The tip vortex structure of a three dimensional hydrofoil at high Reynolds number was measured experimentally in both the 48-in (1.22- m) diameter water tunnel and the 48-in (1.22-m) wind tunnel at the Applied Research Laboratory, Penn State. The flow on and near the hydrofoil was measured using a number of flow visualization techniques, laser velocimetry (tip boundary layers) and pressure taps. The downstream tip vortex was measured with a three-component laser velocimeter at a number of streamwise positions with a detailed planar mapping of the flow in the region of cavitation inception. The effect of Reynolds number and applied tip roughness on the downstream tip vortex was investigated. In addition, the importance of the unsteady pressure fluctuations in the core on cavitation inception is discussed.
{"title":"The Structure of a Three Dimensional Tip Vortex at High Reynolds Numbers","authors":"D. R. Stinebring, K. Farrell, M. Billet","doi":"10.1115/1.2909524","DOIUrl":"https://doi.org/10.1115/1.2909524","url":null,"abstract":"The tip vortex structure of a three dimensional hydrofoil at high Reynolds number was measured experimentally in both the 48-in (1.22- m) diameter water tunnel and the 48-in (1.22-m) wind tunnel at the Applied Research Laboratory, Penn State. The flow on and near the hydrofoil was measured using a number of flow visualization techniques, laser velocimetry (tip boundary layers) and pressure taps. The downstream tip vortex was measured with a three-component laser velocimeter at a number of streamwise positions with a detailed planar mapping of the flow in the region of cavitation inception. The effect of Reynolds number and applied tip roughness on the downstream tip vortex was investigated. In addition, the importance of the unsteady pressure fluctuations in the core on cavitation inception is discussed.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"343 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132035839","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 icebreaking pattern and piece size is studied by photographing the breaking pattern in EG/AD model ice after the icebreaker model has been stopped and backed up. The ice pieces broken by the bow float to the surface and the breaking pattern is evident. Three different scale models or the R-Class icebreaker have been tested (1:40, 1:20, 1:8), as well as a 1:22.5 scale model or the "Kigoriak". The data from these tests are compared to the available full scale data. Comparisons show a realistic breaking pattern in the model ice, but non-dimensionalized piece sizes are larger than those in full scale. Cracks in the model ice pieces indicate a smaller piece size, but this is prevented by what ls believed to be a high residual strength in the model ice.
{"title":"A Preliminary Investigation of Model Ice Failure Pattern and Piece Size Generated by IceBreaker Bow Form","authors":"S. Newbury","doi":"10.5957/attc-1989-017","DOIUrl":"https://doi.org/10.5957/attc-1989-017","url":null,"abstract":"The icebreaking pattern and piece size is studied by photographing the breaking pattern in EG/AD model ice after the icebreaker model has been stopped and backed up. The ice pieces broken by the bow float to the surface and the breaking pattern is evident.\u0000 Three different scale models or the R-Class icebreaker have been tested (1:40, 1:20, 1:8), as well as a 1:22.5 scale model or the \"Kigoriak\". The data from these tests are compared to the available full scale data. Comparisons show a realistic breaking pattern in the model ice, but non-dimensionalized piece sizes are larger than those in full scale. Cracks in the model ice pieces indicate a smaller piece size, but this is prevented by what ls believed to be a high residual strength in the model ice.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134495784","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 matrix data base approach to the modeling of planing craft thrustline in towing tank resistance experiments is presented. The matrix data base approach does not actually attempt to model a specific thrustline geometry in the towing tank. Instead, a matrix of drag and running trims for a discrete range of model weights on water and longitudinal centers of gravity are obtained experimentally with a model fixed in surge, and free in pitch and heave. This matrix is then curve fit and the desired thrustline conditions are either interpolated or extrapolated from the experimentally derived data base. This method provides not only the performance information for the desired ballast and thrustline condition, but also the ability to estimate performance over a fairly large range of gross vehicle weights, longitudinal centers of gravity, and thrustline geometries.
{"title":"A Matrix Data Base Approach to Planing Craft Resistance Model Experiments","authors":"J. Hoyt, M. Dipper","doi":"10.5957/attc-1989-012","DOIUrl":"https://doi.org/10.5957/attc-1989-012","url":null,"abstract":"A matrix data base approach to the modeling of planing craft thrustline in towing tank resistance experiments is presented. The matrix data base approach does not actually attempt to model a specific thrustline geometry in the towing tank. Instead, a matrix of drag and running trims for a discrete range of model weights on water and longitudinal centers of gravity are obtained experimentally with a model fixed in surge, and free in pitch and heave. This matrix is then curve fit and the desired thrustline conditions are either interpolated or extrapolated from the experimentally derived data base. This method provides not only the performance information for the desired ballast and thrustline condition, but also the ability to estimate performance over a fairly large range of gross vehicle weights, longitudinal centers of gravity, and thrustline geometries.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131697469","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}
Although the emphasis of this paper is on gaseous diffusion into a full cavity behind an oscillating flat-plate hydrofoil, the unsteady diffusion theory given below applies also to the limiting case of "steady" supercavitating flow. The entire unbounded flow is assumed to be turbulent and a turbulent diffusivity is employed which enables one to make engineering estimates of the total diffusion rate into or out of the cavity. The theory accounts for fluctuations in cavity gas pressures and in cavity lengths.
