scholarly journals COMPORTAMIENTO DINÁMICO DE UNA EMBARCACIÓN PESQUERA EN EL MAR PERUANO

2017 ◽  
Vol 21 (1) ◽  
pp. 17
Author(s):  
Hugo Eliseo Gamarra Chinchay ◽  
Anwar Julio Yarin Achachagua ◽  
Yasser Hipólito Yarin Achachagua ◽  
Mierwen Palacios Aranda
Keyword(s):  
Energy Spectrum ◽  
Unitary Operator ◽  
Meteorological Data ◽  
Response Spectra ◽  
Sea State ◽  
Palabras Clave ◽  
Peruvian Coast ◽  
Strip Theory ◽  
The Waves ◽  
Shipping Water

El presente trabajo describe la metodología utilizada para predecir el comportamiento presentado por una embarcación de desplazamiento cuando ésta navega en determinada condición de mar. Es importante que el ingeniero naval determine este comportamiento en la fase de proyecto de la embarcación, porque de esta forma puede evaluar los efectos perjudiciales para su desempeño, como por ejemplo la emersión del propulsor, embarque de agua en la cubierta, slamming y excesivas aceleraciones verticales. Los efectos perjudiciales descritos anteriormente son predichos a través de los espectros de respuesta de la embarcación para una determinada condición de mar y para un determinado movimiento. El procedimiento utilizado para la obtención de los Espectros de Respuesta consiste en la superposición del Operador de Respuesta Unitaria en olas regulares de la embarcación para un determinado movimiento (RAO) y el Espectro de Energía de Pierson-Moskowitz, utilizado para representar el mar en una determinada condición. El Operador de Respuesta Unitaria de la embarcación fue determinado utilizando un programa de Dinámica de Navíos basado en la Teoría de las Rebanadas (Strip Theory) y; las diversas condiciones de mar consideradas, fueron caracterizadas utilizando datos metereológicos como la altura significativa (Hs) y periodo medio (Tm) de las olas, siendo estos datos importantes en la generación del Espectro de Energía para determinado estado de mar. Así mismo, se muestran los resultados del comportamiento de una embarcación pesquera operando en diversas condiciones típicas del litoral peruano. Los efectos perjudiciales fueron determinados y se evaluó su severidad en el desempeño de la embarcación a través de criterios de diseño. Palabras clave.- Emersión del propulsor, Operador de respuesta unitaria, Espectro de energía de Pierson-Moskowitz. ABSTRACTThis paper describes the methodology used to predict the behavior presented by a displacement boat when it sails in certain sea conditions. It is important that the naval engineer determines this behavior in the design phase of the boat, because this way you can evaluate the adverse performance, such as the rise of the propellant, shipping water on deck, slamming and excessive accelerations vertical. The harmful effects described above are predicted by the response spectra of the vessel for a given sea condition and for a given movement. The procedure used for obtaining Response Spectra consists of overlapping Unitary Operator Response in regular waves for a given vessel movement (RAO) and the energy spectrum of Pierson-Moskowitz, used to represent the sea in a certain condition. The operator of the boat united response was determined using a Dynamic Vessel program based on the Theory of slices (Strip Theory) and, the various sea conditions considered, were characterized using meteorological data as significant height (Hs) and mean period (Tm) of the waves, these data being important in the generation of the energy spectrum for a given sea state. It also shows the results of the behavior of a fishing vessel operating in various conditions typical of the Peruvian coast. Adverse effects were determined and assessed for severity in the performance of the boat through design. Keywords.- Emersion propeller, Unitary operator response, Energy spectrum Pierson-Moskowitz.

On the Effect of Hull Girder Flexibility on the Vertical Wave Bending Moment for Ultra Large Container Vessels

2012 ◽  
Author(s):  
Ingrid Marie Vincent Andersen ◽  
Jørgen Juncher Jensen
Keyword(s):  
Bending Moment ◽  
Main Concern ◽  
Hull Girder ◽  
Numerical Predictions ◽  
Strip Theory ◽  
Reliability Method ◽  
Non Linear ◽  
Large Container ◽  
The Waves ◽  
Good Agreement

