Computational Modeling of Planing Hull Dynamics and Slamming in Head Waves

2021 ◽  
Author(s):  
Konstantin I. Matveev
Keyword(s):  
Water Surface ◽  
Numerical Approach ◽  
Nonlinear Flow ◽  
Random Waves ◽  
Regular Waves ◽  
Hydrodynamic Loads ◽  
Drag Forces ◽  
Operational Capabilities ◽  
Head Waves ◽  
Numerical Grid

Abstract Fast boats often operate in planing regimes when they skim on the water surface and their weight is supported primarily by hydrodynamic forces. In the presence of waves, such hulls may experience large nonlinear motions and hydrodynamic loads, which limit their operational capabilities. To predict hull motions and loads and to optimize the hull shape and structure, one can take advantage of computational fluid dynamics tools that simulate these complex nonlinear flow processes and provide detailed hydrodynamic data, including pressure distribution on the hull and water spray. However, validation of these modeling approaches is needed in order to confidently use numerical tools for the boat design. In this study, numerical modeling is accomplished for dynamics of a realistic hull previously tested in controlled wave environments in towing tanks. Time-domain simulations were first carried out in regular head waves. Mesh-verification studies suggested appropriate numerical grid resolution. The hull’s heave motions, drag forces and bow accelerations were captured and compared with experimental data. The formal validation procedure was applied to confirm suitability of the current numerical approach. In the investigated regular-wave conditions, very pronounced slamming phenomenon was observed, when the hull re-entered water and experienced peak hydrodynamic loads. Pressure distributions on the hull surface and water surface deformations are presented for several time instances around the slamming event. In addition, numerical simulations were also conducted for random waves with statistical sea-wave parameters resembling those of the studied regular waves. The statistical boat responses, such as bow accelerations, heaving motions and drag forces, are compared to the corresponding metrics obtained in regular waves.

scholarly journals Time Scale for Scour Beneath Pipelines Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Current

2021 ◽  
Vol 9 (2) ◽  
pp. 114
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Time Scale ◽  
Current Flow ◽  
Irregular Waves ◽  
Wave Crest ◽  
Random Wave ◽  
Random Waves ◽  
Flow Conditions ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D

This article derives the time scale of pipeline scour caused by 2D (long-crested) and 3D (short-crested) nonlinear irregular waves and current for wave-dominant flow. The motivation is to provide a simple engineering tool suitable to use when assessing the time scale of equilibrium pipeline scour for these flow conditions. The method assumes the random wave process to be stationary and narrow banded adopting a distribution of the wave crest height representing 2D and 3D nonlinear irregular waves and a time scale formula for regular waves plus current. The presented results cover a range of random waves plus current flow conditions for which the method is valid. Results for typical field conditions are also presented. A possible application of the outcome of this study is that, e.g., consulting engineers can use it as part of assessing the on-bottom stability of seabed pipelines.

scholarly journals Experimental study of hydrodynamic forces acting on ship bow during wave capture

2019 ◽  
pp. 146-152
Author(s):  
Pavel Burakovskiy
Keyword(s):  
Experimental Study ◽  
Test Data ◽  
Model Test ◽  
Hydrodynamic Forces ◽  
Hydrodynamic Loads ◽  
Test Tank ◽  
Head Waves ◽  
Negative Effect

This paper studies behavior of ship in head waves, when her bow dips under water, which leads to hydrodynamic forces and moments to be assessed. This paper presents model test data obtained in the test tank on the model of ship bow (hydrodynamic loads on forecastle deck during wave capture) as well as updates the coefficient of flow around the bow. The study also shows that bulwark has negative effect upon safety in these conditions because it significantly increases hydrodynamic loads on the deck.

scholarly journals Random wave-driven drag forces on near-bed vegetation in shallow water based on deepwater wind conditions

2019 ◽  
Vol 233 (4) ◽  
pp. 1287-1290
Author(s):  
Dag Myrhaug
Keyword(s):  
Shallow Water ◽  
Drag Force ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Random Wave ◽  
Random Waves ◽  
Coastal Zones ◽  
Drag Forces ◽  
Mean Wind Speed ◽  
Wave Induced

This article provides a simple analytical method for giving estimates of random wave-driven drag forces on near-bed vegetation in shallow water from deepwater wind conditions. Results are exemplified using a Pierson–Moskowitz model wave spectrum for wind waves with the mean wind speed at the 10 m elevation above the sea surface as the parameter. The significant value of the drag force within a sea state of random waves is given, and an example typical for field conditions is presented. This method should serve as a useful tool for assessing random wave-induced drag force on vegetation in coastal zones and estuaries based on input from deepwater wind conditions.

