A program was initiated in 1990 to assess new and alternative technologies for application to mid-term fast sealift ships that could be under contract in 1998 or later. A variety of baseline hull configurations have been developed in this program. This paper presents a parametric study of powering performance of three baseline hull configurations. They are a 30-knot, twin-skeg ship, a 20-knot single-shaft ship, and a 35-knot triple-shaft ship. Comparisons of propulsive performance between open-single and contrarotating (CR) propellers are presented. The predictions indicate that CR propellers will improve propulsive efficiency by about 7 to 9 percent for the three baselines. It is concluded that the 30-knot, twin-skeg ship is the most promising candidate for the mid-term fast sealift ship. A model test program is underway to confirm the predicted powering performance for this ship. Single and CR propellers will be designed, manufactured, and tested on the model hull.
{"title":"Propeller Parametric Study for Mid-Term Fast Sealift Ships","authors":"K. Kim, J. F. Fraas","doi":"10.5957/attc-1992-019","DOIUrl":"https://doi.org/10.5957/attc-1992-019","url":null,"abstract":"A program was initiated in 1990 to assess new and alternative technologies for application to mid-term fast sealift ships that could be under contract in 1998 or later. A variety of baseline hull configurations have been developed in this program. This paper presents a parametric study of powering performance of three baseline hull configurations. They are a 30-knot, twin-skeg ship, a 20-knot single-shaft ship, and a 35-knot triple-shaft ship. Comparisons of propulsive performance between open-single and contrarotating (CR) propellers are presented. The predictions indicate that CR propellers will improve propulsive efficiency by about 7 to 9 percent for the three baselines. It is concluded that the 30-knot, twin-skeg ship is the most promising candidate for the mid-term fast sealift ship. A model test program is underway to confirm the predicted powering performance for this ship. Single and CR propellers will be designed, manufactured, and tested on the model hull.","PeriodicalId":211134,"journal":{"name":"Day 1 Thu, June 11, 1992","volume":"383 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131988930","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 brief description of the apparatus for producing controllable density (CD) model ice is given. Ice density is shown to affect nearly all aspects of ice tank testing. Some preliminary results are given for ice-propeller interaction, presawn ice resistance, rubble ice resistance and level ice resistance. The level of ice-propeller interaction is reduced using low density level ice primarily by increasing the minimum model speed before ice in ingested in to the propellers. This leads to a significant reduction in propeller milling at low speed. Rubble ice resistance is shown to be dominated by the ice buoyancy with an approximate 400% increase in resistance as ice density was reduced from 930 kg/m3 to 750 kg/m3. Presawn ice resistance has a buoyancy dependent component which is important at low speed. Ice buoyancy is seen to significantly increase this component. The effect of ice density on level ice resistance is quite insidious in that it can alter the icebreaking process significantly increasing the resistance of certain bow forms. The increased buoyancy of the broken ice cusps causes them to float higher as they are rotated by the advancing bow. These pieces may then have a higher incidence of jamming between the hull and the unbroken ice sheet leading to crushing events and large loads in the shoulder region.
{"title":"CD Model Ice - Preliminary Observations on the Effect of Density on Tank Testing","authors":"D. Spencer","doi":"10.5957/attc-1992-032","DOIUrl":"https://doi.org/10.5957/attc-1992-032","url":null,"abstract":"A brief description of the apparatus for producing controllable density (CD) model ice is given. Ice density is shown to affect nearly all aspects of ice tank testing. Some preliminary results are given for ice-propeller interaction, presawn ice resistance, rubble ice resistance and level ice resistance. The level of ice-propeller interaction is reduced using low density level ice primarily by increasing the minimum model speed before ice in ingested in to the propellers. This leads to a significant reduction in propeller milling at low speed. Rubble ice resistance is shown to be dominated by the ice buoyancy with an approximate 400% increase in resistance as ice density was reduced from 930 kg/m3 to 750 kg/m3. Presawn ice resistance has a buoyancy dependent component which is important at low speed. Ice buoyancy is seen to significantly increase this component. The effect of ice density on level ice resistance is quite insidious in that it can alter the icebreaking process significantly increasing the resistance of certain bow forms. The increased buoyancy of the broken ice cusps causes them to float higher as they are rotated by the advancing bow. These pieces may then have a higher incidence of jamming between the hull and the unbroken ice sheet leading to crushing events and large loads in the shoulder region.","PeriodicalId":211134,"journal":{"name":"Day 1 Thu, June 11, 1992","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133068730","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 order to assess the maneuvering qualities of a 120 ft USCG patrol boat design, straight-course and rotating-arm captive model tests were conducted. Tests were carried out at two speeds, two turning radii (plus straight course), at a range of drift and roll angles, for a single load and LCG combination. The data were analyzed to obtain simple expressions for hydrodynamic forces and moments in terms of the test parameters. These expressions were used in conjunction with the equations of motion of the vessel in four degrees of freedom to obtain trajectory predictions (including roll behavior) for the patrol boat.
{"title":"Directional Stability Tests and Maneuvering Predictions for a High-Speed Patrol Boat","authors":"E. Lewandowski","doi":"10.5957/attc-1992-001","DOIUrl":"https://doi.org/10.5957/attc-1992-001","url":null,"abstract":"In order to assess the maneuvering qualities of a 120 ft USCG patrol boat design, straight-course and rotating-arm captive model tests were conducted. Tests were carried out at two speeds, two turning radii (plus straight course), at a range of drift and roll angles, for a single load and LCG combination.\u0000 The data were analyzed to obtain simple expressions for hydrodynamic forces and moments in terms of the test parameters. These expressions were used in conjunction with the equations of motion of the vessel in four degrees of freedom to obtain trajectory predictions (including roll behavior) for the patrol boat.","PeriodicalId":211134,"journal":{"name":"Day 1 Thu, June 11, 1992","volume":"2026 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127461888","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 supercavitating hydrofoil experiment is performed at the MIT Variable Pressure water tunnel, at several angles of attack and cavitation numbers. The velocity is measured on a rectangular contour surrounding the foil and cavity, and the results are compared to those from an analysis method. Forces are inferred from momentum integrations of the measured velocities and also compared to those predicted from the analysis.
{"title":"Numerical vs. Experimental Cavitation Tunnel (A supercavitating hydrofoil experiment)","authors":"S. Kinnas, C. Mazel","doi":"10.1115/1.2910209","DOIUrl":"https://doi.org/10.1115/1.2910209","url":null,"abstract":"A supercavitating hydrofoil experiment is performed at the MIT Variable Pressure water tunnel, at several angles of attack and cavitation numbers. The velocity is measured on a rectangular contour surrounding the foil and cavity, and the results are compared to those from an analysis method. Forces are inferred from momentum integrations of the measured velocities and also compared to those predicted from the analysis.","PeriodicalId":211134,"journal":{"name":"Day 1 Thu, June 11, 1992","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129779905","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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