Tim Gourlay - Academia.edu (original) (raw)

Papers by Tim Gourlay

Ship Motion Measurements for Ship Under-Keel Clearance in the Port of Geraldton

Analysis of Flow around a Ship Propeller using OpenFOAM

This dissertation analyses a propeller based off the coordinates of model KCD 32 (Emerson and Sin... more This dissertation analyses a propeller based off the coordinates of model KCD 32 (Emerson and Sinclair, 1967). Using Matlab to recreate the blade and mesh a three dimensional model, analysis was conducted. The study was completed using a computational program, OpenFOAM, and the pressure distribution and effects of cavitation were compared to experimental results. Reasonable results were produced such that the thrust, torque and efficiency trends were in good agreement with experimental data. It was also found that OpenFOAM had good prediction of when and where cavitation would occur on the propeller. Acknowledgements I would like to thank Tim Gourlay for the help and knowledge that he has given me over the entire duration of my project. The Lecturers and staff at Curtin University have been most kind and assisted me when I have needed it. I would also like to thank my family who have supported me throughout my whole life. My parents

We report on a recent project to accurately measure full scale sinkage, trim and roll of 16 deep-... more We report on a recent project to accurately measure full scale sinkage, trim and roll of 16 deep-draft containerships entering or leaving a major container port. Measurements were performed using high-accuracy GPS receivers and a fixed base station. Results were used to calculate the sinkage of the bow, stern and bilge corners, as compared to the static condition. Overall dynamic draft increase and the governing factors affecting underkeel clearance of containerships are discussed.

These notes concern the effect of boat wakes and wind waves on shoreline erosion, and are a revie... more These notes concern the effect of boat wakes and wind waves on shoreline erosion, and are a review of the relevant literature on the topic. The relevance of wave height, period, energy density and transmitted energy, as measures of erosion likelihood, are discussed. Examples are given from measurements made on the Swan River.

This article proposes a new method to assist with under-keel clearance (UKC) management, using re... more This article proposes a new method to assist with under-keel clearance (UKC) management, using realtime kinematic (RTK) GPS receivers. The proposed GPS method is intended to be integrated with existing UKC planning methods. The current state of the art in RTK GPS technology is discussed, and a method is outlined for using such measurements to monitor the clearance between a ship's keel and the sea floor. The method uses permanently installed GPS base stations in the area of interest, together with surveyedin GPS receivers on ships wishing to use the system. An example use of the method is given based on measurements taken in Torres Strait.

For RAN ships operating in shallow water, it is important to understand the phenomena of squat an... more For RAN ships operating in shallow water, it is important to understand the phenomena of squat and wave-induced motions so as to avoid grounding. The British Admiralty Manual of Navigation gives guidelines to predict squat allowances in different conditions. In this article, we discuss current research in this field, and highlight the important phenomenon of transcritical squat and its implications for frigateand destroyer-type ships. What is squat? Squat is a ship’s tendency to sit lower in the water as it travels faster. This is caused by the Bernoulli effect. Water is accelerated along the sides of and beneath the hull, and the free surface must drop downwards to maintain energy conservation. The ship essentially makes its own wave trough in which it sits, as shown in Figure 1. This effect is additional to the trailing wave pattern with which we are all familiar. Figure 1: The squat effect. (Top) Ship at rest. (Bottom) Ship under way. Squat comprises a midship sinkage and a chang...

International Journal of Maritime Engineering, 2008

In the trials, measurements were made of the vertical elevation of three points on each ship, usi... more In the trials, measurements were made of the vertical elevation of three points on each ship, using real-time kinematic GPS receivers measuring at 1 second intervals. By comparing the dynamic readings to stationary readings taken at the berth, the change in vertical position of the ship when under way (relative to the static position) could be determined. Corrections were made for the changing tide height and geoid undulation.

This paper presents a comparison of numerical methods with model test results for squat (sinkage ... more This paper presents a comparison of numerical methods with model test results for squat (sinkage and trim) of a 1:75 KVLCC2 model in the Flanders Hydraulics Research towing tank, at a range of rectangular canal widths and depths. The numerical methods are the Linear-2D and Nonlinear-1D methods in ShallowFlow, the Double-Body method in HullWave and the Rankine-Source method in GL Rankine. Analysis of the model tests showed that in the narrowest canals, mass flux past the ship was not conserved, nevertheless it appears that the Nonlinear-1D method may give good results for the narrowest canals. The Linear-2D method was found to give good results in the widest canal, particularly at the shallowest water depth. The Rankine-Source method was found to give good results for the widest canal, particularly at high speed. The Double-Body method was found to give quite consistently good results across all conditions.

