Topics: Radio Program, Weather, Planetary science, Sun, Solar phenomena, Concepts in physics, Space...

The theoretical procedures commonly used by aeroelasticians were applied to predict the flutter speed of a rigid hydrofoil that had two degrees of freedom. The results, compared with corresponding experimental measurements, indicated a discrepancy between theoretical and experimental flutter speeds at low density ratios; the predicted asymptotic behavior of flutter speeds occurred, but at a lower density-ratio. In addition, the accuracy of the circulation terms is more doubtful than that of the...

Topics: DTIC Archive, HENRY, CHARLES J, STEVENS INST OF TECH HOBOKEN NJ DAVIDSON LAB, *AIRFOILS, *FLUTTER,...

Four hydrofoil flutter tests were performed in a towing basin and a 36-inch water tunnel using a two-degree-of-freedom hydrofoil in two-dimensional flow. Mass ratio, mass unbalance, heave stiffness, angle of attack, and foil depth were varied. All of these parameters significantly affected the flutter boundaries. Comparisons were made with a flutter theory based on the Theodorsen analysis. Theory gave good flutter predictions at high mass ratios but failed at low mass ratios.

Topics: DTIC Archive, Cieslowski, Daniel S, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER...

A description of some experiments involving a two-dimensional, partially cavitating, plano-convex hydrofoil is presented in this report. The data obtained were compared to two theories for two-dimensional partially cavitating flow; the camber line theory of Geurst and the theory for a plano-convex hydrofoil which included the effects of thickness. The latter theory involves assumptions identical to those of Wade, but the solution is purely numerical, being the determination of the strengths of...

Topics: DTIC Archive, Uhlman,James S , Jr, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING,...

A large body of experimental and theoretical flutter results for hydrofoil struts were analyzed to determine significant characteristics. Flutter was found to occur in two different structural mode shapes, corresponding to a predominantly bending mode and a predominantly torsional mode, respectively. The flutter mode shape was related to the vibration mode shapes and the generalized mass ratio of the strut at zero speed. The behavior of the hydroelastic modes of typical struts as a function of...

Topics: DTIC Archive, Besch, Peter K, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

Topics: DTIC Archive, STEINBERG, HERBERT, CONTROL DATA CORP MELVILLE NY TRG DIV, *HYDROFOILS, INTEGRALS,...

The flutter characteristics of a two-dimensional hydrofoil near a free surface are analyzed, with consideration given to the cases of both one and two degrees of freedom. The flutter equations incorporate lift and moment as determined from an exact linearized potential solution. Free-surface effects are included without approximation. Results indicate that for the system having two degrees of freedom, the free surface has very little effect on flutter boundaries, despite the large changes in...

Topics: DTIC Archive, CORNELL AERONAUTICAL LAB INC BUFFALO NY, *FLUTTER, *HYDROFOILS, HYDRODYNAMICS, LIFT,...

The report presents design procedures and parametric trends that can be used to avoid flutter and divergence of hydrofoil strut-foil systems. Flutter stability of conventional T-foils can be achieved by scaling existing prototype systems which are stable; scaled flutter models must be used to determine the stability of new designs. Several stable T-foil designs are available for craft with displacements of up to 300 tons at subcavitating speeds (below 50 knots). The availability of higher speed...

Topics: DTIC Archive, Besch, Peter K, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

The general problem of the response of a cantilevered beam to flow over its surface is considered experimentally and theoretically. The measured flow induced modal vibratory motion of a nonsinging beam is compared to theoretical estimates of inflow turbulence excitation and boundary-layer excitation. The comparison indicates that while the response to turbulent inflow is dominant at low frequencies, the response of the strut to its own boundary layer is important at high frequencies. The...

Topics: DTIC Archive, Blake, William K, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

Historically, two-dimensional airfoil or hydrofoil section characteristics have been obtained by measuring individually the lift, drag and pitching moment by the most accurate technique available. The use of force balances to measure the three quantities simultaneously has met with only partial success. Although the lift and pitching moment data have usually been acceptable, the drag data have varied by as much as an order of magnitude from the accepted NACA reference data. To investigate the...

Topics: DTIC Archive, Treaster,A L, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *DATA...

A practical approach for predicting partially cavitating flow characteristics of foil sections is presented. The method take into account indirectly the viscous flow effects and the interaction between the fully wetted and perturbed cavitating flows. The partially cavitating flow characteristics are found to be sensitive to variations in the angle of attack, camber, thickness, and the thickness distribution. Some comparisons between the calculated and measured cavity lengths are made, and the...

Topics: DTIC Archive, Hsu,C C, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD,...