Currently, a number of very large container ships are being built and more are on order, and some concerns have been expressed about the importance of the reduced hull girder stiffness to the wave-induced loads. The main concern is related to the fatigue life, but also a possible increase in the global hull girder loads as consequence of the increased hull flexibility must be considered. This is especially so as the rules of the classification societies do not explicitly account for the effect of hull flexibility on the global loads. In the present paper an analysis has been carried out for the 9,400 TEU container ship used as case-ship in the EU project TULCS (Tools for Ultra Large Container Ships). A non-linear time-domain strip theory is used for the hydrodynamic analysis of the vertical bending moment amidships in sagging and hogging conditions for a flexible and a rigid modelling of the ship. The theory takes into account non-linear radiation forces (memory effects) through the use of a set of higher order differential equations. The non-linear hydrostatic restoring forces and non-linear Froude-Krylov forces are determined accurately at the instantaneous position of the ship in the waves. Slamming forces are determined by a standard momentum formulation. The hull flexibility is modelled as a non-prismatic Timoshenko beam. Generally, good agreement with experimental results and more accurate numerical predictions has previously been obtained in a number of studies. The statistical analysis is done using the First Order Reliability Method (FORM) supplemented with Monte Carlo simulations. Furthermore, strip-theory calculations are compared to model tests in regular waves of different wave lengths using a segmented, flexible model of the case-ship and good agreement is obtained for the longest of the waves. For the shorter waves the agreement is less good. The discrepancy in the amplitudes of the bending moment can most probably be explained by an underestimation on the effect of momentum slamming in the strip-theory applied.

Response Based Identification of Critical Wave Scenarios

2012 ◽  
Author(s):  
Günther F. Clauss ◽  
Marco Klein ◽  
Carlos Guedes Soares ◽  
Nuno Fonseca
Keyword(s):  
Linear Method ◽  
Bending Moment ◽  
Extreme Wave ◽  
Offshore Structure ◽  
Sea State ◽  
Worst Case ◽  
Strip Theory ◽  
Wave Conditions ◽  
Vertical Bending Moment ◽  
Method Approach

In the last years the identification and investigation of critical wave sequences regarding offshore structure responses became one of the main topics in the ocean engineering community. Thereby the area of interest covers the entire field of application spectra at sea — from efficient and economic offshore operations in moderate sea states to reliability as well as survival in extreme wave conditions. For most cases, the focus lies on limiting criteria for the design, such as maximum global loads, maximum relative motions between two or more vessels or maximum accelerations, at which the floating structure has to operate or to survive. These criteria are typically combined with a limiting characteristic sea state (Hs, Tp) or a rogue wave. For the investigation of offshore structures as well as the identification of critical wave sequences, different approaches are available — most of them are based on linear transfer functions as it is an efficient procedure for the fast holistic evaluation. But, for some cases the linear method approach implies uncertainties due to nonlinear response behavior, in particular in extreme wave conditions. This paper presents an approach to these challenges, a response based optimization tool for critical wave sequence detection. This tool, which has been successfully introduced for the evaluation of the applicability of a multi-body system based on the linear method approach, is adjusted to a nonlinear task — the vertical bending moment of a chemical tanker in extreme wave conditions. Therefore a nonlinear strip theory solver is introduced into the optimization routine to capture the nonlinear effects on the vertical bending moment due to steep waves acting on large bow flares. The goal of the procedure is to find a worst case wave sequence for a certain critical sea state. This includes intensive numerical investigation as well as model test validation.

scholarly journals Characteristics and Applications of the Ground-Based X Band Low Elevation Angle Brightness Temperatures under Low Sea State Based on Measured Data

2020 ◽  
Vol 12 (11) ◽  
pp. 1736
Author(s):  
Zhongqing Cao ◽  
Lixin Guo ◽  
Shifeng Kang ◽  
Xianhai Cheng ◽  
Qingliang Li ◽  
...  
Keyword(s):  
Wind Speed ◽  
Meteorological Data ◽  
Surface Wind ◽  
Elevation Angle ◽  
Surface Wind Speed ◽  
Sea Surface ◽  
Sea State ◽  
Sea Surface Wind Speed ◽  
Sea Surface Wind ◽  
X Band

In ground-based microwave radiometer remote sensing, low-elevation-angle (−3°~3°) radiation data are often discarded because they are considered to be of little value and are often difficult to model due to the complicated mechanism. Based on the observed X-band horizontal polarization low elevation angle microwave radiation data and the meteorological data at the same time, this study investigated the generation mechanism of low elevation angle brightness temperature (LEATB) and its relationship with meteorological data, i.e., temperature, humidity, and wind speed, under low sea state. As a result, one could find that the LEATB was sensitive to the atmosphere at the elevation angle between 1° to 3°, and a diurnal variation of the LEATB reached up to 10 K. This study also found a linear relationship between the LEATB and sea surface wind speed under low sea state at an elevation range from −3° to 0°, i.e., the brightness temperature decreased as the wind speed increased, which was inconsistent with the observations at the elevation angle from −10° to −5°. The variation of the LEATB difference according to the change in the over-the-horizon detection capability (OTHDC) of the shipborne microwave radar was examined to identify the reason for this phenomenon theoretically. The results showed that the LEATB difference was significantly influenced by a change in the OTHDC. Further, this study examined a remote sensing method to extract the sea surface wind speed data from experimental LEATB data under low sea state. The results demonstrated that the X-band horizontal polarization LEATBs were useful to retrieve the sea surface wind speed data at a reasonable accuracy—the root mean square error of 0.02408 m/s. Overall, this study proved the promising potential of the LEATB data for retrieving temperature profiles, humidity profiles, sea surface winds, and the OTHDC.

