Interaction of Waves With a Steady Intake/Discharge Flow Emanating From a 3D Body

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Bala Padmanabhan ◽  
R. Cengiz Ertekin
Keyword(s):  
Steady Flow ◽  
Surface Condition ◽  
Linear Potential ◽  
Intake Rate ◽  
Mooring Lines ◽  
Incoming Wave ◽  
Total Potential ◽  
Warm Surface Water ◽  
Linear Potential Theory ◽  
Steady Potential

It has been proposed that the warm surface-water intake pipes distributed around an OTEC plant can generate adequate momentum to globally position a platform to overcome the second-order drift forces, thereby eliminating the need for additional power for thrusters or for mooring lines. It is evident that if the intake rate of the flow is high, there will be interaction among the locally created steady flow due to the intake, the incoming wave, and the ensuing platform motions. In this work, we address such concerns by developing a linear theory for obtaining the motions (in the presence of incoming waves) of arbitrary 3D bodies from which there is a steady intake/discharge. The boundary-value problem is formulated within the assumption of the linear potential theory by decomposing the total potential into oscillatory and steady components. The steady potential is further decomposed into double-model and perturbation potentials. The time harmonic potential is coupled with the steady potential through the free-surface condition. The potentials are obtained using the quadratic boundary-element method. The effect of the steady flow on hydrodynamic force coefficients and response amplitude operators is studied.

Interaction of Waves With Steady Intake/Discharge Flow Emanating From a 3-D Body

2007 ◽  
Author(s):  
Bala Padmanabhan ◽  
R. Cengiz Ertekin
Keyword(s):  
Steady Flow ◽  
Surface Condition ◽  
Linear Potential ◽  
Intake Rate ◽  
Mooring Lines ◽  
Incoming Wave ◽  
Total Potential ◽  
Warm Surface Water ◽  
Linear Potential Theory ◽  
Steady Potential

It has been proposed that the warm surface-water intake pipes distributed around an OTEC plant can generate adequate momentum to globally position a platform to overcome the second-order drift forces, thereby eliminating the need for additional power for thrusters or for mooring lines. It is evident that if the intake rate of the flow is high, there will be interaction among the locally created steady flow due to the intake, the incoming wave and the ensuing platform motions. In this work, we address such concerns by developing a linear theory for obtaining the motions (in the presence of incoming waves) of arbitrary 3-D bodies from which there is a steady intake/discharge. The boundary-value problem is formulated within the assumption of linear potential theory by decomposing the total potential into oscillatory and steady components. The steady potential is further decomposed into double-model and perturbation potentials. The time harmonic potential is coupled with the steady potential through the free-surface condition. The potentials are obtained using the quadratic boundary-element method. The effect of the steady flow on hydrodynamic force coefficients and RAOs are studied.

On the Interaction of Waves With Intake/Discharge Flows Originating From a Freely-Floating Body

2002 ◽  
Author(s):  
B. Padmanabhan ◽  
R. C. Ertekin
Keyword(s):  
Free Surface ◽  
Surface Condition ◽  
Floating Body ◽  
Wave Forces ◽  
Linear Potential ◽  
Rankine Source ◽  
Total Potential ◽  
Low Froude Number ◽  
Linear Potential Theory ◽  
Steady Potential

This work is motivated by the many instances of intake/discharge flows from openings on floating or submerged ocean vessels and structures that may affect the wave field around them. Damaged vessels may release oil, or water may enter these vessels through openings. In oil skimming operations, for example, a very thin layer of oil must be skimmed off a large surface area, and therefore, oil skimming vessels require large intakes. Floating OTEC plants also require large intake and discharge volumes to sustain their operations. A linear theory is developed to obtain the motions of a 2-dimensional, freely floating body (from which steady intake/discharge flows originate) that encounters incoming waves. The boundary-value problem is formulated within the assumptions of linear potential theory by decomposing the total potential into its oscillatory and steady components. The steady potential is further decomposed into the double-model and perturbation potentials. The time-harmonic potential is coupled with the steady potential through the free-surface condition. The potentials are obtained by use of the quadratic boundary-element method based on the Rankine source. The effect of the steady intake/discharge flows on the diffraction loads, hydrodynamic force coefficients, as well as the motions of a 2-dimensional prismatic body floating on the free surface are presented. It is shown that the exciting wave forces and the hydrodynamic coefficients other than the damping coefficients are not appreciably affected by the intake/discharge flows of low Froude number for a 100MW floating OTEC plant.