Three supercavitating hydrofoil section shapes were designed at the David W. Taylor Naval Ship R and D Center, using fully nonlinear theory. The foils was built and tested at the California Institute of Technology (C.I.T.), in order to obtain experimental verification of the design-method. This report compares the DTNSRDC predicted foil performance (including wall-effects) with the experimental data of C.I.T. Agreement is good for the lift and moment results, but only at cavitation numbers near...

Topics: DTIC Archive, Fisher,Barry L, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD...

The bound-vortex drag was computed for different lift distributions of a single, straight bound-vortex line which, in conformance with Prandtl's airplane wing theory, replaced the hydrofoil. The bound-vortex line was parallel to the undisturbed interface and approximately at the centers of lift of the wing sections of the hydrofoil. The analysis neglected viscous forces and assumed irrotational fluid motion everywhere outside the bound vortex and trailing vortex sheet. Equations give the drag...

Topics: DTIC Archive, Meyer, R. X., HYDROFOIL CORP ANNAPOLIS MD, *HYDROFOILS, *NAVAL ARCHITECTURE,...

Historically, two-dimensional airfoil or hydrofoil section characteristics have been obtained by measuring individually the lift, drag and pitching moment by the most accurate technique available. The use of force balances to measure the three quantities simultaneously has met with only partial success. although the lift and pitching moment data have usually been acceptable, the drag data have varied by as much as an order or magnitude from previous reference data. To investigate the parameters...

Topics: DTIC Archive, Treaster,A L, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB,...

Bent trailing edges and erosion, which are often observed on marine propellers, are attributed mainly to unsteady cavitation caused by the nonuniformity of flow field behind ship's hull. In order to improve the physical understanding, the formation of cloud cavitation and bubble collapse on marine propellers, a two-dimensional hydrofoil was tested at the DTNSRDC 36-inch water tunnel under pitching oscillation. The inception of cavitation, cavity growth and collapse were investigated in terms of...

Topics: DTIC Archive, Shen,Young T, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD...

The dynamic lift and drag response of a large 8 ft (2.43 m) span, aspect ratio 6 hydrofoil operating in regular waves was experimentally determined for a range of chord Froude numbers varying from 1.22 to 3.66. The amplitude of the fundamental frequency lift response was found to increase significantly with decreasing chord Froude number, while the second harmonic lift response was zero. The amplitude of the first and second harmonic drag response also varied with chord Froud number. The first...

Topics: DTIC Archive, Karafiath,Gabor, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

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Jun 21, 2010
06/10

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Topics: ANNOTATIONS, OPERATIONS RESEARCH, PRESSURE DISTRIBUTION, HYDROFOILS, ABSTRACTS, AERODYNAMICS,...

A method is disclosed for controlling the dispersion of effluents in a flowing liquid. A vortex generator for creating a distinct recirculating vortical flow is disposed in a flowing liquid and effluents are discharged into the vortical flow. The effluents are entrained in the vortical flow and by selectively positioning the vortex generator the dispersion of the entrained effluents can be controlled.

Topics: NASA Technical Reports Server (NTRS), EFFLUENTS, FLUID FLOW, VORTEX GENERATORS, DISPERSING,...

Lift and drag data were obtained by the David W. Taylor Naval Ship Research and Development Center (DTNSRDC) for two NACA foil shapes geometrically similar to the forward foil system of the PCH hydrofoil craft. The NACA foil shapes were the 16-309 (presently used on PCH) and a modified 64A309 section. Information was obtained for flap angles up to 17.5 degrees and pitch angles up to 12 degrees. There was good agreement between similar measurements made in the High-Speed Tow Facility and in the...

Topics: DTIC Archive, Layne,Douglas E, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

The test handbook is concerned with the tests of the LVW, LVH1, LVH2, ARCK, the LVK and their successors all of which can exceed a speed of 25 knots.

Topics: DTIC Archive, SELWOOD RESEARCH INC KENSINGTON MD, *AMPHIBIOUS VEHICLES, *HYDROFOILS, HANDBOOKS,...

Experimental results obtained at high Froude number for a series of NACA 4 digit airfoil section surface-piercing struts show that the spray drag is essentially independent of operating Froude number and strut leading edge radius. The spray drag increases with strut thickness ratio and can be as much as 40% of the strut profile drag for typical operating conditions.

Topics: DTIC Archive, Savitsky, Daniel, STEVENS INST OF TECH HOBOKEN NJ DAVIDSON LAB, *DRAG, *HYDROFOILS,...

