During dynamic operation of an air cushion system, the fan operating point as seen at the cushion does not move along a static characteristic. Instead, it moves on a loop. It is shown that loop type behavior can be predicted theoretically. The theory models the fan-duct-plenum system as a one dimensional acoustic vibration system. It uses the method of characteristics and a finite difference technique known as the method of specified time intervals to solve for the pressure and flow variations which occur along the duct during unsteady operation. Several practical situations where the loop behaviour may be of importance are discussed.
{"title":"Duct effects on the dynamic fan characteristics of air cushion systems","authors":"M. Hinchey, P. Sullivan","doi":"10.2514/3.48164","DOIUrl":"https://doi.org/10.2514/3.48164","url":null,"abstract":"During dynamic operation of an air cushion system, the fan operating point as seen at the cushion does not move along a static characteristic. Instead, it moves on a loop. It is shown that loop type behavior can be predicted theoretically. The theory models the fan-duct-plenum system as a one dimensional acoustic vibration system. It uses the method of characteristics and a finite difference technique known as the method of specified time intervals to solve for the pressure and flow variations which occur along the duct during unsteady operation. Several practical situations where the loop behaviour may be of importance are discussed.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129512278","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":"Turbulent flow over a step with nonzero angle of inclination of the plates","authors":"C. Liu, S. Foo, K. H. Ling","doi":"10.2514/3.48153","DOIUrl":"https://doi.org/10.2514/3.48153","url":null,"abstract":"","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123872892","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}
Yurnerical results are given for the addcd mass o l wrticnl nxisrmmetric br~dies piercing a free surface when Ihe fwql~cncy tends tu zeru. The numerical scheme employ a liniiu-ulumunl mrlhud which is based an the lheorv of calcutu o f vnr ia l ims. Spccifir. body geometries treated here are a family of sphuruids (oblate and pmlale sphemids) and a Fumily ~ r l vcrticlil circular cylinders with xarioos slenderness ratios. Thu cast when the free hurface plaw dues not intersect the center nC thr spheroid i* Iruatvd. Specifirally. Ihe heave and pitch rnoiionb are confidered. sincc clashiral annlj-tir resalts are availalde for thr hwag m d v n uf fl spheroid. ' l l ~ e present numerical resulls can he used in conncrclinn wilh ocean buoy or ocean platform motions hy ahwining lhat the hod) geomcrry i k c n cmnll cumpared wi th the warelenyth of rurfacr waves.
{"title":"Zero-Frequency Hydrodynamic Coefficients of Vertical Axisymmetric Bodies at a Free Surface","authors":"K. Bai","doi":"10.2514/3.63203","DOIUrl":"https://doi.org/10.2514/3.63203","url":null,"abstract":"Yurnerical results are given for the addcd mass o l wrticnl nxisrmmetric br~dies piercing a free surface when Ihe fwql~cncy tends tu zeru. The numerical scheme employ a liniiu-ulumunl mrlhud which is based an the lheorv of calcutu o f vnr ia l ims. Spccifir. body geometries treated here are a family of sphuruids (oblate and pmlale sphemids) and a Fumily ~ r l vcrticlil circular cylinders with xarioos slenderness ratios. Thu cast when the free hurface plaw dues not intersect the center nC thr spheroid i* Iruatvd. Specifirally. Ihe heave and pitch rnoiionb are confidered. sincc clashiral annlj-tir resalts are availalde for thr hwag m d v n uf fl spheroid. ' l l ~ e present numerical resulls can he used in conncrclinn wilh ocean buoy or ocean platform motions hy ahwining lhat the hod) geomcrry i k c n cmnll cumpared wi th the warelenyth of rurfacr waves.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"359 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123607786","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":"Isothermal Flows in Water","authors":"M. Rao, N. K. Purohit","doi":"10.2514/3.63205","DOIUrl":"https://doi.org/10.2514/3.63205","url":null,"abstract":"","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126256827","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":"Aero/Hydrodynamic Forces and Moments on Self -Propelled Slender Bodies in Incompressible Flow","authors":"J. Schetz, Edward B. Daffant","doi":"10.2514/3.63199","DOIUrl":"https://doi.org/10.2514/3.63199","url":null,"abstract":"","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114527470","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":"On the calculation of boundary layers along rotating cylinders","authors":"J. S. Tennant, W. Johnson, D. Keaton","doi":"10.2514/3.48154","DOIUrl":"https://doi.org/10.2514/3.48154","url":null,"abstract":"","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125721670","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 convenient geometric fnlutinn to the wind Irinnglc rel.alinnhip For a ailing crafl is de+elr~pcrl whwh is directly related to the armdynamic and hydrodynamic chnrncteriatics of Ihc cralt. Manimitiny rhc peed made good tu wiiideard is examined, and a relationship between the aerodynarnicr and hgdrodynamic nC the craft which bounds !he windward performance and is a necessav conditioir fur ~na~imum speed to windward is developed. A brief discussion of windward perfornunre tradeuffs is induded based vn thiv res~~lt.
