Download or read book Cavitation investigations at one family of NACA hydrofoils at different angles of attack as a contribution to the clarification of scale effects at cavitation inception written by A.P. Keller and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Friction Factors in Alluvial Rivers written by Mehmet Selim Yalin and published by . This book was released on 1988 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theoretical and Experimental Investigation of Supercavitating Hydrofoils Operating Near the Free Water Surface written by Virgil E. Johnson and published by . This book was released on 1961 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Boundary layer Development on Cavitation Noise and Inception on a Hydrofoil written by and published by . This book was released on 1976 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigation of Aspect ratio 1 Supercavitating Hydrofoils at Speeds Up to 185 Feet Per Second written by Kenneth W. Christopher and published by . This book was released on 1960 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theoretical and Experimental Investigation of Arbitrary Aspect Ratio Supercavitating Hydrofoils Operating Near the Free Water Surface written by Virgil E. Johnson and published by . This book was released on 1957 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The existing two-dimensional theory for the characteristics of supercavitating hydrofoils operating at zero cavitation number is modified to include the effects of camber, aspect ratio, and depth of submersion. For a comparison with the theory, two aspect-ratio-1 hydrofoils, a flat plate and one with a cambered lower surface, were tested by operating them near the water surface so that their upper surfaces were completely ventilated. The data obtained verified the theory to within 3 percent. Some experimental data are also presented for the models operating at nonzero cavitation number for both air and water-vapor-filled cavities.
Download or read book Cavitating Flow Over Stationary and Oscillating Hydrofoils written by and published by . This book was released on 2008 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern ships are usually designed for a broad range of sea conditions. In particular, much of the effort during ship design is focused on reduction of ship roll due to rough sea. Ship roll has always been of significant concern as it largely affects the ship performance. In order to mitigate the detrimental effects of ship roll, many kinds of ship stabilization systems have been tried and tested. One such system that is currently investigated in this work is the active-fin ship stabilization system. It consists of a system of dynamically oscillating hydrofoils, responding to cancel ship roll by producing counter acting lift. Below the dynamic stall angle, the lift force produced by hydrofoils is proportional to angle of attack. So ship stabilization systems are often operated between large angles of attack. However, at large angle of attack, a region of low pressure forms over the suction side of the hydrofoil. The low pressure results in localized increase in cavitation. Cavitation affects the performance of fin stabilization systems, and it is therefore necessary to study and understand the flow physics involving cavitation, occurring over on oscillating fin stabilizers. In this study, the active fin stabilization system is simplified to a 2D NACA0015 hydrofoil geometry, and the aperiodic fin oscillation is simplified to a periodic hydrofoil oscillation and, to stay close to reality, a near trapezoidal hydrofoil oscillation profile is used. The present work is a contribution to the numerical simulation of cavitating flows over 2D NACA 0015 stationary and oscillating hydrofoils. The primary objective of this research is to establish a methodology to accurately identify the onset of cavitation, and to study and quantify the deleterious effects of cavitation on performance. In order to investigate and quantify the detrimental effects of cavitation on the present ship stabilization system, the commercial flow solver FLUENT v6.3 is employed. A detailed formulation of the numerical model is described, and its application to simulate cavitating flow over stationary and oscillating 2D NACA 0015 hydrofoils is demonstrated. Validation studies for the turbulence viscosity modifications for the RNG k epsilon equation have been presented. For both the stationary and oscillating cases, good agreement between the predictions and measurements is obtained. Simulation of cavitating flow over stationary hydrofoils is carried out, to understand the different steady and unsteady cavitating regimes, and to identify an approximate cavitation inception angle. The scillating hydrofoil analysis is carried out using a dynamic hybrid grid where the boundaries of the outer domain are fixed, and the hydrofoil and the inner domain surrounding the hydrofoil oscillate periodically according to a prescribed profile non sinusoidal. A user defined function (UDF) is coupled with the flow solver to oscillate the hydrofoil with its prescribed oscillation profile. A comparative study on effects of grid topology, flow regime and cavitation has been carried out at 5 Reynolds numbers.
Download or read book Theoretical Determination of Low drag Supercavitating Hydrofoils and Their Two dimensional Characteristics at Zero Cavitation Number written by Virgil E. Johnson and published by . This book was released on 1957 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Two new low-drag hydrofoils for operation at zero cavitation number are derived by the application of the Tulin-Burkart linearized theory. The two-dimensional lift-drag ratios of these two hydrofoils operating at design angle of attack are shown to be, theoretically, about 45 and 80 percent greater than the Tulin-Burkart configuration. A simplified calculation of the location of the upper cavity streamline for arbitrary configurations is also presented.
