Identification of the Vertical Plane Motion Model of a High Speed Craft by Model Testing in Irregular Waves

1998 ◽  
Vol 31 (30) ◽  
pp. 257-262 ◽  
Author(s):  
J.M. de la Cruz ◽  
J. Aranda ◽  
P. Ruipérez ◽  
J.M. Díaz ◽  
A. Marón
Keyword(s):  
High Speed ◽  
Vertical Plane ◽  
Plane Motion ◽  
Model Testing ◽  
Irregular Waves ◽  
Motion Model

A Linear Model Analysis of the Unsteady Force Response of a Planing Hull Through Forced Vertical Plane Motion Simulations

2020 ◽  
Author(s):  
Nicholas Husser ◽  
Stefano Brizzolara
Keyword(s):  
Linear Model ◽  
High Speed ◽  
Vertical Plane ◽  
Added Mass ◽  
Plane Motion ◽  
Force Response ◽  
Strip Theory ◽  
Planar Motion Mechanism ◽  
Unsteady Force ◽  
Traditional Approaches

The prediction of planing hull motions and accelerations in a seaway is of paramount importance to the design of high-speed craft to ensure comfort and, in extreme cases, the survivability of passengers and crew. The traditional approaches to predicting the motions and accelerations of a displacement vessel generally are not applicable, because the non-linear effects are more significant on planing hulls than displacement ships. No standard practice for predicting motions or accelerations of planing hulls currently exists, nor does a nonlinear model of the hydrodynamic forces that can be derived by simulation. In this study, captive and virtual planar motion mechanism (VPMM) simulations, using an Unsteady RANSE finite volume solver with volume of fluid approach, are performed on the Generic Prismatic Planing Hull (GPPH) to calculate the linearized added mass, damping, and restoring coefficients in heave and pitch. The linearized added mass and damping coefficients are compared to a simplified theory developed by Faltinsen [6], which combines the method of Savitsky [12] and 2D+t strip theory. The non-linearities in all coefficients will be investigated with respect to both motion amplitude and frequency. Nonlinear contributions to the force response are discussed through comparison of the force response predicted by the linear model and force response measured during simulation. Components of the planing hull dynamics that contribute to nonlinearities in the force response are isolated and discussed.

Modern Nonlinear Dynamical Analysis of Vertical Plane Motion of Planing Hulls

1993 ◽  
Vol 37 (03) ◽  
pp. 189-199 ◽  
Author(s):  
Armin W. Troesch ◽  
Jeffrey M. Falzarano
Keyword(s):  
High Speed ◽  
Vertical Plane ◽  
Nonlinear Effects ◽  
Plane Motion ◽  
Dynamical Analysis ◽  
Regular Waves ◽  
Nonlinear Dynamical ◽  
Dynamical Systems Analysis ◽  
Extreme Behavior ◽  
Nonlinear Dynamical Analysis

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.

Experimental Investigation of the Behaviour of a Large Ship in Irregular Waves

2016 ◽  
Vol 23 ◽  
pp. 103-112
Author(s):  
Christiaan Adika Adenya ◽  
Hui Long Ren ◽  
Jialong Jiao
Keyword(s):  
Experimental Investigation ◽  
Vertical Plane ◽  
Bending Moment ◽  
Plane Motion ◽  
Irregular Waves ◽  
Scaled Model ◽  
Load Response ◽  
Head Waves ◽  
Large Ship ◽  
Wave Conditions

A towing tank experimental investigation was carried out using a segmented scaled model of a large ship prototype to study its behaviour when sailing in irregular head waves. The tests were carried out for typical sailing speeds and wave conditions that would be encountered by the large ship at sea. The vertical plane motion of heave, pitch, and the accelerations at bow and stern, and the vertical bending moment load responses of the ship were measured and analyzed. The significant amplitude values of motion and load response of the ship for the investigated wave conditions and speeds were determined by using spectral analysis. Slamming induced whipping loads were also investigated for the studied sailing conditions. In addition, the load response characteristics were evaluated in both time-domain and frequency-domain. Increasing the sea state had a greater effect on the motion and load responses of the large ship than increasing the sailing speed.