Coupling Between Roll Motions of an FLNG Vessel and Internal Sloshing

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Wenhua Zhao ◽  
Jianmin Yang ◽  
Zhiqiang Hu ◽  
Longbin Tao
Keyword(s):  
Water Surface ◽  
Measured Data ◽  
Liquefied Natural Gas ◽  
Wave Profile ◽  
Coupling Mechanism ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Regular Waves ◽  
Surface Modes ◽  
Band Limited

A series of two-dimensional model tests has been conducted to study the coupling between global roll motions of a floating liquefied natural gas (FLNG) vessel and internal sloshing. The model of the FLNG is allowed to move freely in roll under the excitations of an initial heel angle, band-limited waves, and regular waves. To clarify the coupling effects, the FLNG vessel in different filling conditions is ballasted in fresh water and equivalent steel ballast weights, respectively. Time series of both the internal sloshing and the global motions of the vessel are measured. Statistical and spectral analyses have been carried out on the measured data. Sloshing oscillations in different surface modes have been observed. Asymmetry of the internal wave profile relative to still-water surface is also observed. Attempts are made to clarify the influences of the internal sloshing on the global roll motions through the comparison of the experiment results between the liquid and steel ballasting cases. The coupling phenomenon is found to be sensitive to the period and height of excitation waves. Further discussion has been made on the experiment results, and some conclusions regarding the coupling mechanism between global motions and internal sloshing are drawn based on the present study.

Application of a Boundary Element Method for Wave-Body Interaction Problems Considering the Non-Linear Water Surface

2017 ◽  
Author(s):  
Daniel Ferreira González ◽  
Jonas Bechthold ◽  
Moustafa Abdel-Maksoud
Keyword(s):  
Water Surface ◽  
Three Dimensional ◽  
Free Water ◽  
Numerical Approach ◽  
Panel Method ◽  
The Body ◽  
Time Step ◽  
Non Linear ◽  
Wigley Hull ◽  
Tank Test

In this paper an existing time domain panel method, which was originally developed for propeller flow simulations, is extended by implementing the mixed Eulerian-Lagrangian approach for the computation of the non-linear free water surface. The three-dimensional panel method uses a constant source and doublet density distribution on each panel and a Dirichlet boundary condition to solve the velocity potential in every time step. Additionally, a formulation for the acceleration potential is included in order to determine the hydrodynamic forces accurately. The paper gives an overview on the governing equations and introduces the numerical approach. Validation results of the developed method are presented for the wave resistance of a submerged spheroid and a wigley hull. Additionally, the wave diffraction due to a surface piercing cylinder in regular waves is validated regarding the forces and the water surface elevation around the body. Here, the computations are compared with other numerical methods as well as tank test results. Apart from this, the paper deals with an application example showing simulations of an artificial service vessel catamaran in waves. The forces on the hull with and without forward speed are presented. The paper concludes with a discussion of the presented results and a brief outlook on further work.

Numerical Study of the Motions in Shallow Water Waves of Floating Bodies Elastically Linked to Bottom

2009 ◽  
Author(s):  
Marcio Michiharu Tsukamoto ◽  
Liang-Yee Cheng ◽  
Kazuo Nishimoto
Keyword(s):  
Shallow Water ◽  
Water Waves ◽  
Large Amplitude ◽  
Numerical Study ◽  
Numerical Approach ◽  
Floating Bodies ◽  
Restoring Force ◽  
Hydrodynamic Loads ◽  
Elastic Links ◽  
Analytical Approaches