5. = n F . “Deep water” can be considered to be a depth of 50% of the ship’s waterline length or ... more 5. = n F . “Deep water” can be considered to be a depth of 50% of the ship’s waterline length or greater. The wave resistance curve has marked changes in gradient near this “hump speed”, while the wave resistance coefficient has a pronounced maximum, as shown in Figure 1.

Applied Ocean Research, 2018

Computer codes implementing three different numerical methods for the prediction of ship squat at... more Computer codes implementing three different numerical methods for the prediction of ship squat at transcritical speeds in shallow open-water are tested. SlenderFlow is a potential flow code specifically for ships in very shallow water, based on partially dispersive slender body theory. Flotilla is a potential flow code based on fully dispersive thin-ship theory. Rapid is a general nonlinear free-surface panel code. Code predictions of transcritical sinkage, trim and resistance in laterally unrestricted water were compared to the experimental results of Graff (1964) for two Taylor series hulls in a finite-width towing tank. Once tank width effects were accounted for, each of the three codes was found to give good predictions within the valid range of the underlying theory. A simple method for estimating transcritical wave resistance from trim is presented.

The RS:X Olympic sailboard is an all-round board designed to be raced in 4 to 25 knots of wind, a... more The RS:X Olympic sailboard is an all-round board designed to be raced in 4 to 25 knots of wind, and is an example of the current state-of-the-art in sailboard des ign. This board has been chosen as the specific example for an overview of sailboard aero-hydrodynamics. The current article brings together previous research on sailboard sail and fin lift, and applies it to the case of the RS:X sailboard. Measured sail cambe r and twist, as well as mast stiffness and deflection, are described for realistic upwind racing settings. The three-dimensional force and moment balance of an RS:X sai ling upwind is investigated, in order to determine the limits on righting moment, sail lift and fin lift for different wind strengths. Finally a planing analysis is performed on the RS:X sailboard to calculate trim, wett ed length and resistance.

Tim Gourlay, Perth Hydro, Australia Evert Lataire, Maritime Technology Division, Ghent University... more Tim Gourlay, Perth Hydro, Australia Evert Lataire, Maritime Technology Division, Ghent University, Belgium Guillaume Delefortrie, Flanders Hydraulics Research & Maritime Technology Division, Ghent University, Belgium Luca Donatini, Maritime Technology Division, Ghent University, Belgium Manasés Tello Ruiz, Maritime Technology Division, Ghent University, Belgium Daniel Veen, Bentley Systems, Australia Tim Bunnik, Marin, The Netherlands Reint Dallinga, Marin, The Netherlands

This paper presents a comparison of numerical methods for the modelling of pile driving noise in ... more This paper presents a comparison of numerical methods for the modelling of pile driving noise in the near field of the pile. The numerical models considered consist of (1) an axisymmetric time domain finite difference method (FDM), developed by the Centre for Marine Science and Technology in the Matlab programming language, and (2) an axisymmetric time domain finite element method (FEM), which is available as part of the PAFEC‐FE commercial software suite. The FDM employs thin-shell theory to model the cylindrical steel pile and the acoustic wave equation to model the water and fluid seabed, while the FEM employs the elastic and acoustic wave equations to model sound propagation in the pile and water/fluid seabed respectively. A one‐way coupling of the pile displacements to the fluid pressures is utilised in the FDM to model the acoustic radiation from the pile excitation, while the FEM employs a fully coupled fluid-structure interaction at the solid‐fluid interface. Numerical resul...

Journal of Ship Research, 2008

A theoretical method is put forward for predicting the sinkage and trim of a fast displacement ca... more A theoretical method is put forward for predicting the sinkage and trim of a fast displacement catamaran in shallow water. Special emphasis is placed on the trans-critical speed range, where sinkage and trim reach a maximum and the risk of grounding is at its highest. Results are condensed into simple formulas for estimating maximum sinkage and trim of a fast displacement catamaran through the transcritical speed range.

