The effect of lateral ice pressure on the level ice resistance of a 1/30 scale model of an OBO is examined experimentally. The model was equipped with an instrumented side panel. The apparatus for producing lateral pressure is described, as well as the model tests themselves. Rubble thickness and applied pressure were varied during the experiments. A model is developed to describe the observed change in resistance. The model assumes that the resistance increase is due to ice-hull friction resulting from the ice pressure. The results from the instrumented panel suggest that approximately 2/3 of the applied pressure is seen at the hull. The study also found that the pressure only acts on the bow region and parallel middle body.
{"title":"Modelling the Effect of Lateral Ice Pressure on Icebreaking Resistance","authors":"D. Spencer, Ken Hardiman","doi":"10.5957/attc-1995-007","DOIUrl":"https://doi.org/10.5957/attc-1995-007","url":null,"abstract":"The effect of lateral ice pressure on the level ice resistance of a 1/30 scale model of an OBO is examined experimentally. The model was equipped with an instrumented side panel. The apparatus for producing lateral pressure is described, as well as the model tests themselves. Rubble thickness and applied pressure were varied during the experiments. A model is developed to describe the observed change in resistance. The model assumes that the resistance increase is due to ice-hull friction resulting from the ice pressure. The results from the instrumented panel suggest that approximately 2/3 of the applied pressure is seen at the hull. The study also found that the pressure only acts on the bow region and parallel middle body.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126595041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
After many decades of study, two wave energy conversion systems have been shown to be the most effective in producing either electricity or potable water at remote location, such as the over 100,000 inhabited islands of the world. Those systems are the McCabe Wave Pump (MWP) and the Backward Bent Duct Barge (BBDB). Both of these are floating systems with well defined missions for remote locations. The BBDB is primarily designed to provide electricity, while the MWP's primary mission is to provide potable water. Both systems are resonant systems, in that they are designed to operate most efficiently in the neighborhoods of specific wave periods. In random seas, the operational ranges of each are within the half-power bandwidth of the center band resonant periods. The BBDB is an oscillating water column system in which a horizontal column of water, with its mouth facing aft and its internal free,-surface facing upward through a 90° bend at the bow of the floating structure, excites a pneumatic turbogenerator above the internal free-surface by the wave-induced motions of the water column. In other words, the water column acts as a flexible piston. The MWP is a mechanical-hydraulic system which provides high-pressure, pre-treated water to reverse osmosis desalination systems by the motions of hinged barges. The BBDB is now operational in Japan and China, while a prototype of the MWP is now deployed in the Shannon Estuary in Ireland. The operations of these two systems, as related to the hull dynamics, are discussed.
{"title":"Recent Advances in Wave Energy Utilization","authors":"M. Mccormick, D. Hayden","doi":"10.5957/attc-1995-016","DOIUrl":"https://doi.org/10.5957/attc-1995-016","url":null,"abstract":"After many decades of study, two wave energy conversion systems have been shown to be the most effective in producing either electricity or potable water at remote location, such as the over 100,000 inhabited islands of the world. Those systems are the McCabe Wave Pump (MWP) and the Backward Bent Duct Barge (BBDB). Both of these are floating systems with well defined missions for remote locations. The BBDB is primarily designed to provide electricity, while the MWP's primary mission is to provide potable water. Both systems are resonant systems, in that they are designed to operate most efficiently in the neighborhoods of specific wave periods. In random seas, the operational ranges of each are within the half-power bandwidth of the center band resonant periods. The BBDB is an oscillating water column system in which a horizontal column of water, with its mouth facing aft and its internal free,-surface facing upward through a 90° bend at the bow of the floating structure, excites a pneumatic turbogenerator above the internal free-surface by the wave-induced motions of the water column. In other words, the water column acts as a flexible piston. The MWP is a mechanical-hydraulic system which provides high-pressure, pre-treated water to reverse osmosis desalination systems by the motions of hinged barges. The BBDB is now operational in Japan and China, while a prototype of the MWP is now deployed in the Shannon Estuary in Ireland. The operations of these two systems, as related to the hull dynamics, are discussed.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"191 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133395620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This report describes the development and implementation of a procedure to repair the surface of the support track for a hydrodynamic test carriage at the Naval Surface Warfare Center's, Bethesda, Maryland ship-model towing basin. About 50 years of use had caused localized wear at the track joints, wear that was limiting the precision of hydrodynamic tests. Because of its special shape and precise installation, replacing the original track was not economically feasible. A welding electrode was found that could match the original properties of the track surface, and a repair procedure was developed that rebuilt the track ends to their original geometry and properties. After the repair, accelerometer measurements on the carriage showed that the repair reduced the vibration due to the wear by over 75 percent, an improvement that returned the track to well within an acceptable range for the hydrodynamic tests.