The motion of floating bodies linked elastically to the bottom of seas and waterways is of great interest in the analysis of the wave suppressing devices, such as wave breakers, and the behaviors of the floating structures, such as buoys and tension leg platforms (TLP). For the modeling of the dynamics, the coupling between the hydrodynamic loads due to waves and the restoring forces due to the elastic link must be considered. In some simpler cases, the analytical approaches are available. However, in case of large amplitude waves and floating bodies with complex geometries, the analytical solutions do not give accurate results. In the present study, a numerical model based on MPS (moving particle semi-implicit method) for the hydrodynamic loads coupled with the Hook’s Law for the restoring force is adopted to analyze the motion of floating bodies with one or several elastic links to the bottom of shallow water under large amplitude waves. Initially, the results of 2D numerical simulation of simple oscillating buoys are compared with the analytical and experimental ones to validate the numerical approach. After that, the approach is applied to the study of the shallow water wave supressing devices. Heave, surge and pitching motions of the floaters are assessed as well as the hydrodynamic coefficients to show the effect of the elastic links in the nonlinear wave hydrodynamics.

Drag forces on aquatic plants in nonlinear random waves plus current

2015 ◽  
Vol 165 ◽  
pp. 10-24 ◽  
Author(s):  
Pierre-Yves Henry ◽  
Dag Myrhaug ◽  
Jochen Aberle
Keyword(s):  
Aquatic Plants ◽  
Random Waves ◽  
Drag Forces ◽  
Nonlinear Random Waves

scholarly journals A Numerical Approach to the Dynamic Response of the Deployment System during a Circular Cylinder Crossing through the Wave Zone

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Xiaozhou Hu ◽  
Daojun Cai ◽  
Yiyao Jiang
Keyword(s):  
Circular Cylinder ◽  
Dynamic Response ◽  
Numerical Approach ◽  
Dynamic Responses ◽  
Regular Waves ◽  
Cable Dynamics ◽  
Input Parameters ◽  
Solution Methods ◽  
Wave Heights ◽  
Phase Angles

The dynamic response of the deployment system while deploying a circular cylinder crossing wave surface and the following submerging process are investigated numerically. The present numerical approach is based on the combination of solution methods of cable dynamics and computational fluid dynamics (CFD). For the implementation of the numerical approach, a cosimulation platform based on a CFD code and MATLAB is developed to study the fluid-solid interaction problem in the process. To generate regular waves, a numerical wave tank is built based on a piston-type wave generation method and a wave damping method applying porous media. Numerical simulations are performed based on the cosimulation platform. The sensitivities of cable tension, velocity, and acceleration of deployed body to different input parameters are investigated, including phase angles, wave heights, and periods of regular waves and deploying velocities, and the effects of those input parameters on dynamic responses of the deployment system are also discussed.

Earthquake-induced hydrodynamic forces on reservoir roofs

2010 ◽  
Vol 37 (8) ◽  
pp. 1107-1115 ◽  
Author(s):  
Michael Isaacson
Keyword(s):  
Laboratory Test ◽  
Storage Tank ◽  
Water Surface ◽  
Design Procedure ◽  
Hydrodynamic Forces ◽  
Surface Elevation ◽  
Test Results ◽  
Hydrodynamic Loads ◽  
Laboratory Test Results ◽  
New Formulation

The present paper describes the hydrodynamic loads on the roof of a water-filled reservoir or storage tank due to earthquake-induced sloshing. Initially, the paper summarizes available solutions for the water surface elevation in a rectangular reservoir subjected to harmonic and earthquake base motions, and as well an available formulation for the force on the roof of a rectangular reservoir. With this background, a new formulation for the force on the roof is developed, and selected results based on this are presented. A recommended design procedure is thereby proposed, and an example application is provided. The potential extension of the proposed formulation to other reservoir configurations is discussed. Although a validation of the proposed formulation based on laboratory test results is needed, it is suggested that in the interim the proposed formulation is adopted for design.

Burial and Scour of Short Cylinders and Truncated Cones Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Currents

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Muk Chen Ong ◽  
Dag Myrhaug
Keyword(s):  
Narrow Band ◽  
Three Dimensional ◽  
Wave Crest ◽  
Height Distribution ◽  
Random Waves ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D ◽  
The Waves ◽  
Crest Height

This paper provides a practical stochastic method by which the burial and scour depths of short cylinders and truncated cones exposed to long-crested (two-dimensional (2D)) and short-crested (three-dimensional (3D)) nonlinear random waves plus currents can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall second-order wave crest height distribution representing both 2D and 3D nonlinear random waves. Moreover, the formulas for the burial and the scour depths for regular waves plus currents presented by previous published work for short cylinders and truncated cones are used.

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