{"title":"Unsteady Gaseous Diffusion Associated with a Fully Cavitating Oscillating Flat-Plate Hydrofoil","authors":"K. Ravindra, B. Parkin","doi":"10.1115/1.2909494","DOIUrl":"https://doi.org/10.1115/1.2909494","url":null,"abstract":"Although the emphasis of this paper is on gaseous diffusion into a full cavity behind an oscillating flat-plate hydrofoil, the unsteady diffusion theory given below applies also to the limiting case of \"steady\" supercavitating flow. The entire unbounded flow is assumed to be turbulent and a turbulent diffusivity is employed which enables one to make engineering estimates of the total diffusion rate into or out of the cavity. The theory accounts for fluctuations in cavity gas pressures and in cavity lengths.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133141752","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}
Analysis of a number of friction experiments, mostly between ice and various materials, has shown that in all cases the frictional force is a linear function of the normal load rather than proportional to some fractional power of it as predicted by Oksanen's theoretical equation. This could indicate that Oksanen's basic assumption that "the only cause of friction is the water layer formed by frictional heating between the ice and any given surface on which it is sliding” may be invalid, in particular when the roughness height of the surfaces is greater that the water layer thickness. Other processes, gouging or mechanical abrasion, may then become predominant.
{"title":"Effect of Normal Pressure on Kinetic Friction Coefficient: Myth or Reality?","authors":"J. Tatinclaux","doi":"10.5957/attc-1989-016","DOIUrl":"https://doi.org/10.5957/attc-1989-016","url":null,"abstract":"Analysis of a number of friction experiments, mostly between ice and various materials, has shown that in all cases the frictional force is a linear function of the normal load rather than proportional to some fractional power of it as predicted by Oksanen's theoretical equation. This could indicate that Oksanen's basic assumption that \"the only cause of friction is the water layer formed by frictional heating between the ice and any given surface on which it is sliding” may be invalid, in particular when the roughness height of the surfaces is greater that the water layer thickness. Other processes, gouging or mechanical abrasion, may then become predominant.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130166304","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 problem of ship resistance in ice floe infested waters has been investigated experimentally in the Towing Tank of Memorial University of Newfoundland. Ships and ice have been modelled to simulate the natural condition of ships sailing in waters covered with ice fragments. Ships advancing in waters coveted with ice floes of moderate size, with less than 100% concentration and with no lateral pressure seldom break any ice. The ship and the ice floes have therefore, been treated in this investigation as freely floating rigid bodies. Both the ice floes and the ship have, therefore been modelled in accordance with Froude principles. The ice cover was modelled using blocks of paraffin wax spread over the water surface. Slabs of wax were cut into small blocks having thickness and size in accordance with the required geometrical modelling scale. Wax blocks were spread over the water surface according to the required ice cover concentration. Ship models were towed in the tank at different speeds. The model resistance for each run was measured and recorded. Results obtained from model testing experiments are presented in this paper. The results cover a number of ship model runs at different ship speeds, and for a variety of ice cover conditions. The results have been compared with ice floe resistance data available in the literature.
{"title":"Ship Model Testing in Simulated Ice Flow Covered Waters","authors":"A. F. Aboulazm, D. Muggeridge","doi":"10.5957/attc-1989-019","DOIUrl":"https://doi.org/10.5957/attc-1989-019","url":null,"abstract":"The problem of ship resistance in ice floe infested waters has been investigated experimentally in the Towing Tank of Memorial University of Newfoundland. Ships and ice have been modelled to simulate the natural condition of ships sailing in waters covered with ice fragments.\u0000 Ships advancing in waters coveted with ice floes of moderate size, with less than 100% concentration and with no lateral pressure seldom break any ice. The ship and the ice floes have therefore, been treated in this investigation as freely floating rigid bodies. Both the ice floes and the ship have, therefore been modelled in accordance with Froude principles.\u0000 The ice cover was modelled using blocks of paraffin wax spread over the water surface. Slabs of wax were cut into small blocks having thickness and size in accordance with the required geometrical modelling scale. Wax blocks were spread over the water surface according to the required ice cover concentration. Ship models were towed in the tank at different speeds. The model resistance for each run was measured and recorded.\u0000 Results obtained from model testing experiments are presented in this paper. The results cover a number of ship model runs at different ship speeds, and for a variety of ice cover conditions. The results have been compared with ice floe resistance data available in the literature.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132145416","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 single phase and cavitating tip vortex shed by a NACA .66-209 rounded tip hydrofoil has been studied. Single phase measurements of instantaneous flow velocity were made by taking double pulsed holograms of microbubbles moving in and around the vortex core. The tailored air bubble technique of Ooi and Acosta (1983) was employed to measure both the mean and fluctuating single phase vortex core static pressure. Cavitation inception was determined visually. The flow in the vortex core is highly unsteady. The r.m.s. axial velocity fluctuation can be as high as 0.2Uoo Core pressure fluctuations greater than the freestream dynamic pressure have been measured. These fluctuations are thought to accompany local axial velocity fluctuations. With saturated water, inception occurs at mean core pressures above the vapour pressure. However, the pressure fluctuations are certainly substantial enough to account for these elevated inception indices. The fluctuations also explain why inception occurs immediately downstream of the hydrofoil. The rapid establishment of fully developed trailing vortex cavitation when the cavitation number is reduced below inception is attributable to the small variation in mean core pressure with downstream distance. The inception index decreases dramatically with decreasing dissolved air content. The cause of this decrease is not known.
