{"title":"Reply by Authors to P. T. Pedersen","authors":"T. Goodman, J. Breslin","doi":"10.2514/3.63088","DOIUrl":"https://doi.org/10.2514/3.63088","url":null,"abstract":"","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124950443","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}
Presents a simple, general method for readily comparing the performances of chemically powered submersibles. Particularly useful in the preliminary design phase, the methodology permits quick assessemnt of the effects on vehicle range of variations in vehicle, engine, and reactant parameters. Criteria are given for determining when the system is weight or volume-limited. The application of the methodology is illustrated for a submarine displacing 10,000 cubic feet, showing the extended cruise range of a dual-engine system with one engine designed for high speed, the other for low speed. The sensitivities of the cruise and dash ranges to variations in design parameters are illustrated. The paper also discusses the effects of various system parameters on the criteria determining whether the vehicle is weight- or volume-limited for vehicles displacing 10,000 cubic feet and 20 cubic feet.
{"title":"A Methodology for Comparing the Range Performance of Chemically Fueled Submersibles","authors":"B. Pinkel, E. C. Gritton","doi":"10.2514/3.63084","DOIUrl":"https://doi.org/10.2514/3.63084","url":null,"abstract":"Presents a simple, general method for readily comparing the performances of chemically powered submersibles. Particularly useful in the preliminary design phase, the methodology permits quick assessemnt of the effects on vehicle range of variations in vehicle, engine, and reactant parameters. Criteria are given for determining when the system is weight or volume-limited. The application of the methodology is illustrated for a submarine displacing 10,000 cubic feet, showing the extended cruise range of a dual-engine system with one engine designed for high speed, the other for low speed. The sensitivities of the cruise and dash ranges to variations in design parameters are illustrated. The paper also discusses the effects of various system parameters on the criteria determining whether the vehicle is weight- or volume-limited for vehicles displacing 10,000 cubic feet and 20 cubic feet.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125401845","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 moored body system consists of an anchor, a mooring line, and the moored body itself. If the mechanics of the moored body and the mooring line are known, the motions of the system in the sea and the associated forces can be determined. Most past work on the mechanics of mooring lines has been oriented toward the development of mathematical models for their mechanics. If only the body motions, the forces in the body, and the connection between body and line are to be found, knowledge of all of the mechanics of the line is not necessary. The only required information about the mooring line is the relations between the forces and motions of the termination of the line attached to the moored body. To solve the problem of body motions and forces, an alternative to a mathematical model for the mooring line is a catalog of relations between line termination forces and motions for various mooring line geometries and current distributions. This paper sets out these ideas and reports the results of an experimental program for determining the relations between mooring line endpoint motions and forces for three different lines having different diameters and weights, but otherwise deployed in identical mooring geometries. The experiments were carried out in the absence of a current so as to have the most straightforward situations possible for the first experiments of this type which have ever been done. It was found that the relationship between mooring line endpoint forces and motions could be well approximated by linear relations, so that the concepts of impedances and admittances could be used.
{"title":"Experimental Determination of the Dynamics of a Mooring System","authors":"E. Kern, J. Milgram, W. B. Lincoln","doi":"10.2514/3.63083","DOIUrl":"https://doi.org/10.2514/3.63083","url":null,"abstract":"A moored body system consists of an anchor, a mooring line, and the moored body itself. If the mechanics of the moored body and the mooring line are known, the motions of the system in the sea and the associated forces can be determined. Most past work on the mechanics of mooring lines has been oriented toward the development of mathematical models for their mechanics. If only the body motions, the forces in the body, and the connection between body and line are to be found, knowledge of all of the mechanics of the line is not necessary. The only required information about the mooring line is the relations between the forces and motions of the termination of the line attached to the moored body. To solve the problem of body motions and forces, an alternative to a mathematical model for the mooring line is a catalog of relations between line termination forces and motions for various mooring line geometries and current distributions. This paper sets out these ideas and reports the results of an experimental program for determining the relations between mooring line endpoint motions and forces for three different lines having different diameters and weights, but otherwise deployed in identical mooring geometries. The experiments were carried out in the absence of a current so as to have the most straightforward situations possible for the first experiments of this type which have ever been done. It was found that the relationship between mooring line endpoint forces and motions could be well approximated by linear relations, so that the concepts of impedances and admittances could be used.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133505563","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 hydrodynamic interactions of two vessels moving at the same speed in nearfield is considered by applying the slender-body theory. It is shown that, for a water depth that is the same order as the beam of the vessel, the problem reduces to a sequence of inner problems in the cross-flow plane. This reduction to strip-theory allows one to obtain the solution without the necessity of solving an outer problem. Applications were made to two pairs of ship models. Theoretical predictions generally are high as compared with available experimental measurments, but offer a fairly satisfactory qualitative description of the interaction phenomenon when the length of the overlap of the vessels is large as compared with the separation.