Marine Technology and SNAME News, 2006

A simple formula is developed for predicting the maximum squat of a displacement ship as it passe... more A simple formula is developed for predicting the maximum squat of a displacement ship as it passes through the transcritical speed range. This is given in terms of a maximum sinkage coefficient, which is almost constant across a wide range of hull forms. Satisfactory agreement is shown with model test results, and it is shown that large stern sinkages in the order of 3 to 6 meters are predicted for frigate and destroyer type hulls in shallow calm water.

Journal of Ship Research, 2006

This article looks at the case of a large, flat-bottomed ship, such as a bulk carrier, moving in ... more This article looks at the case of a large, flat-bottomed ship, such as a bulk carrier, moving in close proximity to a flat sea floor. It is shown that the flow beneath the ship can be modeled as a shear flow between two parallel plates, one of which is moving. The resulting flow can be represented using laminar Couette flow at low Reynolds numbers (possible at model scale) or the very different turbulent Couette flow at high Reynolds numbers (full scale). Implications of these flow models on squat and viscous resistance are discussed.

Journal of Ship Research, 2001

A ship moving steadily forward in shallow water of constant depth h is usually subject to downwar... more A ship moving steadily forward in shallow water of constant depth h is usually subject to downward forces and hence squat, which is a potentially dangerous sinkage or increase in draft. Sinkage increases with ship speed, until it reaches a maximum at just below the critical speed Here we use both a linear transcritical shallow-water equation and a fully dispersive finite-depth theory to discuss the flow near that critical speed and to compute the maximum sinkage, trim angle, and stern displacement for some example hulls.

ANZIAM Journal, 2010

The speed of linear waves in shallow water approaches a constant value as the wavelength becomes ... more The speed of linear waves in shallow water approaches a constant value as the wavelength becomes large relative to the water depth. For ships travelling in shallow water, this speed is known as the 'critical speed' and acts as a barrier, similar to the speed of sound for aeroplanes. The possibility of travelling at transcritical and supercritical speeds is discussed for existing monohull and catamaran ships. We explore the predicted linearised flow around a ship as it approaches the critical speed, and the singularities that result. Experimental results show the actual flow patterns that occur at ship speeds close to the critical speed, for monohulls or catamarans, in open water or confined channels.

Full-Scale Measurements and Method Validation of Container Ship Wave-Induced Motion at the Port of Fremantle

Journal of Waterway, Port, Coastal, and Ocean Engineering, 2018

Ship Motion Measurements for Ship Under-Keel Clearance in the Port of Geraldton

Analysis of Flow around a Ship Propeller using OpenFOAM

This dissertation analyses a propeller based off the coordinates of model KCD 32 (Emerson and Sin... more This dissertation analyses a propeller based off the coordinates of model KCD 32 (Emerson and Sinclair, 1967). Using Matlab to recreate the blade and mesh a three dimensional model, analysis was conducted. The study was completed using a computational program, OpenFOAM, and the pressure distribution and effects of cavitation were compared to experimental results. Reasonable results were produced such that the thrust, torque and efficiency trends were in good agreement with experimental data. It was also found that OpenFOAM had good prediction of when and where cavitation would occur on the propeller. Acknowledgements I would like to thank Tim Gourlay for the help and knowledge that he has given me over the entire duration of my project. The Lecturers and staff at Curtin University have been most kind and assisted me when I have needed it. I would also like to thank my family who have supported me throughout my whole life. My parents

We report on a recent project to accurately measure full scale sinkage, trim and roll of 16 deep-... more We report on a recent project to accurately measure full scale sinkage, trim and roll of 16 deep-draft containerships entering or leaving a major container port. Measurements were performed using high-accuracy GPS receivers and a fixed base station. Results were used to calculate the sinkage of the bow, stern and bilge corners, as compared to the static condition. Overall dynamic draft increase and the governing factors affecting underkeel clearance of containerships are discussed.

These notes concern the effect of boat wakes and wind waves on shoreline erosion, and are a revie... more These notes concern the effect of boat wakes and wind waves on shoreline erosion, and are a review of the relevant literature on the topic. The relevance of wave height, period, energy density and transmitted energy, as measures of erosion likelihood, are discussed. Examples are given from measurements made on the Swan River.

This article proposes a new method to assist with under-keel clearance (UKC) management, using re... more This article proposes a new method to assist with under-keel clearance (UKC) management, using realtime kinematic (RTK) GPS receivers. The proposed GPS method is intended to be integrated with existing UKC planning methods. The current state of the art in RTK GPS technology is discussed, and a method is outlined for using such measurements to monitor the clearance between a ship's keel and the sea floor. The method uses permanently installed GPS base stations in the area of interest, together with surveyedin GPS receivers on ships wishing to use the system. An example use of the method is given based on measurements taken in Torres Strait.

