Day 2 Sun, October 25, 1998最新文献

{"title":"Nonlinear Ship Motions and Wave Induced structural Loads","authors":"P. Sclavounos, Yonghwan Kim","doi":"10.5957/attc-1998-024","DOIUrl":"https://doi.org/10.5957/attc-1998-024","url":null,"abstract":"The theoretical model and the associated computational algorithm is presented for the simulation of the linear and nonlinear motions of ships in waves of small and large steepness. The solution method is based on a three dimensional Rankine Panel Method which has been shown to be accurate, robust and efficient for the treatment of steady and unsteady potential flows past realistic ship hulls. In this article new results are presented for the seakeeping of the 5415 destroyer in waves of moderate steepness. Oblique wave seakeeping computations are presented in steep waves for the S-175 containership which confirm the importance of nonlinear effects.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"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":"122651808","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":"Recent Work at the NUWC/NASA Langley Seawater Tow Tank","authors":"C. Henoch, C. Beauchamp, R. Philips, E. Dow, Genevieve Nuttall, D. Brown","doi":"10.5957/attc-1998-027","DOIUrl":"https://doi.org/10.5957/attc-1998-027","url":null,"abstract":"The Langley seawater tow tank, located on Langley Airbase in Hampton, Virginia, was designed and built by NACA in 1931 for seaplane research and has been in various states of use since then. Since 1983, NUWC has maintained stewardship of the tank and has conducted a large number of tests there. This paper will present an overview of the facility and its capabilities as well as discuss several recent test results.\u0000 The tank is reinforced concrete, 2880 feet long, 12 feet deep, and 24 feet wide, and can be filled with 5.4 million gallons of either fresh or baywater. Baywater can be filtered to 25 microns and has a salinity about half that of seawater. The carriage is powered by eight 75 hp D.C. motors with trolley style cables and can attain speeds of up to 40 knots. Power is generated by a 850 kW motor generator. Several struts exist for model towing and the carriage bas 110/120 V.A.C. and 3 phase 208 A.C. volt available power. A workshop is in the building and a variety of instrumentation and data acquisition is on hand.\u0000 Unique possibilities exist at the LTT due to the organic and physical properties of seawater. For example, one of the largest ever artificial colonies of plankton was grown there. Furthermore, because of the electrical conductivity of the water, research into the control of turbulent flows by magnetohydrodynamic forces can be, and bas been, performed there. To illustrate the variety of test configurations an capabilities, results are presented from three recent test programs performed at the tank.\u0000 The first will be the set-up and test results of a fully submerged axisymmetric 180 inch long cylindrical sting mounted model. The test rig will be shown including the floating swing balance which is coupled to an axial load cell. Test results will be shown for hydrodynamic resistance versus speed at zero and non-zero attack angles.\u0000 The second set of results shown will be those of a towed cylindrical body equipped with remotely actuated hydrodynamic drag brakes which was released in flight an allowed to come to rest Drag measurements made at different drag brake settings and speeds will be presented as well as photographic documentation.\u0000 Finally, a recent set of test results will be presented; taken on a submerged cylindrical body, strut mounted to a 6 degree of freedom load balance. Results to be presented will include force and moment measurements as a function of speed and attack angle.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"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":"130412211","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":"PIV Turbulence Measurements of the Bow Wave on a DDG-51 Destroyer","authors":"G. Roth, Daniel T. Mascenik, J. Katz","doi":"10.5957/attc-1998-028","DOIUrl":"https://doi.org/10.5957/attc-1998-028","url":null,"abstract":"Particle image velocimetry (PIV) measurements around a 7-m-long DDG-51 destroyer model focus on the flow within the attached liquid sheet, upstream of the point at which the bow wave separates from the model. The measurements are performed in Carderock, NSWC's 140-ft model basin at Reynolds number 1.6x10^7 and Froude number 0.30 (both based on ship length L).\u0000 The PIV system uses a 1k x 1k submerged digital camera and a 25-mj/pulse dual-head Nd-YAG laser. The data cover a 20-cm x 20-cm area of the flow within the bow wave near the free surface. As the model passes the camera, data are collected at 2.5-cm intervals beginning from upstream of the model until X/L = 0.1.\u0000 Individual vector maps show a growing region of negative vorticity originating at the toe of the wave and positive vorticity on the top and forward face of the wave. 92 instantaneous velocity distributions are repeated at X/L = 0.0690 to calculate mean flow and turbulent stresses.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"264 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":"114410983","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":"Unique Calibration of a \"5-hole\" Pitot Rake and Application for Wake Survey","authors":"N. A. Brown","doi":"10.5957/attc-1998-030","DOIUrl":"https://doi.org/10.5957/attc-1998-030","url":null,"abstract":"A rake of five “5-hole\" directional Pitot tubes (actually \"6-hole\" because static taps are included) was calibrated for angular sensitivity, as well as velocity, in a towing tank. This was; accomplished by deploying the rake on a tubular shaft out of the bow of a propeller boat. Combinations of propeller boat yaw angle and rotation angle of the rake shaft provided a full and systematic coverage of flow angles in tangential and radial planes of each probe. Thirty single ended pressure transducers were used, one for each hole in each of five probes, to measure pressures. The transducers resided below the waterline, making air purging practical. Calibration required forty one runs.