{"title":"A High-Speed Towed Planing Vehicle","authors":"D. B. Coakley, William M. Holt","doi":"10.5957/attc-1998-006","DOIUrl":"https://doi.org/10.5957/attc-1998-006","url":null,"abstract":"A wave-following towed planing vehicle operates in head seas, Sea State l and 2, at speeds in excess of l 6 knots (824 m/s). The as-built beam of the vehicle is either 4.25 in (10.8 cm) or 7.75 in (19.7 cm), for the two configurations; V-hull (deadrise pointing outboard) or catamaran (deadrise of each hull pointing inboard). Thus the Froude number is in excess of 8.1 or 5.9, respectively. For stable operation the vehicle requires a tail attached to the stem of its deck. The most successful tail tested consists of several feet of cord tied to a materially dense truncated cone or drogue, which provides drag as it plows through the water.\u0000 The vehicle is apparently always stable in calm seas. In head seas, the stability of the vehicle depends on the cable angle (the angle measured between the freestream flow direction and the tangent to the tow cable) where the cable attaches to the body. The vehicle is apparently always stable at speeds up to 22 knots (11.3 m/s) at cable angles above 0.185 radians (10.6 arc degrees). At smaller cable angles the vehicle is apparently stable up to 16 knots (824 m/s) in head seas. Tow cable tension measurements reveal tension between 180 and 360 N ( 40 and 80 lb), with tension spikes occurring at frequencies approximately equal to the wave encounter frequency. Heave and roll acceleration measurements on the vehicle indicate average acceleration values of approximately 4-6 g's, with spikes up to 12 g's.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115641846","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":"Application of NURBS Surfaces for Propeller Geometry","authors":"S. K. Neely","doi":"10.5957/attc-1998-015","DOIUrl":"https://doi.org/10.5957/attc-1998-015","url":null,"abstract":"This paper describes the application of Non-Uniform Rational B-Spline (NURBS) surfaces for representation of propeller geometry. Use of NURBS surface representation can facilitate the generation of computational grids, the generation of tool paths for manufacturing, or the evaluation of inspection data. Representation of propeller geometry with spline surfaces provides a unique definition of the geometry such that different persons or organizations can interpret the geometry precisely. Propeller geometry has many difficult regions, such as the leading edge, trailing edge, and tip, which can lead to problems in generating a high quality surface. Techniques are provided that help to avoid common problems in generating propeller surfaces.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124798800","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":"Tests of Impact Acceleration on a Flat Bow Plate for a High Speed Craft","authors":"S. Cohen","doi":"10.5957/attc-1998-008","DOIUrl":"https://doi.org/10.5957/attc-1998-008","url":null,"abstract":"Model tests of vertical impact acceleration of a planing boat bow flap at zero speed in calm water showed significant differences between a zero-angle and 12-degree angle of entry. The results differed from pressure measurements of impact found in the literature since the plates were flat and had no deadrise. However, the force proportionality with height, that is with v2, is confirmed. The structures can be represented by a single degree of freedom, with no consideration for trapped air, or water spray jets. Results indicate that the water provides a suction force, and preliminary theoretical calculations give a similar indication.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128745630","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":"The Design of a Slow Speed Bulbous Bow for the T-AO 187 Class Ships","authors":"Ian Mutnick","doi":"10.5957/attc-1998-011","DOIUrl":"https://doi.org/10.5957/attc-1998-011","url":null,"abstract":"A low speed retrofit bulbous bow that is capable of reducing resistance over a wide speed and displacement range has been designed for the T-AO 187 class ships. Preliminary model towing tests to simulate bulbs of different volumes and locations were performed with simple bodies of revolutions fitted to the stem of a T-AO 187 model. Data from these model towing tests aided in selecting the volume and location of the final bulb design. Resistance and propulsion model towing tests confirmed that a small volume bulb reduces resistance over a wide speed and displacement range in calm water. The bulbous bow designed for the T-AO 187 class ships reduces resistance across the entire speed range, 10 to 22 knots, at design displacement and provides for reduced fuel consumption.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130322125","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":"Measurement and Analysis of Ship Resistance in an Offshore Model Basin","authors":"Suhrata K. Chakraharti","doi":"10.5957/attc-1998-002","DOIUrl":"https://doi.org/10.5957/attc-1998-002","url":null,"abstract":"The purpose of this paper is to discuss the measurement of resistance of a ship or an offshore structure in transit or under tow. Since a small replicate of the prototype is used, several simulation difficulties are experienced in the small scale testing. A few of the difficulties of the resistance or drag test and the remedial measures used in the setup and in the scaling up of the model data are discussed here.\u0000 The standard measurement technique for the resistance of a ship in a towing tank employs a towing staff attached to a dynamometer used for the measurement of the towing resistance. The towing staff is attached to the towing carriage in such a way that the system allows the ship to heave and pitch about the attachment point on the ship, but restrains its motion in the transverse direction. The aft end of the ship model is sometimes provided with a guide system for the side restraint. Offshore structures, however, are often towed in a restraint position, such as in the simulation of current drag.\u0000 A two staff arrangement for the towing tests is seldom used and is considered unconventional by many of the traditional basins. This paper addresses the difference of towing a· floating offshore model with a single staff (including a guide) versus a two staff arrangement. A ship model was consecutively tested at the simulated transit and loitering speeds in the Offshore Model Basin (0MB) at Escondido, CA in both a two staff and the traditional one staff arrangement. Both the inline and transverse loads were measured during these tests. In addition, the heave and pitch motions of the ship model were also measured. It is found that the results from the two series of tests were identical.