{"title":"Nearfield Hydrodynamic Interactions of Ships in Shallow Water","authors":"R. W. Yeung, W. Hwang","doi":"10.2514/3.63085","DOIUrl":"https://doi.org/10.2514/3.63085","url":null,"abstract":"The hydrodynamic interactions of two vessels moving at the same speed in nearfield is considered by applying the slender-body theory. It is shown that, for a water depth that is the same order as the beam of the vessel, the problem reduces to a sequence of inner problems in the cross-flow plane. This reduction to strip-theory allows one to obtain the solution without the necessity of solving an outer problem. Applications were made to two pairs of ship models. Theoretical predictions generally are high as compared with available experimental measurments, but offer a fairly satisfactory qualitative description of the interaction phenomenon when the length of the overlap of the vessels is large as compared with the separation.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131067114","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}
I Ref. 1, Goodman and Breslin determined the effect of hydrostatic pressure on an extensible cable in a heavy liquid by an integration of the fluid pressure on the cable surface. A different and more direct approach to this problem has been presented for the case of an inextensible cable, but, as will be seen in the following, the extensibility of the cable is easy to include. Let us first consider a segment of the cable of length ds. The total buoyance of the segment with "open ends" equals wb = pgA0ds and acts in the vertical z direction (see Fig. 1). Because of the assumption of an incompressible material, there will be no strain due to this pure hydrostatic pressure. Now, in order to compensate for the lack of pressure at the ends of the segment, we have to introduce axial tension as shown in Fig. 1. This axial tension introduces strain in the segment such that the area changes from A0 to A0/(l +e). Combination of the two end forces and the buoyant force wb results in a net buoyant force dFn, which acts in the center of gravity of the segment in a direction normal to the centerline and with the mangitude
{"title":"Comment on \"Statics and Dynamics of Anchoring Cables in Waves\"","authors":"P. T. Pedersen","doi":"10.2514/3.63087","DOIUrl":"https://doi.org/10.2514/3.63087","url":null,"abstract":"I Ref. 1, Goodman and Breslin determined the effect of hydrostatic pressure on an extensible cable in a heavy liquid by an integration of the fluid pressure on the cable surface. A different and more direct approach to this problem has been presented for the case of an inextensible cable, but, as will be seen in the following, the extensibility of the cable is easy to include. Let us first consider a segment of the cable of length ds. The total buoyance of the segment with \"open ends\" equals wb = pgA0ds and acts in the vertical z direction (see Fig. 1). Because of the assumption of an incompressible material, there will be no strain due to this pure hydrostatic pressure. Now, in order to compensate for the lack of pressure at the ends of the segment, we have to introduce axial tension as shown in Fig. 1. This axial tension introduces strain in the segment such that the area changes from A0 to A0/(l +e). Combination of the two end forces and the buoyant force wb results in a net buoyant force dFn, which acts in the center of gravity of the segment in a direction normal to the centerline and with the mangitude","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130294298","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}
Forces on submerged, two-dimensional bodies of constant circular or square cross section oscillating in water of infinite depth have been measured using a forced oscillation test. The bodies were forced to sway and heave sinusoidally with small amplitudes, for several submergences below a free surface. The added-mass and wavedamping coefficients are shown to be influenced strongly by the free-surface effect and are presented as a function of frequency and direction of oscillation and of depth of submergence from the free surface. There appears to be a critical frequency that was measured consistently for heave oscillations near the free surface and was not predicted by existing theories. The measured coefficient values for the sway and heave oscillations of the circular cross section near the free surface were shifted in frequency, whereas the corresponding theoretical coefficients are identical. Comparisons of the experimental results with computations by a potential theory show reasonably good agreement. Use of the coefficients in equations of motion for floating ocean structures is described.