On the Interaction of Waves With Intake/Discharge Flows Originating From a Freely-Floating Body

2003 ◽  
Vol 125 (1) ◽  
pp. 41-47 ◽  
Author(s):  
B. Padmanabhan ◽  
R. C. Ertekin
Keyword(s):  
Free Surface ◽  
Surface Condition ◽  
Floating Body ◽  
Wave Forces ◽  
Linear Potential ◽  
Two Dimensional ◽  
Rankine Source ◽  
Total Potential ◽  
Linear Potential Theory ◽  
Steady Potential

A linear theory is developed to obtain the motions of a two-dimensional, freely floating body (from which steady intake/discharge flows originate) that encounters incoming waves. The boundary-value problem is formulated within the assumptions of linear potential theory by decomposing the total potential into its oscillatory and steady components. The steady potential is further decomposed into the double-model and perturbation potentials. The time-harmonic potential is coupled with the steady potential through the free-surface condition. The potentials are obtained by use of the quadratic boundary-element method based on the Rankine source. The effect of the steady intake/discharge flows on the diffraction loads, hydrodynamic force coefficients, as well as the motions of a two-dimensional prismatic body floating on the free surface are presented. It is shown that the exciting wave forces and the hydrodynamic coefficients other than the damping coefficients are not appreciably affected in the case of low intake/discharge Froude numbers that are estimated, for example, for a 100 MW floating OTEC plant.

scholarly journals Performance of an Array of Oscillating Water Column Devices in Front of a Fixed Vertical Breakwater

2020 ◽  
Vol 8 (11) ◽  
pp. 912
Author(s):  
Dimitrios N. Konispoliatis
Keyword(s):  
Water Column ◽  
Power Efficiency ◽  
Wave Train ◽  
Linear Potential ◽  
Angle Of Incidence ◽  
Oscillating Water Column ◽  
Incoming Wave ◽  
Reflected Waves ◽  
Vertical Breakwater ◽  
Linear Potential Theory

The present study explores the performance of an array of cylindrical oscillating water column (OWC) devices, having a vertical symmetry axis, placed in front of a bottom seated, surface piercing, vertical breakwater. The main goal of this study is the investigation of a possible increase in the power efficiency of an OWC array by applying, in the vicinity of the array, a barrier to the wave propagation, aiming at amplifying the scattered and reflected waves originating from the presence of the devices and the wall. To cope with the set goal, a theoretical analysis is presented in the framework of linear potential theory, based on the solution of the proper diffraction, and pressure-radiation problems in the frequency domain, using the image theory, the matched axisymmetric eigenfunction expansion formulation, and the multiple scattering approach. Numerical results are presented and discussed in terms of the expected power absorption by the OWCs comparing different array’s characteristics i.e.,: (a) angle of incidence of the incoming wave train; (b) distances from the breakwater; and (c) geometric characteristics of the different arrangements. The results show that compared to the isolated OWC array (i.e., no presence of the wall), the power efficiency of the OWCs in front of a breakwater is amplified at specific frequency ranges.