A WPB hydrofoil (WPB-H) feasibility design to meet specific U.S. Coast Guard requirements was developed. This report contains the technical details and conceptual drawings of the WPB-H design. Included are a description of the physical characteristics with a weight breakdown, in addition to engineering and operational characteristics. This baseline, 35-knot fully submerged hydrofoil at a full load weight of 137 L tons, satisfies the 5-day USCG mission requirement at a 30 knot foilborne cruise...

Topics: DTIC Archive, King, J H, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD SHIP...

Historically, two-dimensional airfoil or hydrofoil section characteristics have been obtained by measuring individually the lift, drag and pitching moment by the most accurate technique available. The use of force balances to measure the three quantities simultaneously has met with only partial success. Although the lift and pitching moment data have usually been acceptable, the drag data have varied by as much as an order of magnitude from the accepted NACA reference data. To investigate the...

Topics: DTIC Archive, Treaster,A L, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *DATA...

This paper is a summary of some possible advances in the naval architecture of fast surface warships, as forecast for a recent NATO Long-Term Scientific Study. The forecasts cover resistance and propulsion, seakeeping, stability and control, materials and structures, and power plants, considering both conventional and unconventional hull types. They do not address any aspect of the combat systems or other outfit installed. On the basis of these forecasts, the potential of promising types of...

Topics: DTIC Archive, Eames, Michael C, DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA),...

Historically, two-dimensional airfoil or hydrofoil section characteristics have been obtained by measuring individually the lift, drag and pitching moment by the most accurate technique available. The use of force balances to measure the three quantities simultaneously has met with only partial success. Although the lift and pitching moment data have usually been acceptable, the drag data have varied by as much as an order of magnitude from the accepted NACA reference data. To investigate the...

Topics: DTIC Archive, Treaster,A L, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *DATA...

Topics: DTIC Archive, JEWELL, D A, DAVID TAYLOR MODEL BASIN WASHINGTON DC, *HYDRODYNAMICS, *HYDROFOILS,...

At the start of this research effort, extensive numerical computations with Navier-Stokes equations for marine propulsors were not routinely conducted anywhere. Now with the advent of much improved computer resources, these computations are carried out regularly to study the complex flow fields, to improve existing designs, and to guide new designs. Looking ahead, computational modeling of marine propulsors has turned a new page. More efficient, more reliable and more robust N-S solvers with...

Topics: DTIC Archive, Merkle, Charles L., PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF MECHANICAL...

Topics: DTIC Archive, Street, Robert L, STANFORD UNIV CA, *FLUID FLOW, *HYDROFOILS, *CAVITATION, VORTICES,...

The two-dimensional flow under a free surface with non-zero cavitation number is considered using a point drag cavity model. The drag coefficients obtained in closed form as a function of the cavitation number and the curvature at the cavity end (or nose), but not explicitly of the depth. The thickness-length ratio of the cavity is calculated numerically and compared with the case of an elliptic cylinder under a free surface. The three-dimensional effect on the cavity is also considered by the...

Topics: DTIC Archive, Yim, B, HYDRONAUTICS INC LAUREL MD, *CAVITATION, *HYDROFOILS, VELOCITY, INTEGRALS,...

This test program was conducted to measure the hydrodynamic characteristics of a series of supercavitating and transcavitating hydrofoil models with various planforms and sections to provide a design procedure to predict hydrodynamic characteristics for this type hydrofoil. Twenty hydrofoil models were tested in the Grumman Whirling Tank at three depths and at a sufficient number of speeds and angles of attack to fully define their hydrodynamic characteristics. Lift, drag, pitching moment, and...

Topics: DTIC Archive, Wright, H. R., GRUMMAN AIRCRAFT ENGINEERING CORP BETHPAGE NY, *HYDROFOILS, MODEL...

Historically, two-dimensional airfoil or hydrofoil section characteristics have been obtained by measuring individually the lift, drag and pitching moment by the most accurate technique available. The use of force balances to measure the three quantities simultaneously has met with only partial success. Although the lift and pitching moment data have usually been acceptable, the drag data have varied by as much as an order of magnitude from the accepted NACA reference data. To investigate the...

Topics: DTIC Archive, Treaster,A L, PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB, *DATA...

The leading edge modified hydrofoils generally create lift equal to or greater than their baseline counterparts at higher angles of attack (beyond the baseline stall angle) whereas at lower angles of attack the baseline models produce lift coefficients equal to or greater than the modified models. The drag coefficients of all modified hydrofoils are either equal to or greater than their baseline counterparts. The relative increase in drag associated with the leading edge protuberances, in turn,...

Topics: DTIC Archive, CALIFORNIA STATE UNIV NORTHRIDGE DEPT OF MECHANICAL ENGINEERING, *HYDROFOILS,...