Analysis, Design, and Optimization of High Speed Vehicle Suspensions Using State Variable Techniques

1974 ◽  
Vol 96 (2) ◽  
pp. 193-203 ◽  
Author(s):  
J. K. Hedrick ◽  
G. F. Billington ◽  
D. A. Dreesbach
Keyword(s):  
High Speed ◽  
Optimization Problems ◽  
Vertical Plane ◽  
Computer Application ◽  
Vehicle Suspension ◽  
State Variables ◽  
State Variable ◽  
Suspension Parameters ◽  
Suspension Model ◽  
High Speed Vehicle

This article applies state variable techniques to high speed vehicle suspension design. When a reasonably complex suspension model is treated, the greater adaptability of state variable techniques to digital computer application makes it more attractive than the commonly used integral transform method. A vehicle suspension model is developed, state variable techniques are applied, numerical methods are presented, and, finally, an optimization algorithm is chosen to select suspension parameters. A fairly complete bibliography is included in each of these areas. The state variable technique is illustrated in the solution of two suspension optimization problems. First, the vertical plane suspension of a high speed vehicle subject to guideway and aerodynamic inputs will be analyzed. The vehicle model, including primary and secondary suspension systems, and subject to both heave and pitch motions, has thirteen state variables. Second, the horizontal plane suspension of a high speed vehicle subject to guideway and lateral aerodynamic inputs is analyzed. This model also has thirteen state variables. The suspension parameters of both these models are optimized. Numerical results are presented for a representative vehicle, showing time response, mean square values, optimized suspension parameters, system eigenvalues, and acceleration spectral densities.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

scholarly journals WAVE LOADS ON HORIZONTAL CYLINDERS

1978 ◽  
Vol 1 (16) ◽  
pp. 147
Author(s):  
P. Holmes ◽  
J.R. Chaplin
Keyword(s):  
Oscillatory Flow ◽  
Vertical Plane ◽  
Vertical Cylinder ◽  
Irregular Waves ◽  
Wave Loads ◽  
Incident Flow ◽  
Cylinder Axis ◽  
Straight Line ◽  
Horizontal Cylinders ◽  
Wave Induced

The problem of predicting wave induced loads on cylinders is an enormously complex one. It is clear from the scatter present in most experimental determinations of force coefficients that there are many individual factors which influence the mechanisms of flow induced loading. Among these are some, for instance Reynolds number, separation and periodic vortex shedding, which are inter-related and whose influences cannot be studied in isolation. Others, such as shear flow, irregular waves and free surface effects, can at least be eliminated in the laboratory, in order to approach an understanding of the more fundamental characteristics of the flow. A vertical cylinder in uniform waves experiences an incident flow field which can be described in terms of rotating velocity and acceleration vectors, always in the same vertical plane, containing also the cylinder axis, whose magnitudes are functions of time and of position along the length of the cylinder. Some of the essential features of this flow can be studied under two-dimensional oscillatory conditions, in which either the cylinder or the fluid is oscillated relative to the other along a straight line (planar oscillatory flow). The incident velocity and acceleration vectors are then always concurrent, normal to the cylinder axis, and oscillating in magnitude with time.

SLAM CHARACTERISTICS OF A HIGH-SPEED WAVE PIERCING CATAMARAN IN IRREGULAR WAVES

2021 ◽  
Vol 156 (A1) ◽  
Author(s):  
B J French ◽  
G A Thomas ◽  
M R Davis
Keyword(s):  
Vertical Velocity ◽  
Significant Wave Height ◽  
High Speed ◽  
Irregular Waves ◽  
Two Dimensional ◽  
Towing Tank ◽  
Filling Height ◽  
Load Distributions ◽  
Poor Indicator ◽  
Wave Elevations

Slam characteristics of a 112m INCAT wave piercing catamaran in a range of realistic irregular sea conditions are presented in this paper. Towing tank testing of a 2.5 m hydroelastic segmented catamaran model was used to gather a database of slam events in irregular seas. The model was instrumented to measure motions, centrebow surface pressures and forces, encountered wave elevations and wave elevations within the bow area tunnel arches. From these measurements characteristics of the vessel slamming behaviour are examined: in particular relative vertical velocity, centrebow immersion, archway wave elevations and slam load distributions. A total of 2,098 slam events were identified over 22 different conditions, each containing about 80 to 100 slam events. The data, although inherently scattered, shows that encounter wave frequency and significant wave height are important parameters with regard to centrebow slamming. Relative vertical velocity was found to be a poor indicator of slam magnitude and slams were found to occur before the centrebow arch tunnel was completely filled, supporting the application of a two-dimensional filling height parameter as a slam indicator.

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

2018 ◽  
Vol 233 (4) ◽  
pp. 1068-1081
Author(s):  
Manudul Pahansen de Alwis ◽  
Karl Garme
Keyword(s):  
Real Time ◽  
High Speed ◽  
High Performance ◽  
Severity Index ◽  
Irregular Waves ◽  
Vibration Exposure ◽  
Data Set ◽  
Real Time Analysis ◽  
Impact Acceleration ◽  
The Impact

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.

Computer Aided Resistance Prediction Of High Speed Planing Hull Forms

1994 ◽  
pp. 23-43
Author(s):  
Mohd. Ramzan Mainal
Keyword(s):  
High Speed ◽  
Computational Procedure ◽  
Model Testing ◽  
Experimental Results ◽  
Total Resistance ◽  
Computer Prediction ◽  
Computer Aided ◽  
Tremendous Amount ◽  
Resistance Prediction ◽  
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.

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