Download or read book Experimental Investigation of Two Low drag Supercavitating Hydrofoils at Speeds Up to 200 Feet Per Second written by Kenneth W. Christopher and published by . This book was released on 1960 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effects of Surface Roughness on Cavitation Inception Speeds of a Hydrofoil written by William G. Souders and published by . This book was released on 1968 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Methods recently derived for the prediction of cavitation inception velocities over isolated roughnesses on arbitrary hydrodynamic bodies were applied to an NACA 16 series hydrofoil section. The required foil pressure distribution and boundary layer growth are calculated theoretically. The results present the minimum or critical height of several types of roughness elements which would produce cavitation inception as a function of foil station, speed, angle of attack, and submergence depth. The results show the deteriorating effect of various roughness geometries on the cavitation inception speed and indicate the necessity for rigid tolerances in the design, fabrication, and maintenance of hydrofoil surfaces. (Author).
Download or read book Scale Effects in Cavitating Flow written by Blaine Raphael Parkin and published by . This book was released on 1951 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Boundary Layer Development on Cavitation Noise and Inception on a Hydrofoil written by and published by . This book was released on 1976 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 the other. The turbulent boundary layer was formed downstream of a trip, which was positioned near the leading edge. High-speed photographs show patterns of cavitation obtained in each case. Cavitation was also generated on the high-pressure side at negative angles of attack. The noise is shown to depend on the type of cavitation produced; for each type, dependence on speed and cavitation index has been determined. (Author).
Download or read book Cavitation Inception Scale Effects 1 Nuclei Distributions in Natural Waters 2 Cavitation Inception in a Turbulent Shear Flow written by Timothy J. O'Hern and published by . This book was released on 1987 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental investigations were made into the two major aspects of cavitation scale effects, susceptibility of the water to cavitation and flow field effects. In situ investigations of marine cavitation nuclei populations were made using underwater holography. Relatively high bubble concentrations during calm sea conditions, and their population inversion below the thermocline where organism activity was high, indicate a possible biological source of bubble production. Measured bubble sizes can be used to indicate that the average tensile strength of the ocean waters examined should be on the order of several thousands Pascals, with a minimum expected value of about one hundred Pascals. A concentration of at least 3 bubbles per cu cm in the 5 to 20 micrometers radius range is needed in test facility water to model marine conditions. The inception processes in a turbulent free shear layer were examined at Reynolds numbers up to 2 million. Two distinct types of vortex motion were evident, the primary spanwise and the secondary longitudinal vortices. Cavitation inception occurs in the secondary shear layer vortices and more fully developed cavitation is visible in both structures. A Rankine vortex model indicates that the secondary vortex strength is less than 10% of that of the primary structure.
Download or read book Measurement of Cavity Shapes Above Ventilated Hydrofoils written by R. J. Altmann and published by . This book was released on 1965 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent test programs indicate that theoretical streamlines above a supercavitating hydrofoil may be considerably higher than those actually generated. To check theoretical predictions a three-dimensional traversing probe was constructed and used to map the upper cavity surfaces generated by two different two-dimensional hydrofoils. Experimental contours were found to fall below those predicted by theory at all angles of attack and depths of submergence tested. The rate of change of cavity ordinates with changes in angle of attack or depth of submergence is about the same as that predicted by theory. The contribution of angle of attack to cavity shape is responsible for the greater part of the difference between theoretical and measured cavity shapes. (Author).
Download or read book Initial Investigation of Stationary Hydrofoil Cavitation and Cavitation Noise Scaling written by D. E. Thompson and published by . This book was released on 1977 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of experiments were conducted in order to determine scaling laws for sheet type surface cavitation and the resulting noise. Four geometrically similar 10.6 percent thick symmetrical Joukowski hydrofoils with chord lengths of 1.5, 3, 6, and 12 inches were tested. Pressure distributions on the two largest hydrofoils were measured at several angles of attack. All noise measurements were made at an attack angle of 70 to produce the desired sheet cavitation. Desinent cavitation numbers were obtained as a function of velocity for each hydrofoil at several angles of attack. The noise resulting from various amounts of cavitation on each hydrofoil was measured. The amount of cavitation was determined by the ratio of cavity length (L) to chord length (c). The relative length (L/c) was varied from zero to one-third. Noise measurements included directivity patterns and spectra. The variation of cavitation noise with cavitation number, velocity, and Reynolds number was determined. (Author).
Download or read book Experimental and Theoretical Investigation of Cavitation in Water written by J. Ackeret and published by . This book was released on 1936 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigations of Three dimensional Effects on Cavitating Hydrofoils written by Robert W. Kermeen and published by . This book was released on 1960 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