\u0000 Another area of uncertainty is the effect of Reynolds number. The distortion of Reynolds number in the model necessitates certain corrective measures in the model tests. Use of the turbulence stimulator and the quantitative difference in the results with and without this stimulator for an offshore structure model is shown. The simulation of cu t load on an offshore structure is often done by towing e model. The difference between the current load and the equivalent towing load on a particular floating structure model is shown. It is shown that the towing loa were generally smaller than the corresponding current loads.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122741917","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":"An Updated Study of Planing Craft Porpoising Using Towing Tank Methods","authors":"Tullio Celano","doi":"10.5957/attc-1998-007","DOIUrl":"https://doi.org/10.5957/attc-1998-007","url":null,"abstract":"Research was conducted during the 1997-98 academic year into the porpoising of \"V-hulled\" planing craft. The purpose of the study was to first correlate the porpoising inception results published by 1952 Webb Institute seniors Day & Haag at a much larger scale, then advance porpoising prediction methods to include higher deadrise hulls and the effects of trim tabs upon the inception of porpoising. The towing equipment and methods of testing the models in the U.S. Naval Academy's 380' High-Speed Towing Tank are the subjects of this paper.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133529623","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":"A 3-D Euler Solver and its Application on the Analysis of Cavitating Propellers","authors":"Jin-Keun Choi, S. Kinnas","doi":"10.5957/attc-1998-018","DOIUrl":"https://doi.org/10.5957/attc-1998-018","url":null,"abstract":"An Euler solver, based on a finite volume approach, is developed and applied to the prediction of the effective wake for propellers subject to non-axisymmetric inflows. The method is coupled with an existing lifting-surface vortex-lattice method for the analysis of unsteady cavitating propeller flows. An axisymmetric and a fully three-dimensional version of the method are presented. The results are validated against analytical solutions from potential flow and actuator disk theory. The effect of the grid parameters on the results ( circumferential average and amplitudes of harmonics of the predicted effective wake) is found to be very weak. The predicted total velocity field correlates very well with that measured in propeller experiments in axisymmetric flow.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130127730","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":"Hydrofoil Cavitation Improvements with Elastically Coupled Composite Materials","authors":"S. Gowing, Paul C Coffin, C. Dai","doi":"10.5957/attc-1998-019","DOIUrl":"https://doi.org/10.5957/attc-1998-019","url":null,"abstract":"Laminate construction technology is used to reduce the local angle of attack at the tip of an elliptic foil to delay the inception of tip vortex cavitation. As the angle of attack is increased on the foil, the increased lift causes the tip to flex in a direction that relieves the hydrodynamic loading in that region, resulting in delay of the inception of tip vortex cavitation. The global decrease in lift of the foil caused by unloading of the tip is very small, and cavitation is still delayed with respect to the same overall foil lift.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129880897","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":"Full Scale Planing Experiment and Analysis","authors":"R. Royce, W. Vorus","doi":"10.5957/attc-1998-010","DOIUrl":"https://doi.org/10.5957/attc-1998-010","url":null,"abstract":"Experimental planing research outside the confines of the traditional towing tank laboratory is difficult to conduct. Many factors such as cross wind, random waves, clouds, curious on-lookers, and fuel consumption, which are absent in the towing tank, complicate full scale experimentation. With little control over these outside factors, this type of experimental research becomes an arduous process. This paper describes the experimental procedures used to determine the hydrodynamic pressure distribution on a 21 ft. competition ski boat. Specifically, manometry was used for pressure.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"8 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127513701","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}
M. Beddhu, S. Nichols, M. Jiang, C. Sheng, D. Whitfield, L. K. Taylor
{"title":"Comparison of EFD and CFD Results of the Free Surface Flow Field About the Series 60 CB=0.6 Ship","authors":"M. Beddhu, S. Nichols, M. Jiang, C. Sheng, D. Whitfield, L. K. Taylor","doi":"10.5957/attc-1998-001","DOIUrl":"https://doi.org/10.5957/attc-1998-001","url":null,"abstract":"Series 60 CB = 0.6 represents an important class of ships for which vast amount of experimental data is available. Thus, it represents an ideal test bed for validating Computational Fluid Dynamics (CFD) codes. The code UNCLE incorporates the recently introduced algorithm for tracking unsteady free surface flows in a time accurate manner. In this algorithm, to facilitate the tracking unsteady free surface flows in a time accurate manner. In this algorithm, to facilitate the tracking of the free surface, a background grid is employed. Using the background grid the free surface grid points are forced to move along predetermined paths in order to simplify the grid regeneration process at the new time level. Newton's method is used to find the intersection of the background grid lines with the free surface. This allows to preserve the shape of the free surface during various grid operations at a given time level. The governing equations of the flow field are cast with respect to an unsteady Eulerian coordinate system and solved using the modified artificial compressibility method. The resulting numerical algorithm is implicit and time accurate and is formulated based on a finite volume approach. Roe's formulation is used for obtaining the first order inviscid numerical fluxes and van Leer's MUSCL approach is used for obtaining higher order (third) corrections. Central differencing is used for the viscous terms and a two point backward Euler formula is used for the time derivative. The same algorithm is also used for implicitly solving the free surface kinematic condition which is cast with respect to surface curvilinear coordinates. The numerical results are compared with the experimental results. The flow conditions are Fr= 0.316 and Re= 4,020,000. The results are quite encouraging.","PeriodicalId":202192,"journal":{"name":"Day 1 Sat, October 24, 1998","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126362346","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}