Simulation of Multiliquid-Layer Sloshing With Vessel Motion by Using Moving Particle Semi-Implicit Method

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Kyung Sung Kim ◽  
Moo-Hyun Kim ◽  
Jong-Chun Park
Keyword(s):  
Gas Production ◽  
Particle Simulation ◽  
Small Scale ◽  
Linear Potential ◽  
Operational Effectiveness ◽  
Mps Method ◽  
Moving Particle ◽  
Vessel Motion ◽  
Linear Potential Theory ◽  
Oil Gas

For oil/gas production/processing platforms, multiple liquid layers can exist and their respective sloshing motions can also affect operational effectiveness or platform performance. To numerically simulate those problems, a new multiliquid moving particle simulation (MPS) method is developed. In particular, to better simulate the relevant physics, robust self-buoyancy model, interface searching model, and surface-tension model are developed. The developed multiliquid MPS method is validated by comparisons against experiment in which three-liquid-sloshing experiment and the corresponding linear potential theory are given. The validated multiliquid MPS program is subsequently coupled with a vessel-motion program in time domain to investigate their dynamic-coupling effects. In case of multiple liquid layers, there exists a variety of sloshing natural frequencies for respective interfaces, so the relevant physics can be much more complicated compared with the single-liquid-tank case. The simulation program can also reproduce the detailed small-scale interface phenomenon called Kelvin–Helmholtz instability. The numerical simulations also show that properly designed liquid cargo tank can also function as a beneficial antirolling device.

Hydroelastic Motion of Aircushion Type Large Floating Structures With Several Aircushions Using a Three-Dimensional Theory

2009 ◽  
Author(s):  
Tomoki Ikoma ◽  
Koichi Masuda ◽  
Chang-Kyu Rheem ◽  
Hisaaki Maeda ◽  
Mayumi Togane
Keyword(s):  
Theoretical Calculations ◽  
Three Dimensional ◽  
Prediction Method ◽  
Free Water ◽  
Bending Moment ◽  
Linear Potential ◽  
Floating Structures ◽  
Wide Wavelength Range ◽  
Linear Potential Theory ◽  
Vertical Bending Moment

This paper describes hydroelastic motion and effect of motion reduction of aircushion supported large floating structures. Motion reduction effects due to presence of aircushions have been confirmed from theoretical calculations with the zero-draft assumption. A three-dimensional prediction method has been developed for considering draft influence of division walls of aircushions. It is investigated that hydroelastic motion reduction is possible or not by using the three-dimensional theoretical calculations. In addition, the aircushion types are supported by many aircushions which are small related to wavelengths. The Green’s function method is applied to the prediction method with the linear potential theory in which effect of free water surfaces within aircushions are considered. Hydroelastic responses are estimated as not only elastic motion but also a vertical bending moment. From the results, the response reduction is confirmed, in particular, to the vertical bending moment in wide wavelength range and in whole structure area.

Wind Effects on Sloshing of a Floating Roof in a Cylindrical Liquid Storage Tank

2008 ◽  
Author(s):  
Tetsuya Matsui ◽  
Yasushi Uematsu ◽  
Koji Kondo ◽  
Takuo Wakasa ◽  
Takashi Nagaya
Keyword(s):  
Storage Tank ◽  
Wind Tunnel Test ◽  
Dynamic Interaction ◽  
Measured Data ◽  
Wind Pressure ◽  
Wind Loads ◽  
Linear Potential ◽  
Liquid Storage ◽  
Liquid Storage Tank ◽  
Linear Potential Theory

Sloshing of a floating roof in an open-topped cylindrical liquid storage tank under wind loads is investigated analytically. Wind tunnel test in a turbulent boundary layer is carried out to measure the wind pressure distributing over the roof surface. The measured data for the wind pressure is then utilized to predict the wind-induced dynamic response of the floating roof, which is idealized herein as an isotropic elastic plate of uniform stiffness and mass. The dynamic interaction between the liquid and the floating roof is taken into account exactly within the framework of linear potential theory. Numerical results are presented which illustrate the significant effect of wind loads on the sloshing response of the floating roof.

Sign in / Sign up

Export Citation Format

Share Document