Parametric Study of Operability for a Tourist Submarine

2004 ◽  
Author(s):  
R. T. Paein Koulaei ◽  
M. Rad ◽  
S. M. Mousaviraad ◽  
S. H. Sadathosseini
Keyword(s):  
Parametric Study ◽  
Point Of View ◽  
Hydrodynamic Problem ◽  
Sea State ◽  
Strip Theory ◽  
Speed Effect ◽  
Duration Of Operation

These days, tourist submarine industry has become of increasing interest and prosperity. A tourist submarine operating beneath a seaway suffers different undesired motions which may cause difficulty in operability for the vehicle and habitability of its passengers. From this point of view, this paper studies the hydrodynamic problem of submarine operability in waves. In this investigation strip theory has been used and effects of different parameters of sea state, sea direction, depth, speed and duration of operation have been considered. Results of presented case study indicate that speed effect is insignificant while the operating depth role seems more important.

scholarly journals Generation of 3-hr Long-Crested Waves of Extreme Sea States With HOS-NWT Solver

2020 ◽  
Author(s):  
Maxime Canard ◽  
Guillaume Ducrozet ◽  
Benjamin Bouscasse
Keyword(s):  
Energy Spectrum ◽  
Wave Energy ◽  
Wave Spectrum ◽  
Wave Structure ◽  
Spatial Discretization ◽  
Ocean Engineering ◽  
Sea State ◽  
Wave Condition ◽  
Highly Nonlinear ◽  
Wave Energy Spectrum

Abstract The accurate control of wave fields generated in experiments and numerical simulations is of great interest for the ocean engineering community. In the context of wave-structure interactions, the recommended practices of classification societies are indeed based on the definition of a wave spectrum, that needs to be reproduced. The present work intends to address this problem from the numerical point of view, using a Numerical Wave Tank equipped with a wavemaker and an absorbing beach, based on the High-Order Spectral method (HOS-NWT). The challenging case of the generation of 3-hours long-crested extreme sea states is studied in details. An iterative procedure to reproduce a target wave spectrum at a given distance from the wavemaker is proposed. The quality of the sea state obtained is evaluated using several criteria defined from spectral quantities. A validation is first performed with a highly nonlinear but non-breaking sea-state. Statistical crest distributions obtained are compared with the Forristall and Huang distributions [1,2]. Then, the Gulf of Mexico 1,000 Year Return Period wave condition is generated. This corresponds to an extreme sea state with significant wave breaking occurrence. The numerical solver needs to be able to account for this phenomenon [3]. The Tian breaking model [4, 5] is calibrated to realistically reproduce the dissipation due to breaking, with particular attention paid to the spatial discretization, enlightening its significant effect on breaking model actions. Consequences on the iterative correction process are studied. The computed statistical quantities appear to be significantly different changing the spatial discretization, while the wave energy spectrum stands the same. It questions the relevance of the characterization of a sea state with the sole wave energy spectrum.

Effects of Avoidance of Heavy Weather on the Wave Induced Load on Ships

2006 ◽  
Author(s):  
Zhi Shu ◽  
Torgeir Moan
Keyword(s):  
Green Water ◽  
Vertical Acceleration ◽  
Sea State ◽  
Hull Girder ◽  
Term Prediction ◽  
Strip Theory ◽  
Operational Criteria ◽  
Wave Induced ◽  
Long Term Prediction

This paper is concerned with evaluating the effect of avoidance of heavy weather on the long term wave induced loads on ships. Two hydrodynamic codes VERES based on a 2D strip theory and WASIM based on a 3D Rankine panel method are employed to calculate the wave induced loads and motions on various vessels. Two models for heavy weather avoidance are proposed. The first is based upon the assumption that operational criteria relevant to vertical acceleration, green water and bottom slamming are fulfilled. The second one is based upon the assumption that the sea state forecasts are available to the ship master, and that rerouting is made. And based on the first model considering avoidance of heavy weather and the hydrodynamics results calculated from two codes, the wave induced hull girder loads are obtained. The results are discussed. In particular, the effect of different hydrodynamic codes and various scatter diagrams are assessed. After all, the long term prediction of wave induced hull girder loads considering the effect of avoidance of heavy weather will give a relatively more realistic evaluation of the extreme hull girder loads. Finally the results from ship rules will also be re-evaluated compared with the long term prediction with and without heavy weather avoidance.