For RAN ships operating in shallow water, it is important to understand the phenomena of squat an... more For RAN ships operating in shallow water, it is important to understand the phenomena of squat and wave-induced motions so as to avoid grounding. The British Admiralty Manual of Navigation gives guidelines to predict squat allowances in different conditions. In this article, we discuss current research in this field, and highlight the important phenomenon of transcritical squat and its implications for frigateand destroyer-type ships. What is squat? Squat is a ship’s tendency to sit lower in the water as it travels faster. This is caused by the Bernoulli effect. Water is accelerated along the sides of and beneath the hull, and the free surface must drop downwards to maintain energy conservation. The ship essentially makes its own wave trough in which it sits, as shown in Figure 1. This effect is additional to the trailing wave pattern with which we are all familiar. Figure 1: The squat effect. (Top) Ship at rest. (Bottom) Ship under way. Squat comprises a midship sinkage and a chang...

International Journal of Maritime Engineering, 2008

In the trials, measurements were made of the vertical elevation of three points on each ship, usi... more In the trials, measurements were made of the vertical elevation of three points on each ship, using real-time kinematic GPS receivers measuring at 1 second intervals. By comparing the dynamic readings to stationary readings taken at the berth, the change in vertical position of the ship when under way (relative to the static position) could be determined. Corrections were made for the changing tide height and geoid undulation.

This paper presents a comparison of numerical methods with model test results for squat (sinkage ... more This paper presents a comparison of numerical methods with model test results for squat (sinkage and trim) of a 1:75 KVLCC2 model in the Flanders Hydraulics Research towing tank, at a range of rectangular canal widths and depths. The numerical methods are the Linear-2D and Nonlinear-1D methods in ShallowFlow, the Double-Body method in HullWave and the Rankine-Source method in GL Rankine. Analysis of the model tests showed that in the narrowest canals, mass flux past the ship was not conserved, nevertheless it appears that the Nonlinear-1D method may give good results for the narrowest canals. The Linear-2D method was found to give good results in the widest canal, particularly at the shallowest water depth. The Rankine-Source method was found to give good results for the widest canal, particularly at high speed. The Double-Body method was found to give quite consistently good results across all conditions.

5. = n F . “Deep water” can be considered to be a depth of 50% of the ship’s waterline length or ... more 5. = n F . “Deep water” can be considered to be a depth of 50% of the ship’s waterline length or greater. The wave resistance curve has marked changes in gradient near this “hump speed”, while the wave resistance coefficient has a pronounced maximum, as shown in Figure 1.

Applied Ocean Research, 2018

Computer codes implementing three different numerical methods for the prediction of ship squat at... more Computer codes implementing three different numerical methods for the prediction of ship squat at transcritical speeds in shallow open-water are tested. SlenderFlow is a potential flow code specifically for ships in very shallow water, based on partially dispersive slender body theory. Flotilla is a potential flow code based on fully dispersive thin-ship theory. Rapid is a general nonlinear free-surface panel code. Code predictions of transcritical sinkage, trim and resistance in laterally unrestricted water were compared to the experimental results of Graff (1964) for two Taylor series hulls in a finite-width towing tank. Once tank width effects were accounted for, each of the three codes was found to give good predictions within the valid range of the underlying theory. A simple method for estimating transcritical wave resistance from trim is presented.

The RS:X Olympic sailboard is an all-round board designed to be raced in 4 to 25 knots of wind, a... more The RS:X Olympic sailboard is an all-round board designed to be raced in 4 to 25 knots of wind, and is an example of the current state-of-the-art in sailboard des ign. This board has been chosen as the specific example for an overview of sailboard aero-hydrodynamics. The current article brings together previous research on sailboard sail and fin lift, and applies it to the case of the RS:X sailboard. Measured sail cambe r and twist, as well as mast stiffness and deflection, are described for realistic upwind racing settings. The three-dimensional force and moment balance of an RS:X sai ling upwind is investigated, in order to determine the limits on righting moment, sail lift and fin lift for different wind strengths. Finally a planing analysis is performed on the RS:X sailboard to calculate trim, wett ed length and resistance.

