{"title":"Numerical Studies of Directional Wavemaker Performance","authors":"J. N. Newman","doi":"10.5957/attc-2007-002","DOIUrl":"https://doi.org/10.5957/attc-2007-002","url":null,"abstract":"The performance of a multi-unit wavemaker for generating directionally-spread waves has been studied using the three-dimensional, radiation-diffraction code WAMIT. Design choices of wavemaker geometry (including type of motion, total number of units and size of individual units) affects various parameters of performance, including quality of radiated waves and inertial load that actuators must overcome. The sensitivity of generated waves to these variables is demonstrated.","PeriodicalId":331157,"journal":{"name":"Day 2 Thu, August 09, 2007","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128153370","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}
T. Fu, L. Russell, J. Rice, A. Fullerton, T. Ratcliffe
{"title":"High-Speed Planing Craft Model Tow Tank Testing","authors":"T. Fu, L. Russell, J. Rice, A. Fullerton, T. Ratcliffe","doi":"10.5957/attc-2007-004","DOIUrl":"https://doi.org/10.5957/attc-2007-004","url":null,"abstract":"Tow tank testing of high speed planing craft differs from traditional displacement hull testing in several aspects, even when the objectives are similar. While the sinkage and trim of a displacement ship does change with speed, the changes are relatively small and do not result in large changes to their waterline length and wetted surface area. Planing craft, due to dynamic lift, undergo large changes in waterline length and wetted surface area from their at rest values. Additionally, validation of computational fluid dynamics codes for conventional monohull and unconventional multihull planning craft has made necessary the measurement of additional data beyond just resistance and the development of specialized capabilities for planing craft testing. This paper will describe several of the measurement techniques and procedures now utilized at the Naval Surface Warfare Center Carderock Division (NSWCCD) when tow tank testing planing craft.","PeriodicalId":331157,"journal":{"name":"Day 2 Thu, August 09, 2007","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133838844","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}
{"title":"Ventilation effects on Cavitating Wedges and Struts","authors":"S. Gowing, Y. Shen","doi":"10.5957/attc-2007-005","DOIUrl":"https://doi.org/10.5957/attc-2007-005","url":null,"abstract":"Reduction of ship hull skin friction can represent significant drag reduction for high-speed ships, especially those designed for low wave drag or using catamaran-type hull designs. A method is proposed to reduce this friction by shielding the side portions of the hull from the water using ventilated cavities created with protruding wedges. These wedges create low-pressure regions in their wake that naturally ingest air at the surface, reducing the drag of the wedge while lengthening their trailing cavities. The proposed scheme takes advantage of the natural combination of high speeds and low pressures that exist at the waterline of a high-speed ship without requiring auxiliary pumps or machinery. As a first step for engineering estimates of drag reduction, preliminary experiments are presented that use two-dimensional wedges and similarly shaped struts to validate theoretical ventilated-cavity predictions. Tests are conducted on parabolic and wedge-shaped sections and struts in a closed-jet water tunnel at 20 and 30 knots, using a pipe to ventilate behind the strut using natural suction. The wedge drag and back pressure and resulting cavity lengths are measured over a range of ventilation flows. The two-dimensional wedge drag shows fair agreement with linearized theory predictions at low cavitation numbers, and this drag can be reduced over 50% from its fully wetted value using natural ventilation. The change in drag is attributed mostly to the change in the pressure on the back of the wedge caused by the ventilation. The measured ventilated cavity lengths are close to linear theory models using a double spiral vortex for cavity closure conditions. For the range of ventilated conditions tested, the air flow rates required for ventilation are only a few percent of the equivalent flow rate swept out by the passage of the strut through the water. These flowrates could become much greater at lower pressures representative of shallower depths.","PeriodicalId":331157,"journal":{"name":"Day 2 Thu, August 09, 2007","volume":"79 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129283933","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}
{"title":"Facility Upgrades at the U.S. Naval Academy Hydromechanics Laboratory","authors":"J. Zseleczky","doi":"10.5957/attc-2007-001","DOIUrl":"https://doi.org/10.5957/attc-2007-001","url":null,"abstract":"The United States Naval Academy (USNA) is located on a prime piece of Annapolis real estate that overlooks the mouth of the Severn River. The yard (campus) is bordered by water on two of four sides. This makes it easy to access the large fleet of sailing dinghies, ocean going sail training craft and 108 foot long yard patrol craft on which our future naval officers train.\u0000 On the night of September 18, 2003, a storm surge created by hurricane Isabel raised the waters in the Severn eight feet above the normal astronomical tide line (Beven and Cobb, 2003). A storm surge of this magnitude was unprecedented and flooded many of the buildings at the academy which brought about an unplanned re-build of many of the expensive lab facilities located on the ground floor. This paper provides an overview of upgrades made to the Hydromechanics Laboratory (NAHL) in the recovery from this disaster. On a positive note, the NAHL is now in much better condition than it was before Isabel.","PeriodicalId":331157,"journal":{"name":"Day 2 Thu, August 09, 2007","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115531123","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}
{"title":"DDG 1000 Large Scale Experimentation","authors":"T. Carrico","doi":"10.5957/attc-2007-003","DOIUrl":"https://doi.org/10.5957/attc-2007-003","url":null,"abstract":"In the spring of 2005, NAVSEA PMS 500 initiated a model experiment program to quantify the intact dynamic stability and seakeeping performance of a large-scale DDG 1000 model operating in a random wind driven seaway for extended periods of time. A secondary task was the measurement of calm water maneuvering performance. The Seakeeping Division of the Naval Surface Warfare Center Carderock Division (NSWCCD) was given the responsibility of performing these tasks. NSWCCD personnel developed and tested a free running radio controlled 20th scale model. Model 5643 was constructed to represent the DDG 1000 hull Baseline 5.2 configuration. It was operated in the Chesapeake Bay at the Patuxent River Naval Air Station during the spring and fall of 2006. This paper discusses the two year NSWCCD technological effort. Specifically, it addresses the design, construction, instrumentation, and testing aspects of this unique experiment.","PeriodicalId":331157,"journal":{"name":"Day 2 Thu, August 09, 2007","volume":"190 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114857275","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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