Journal Article•
Improved time domain simulation of planing hulls in waves by correction of the near-transom lift
TL;DR: In this paper, a time-domain strip model for simulation of the planing hull in waves is presented. But the model is based on a wave height measurement signal and is not suitable for full-scale measurement data.
Abstract: Simulation of the planing hull in waves has been addressed during the last 25 years and basically been approached by strip methods. This work follows that tradition and describes a time-domain strip model for simulation of the planing hull in waves. The actual fluid mechanical problem is simplified through the strip approach. The load distribution acting on the hull is approximated by determining the section load at a number of hull sections, strips. The section-wise 2-dimensional calculations are expressed in terms of added mass coefficients and used in the formulations of both inertia and excitation forces in the equations of motions. The modeling approach starts from the hypothetic assumption that the transient conditions can be modeled based on those section-wise calculations. The equation of motion is solved in the time-domain. The equation is up-dated at each time step and every iteration step with respect to the momentary distribution of section draught and relative incident velocity between the hull and water and catches the characteristic non-linear behavior of the planing craft in waves. The model follows the principles of the pioneering work of E. E. Zarnick differing on model structure and in details such as the modeling of the lift in the transom area. A major part of the work is concerned with experiments and evaluation of simulations with respect to performed model tests and to published experiment data. Simulations of model tests have been performed and comparisons have been made between measured and simulated time series. The link between simulation and experiment is a wave model which is based on a wave height measurement signal. It is developed and evaluated in the thesis. The conclusions are in favor of the 2-dimensional approach to modeling the conditions for the planing hull in waves and among further studies is evaluation of simulated loads and motions to full-scale trial measurement data.
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TL;DR: In this paper, the authors considered the impact of panel-water hull-water impacts on high-speed craft using the finite element code LS-DYNA and a simplified in-house developed method.
94 citations
TL;DR: In this paper, a 2D boundary element method was employed to solve the initial boundary value problems in 2D cross planes, in which nonlinear free-surface conditions and exact body boundary conditions were satisfied.
Abstract: The dynamic response of planing vessels in regular head seas is investigated numerically. Nonlinear time domain simulations were performed using a 2D + t theory (two-dimensional plus time dependent theory). A prismatic hull form was assumed. We employed a two-dimensional (2D) boundary element method to solve the initial boundary value problems in 2D cross planes, in which nonlinear free-surface conditions and exact body boundary conditions were satisfied. At each time step, the total force and moment on the hull could be obtained by using the sectional forces calculated in those 2D planes. Heave and pitch motions were then acquired by solving the equations for those motions. The calculated heave and pitch responses were compared with the experiments by Fridsma (A systematic study of the rough-water performance of planing boats. Davidson Laboratory Report R-1275, 1969) for two different Froude numbers. Three-dimensional (3D) corrections at the transom stern were applied to show the influence of the 3D effect at the stern on the numerical results. Ship motions were affected by the 3D corrections, especially near the resonance frequency, while the phase angles were slightly affected and the acceleration peaks at the bow near the resonance frequency were sensitive to the 3D corrections. Other error sources in the theoretical results are also mentioned.
40 citations
TL;DR: In this paper, a mathematical model based on 2D-asymmetric wedge water entry to model heave and pitch motions of planing hulls at non-zero heel angles is presented.
37 citations
01 Feb 2017
TL;DR: In this paper, a simple mathematical model for predicting the running attitude of warped planing boats fixed in a heel angle and free of trim and sinkage is presented, based on asymptotics.
Abstract: This article presents a simple mathematical model for predicting the running attitude of warped planing boats fixed in a heel angle and free to trim and sinkage. The proposed model is based on asym...
35 citations
01 Nov 2016
TL;DR: In this paper, the roll motion prediction problem is considered as an important problem in planing hull motion, since safety of the craft highly depends on it at high speeds, and the main aim of the present work is to predict the roll motions of the ship at high speed.
Abstract: Prediction of the roll motion is considered as an important problem in planing hull motion, since safety of the craft highly depends on it at high speeds. Accordingly, the main aim of the present s...
32 citations
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404 citations
TL;DR: In this article, the authors derived a theoretical method for predicting the linearized response characteristics of planing boats in head and following waves, and compared the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data.
Abstract: A theoretical method is derived for predicting the linearized response characteristics of constant-deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response-amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed-to-length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.
51 citations
TL;DR: In this article, the authors developed an extension of Tulin (1957) originally by Vorus (1996) and later by Savander (1997), which allows for general variation in deadrise in both the transverse and longitudinal directions.
Abstract: The objective of this work is to continue to develop rationally based tools for hydrodynamic analysis of three-dimensional planing surfaces. The small craft naval architect is in need of a computationally efficient method to analyze planing surfaces allowing for sufficient sensitivity to hull geometric details. Planing surface analysis first received attention during the early part of the 20th century. This development was associated with flying boat applications. Von Karman (1929) and Wagner (1932) are considered the first researchers to develop rational models for planing surface analysis. The work contained herein is derived from the extension of Tulin (1957) originally by Vorus (1996) and later by Savander (1997). The model developed allows for general variation in deadrise in both the transverse and longitudinal directions. Hence, buttock line curvature is included in the formulation. The chine beam of the hull can vary longitudinally. Fundamental theoretical and numerical enhancements have been made to Vorus (1996) and Savander (1997). The current model is compared with constant and variable velocity 2-D impact experiments, prismatic planing model tests, Savitsky (1964) prismatic planing model, and deepwater Series 62 model test results (Clement & Blount 1963). The comparisons in many cases are excellent, especially at high Froude number. The comparisons illustrate the utility of the method. Problematic areas are presented and topics for further research are suggested.
37 citations
TL;DR: In this article, a model was instrumented with pressure transducers and towed in calm water, and the aim of the experiment was time-domain monitoring and analysis of the pressure distribution on planing craft in waves.
Abstract: The aim of the experiment was time-domain monitoring and analysis of the pressure distribution on planing craft inwaves. A model was instrumented with pressure transducers and towed in calm water, ...
29 citations
TL;DR: In this article, a three-dimensional numerical model using vortex lattice methods is developed to solve the steady planing problem, including the zero pressure condition on the free surface and the treatment of the flow off the chines.
Abstract: A three-dimensional numerical model using vortex lattice methods is developed to solve the steady planing problem. This paper examines assumptions related to high-speed planing hydrodynamics, including those used by two-dimensional slender-body theories. Emphasis is placed upon the investigation of various modeling issues such as the zero pressure condition on the free surface and the treatment of the flow off the chines. Numerical results including hydrodynamic forces and pressure distributions are presented and compared with experiments. A simple model to include the effect of gravity in the near field is also examined. The models described here can be incorporated into design methodologies for predicting the hydrodynamic force and moment acting on planing hulls with general shape
25 citations