{"title":"Upright Sailing Craft Performance and Optimum Speed to Windward","authors":"H. Curtiss","doi":"10.2514/3.63201","DOIUrl":"https://doi.org/10.2514/3.63201","url":null,"abstract":"A convenient geometric fnlutinn to the wind Irinnglc rel.alinnhip For a ailing crafl is de+elr~pcrl whwh is directly related to the armdynamic and hydrodynamic chnrncteriatics of Ihc cralt. Manimitiny rhc peed made good tu wiiideard is examined, and a relationship between the aerodynarnicr and hgdrodynamic nC the craft which bounds !he windward performance and is a necessav conditioir fur ~na~imum speed to windward is developed. A brief discussion of windward perfornunre tradeuffs is induded based vn thiv res~~lt.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"135 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114871964","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 semi-balanced rudder has its fixed portion in the upper part of the leading edge and incorporates a balance area without introducing a vertical gap when the rudder is laid over. However, it necessarily incorporates a horizontal break between the top of the balance area and the lower edge of the fixed portion, which has an undesirable influence on its characteristics. An experiment has been carried out using a small plate to seal off the horizontal gap on rudder section shape NACA 0015, which was then tested in a low-speed wind tunnel with a test section of 30 x 30 cm. Surface pressures on the rudder for various degrees of deflection angle were measured. It was found that, at a large deflection angle, the improvement in normal force by sealing off the horizontal gap is approximately 6% and the steamline pattern is improved, added to which the large variation of the centre of pressure of the semi-balanced rudder may also be reduced.
{"title":"IMPROVEMENT PLATE FOR SEMIBALANCED RUDDER","authors":"Chang-yu Liu, Oag Beng Yoke, Tham Kwok Liang","doi":"10.2514/3.63207","DOIUrl":"https://doi.org/10.2514/3.63207","url":null,"abstract":"The semi-balanced rudder has its fixed portion in the upper part of the leading edge and incorporates a balance area without introducing a vertical gap when the rudder is laid over. However, it necessarily incorporates a horizontal break between the top of the balance area and the lower edge of the fixed portion, which has an undesirable influence on its characteristics. An experiment has been carried out using a small plate to seal off the horizontal gap on rudder section shape NACA 0015, which was then tested in a low-speed wind tunnel with a test section of 30 x 30 cm. Surface pressures on the rudder for various degrees of deflection angle were measured. It was found that, at a large deflection angle, the improvement in normal force by sealing off the horizontal gap is approximately 6% and the steamline pattern is improved, added to which the large variation of the centre of pressure of the semi-balanced rudder may also be reduced.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"151 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122967135","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}
This investigation has focused on the initial stages of cavitation erosion using a ductile material in a flowing system employing water as the working fluid. The test models were 0.25-in. (0.635-cm)-diam zero-caliber ogives made of pure annealed aluminum. The damage was in the form of small round depressions in the model surface. In the formation of these pits, there was no material removal. For a range of velocities from 49 to 195 fps (14.9 to 59.3 m/sec), the pitting rate increased by approximately the sixth power of velocity. The average volume of the cavitation damage pits increased by the fifth power of velocity. A relationship between the volume of a pit and the absorbed bubble collapse energy was developed. The rate of total bubble collapse energy absorbed by the model then increases by the eleventh power of velocity. A plot of the distribution of absorbed collapse energies was generated for three flow conditions. The effect of cavitation number and air content of the working fluid were also major areas of investigation. A high-speed motion-picture study of cavity dynamics was undertaken to understand better some of the processes involved in cavitation damage. Lastly, the results of this study were compared with those of previous investigations of cavitation erosion.
{"title":"SCALING OF CAVITATION DAMAGE","authors":"D. R. Stinebring","doi":"10.2514/3.63077","DOIUrl":"https://doi.org/10.2514/3.63077","url":null,"abstract":"This investigation has focused on the initial stages of cavitation erosion using a ductile material in a flowing system employing water as the working fluid. The test models were 0.25-in. (0.635-cm)-diam zero-caliber ogives made of pure annealed aluminum. The damage was in the form of small round depressions in the model surface. In the formation of these pits, there was no material removal. For a range of velocities from 49 to 195 fps (14.9 to 59.3 m/sec), the pitting rate increased by approximately the sixth power of velocity. The average volume of the cavitation damage pits increased by the fifth power of velocity. A relationship between the volume of a pit and the absorbed bubble collapse energy was developed. The rate of total bubble collapse energy absorbed by the model then increases by the eleventh power of velocity. A plot of the distribution of absorbed collapse energies was generated for three flow conditions. The effect of cavitation number and air content of the working fluid were also major areas of investigation. A high-speed motion-picture study of cavity dynamics was undertaken to understand better some of the processes involved in cavitation damage. Lastly, the results of this study were compared with those of previous investigations of cavitation erosion.","PeriodicalId":157493,"journal":{"name":"Journal of Hydronautics","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1977-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122247970","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：