{"title":"Precision Weld Repair of Worn Joints In A Towing Basin Track","authors":"T. Siewert, J. Bradel","doi":"10.5957/attc-1995-014","DOIUrl":"https://doi.org/10.5957/attc-1995-014","url":null,"abstract":"This report describes the development and implementation of a procedure to repair the surface of the support track for a hydrodynamic test carriage at the Naval Surface Warfare Center's, Bethesda, Maryland ship-model towing basin. About 50 years of use had caused localized wear at the track joints, wear that was limiting the precision of hydrodynamic tests. Because of its special shape and precise installation, replacing the original track was not economically feasible.\u0000 A welding electrode was found that could match the original properties of the track surface, and a repair procedure was developed that rebuilt the track ends to their original geometry and properties. After the repair, accelerometer measurements on the carriage showed that the repair reduced the vibration due to the wear by over 75 percent, an improvement that returned the track to well within an acceptable range for the hydrodynamic tests.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117185610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A computational method (HPUF-3A) for the prediction of unsteady propeller blade sheet cavitation is applied to the analysis of supercavitating propellers in steady flow. The method is incorporating a vortex and source lattice scheme. To allow for the treatment of very long supercavities, improvements were introduced in the cavity extent iteration algorithm and in the force calculation procedure. The modeling of the separated flow behind trailing edges with non-zero thickness (very often the case for supercavitating blade sections) was also included. Results of this method are extensively validated and compared with those of another method, as well as with measurements from a supercavitating propeller experiment.
{"title":"Application of Unsteady Vortex-Source Lattice Method on Supercavitating Propellers","authors":"T. Kudo, S. Kinnas","doi":"10.5957/attc-1995-005","DOIUrl":"https://doi.org/10.5957/attc-1995-005","url":null,"abstract":"A computational method (HPUF-3A) for the prediction of unsteady propeller blade sheet cavitation is applied to the analysis of supercavitating propellers in steady flow. The method is incorporating a vortex and source lattice scheme.\u0000 To allow for the treatment of very long supercavities, improvements were introduced in the cavity extent iteration algorithm and in the force calculation procedure. The modeling of the separated flow behind trailing edges with non-zero thickness (very often the case for supercavitating blade sections) was also included.\u0000 Results of this method are extensively validated and compared with those of another method, as well as with measurements from a supercavitating propeller experiment.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124215823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In-Seung Park, S. Im, E. Powers, A. Duggal, Peter Johnson
In this paper we consider the use of so-called sparse Volterra time-domain models to decompose experimentally observed irregular waves into their first- and second order components. By decomposing the wave elevation, the influence of the individual linear and quadratic components on the large, extreme waves are quantified. The performance of the sparse Volterra and full Volterra modeling techniques are compared by implementing them for modeling and prediction of wave elevation as well as wave decomposition.
