedge on the performance of planing craft in calm water are experimentally investigated. Experiments are carried out on three different cases distinguished by the wedge type. The model, built of fiberglass, is a prismatic planing hull with deadrise angle of 24 degrees. Towing tests are conducted at different Froude numbers ranging from 0.21 to 2.1. The total trim angle, resistance, rise up at the CG as well as stern and bow, keel wetted length, chine wetted length, stagnation angle, and the length of stagnation line are measured. They are used to study the effect of installing a wedge on the performance as well as the effect of height on the hydrodynamic characteristics. Based on the observations made, it is concluded that, when the wedge is applied to the hull, the risk of model exhibiting instability diminishes, while total trim angle largely decreases, keel wetted length is enlarged, wetted surface becomes thinner, CG rise up is lowered, and the resistance is reduced. Moreover, experimental measurements and theoretical 2D+T theory are combined to bring deeper insight about physics of the flow and pressure distribution when a wedge is installed on the bottom of a planing hull.

Full-scale measurements of slamming loads and responses on high-speed planing craft in waves

Full-scale trials on a high-speed planing craft in waves were conducted to investigate the characteristics of slamming impacts and related rigid body and structural response. Measurements of acceleration, pressure, strain and global hull deflection were made in different sea conditions and at different speeds and headings. Low pass filtering is used to remove unwanted noise from the acceleration signals and extract the rigid body response. Methods for removing trends from the strain signals and identifying the peaks in the pressure and strain signals are established. Characteristic results including time series, distributions of peak values, averages of the largest 1/3rd and 1/10th peak values and individual impact events, are presented and discussed. The Weibull and Generalized Pareto models are used to describe the pressure and strain peak values and for estimating extreme loads and responses. Automated algorithms for fitting the statistical models to the peak value distributions are developed and the goodness-of-fit of the models to the data is examined.

Exploration of seakeeping and drag performance of planing craft with active control systems

Most available planing craft design tools and guidelines were not envisioned to be used with vessels that have Active Control Systems (ACS). Consequently, vessels with ACS are conventionally designed as “add-ons” in a sequential manner: first the geometry of the vessel is designed using traditional guidelines, and then the ACS is implemented. However, sequential design is not always optimal for systems whose dynamics are affected by control systems. This research explores the design space of a planing craft with an ACS, and performs an exhaustive search in the coupled design space of vessel geometry and ACS parameters using a time-domain simulation program in sea states (SS) 2 and 3. The vessel is assumed to be prismatic, and the controller is a linear quadratic regulator (LQR) whose outputs are forces on the vessel. The results suggest that if the ACS is designed along with the planing craft, the seaway drag could be reduced in some cases by 30% in SS 2, and 10% in SS 3. The seakeeping also shows significant improvements, with 20% reductions in the ISO 2631-5 metric Dz for SS 2, and 50% in SS 3. Thus, it is recommended that if a vessel is expected to have an ACS, co-design should be pursued by considering the vessel's geometry and its controller simultaneously.

Uncertainty Analysis for Calm Water Tow Tank Measurements

Uncertainty quantification is critical in the analysis and interpretation of experimental data. Tow-tank testing of high-speed planing craft is subject to various sources of uncertainty, both systematic and random, which impact the overall uncertainty in the estimate. This paper presents an approach for quantifying and combining the different sources of uncertainty in these types of experiments. A linear mixed-effect model is proposed to account for variability both between experimental runs and within experimental runs in the random uncertainty. Expressions for the combined uncertainty, and associated degrees of freedom, are developed. The paper offers a step-by-step guide for using the proposed method to construct confidence intervals, and shows a detailed example for a single testing condition. The results demonstrate that the proposed method provides larger estimates of random uncertainty when the within-run variability is of a magnitude similar to the between-run variability. This translates to larger combined uncertainties—and wider confidence intervals—when the random uncertainty is a major contributor to the combined uncertainty. The paper includes estimates and associated expanded, combined uncertainties for speed, sinkage, and trim based on experimental data from high-speed model testing conducted at the U.S. Naval Academy in August 2013 and May 2014. 1. Introduction Uncertainty analysis is a critical component to any experimental investigation. When data are collected or measurements are made, it is for the purpose of assisting with decision-making, such as risk assessments in design or validating simulation results. Uncertainty analysis is a way to estimate the likely magnitude of difference between a test result and the "true" value, an unknown quantity. Moffat (1982) states that quantification of "[uncertainty is the prediction of the uncertainty interval which should be associated with an experimental result, based on observations of the scatter in the raw data used in calculating the result." There are significant challenges in identifying and quantifying the uncertainties associated with the measurements, and development of a formal procedure for uncertainty analysis has been progressing for over 60 years (Kline & McClintock 1953; Abernathy et al. 1985; Moffat 1982; Moffat 1985; ISO 1995; Coleman & Steele 2009; AIAA 1995; ASME 2013; ITTC 2008). However, tow tank testing and, in particular, testing of high-speed craft, create unique challenges that are often not covered sufficiently in the existing guidelines.