Tim Gourlay, Perth Hydro, Australia Evert Lataire, Maritime Technology Division, Ghent University... more Tim Gourlay, Perth Hydro, Australia Evert Lataire, Maritime Technology Division, Ghent University, Belgium Guillaume Delefortrie, Flanders Hydraulics Research & Maritime Technology Division, Ghent University, Belgium Luca Donatini, Maritime Technology Division, Ghent University, Belgium Manasés Tello Ruiz, Maritime Technology Division, Ghent University, Belgium Daniel Veen, Bentley Systems, Australia Tim Bunnik, Marin, The Netherlands Reint Dallinga, Marin, The Netherlands

This paper presents a comparison of numerical methods for the modelling of pile driving noise in ... more This paper presents a comparison of numerical methods for the modelling of pile driving noise in the near field of the pile. The numerical models considered consist of (1) an axisymmetric time domain finite difference method (FDM), developed by the Centre for Marine Science and Technology in the Matlab programming language, and (2) an axisymmetric time domain finite element method (FEM), which is available as part of the PAFEC‐FE commercial software suite. The FDM employs thin-shell theory to model the cylindrical steel pile and the acoustic wave equation to model the water and fluid seabed, while the FEM employs the elastic and acoustic wave equations to model sound propagation in the pile and water/fluid seabed respectively. A one‐way coupling of the pile displacements to the fluid pressures is utilised in the FDM to model the acoustic radiation from the pile excitation, while the FEM employs a fully coupled fluid-structure interaction at the solid‐fluid interface. Numerical resul...

Journal of Ship Research, 2008

A theoretical method is put forward for predicting the sinkage and trim of a fast displacement ca... more A theoretical method is put forward for predicting the sinkage and trim of a fast displacement catamaran in shallow water. Special emphasis is placed on the trans-critical speed range, where sinkage and trim reach a maximum and the risk of grounding is at its highest. Results are condensed into simple formulas for estimating maximum sinkage and trim of a fast displacement catamaran through the transcritical speed range.

Marine Technology and SNAME News, 2006

A simple formula is developed for predicting the maximum squat of a displacement ship as it passe... more A simple formula is developed for predicting the maximum squat of a displacement ship as it passes through the transcritical speed range. This is given in terms of a maximum sinkage coefficient, which is almost constant across a wide range of hull forms. Satisfactory agreement is shown with model test results, and it is shown that large stern sinkages in the order of 3 to 6 meters are predicted for frigate and destroyer type hulls in shallow calm water.

Journal of Ship Research, 2006

This article looks at the case of a large, flat-bottomed ship, such as a bulk carrier, moving in ... more This article looks at the case of a large, flat-bottomed ship, such as a bulk carrier, moving in close proximity to a flat sea floor. It is shown that the flow beneath the ship can be modeled as a shear flow between two parallel plates, one of which is moving. The resulting flow can be represented using laminar Couette flow at low Reynolds numbers (possible at model scale) or the very different turbulent Couette flow at high Reynolds numbers (full scale). Implications of these flow models on squat and viscous resistance are discussed.

Journal of Ship Research, 2001

A ship moving steadily forward in shallow water of constant depth h is usually subject to downwar... more A ship moving steadily forward in shallow water of constant depth h is usually subject to downward forces and hence squat, which is a potentially dangerous sinkage or increase in draft. Sinkage increases with ship speed, until it reaches a maximum at just below the critical speed Here we use both a linear transcritical shallow-water equation and a fully dispersive finite-depth theory to discuss the flow near that critical speed and to compute the maximum sinkage, trim angle, and stern displacement for some example hulls.

ANZIAM Journal, 2010

The speed of linear waves in shallow water approaches a constant value as the wavelength becomes ... more The speed of linear waves in shallow water approaches a constant value as the wavelength becomes large relative to the water depth. For ships travelling in shallow water, this speed is known as the 'critical speed' and acts as a barrier, similar to the speed of sound for aeroplanes. The possibility of travelling at transcritical and supercritical speeds is discussed for existing monohull and catamaran ships. We explore the predicted linearised flow around a ship as it approaches the critical speed, and the singularities that result. Experimental results show the actual flow patterns that occur at ship speeds close to the critical speed, for monohulls or catamarans, in open water or confined channels.

Full-Scale Measurements and Method Validation of Container Ship Wave-Induced Motion at the Port of Fremantle

Journal of Waterway, Port, Coastal, and Ocean Engineering, 2018