{"title":"Nonlinear Characteristics of Laboratory-Generated Irregular Waves","authors":"In-Seung Park, S. Im, E. Powers, A. Duggal, Peter Johnson","doi":"10.5957/attc-1995-011","DOIUrl":"https://doi.org/10.5957/attc-1995-011","url":null,"abstract":"In this paper we consider the use of so-called sparse Volterra time-domain models to decompose experimentally observed irregular waves into their first- and second order components. By decomposing the wave elevation, the influence of the individual linear and quadratic components on the large, extreme waves are quantified. The performance of the sparse Volterra and full Volterra modeling techniques are compared by implementing them for modeling and prediction of wave elevation as well as wave decomposition.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126563690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The flow field around a fully ventilated two-dimensional hydrofoil of arbitrary geometry is considered. The presented theory is a non-linear, time marching, potential based boundary element method. The perturbation potential on the cavity is a function of submergence and time. The non-linear cavity geometry is determined iteratively within the solution at each timestep. A linearized free surface condition, at infinite Froude number, is enforced by using the “negative image” approach. The developed analysis is shown to converge well with iterations per timestep, even though the cavity geometry has been found to be sensitive to the panel arrangement at the foil leading edge. Pressure distributions compare very well with linearized analytical results at small angles of attack, but the non-linear effects are noticeable at larger angles of attack.
{"title":"A Numerical Formulation Applicable to Surface Piercing Hydrofoils and Propellers","authors":"C. Savineau, S. Kinnas","doi":"10.5957/attc-1995-002","DOIUrl":"https://doi.org/10.5957/attc-1995-002","url":null,"abstract":"The flow field around a fully ventilated two-dimensional hydrofoil of arbitrary geometry is considered. The presented theory is a non-linear, time marching, potential based boundary element method. The perturbation potential on the cavity is a function of submergence and time. The non-linear cavity geometry is determined iteratively within the solution at each timestep. A linearized free surface condition, at infinite Froude number, is enforced by using the “negative image” approach. The developed analysis is shown to converge well with iterations per timestep, even though the cavity geometry has been found to be sensitive to the panel arrangement at the foil leading edge. Pressure distributions compare very well with linearized analytical results at small angles of attack, but the non-linear effects are noticeable at larger angles of attack.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116269592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Water particle motions on the wave surface are of interest to the designer for various applications that require quantification of particle kinematics. Difficulties in predicting these kinematics lead to other alternatives such as measurements in model tests. The modelled waves themselves as generated in facilities may also be of interest. Devices to measure particle motion adopted from fluid flow measurement equipment, are generally not well suited to measure particle kinematics because of limitations in their response or intrusiveness within the wave field. This paper discusses the use of a motion tracking device to measure wave surface particle kinematics. Small spheres floating on the wave surface are tracked using an optical tracking device and their position is determined as a function of time using monitoring cameras. Tests were carried out in a series of regular and irregular waves. Measured kinematics are compared and discussed in relation to those predicted by wave theories.
{"title":"Measurement of Water Surface Particle Kinematics Using a Motion Tracking System","authors":"J. Murray, M. Sullivan","doi":"10.5957/attc-1995-010","DOIUrl":"https://doi.org/10.5957/attc-1995-010","url":null,"abstract":"Water particle motions on the wave surface are of interest to the designer for various applications that require quantification of particle kinematics. Difficulties in predicting these kinematics lead to other alternatives such as measurements in model tests. The modelled waves themselves as generated in facilities may also be of interest. Devices to measure particle motion adopted from fluid flow measurement equipment, are generally not well suited to measure particle kinematics because of limitations in their response or intrusiveness within the wave field. This paper discusses the use of a motion tracking device to measure wave surface particle kinematics. Small spheres floating on the wave surface are tracked using an optical tracking device and their position is determined as a function of time using monitoring cameras. Tests were carried out in a series of regular and irregular waves. Measured kinematics are compared and discussed in relation to those predicted by wave theories.","PeriodicalId":275396,"journal":{"name":"Day 32 Mon, October 02, 1995","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1995-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129205494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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