A Review of the Surface Drives Employed for High Speed Planing Craft

Marine propulsion systems are the core of high speed planing craft (HSPC), a major factor in creating acceleration, and speed retaining therein. HSPC have used many surface drives to drive the craft. The propulsion systems installed on these vessels are always an important factor for buyers and users, This article reviews and compares the several different of surface drives system been designed for planing boat and the important factors to evaluate a surface drive system have later been investigated, The overall results show that the best propulsion system have higher safety and reasonable price and lower maintenance cost per year and can provide more speed for boats. Hence, the articulated surface drives while having high hydrodynamic efficiency will be a priority for installed on most new planing craft.

Statistical analysis of vertical accelerations of planing craft: Common pitfalls and how to avoid them

A careful review of the literature on the analysis of vertical accelerations of high-speed watercraft reveals that a number of statistical misconceptions are pervasive. These include: (1) ignoring vertical thresholding in analysis, (2) misunderstanding the relationships between the Exponential and other distributions, (3) failing to report uncertainty, and (4) failing to discuss alternative methods for estimation. This article brings these issues to the fore and shows how popular methods, when applied to simulated data, can give inaccurate results. We set forth proper methods for analysis and illustrate their use on a data set from a full-scale planing craft.

The Naples warped hard chine hulls systematic series

An experimental study was carried out to evaluate still water performance of a Systematic Series of hard chine hulls in planing and semiplaning speed range. Models of the Naples Systematic Series (NSS) were of varying length-to-beam ratios of the parent hull. The parent hull, shaped with warped bottoms, was derived from a pre-existing hull extensively tested in a towing tank. This hull was validated by many work boats built in the last fifteen years. To simplify the construction of vessels with rigid panels (aluminium alloy, plywood or steel) the original hull form was transformed to obtain developable hull surfaces. The models were tested at Re>3.5×106, in speed ranges Fr=0.5−1.6 and Fr∇=1.1−4.3. The series studies the influence of LP/BC and Ⓜ ratios that vary respectively in the ranges of 3.45–6.25 and 4.83–7.49, for two positions of CG. All the models were tested both with and without interceptors. To enable model-ship correlation following the ITTC recommendations, in addition to the resistance coefficients of the models, dynamic wetted lengths and surfaces were provided as tables. To facilitate the implementation of Velocity Predict Programs, all the data (resistances, lengths and surfaces) were also furnished in polynomial form. In addition to the use of series in the design field, this study was done to provide data to improve the numerical simulations of a planing craft. With this aim, in addition to the resistance data, the wave profiles, obtained by wave cuts, were provided to carry out validation procedures.

A simplified method to calculate trim and resistance of a two-stepped planing hull

ABSTRACTIn a creative design process of planing craft, stepped hulls could fill a gap in the planing craft industries in response to low drag and high speed demands. However, there exists a need for new computational tools for performance prediction of such hulls. Therefore, in the current work, an attempt has been made to develop a mathematical model for performance prediction of two-stepped hulls. Savitsky's mathematical model has been modified, and in conjunction with linear wake theory, a new mathematical model has been proposed, which would enable prediction of trim, resistance and other parameters related to planing hulls with transverse steps. To validate the proposed model, existing experimental data have been used. The obtained results are in good agreement with experimental data. As such, developed mathematical model can be used in conceptual design phase of stepped hulls with transverse steps.