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"84 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":"129267147","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":"Dynamic Bending Moment Identification Using Neural Networks","authors":"Frederick Rogers, M. Haddara, D. Molyneux","doi":"10.5957/attc-1998-022","DOIUrl":"https://doi.org/10.5957/attc-1998-022","url":null,"abstract":"An alternative method for the prediction of a ship's dynamic bending stresses at sea is presented and examined in this paper. The method uses a ship's heave and pitch motion to determine the dynamic bending moment at a point along the ship's length. This can be combined with the known still water bending moment, and known ship sectional properties to determine deck and keel stresses. A combination of mathematical modeling, the random decrement, and neural network techniques have been used to determine the relationship between ship motion and bending moment, without any prior knowledge of the wave excitation level To test this method, two sets of model experiments have been used. One set from a Great Lakes bulk carrier, the other from a Canadian patrol frigate. In each experiment, the mean and variance of the bending moment have been successfully predicted, demonstrating this method as a valid approach.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"26 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":"131426434","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":"IIHR Towing-Tank Wavemaker","authors":"J. Longo, S. Rhee, David K Kuhl, B. Metcalf, Fred Stem","doi":"10.5957/attc-1998-029","DOIUrl":"https://doi.org/10.5957/attc-1998-029","url":null,"abstract":"A description is provided of the acqms1tton and calibration of a plunger wavemaker for the Iowa Institute of Hydraulic Research 100x3.048x3.048 m towing tank. The collaboration procedure determines the wavemaker response function, i.e., nature of generated waves over range of single (regular waves) or multiple (irregular waves) input plunger frequencies, strokes, and phase angles. Capacitance wires are used to measure wave time. histories, which are analyzed (using average wave crests and troughs, Fast Fourier Transforms, and Fourier series) for evaluation of wave amplitudes and frequencies. Only regular waves are investigated for input frequencies and strokes corresponding to wavelengths 0.5-6.0 m and steepnesses 0.025-0.3. The uncertainty assessment methodology follows the AIAA Standard S--071-1995.\u0000 The results indicate that the primary frequency wave frequency response is equal to the input wavemaker frequency within the uncertainty in the data and analysis, i.e., 1-3% for low-high frequency, whereas the primary frequency wave amplitude significantly exceeds the wavemaker stroke for most wavelengths and steepnesses. The wavemaker meets the design requirements and limits. The response function is less than the theoretical prediction used in its design. The certainty in the wave-elevation measurement is small compared to the magnitude and trends of the primary frequency amplitude response such that the magnitudes and trends exhibited are much larger than the noise. The sub-frequency amplitudes are small, except for small wavelength and steepness. The super-frequency amplitudes are also small. but do show the trend of increasing with wave steepness and correlate with second-order Stokes wave theory.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"20 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":"131138711","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 state of the Art in Modeling Ship Stability in Waves","authors":"D. Vassalos, H. Hamamoto, J. Kat, D. Molyneux, A. Papanikolaou","doi":"10.5957/attc-1998-023","DOIUrl":"https://doi.org/10.5957/attc-1998-023","url":null,"abstract":"In 1996, the 22nd ITTC formed a Specialist Committee on Ship Stability. There were two main mandates given to this committee. Toe first was to examine the techniques for carrying out model experiments used to investigate the capsize of intact and damaged ships and provide guidelines for carrying out these experiments. Toe second was to assess the methods available for numerical simulations of the capsize of intact and damaged ships.\u0000 This paper describes the findings of the committee so far, at the end of its second year of a three year term. The committee has prepared a summary of the state of art in the areas of numerical and physical modeling of intact and damaged ships. It has also circulated a questionnaire concerning the type of numerical methods used by ITTC member organizations for predicting the capsize of intact and damaged ships. Another major objective of the committee is to 'benchmark' codes against a standard hull form, for which there are well documented experiments. The hull form chosen was a container ship tested at Osaka University.\u0000 This paper provides a brief summary of the findings of the committee in each of the four subject areas and makes recommendations for standard model test methods for intact and damage capsize predictions. It also discusses the preliminary findings from the questionnaire.","PeriodicalId":134628,"journal":{"name":"Day 2 Sun, October 25, 1998","volume":"9 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":"117026442","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}