scholarly journals Nonlinear dynamics of wave-groups in random seas: unexpected walls of water in the open ocean

2015 ◽  
Vol 471 (2184) ◽  
pp. 20150660 ◽  
Author(s):  
Thomas A. A. Adcock ◽  
Paul H. Taylor ◽  
Scott Draper
Keyword(s):  
Extreme Event ◽  
Open Ocean ◽  
Extreme Waves ◽  
Wave Direction ◽  
Sea State ◽  
Wave Groups ◽  
Large Wave ◽  
Linear Evolution ◽  
Random Seas ◽  
The Waves

This paper investigates the size and structure of large waves on the open ocean. We investigate how nonlinear physics modifies waves relative to those predicted by a linear model. We run linear random simulations and extract extreme waves and the surrounding sea-state. For each extreme event, we propagate the waves back in time under linear evolution before propagating the wave-field forward using a nonlinear model. The differences between large linear and nonlinear wave-groups are then examined. The general trends are that under nonlinear evolution, relative to linear evolution, there is, on average, little or no extra amplitude in the nonlinear simulations; that there is an increase in the width of the crest of the wave-group and a contraction of large wave-groups in the mean wave direction; that large waves tend to move to the front of a wave-packet meaning that the locally largest wave is relatively bigger than the wave preceding it; and that nonlinearity can increase the duration of extreme wave events. In all these trends, there is considerable scatter, although the effects observed are clear. Our simulations show that nonlinearity does play an important part in the formation of extreme waves on deep water.

Prediction of Fatigue Life of Shallow Water Offshore Platforms Using Spectral Fatigue Analysis Method

2010 ◽  
Author(s):  
Qin Feng ◽  
Richard Large
Keyword(s):  
Shallow Water ◽  
Transfer Functions ◽  
Structural Response ◽  
Response Spectra ◽  
Fatigue Analysis ◽  
Offshore Platforms ◽  
Analysis Method ◽  
Technical Approach ◽  
Sea State ◽  
Platform Design

Spectral fatigue analysis approach is highly recommended for fixed offshore platform design and reassessment by API. This method is a computationally efficient method, being able to handle the random nature of environmental ocean wave conditions during calculating wave loads on the offshore platforms and subsequent structural responses. However, its fundamental theory is based on the assumption of linearity of both structural system and wave loading mechanism. Although this method is critically appropriate to be applied in offshore platform design and fatigue assessment for deep water scenarios where wave and force nonlinearities are not very severe, it has still been widely utilized for the design and assessment of shallow water platforms in offshore industry without carefully considering possible errors caused by strong nonlinear factors between ocean waves and forces. The source giving rise to the errors is because of the difficulties in choosing suitably correct wave heights for a series of wave periods required for producing transfer functions between sea state spectra and structural response spectra. Therefore, the studies to justify the possible errors of the spectral fatigue analysis method for shallow water platforms have been provoked. This paper presents the results of the studies of investigating the errors from currently existing spectral fatigue analysis method. A new technical approach that can reduce the errors in the spectral fatigue analysis of shallow water platforms is introduced. The proposed technical approach is mainly focused on producing realistic transfer functions between sea state spectra and structural response spectra, which can reasonably reflect the individually local sea state data by using wave height-period joint probability density function. Hence the fatigue damage and life at the tubular joints of offshore platforms can be more precisely predicted. The spectral fatigue analysis of a practical shallow water jacket platform in the recent platform design project has been performed using the proposed approach and the results are discussed.

Navigation Condition Effect on Ship Motion in some Sea State

2012 ◽  
Vol 490-495 ◽  
pp. 1579-1583 ◽  
Author(s):  
Jie Zhang ◽  
Kai Qu ◽  
Xu Dong Zhang
Keyword(s):  
Wave Theory ◽  
Simulation Software ◽  
Ship Motion ◽  
Sea State ◽  
Motion Equations ◽  
Condition Effect ◽  
Strip Theory ◽  
Wave Energy Spectrum ◽  
Ship Speed ◽  
Navigation Condition

According to analyzing the identity of ocean wave, theory of wave energy spectrum was applied to compute the curve of wave elevation vs. time in some sea state. Based on ship motion equations, ship motion was acquired by the simulation software of the of ship strip theory in some situation. How different navigation conditions effect on ship motion is researched in some sea state. The results show the change of degree of abaft the beam badly influenced the amplitude and periods of pitch, it also influenced periods of heave and amplitude of roll. The change of ship speed influenced the amplitude and periods of pitch, it also influenced periods of heave and roll.

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