Experimental and numerical hydrodynamic analysis of a stepped planing hull

This work addresses the experimental and numerical study of a stepped planing hull and the related fluid dynamics phenomena typically occurring in the stepped hull in the unwetted aft body area behind the step. In the last few years, the interest in high-speed planing crafts, with low weight-to-power ratios, has been increasing significantly, and, in such context, naval architects have been orienting toward the stepped hull solution. Stepped planing hulls ensure good dynamic stability and seakeeping qualities at high speeds. This is mainly due to the reduction of the wetted area, which is caused by the flow separation occurring at the step. This paper presents the experimental results of towing tank tests in calm water on a single-step hull model, which is the first model of a new systematic series. The same flow conditions are analyzed via Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES), with different moving mesh techniques (overset/chimera and morphing grid), performed at different model speeds. The numerical results are in accordance with experimental data, and overset/chimera grid is found to be the best approach between the analyzed ones. The flow patterns obtained numerically through LES on a refined grid appear similar to the ones observed in towing tank investigations through photographic acquisitions. These flow patterns are dominated by a rather complex 3D arrangement of vortices originating from air spillage at both sides of the step. The understanding of these phenomena is important for the effectiveness of stepped hull designs.

Evaluation of planing craft maneuverability using mathematical modeling under the action of the rudder

In the recent years, different mathematical models are suggested for maneuvering of displacement vessels which are capable to estimate the vessel maneuver with acceptable precision. But simulation of planing craft maneuverability through mathematical model is not developed yet. In this paper a mathematical model is developed for planing craft maneuvering by including the rudder forces and moments. Different maneuvers are executed through the mathematical model such as straight-line stability, course keeping and turning circle maneuver. Simulation results were validated with the published experimental results and they are in good agreement. Finally, the influence of rudder angle on maneuverability of planing craft was studied and also the effect of aspect ratio has been investigated. The mathematical model and hydrodynamic coefficients were presented in this paper can be applied for the optimization of planing craft maneuvering and the course control purposes.

First Step Toward the Codesign of Planing Craft and Active Control Systems

This paper takes a novel approach to the design of planing craft with active control systems (ACS) by codesigning the longitudinal center of gravity (lcg) and ACS, and compares its performance with a vessel where the lcg and ACS are designed sequentially (traditional approach). The vessels investigated are prismatic in shape. The ACS are modeled as forces on the vessel. The ACS controller is a linear quadratic regulator (LQR) designed using a reduced-order model of the vessel. In the design, only the calm-water drag is optimized. The simulated codesigned vessel had 10% lower calm water and mean seaway drag than the sequentially designed vessel. However, the codesigned vessel's seakeeping was poorer—vertical acceleration doses 25% higher. Results indicate that the traditional sequential design approach does not fully exploit the synergy between a planing craft and its ACS; as a first step, the stability constraints should be relaxed in the design exploration, and the ACS should be considered early in the design stage.

An experimental investigation into whole body vibration generated during the hydroelastic slamming of a high speed craft

High-Speed planing Craft (HSC) expose their crew to high levels of vibration that regularly exceed the daily exposure limit set out by European directive 2002/44/EU; highest accelerations occur during a slam. Many Whole Body Vibration (WBV) reduction strategies are being researched (e.g. suspension seats), but Coats et al. (2003) and Coe et al. (2013) concluded that a combination of methods is required to reduce the level sufficiently to meet legislation.This paper describes an experimental investigation to determine whether hydroelasticity can affect the WBV of HSC using quasi-2D and full-scale drop tests. The quasi-2D tests revealed that hydroelasticity affected peak acceleration and Vibration Dosage Value (VDV), and that a wooden hull generated higher magnitude WBV than fabric hulls. The full-scale drop tests employed an inflatable lifeboat and the internal pressures of the sponson and keel controlled the hydroelasticity. The full-scale results showed that peak acceleration and VDV reduced while decreasing the internal pressures at the transom and crew locations; however, peak acceleration and VDV increased at the bow. Furthermore, the ability of fabric structures to reduce the mass of HSC is discussed. Incorporating hydroelasticity shows potential, alongside other reduction strategies, to alleviate human exposure to vibration of HSC.

An Extended Verification and Validation Study of CFD Simulations for Planing Hulls

In the context of marine application of computational fluid dynamic (CFD), it is well known that the numerical simulations of planing craft are significantly less reliable than that of displacement ships. For this reason, it is important to perform a comprehensive approach to the verification and validation (V&V) methodology and procedures for simulating CFD planing craft. In the first part of this paper, an assessment of the accuracy and effectiveness of different simulation setups and techniques for planing craft is performed. In the second part, the results of the V&V study are reported for three different hull models at four Froude numbers (Fr). The Unsteady Reynolds-Averaged Navier-Stokes code results were validated using benchmark experimental data obtained for three hull models characterized by systematic variation of the length to beam ratio. Grid independence, iteration, and time-step convergence analysis for response variables (resistance coefficients, wetted surfaces, and dynamic trim angles) were conducted using the main error and uncertainty estimation methods available in the literature. The same procedures were followed for the profiles of the wave patterns. The results showed that there was improved reliability of the numerical simulation of the planing craft in terms of the errors and uncertainties, related to the predictions of resistance, running attitude, and wave pattern. The results of the V&V study highlighted the fact that modeling of the planing craft is a critical point to improve the reliability of the numerical simulation.