Results of an analytical investigation of the cavitation properties of modified marine propeller-type hydrofoils are presented. In particular, dependence of the critical cavitation number and the cavitation-free, angle-of- incidence range on changes in the leading-edge thickness is determined. It is shown that within a narrow range of changes of leading-edge thickness, a delay in inception is possible, depending on the design problem under consideration. An increase in critical inception speed,...

Topics: DTIC Archive, Valentine, Daniel T, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER...

Measurements are described of noise from cavitating flow over hydrofoils. The experiments were performed in a variable pressure water tunnel that was acoustically calibrated so that sound power levels could be deduced from the sound measurements. It was partially reverberant in the frequency range of interest. Cavitation was generated on the low-pressure side of a hydrofoil in the presence of a separated laminar boundary layer on the one hand and of a fully turbulent attached boundary layer on...

Topics: DTIC Archive, Blake,William K, Wolpert,Melvin J , III, Geib,Frank E , Jr, Wang,Henry T, DAVID W...

In modern machinery, a major cause of unscheduled downtime is the wear and eventual failure of load carrying components such as shafts, gears, and bearings. These wear and fatigue failures precipitate wear particles such as metal fragments, shavings, and chips. The mechanisms involved in the formation of wear particles, if understood, would lead to an optimization of the failure prediction method. A potentially important mechanism of wear is the application and release of a local high pressure...

Topics: DTIC Archive, Hickman,Scott E, DAEDALEAN ASSOCIATES INC WOODBINE MD, *SPHERES, *EROSION,...

The primary objective of this work was to demonstrate the feasibility of a new oil control/recovery system concept in a fast current environment. This system consists of two basic components, the control function (a vented hydrofoil) and a recovery function (a rotating belt of polyurethane foam). The system is operated in the following manner: A thin layer of oil and water is separated by and passes over the top of the lead hydrofoil. A large portion of the remaining water in the oil/water...

Topics: DTIC Archive, Trentacoste, Nicholas P, SCIENCE APPLICATIONS INC MCLEAN VA, *BELTS, *HYDROFOILS,...

A flutter theory based on modified Yates hydrodynamic loading was used to predict the flutter characteristics of five hydrofoil flutter models. Theoretical flutter speeds were noted when flutter was predicted to occur in a predominantly bending mode and when flutter was predicted to occur in a predominantly torsional mode. The theory may be useful for hydrofoils which are susceptible to flutter in a torsional mode.

Topics: DTIC Archive, Liu, Yuan-Ning, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

Leading edge flutter is a problem that is unique to a supercavitating hydrofoil. At high speed, the leading edge portion has been observed to oscillate while the trailing edge remains motionless. In this study, several flat plate hydrofoils were tested. The experimental results indicate that the phenomenon is a complex function of speed, angle of attack, cavitation number and mass ratio. Leading edge flutter was also observed to cause cavity pinching. A theoretical study was also conducted. Two...

Topics: DTIC Archive, Oey,Kiam Thian, CALIFORNIA INST OF TECH PASADENA, *FLUTTER, *HYDROFOILS, VELOCITY,...

Cetaceans (whales, dolphins and porpoises) have evolved flippers that aid in effective locomotion through their aquatic environments. Differing evolutionary pressures upon cetaceans, including hunting and feeding requirements, and other factors such as animal mass and size have resulted in flippers that are unique among each species. Cetacean flippers may be viewed as being analogous to modern engineered hydrofoils, which have hydrodynamic properties such as lift coefficient, drag coefficient...

Topics: DTIC Archive, DUKE UNIV DURHAM NC DEPT OF MECHANICAL ENGINEERING AND MATERIALS SCIENCE, *FLIPPERS,...

The compressible hydrodynamic approach previously developed for small Mach number non-cavitating flows has been extended to simulate cavitating flows as well as non-cavitating flows. The extension is made possible by assuming a complex equation of state relating density and pressure to cover the liquid phase and the gas phase. Thus, the cavitation phenomenon is regarded as a single-phase flow phenomenon enabling the elimination of the cavity closure condition. The numerical model is an unsteady...

Topics: DTIC Archive, Song, Charles C., MINNESOTA UNIV MINNEAPOLIS ST ANTHONY FALLS HYDRAULIC LAB,...

Some new calculations of the flutter speed of the fully submerged subcavitating hydrofoil model are presented. Variations in lift curve slope and in center of pressure location are found to have a most profound influence on both flutter speed and frequency. When variations in these parameters are combined with a relaxation of the Kutta condition (proposed previously), excellent agreement with the measured flutter speed is obtained.