{"title":"Relating Trailing Vortex Cavitation Inception To Single Phase Flow Measurements","authors":"S. Green, A. Acosta","doi":"10.5957/attc-1989-003","DOIUrl":"https://doi.org/10.5957/attc-1989-003","url":null,"abstract":"The single phase and cavitating tip vortex shed by a NACA .66-209 rounded tip hydrofoil has been studied. Single phase measurements of instantaneous flow velocity were made by taking double pulsed holograms of microbubbles moving in and around the vortex core. The tailored air bubble technique of Ooi and Acosta (1983) was employed to measure both the mean and fluctuating single phase vortex core static pressure. Cavitation inception was determined visually.\u0000 The flow in the vortex core is highly unsteady. The r.m.s. axial velocity fluctuation can be as high as 0.2Uoo Core pressure fluctuations greater than the freestream dynamic pressure have been measured. These fluctuations are thought to accompany local axial velocity fluctuations. With saturated water, inception occurs at mean core pressures above the vapour pressure. However, the pressure fluctuations are certainly substantial enough to account for these elevated inception indices. The fluctuations also explain why inception occurs immediately downstream of the hydrofoil. The rapid establishment of fully developed trailing vortex cavitation when the cavitation number is reduced below inception is attributable to the small variation in mean core pressure with downstream distance. The inception index decreases dramatically with decreasing dissolved air content. The cause of this decrease is not known.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116192940","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 tip vortex roll-up process from an elliptic wing was experimentally investigated. Cavitation provided an excellent method for visualizing the mechanism of vortex roll-up. The velocity profiles of the non-cavitating vortex were first obtained with a laser Doppler velocimeter. The measured asymmetry of the velocity profile and the computed pressure distribution in the vortex core are discussed. In the case of fully developed cavitation, the vortex trajectory was analyzed and compared with theory. The cavity core radius increased with reduced pressure until the developed cavity forms a twisted ribbon structure. The core thickness and the wave length of these structures are also discussed.
{"title":"The Structure of Tip Vortices Over a Range of Cavitation Number","authors":"H. Higuchi, R. Arndt, V. Arakeri, J. Killen","doi":"10.5957/attc-1989-002","DOIUrl":"https://doi.org/10.5957/attc-1989-002","url":null,"abstract":"The tip vortex roll-up process from an elliptic wing was experimentally investigated. Cavitation provided an excellent method for visualizing the mechanism of vortex roll-up. The velocity profiles of the non-cavitating vortex were first obtained with a laser Doppler velocimeter. The measured asymmetry of the velocity profile and the computed pressure distribution in the vortex core are discussed. In the case of fully developed cavitation, the vortex trajectory was analyzed and compared with theory. The cavity core radius increased with reduced pressure until the developed cavity forms a twisted ribbon structure. The core thickness and the wave length of these structures are also discussed.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132025438","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}
Ridges are important features of the ice environment which can greatly effect the performance of ice breaking vessels. The performance of ships the ridges is an area that is not well understood at present as the vork to date has generally been focused on the performance of ships in level ice.
{"title":"Ridge Modelling: Model Scale Simulation of Ridge Ramming Event with the USCG Polar Star","authors":"G. Comfort, A. Keinonen","doi":"10.5957/attc-1989-015","DOIUrl":"https://doi.org/10.5957/attc-1989-015","url":null,"abstract":"Ridges are important features of the ice environment which can greatly effect the performance of ice breaking vessels. The performance of ships the ridges is an area that is not well understood at present as the vork to date has generally been focused on the performance of ships in level ice.","PeriodicalId":400734,"journal":{"name":"Day 1 Tue, August 08, 1989","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134121939","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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