An Extended Verification and Validation Study of CFD Simulations for Planing Hulls

In the context of marine application of computational fluid dynamic (CFD), it is well known that the numerical simulations of planing craft are significantly less reliable than that of displacement ships. For this reason, it is important to perform a comprehensive approach to the verification and validation (V&V) methodology and procedures for simulating CFD planing craft. In the first part of this paper, an assessment of the accuracy and effectiveness of different simulation setups and techniques for planing craft is performed. In the second part, the results of the V&V study are reported for three different hull models at four Froude numbers (Fr). The Unsteady Reynolds-Averaged Navier-Stokes code results were validated using benchmark experimental data obtained for three hull models characterized by systematic variation of the length to beam ratio. Grid independence, iteration, and time-step convergence analysis for response variables (resistance coefficients, wetted surfaces, and dynamic trim angles) were conducted using the main error and uncertainty estimation methods available in the literature. The same procedures were followed for the profiles of the wave patterns. The results showed that there was improved reliability of the numerical simulation of the planing craft in terms of the errors and uncertainties, related to the predictions of resistance, running attitude, and wave pattern. The results of the V&V study highlighted the fact that modeling of the planing

Longitudinal Stability Augmentation of Seaplanes in Planing

The towing tank experiments conducted at Yokohama National University from November 30 to December 9 in 2005 suggested a new way of suppressing a dangerous coupled motion between heave and pitch called porpoising. The research in this paper was developed on the observations made in the experiments and conducted numerical simulations to further investigate the parametric design space. Two linear-time-invariant models were developed: rigid-body planing craft (conventional float planes or flying boats), and flexibly supported planing craft. The latter could simulate the new method found in the experiments for suppressing porpoising. In this study, the stability of the oscillatory motions was analyzed to see the effect of design variables on the inception of porpoising. The parametric study of flexibly supported float planes in the context of porpoising was a new contribution in the conceptual design of seaplanes.

The interceptor hydrodynamic analysis for controlling the porpoising instability in high speed crafts

A well-known instability of the high-speed planing crafts is the porpoising instability. This instability involves periodic, coupled heave/pitch oscillations possibly experienced in a planing vessel at high speeds. The porpoising can be controlled by using external devices. Interceptors are vertical blades installed symmetrically at the aft of the craft and have been introduced as a trim control appendage. Here, based on numerical methods and Savitsky porpoising theory, the effects of hydrodynamic interceptors on the porpoising control are investigated. Using computational fluid dynamics, the pressure distribution created by interceptor and its effects on porpoising are computed and then discussed. To model the flow around the vessel model, the Reynolds Average Navier Stokes (RANS) equations are applied. The work deals with craft with and without an interceptor at different heights. A dynamic grid mode involving two degrees of freedom is used. The results show that the interceptor causes an intense pressure at the stern bottom. It also decreases the trim and resistance of the vessel and increases the lift force coefficient which directly affects the porpoising instabilities. Based on the results, the interceptor can completely control the porpoising phenomenon.

On high-speed craft acceleration statistics

Design and operation of high-speed planing craft is ruled by the hydrodynamic impact loads and the related craft responses occurring at violent wave encounters. Simulation, measurement and characterization of these loads and responses is however far from trivial. Hereby the general knowledge about these processes is actually rather limited and it is common to rely on simple semi-empirical formulas when designing and analyzing high-speed craft. This paper presents a unique set of impact acceleration data for a high-speed craft in waves, generated based on non-linear strip simulations. Methods and measures for statistical characterization of the acceleration process are established and evaluated, and by application of these methods on the simulation data a number of issues are clarified, for example: slamming time scales and selection of appropriate sampling rates and filtering levels; identification of peak values in acceleration signals; statistical distributions and convergence; and the relation between the statistical peak fraction averages that are commonly used as design parameters and the actual extreme values. The established methods and generated results form a valuable basis for setting up and analyzing high-speed craft experiments and simulations, and for validating and updating the prevailing semi-empirical methods.