Topics: DTIC Archive, Chu, Wen-Hwa, SOUTHWEST RESEARCH INST SAN ANTONIO TX, *FLUTTER, *HYDROFOILS,...

The phenomenon of cavity resonance is explained as an interaction between the flow of the surrounding liquid and the compression and expansion of the contained gas. The general solution to the linearized problem of a symmetrical forebody performing symmetrical, harmonic motion, in an infinite medium, with a cavity pressure which is varying hermonically, is presented. The phenomenon of cavity resonance behind a stationary slender wedge in an infinite medium is studied in detail; the results show...

Topics: DTIC Archive, HSU, C C, HYDRONAUTICS INC LAUREL MD, *RESONANCE, *CAVITATION, *FLUID FLOW,...

An improved computerized technique has been used to analyze nonstationary cavitation noise from an oscillating hydrofoil. Combined analog and digital signal processing procedures were developed that use ensemble averaging techniques to quantify the average sound pressure variance as a function of the foil's angle of attack. The averages provide a quantitative basis for comparing cavitation noise produced by this hydrofoil under a finite spectrum of specific test conditions. (Author)

Topics: DTIC Archive, Pierce,Robert D, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA...

This document is intended to determine properties of acoustic signals, signal processing and display techniques, and terminal decision procedures which can be used effectively to detect and classify active sonar contacts. To provide in technical reports or as system design assistance, the bases for improved detection and classification techniques in operational systems. Improvements in sonar detection and classification require search for better signal inforamtion and for ways to make more...

Topics: DTIC Archive, Stradling,Cornell S, NAVAL UNDERSEA WARFARE CENTER SAN DIEGO CALIF, *SIGNAL...

This report presents the results of an investigation of the application of numerically-generated boundary-fitted curvilinear coordinate systems in the finite-difference solution of the time-dependent, two-dimensional Navier-Stokes equations for the laminar viscous flow about hydrofoils moving either submerged at a finite depth or in a free surface of a fluid of infinite depth. The hydrofoil may be of arbitrary shape, and its motion may include pitching oscillation or oscillation normal or...

Topics: DTIC Archive, Thompson,Joe F, MISSISSIPPI STATE UNIV MISSISSIPPI STATE ENGINEERING INDUSTRIAL...

Using linear theory, expressions for lift, drag and moments are obtained for hydrofoil operating near the free surface and under transverse gravity. Existing results are easily obtainable for special cases when gravity is neglected, and/or depth below the free surface approaches infinity. Numerical calculations are performed and results are shown by figures. (Author)

Topics: DTIC Archive, Bakhshi,V S, VIRGINIA STATE COLL PETERSBURG DEPT OF MATHEMATICS, *HYDRODYNAMICS,...

This report presents the results of a study to determine the performance and physical characteristics of an ac electrical system intended for use as the propulsion system of large hydrofoils. Section I provides a technical description of the system in terms of performance, weight and component characteristics. Section II describes anticipated problems associated with development of the system and its components, and includes activities through design and fabrication, and qualification of an...

Topics: DTIC Archive, AIRESEARCH MFG CO OF CALIFORNIA TORRANCE, *PROPULSION SYSTEMS, *ELECTRIC GENERATORS,...

A conceptual design study of a flapped, supercavitating foil has been performed in order to assess the structural feasibility of a configuration otherwise acceptable from a hydrodynamic point of view. Consideration has also been given to the design of a single, steerable strut as a supporting member for the foil. The study includes the establishment of a limit load criteria for structural design, a survey of hydrodynamic loading data for supercavitating struts and foils, calculation of design...

Topics: DTIC Archive, Hoyt,Edgar D, DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD,...

Based on potential flow theory, a formulation is given for three-dimensional fully cavitating flow with a Riabouchinsky model. The model is nonlinear and the location of the free surface of the cavity is not known priori. Therefore, an iterative procedure is used to locate the free surface boundary. The employment of a trial-free-boundary approach effectively reduces the fully nonlinear model to a linear one, and the solution at each iteration is obtained by means of the finite element method...

Topics: DTIC Archive, Ko,Peter Y, STANFORD UNIV CALIF DEPT OF CIVIL ENGINEERING, *TURBULENT FLOW,...

A linearized theory for the unsteady motion of a partially cavitated flat hydrofoil in two dimensions is carried out. A second linearization procedure is used, based on ideas of Timman and Guerst, to obtain the unsteady pressure distribution around the hydrofoil and the resulting force and moment, as functions of the cavitation number and Strouhal number for given pitch and/or heave.

Topics: DTIC Archive, Steinberg, Herbert, CONTROL DATA CORP MELVILLE NY TRG DIV, *HYDROFOILS, *CAVITATION,...