{"title":"Forces on Submerged Cylinders Oscillating near a Free Surface","authors":"J. Chung","doi":"10.2514/3.63081","DOIUrl":"https://doi.org/10.2514/3.63081","url":null,"abstract":"Forces on submerged, two-dimensional bodies of constant circular or square cross section oscillating in water of infinite depth have been measured using a forced oscillation test. The bodies were forced to sway and heave sinusoidally with small amplitudes, for several submergences below a free surface. The added-mass and wavedamping coefficients are shown to be influenced strongly by the free-surface effect and are presented as a function of frequency and direction of oscillation and of depth of submergence from the free surface. There appears to be a critical frequency that was measured consistently for heave oscillations near the free surface and was not predicted by existing theories. The measured coefficient values for the sway and heave oscillations of the circular cross section near the free surface were shifted in frequency, whereas the corresponding theoretical coefficients are identical. Comparisons of the experimental results with computations by a potential theory show reasonably good agreement. Use of the coefficients in equations of motion for floating ocean structures is described.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131975597","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}
We present an analysis of the minimum surface overheat, TW — T(XJ that will delay separation of a laminar boundary layer for a prescribed adverse pressure gradient in water. The analysis is for a Falkner-Skan wedge flow corresponding to negative values of ft. The energy and momentum equations are coupled through the viscosity variation with temperature. We employ a high Prandtl number approximation to obtain an asymptotic solution to these equations. The heat-transfer and viscosity variations are localized to a thin layer near the wall, well within the momentum boundary layer, and their primary effect on separation is to provide a "slip" velocity for the outer main parts of the flow, enabling the outer, shear-layer like part of the flow to sustain a more adverse pressure gradient than it could in the absence of heating. Although heating does delay separation, its effect is shown to be small for practical values of wall overheat, particularly compared to the effect of suction. For example, a suction velocity ratio of less than 0.0001 would have a comparable effect in maintaining an attached flow as an overheat of 40°F.
{"title":"Controlling the separation of laminar boundary layers in water - Heating and suction","authors":"J. Aroesty, S. Berger","doi":"10.2514/3.48155","DOIUrl":"https://doi.org/10.2514/3.48155","url":null,"abstract":"We present an analysis of the minimum surface overheat, TW — T(XJ that will delay separation of a laminar boundary layer for a prescribed adverse pressure gradient in water. The analysis is for a Falkner-Skan wedge flow corresponding to negative values of ft. The energy and momentum equations are coupled through the viscosity variation with temperature. We employ a high Prandtl number approximation to obtain an asymptotic solution to these equations. The heat-transfer and viscosity variations are localized to a thin layer near the wall, well within the momentum boundary layer, and their primary effect on separation is to provide a \"slip\" velocity for the outer main parts of the flow, enabling the outer, shear-layer like part of the flow to sustain a more adverse pressure gradient than it could in the absence of heating. Although heating does delay separation, its effect is shown to be small for practical values of wall overheat, particularly compared to the effect of suction. For example, a suction velocity ratio of less than 0.0001 would have a comparable effect in maintaining an attached flow as an overheat of 40°F.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132779268","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":"Steady Transcritical Flow Past Slender Ships: A New Look","authors":"A. Plotkin","doi":"10.2514/3.63082","DOIUrl":"https://doi.org/10.2514/3.63082","url":null,"abstract":"","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124419408","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}
Nomenclature CD(X = drag coefficient assuming a constant entry velocity CP = pressure coefficient Cw = wetting factor, h/h' en = unit vector normal to the body surface h = model depth below effective planar surface h' — model depth below original surface A/z = increment in depth below the effective planar surface in successive steps t = time t*m — VEt/D, where t is time measured from initial model impact t* = VEt/d, where t is the length of time the element centroid has been submerged VE = entry velocity Bc = cone half angle 6 = entry angle (measured from the horizontal) = velocity potential
{"title":"Prediction of Surface Pressures during Water Impact","authors":"A. Wardlaw, P. M. Aronson","doi":"10.2514/3.63076","DOIUrl":"https://doi.org/10.2514/3.63076","url":null,"abstract":"Nomenclature CD(X = drag coefficient assuming a constant entry velocity CP = pressure coefficient Cw = wetting factor, h/h' en = unit vector normal to the body surface h = model depth below effective planar surface h' — model depth below original surface A/z = increment in depth below the effective planar surface in successive steps t = time t*m — VEt/D, where t is time measured from initial model impact t* = VEt/d, where t is the length of time the element centroid has been submerged VE = entry velocity Bc = cone half angle 6 = entry angle (measured from the horizontal) = velocity potential","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123536171","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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