The Hydroelastic Behavior of Flat Plates as Influenced by Trailing Edge Geometry

The Hydroelastic Behavior of Flat Plates as Influenced by Trailing Edge Geometry PDF Author: Arthur T. Ippen
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ISBN:
Category : Hydroelasticity
Languages : en
Pages : 132

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This report presents the results of a theoretical review and an experimental investigation of the hydroelastic vibration of thin flat plates suspended at zero mean angle of attack in a fluid stream. The review indicated that recognized experimental facts such as the influence of trailing edge geometry and the three-dimensional wake structure were inadequately related to theoretical considerations about the vibration phenomenon. The experimental investigation consisted of a detailed determination of the amplitude and frequency spectra of the vibration on a number of flat test plates which were mounted in the test section of a water tunnel at zero mean angle of attack. The effects on the vibrational behavior of trailing edge geometry, geometric and elastic properties of the plate support, free stream velocity and ambient pressure have been explored experimentally. An equation of motion has been written for the test plate - torsion spring system employed. Results of a qualitative analysis of this non-linear equation are compared with the experimental results obtained.

The Hydroelastic Behavior of Flat Plates as Influenced by Trailing Edge Geometry

The Hydroelastic Behavior of Flat Plates as Influenced by Trailing Edge Geometry PDF Author: Arthur T. Ippen
Publisher:
ISBN:
Category : Hydroelasticity
Languages : en
Pages : 132

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Book Description
This report presents the results of a theoretical review and an experimental investigation of the hydroelastic vibration of thin flat plates suspended at zero mean angle of attack in a fluid stream. The review indicated that recognized experimental facts such as the influence of trailing edge geometry and the three-dimensional wake structure were inadequately related to theoretical considerations about the vibration phenomenon. The experimental investigation consisted of a detailed determination of the amplitude and frequency spectra of the vibration on a number of flat test plates which were mounted in the test section of a water tunnel at zero mean angle of attack. The effects on the vibrational behavior of trailing edge geometry, geometric and elastic properties of the plate support, free stream velocity and ambient pressure have been explored experimentally. An equation of motion has been written for the test plate - torsion spring system employed. Results of a qualitative analysis of this non-linear equation are compared with the experimental results obtained.

The Effects of Trailing Edge Geometry and Chord Length on the Early Wake of Stationary Flat Plates

The Effects of Trailing Edge Geometry and Chord Length on the Early Wake of Stationary Flat Plates PDF Author: Peter S. Eagleson
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ISBN:
Category : Reynolds number
Languages : en
Pages : 114

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This report presents the results of an investigation of the average and fluctuating two-dimensional structure of the early wake of fixed, flat plates at zero mean angle of attack as a function of trailing edge configuration and chord length. The experimental program provides for the measurement of the distribution of local mean velocity, static pressure, longitudinal velocity fluctuation and the spectral distribution of the kinetic energy of this turbulence component. The investigation was carried out in the 7-1/2" x 9" test section of an open-circuit water tunnel in the MIT Hydrodynamics Laboratory. An average free stream velocity of approximately 9.5 feet per second and plates of 1/h-inch thickness were used. All measurements were made between 1.50 and 9.75 plate thicknesses downstream of the trailing edge of the test plates, and between 0 and 2.80 plate thicknesses from the longitudinal plate centerline. Plate chord lengths used were 2" and 7". A primary aim of this study is the explanation of the vibrational behavior of the same test plates as found in a previous investigation. An attempt is made, wherever possible, to draw together the related facets of both studies. Information from both investigations is combined to infer certain characteristics of the vortex street and these characteristics are compared with those found by other investigators for bodies of various shapes. The primary conclusions to be drawn from the experiments on these particular plates are: 1. Downstream increase of wake width, for a plate of given trailing edge, is suppressed to a distance dependent upon the boundary layer thickness at the trailing edge. 2. At a plate thickness Reynolds number, It = 1.8 x 10h, transition between the inertial and viscous zones of wake development takes place at approximately x/t = 3.25. 3. With distance in the downstream direction there is an increase in the transverse spacing, h, of the discrete vortices in the wake. 4. The plate thickness Strouhal number varies with trailing edge configuration at a given Reynolds number. 5. The mean drag coefficient decreases as the trailing edge becomes more tapered. 6. The strength of the discrete vortices at a given station in the early wake becomes greater as the trailing edge becomes more tapered. 7. For a plate of given thickness and trailing edge geometry an increase in chord length reduces the frequency of vortex shedding. 8. The proportion of the total wake vorticity which is concentrated in discrete vortices increases with increasing chord length Reynolds number. 9. An increase in chord length decreases the intensity of turbulence, increases the mean velocity defect and decreases the pressure recovery at a given station in the early wake. 10. For constant chord length, the amplitude of plate vibration when pivoted at the leading edge increases with increasing vortex strength and with decreasing mean drag coefficient (both quantities determined with stationary plate). 11. Barring self-excitation of the plate motion, the frequency of plate vibration is precisely that at which discrete vorticity is shed into the wake from the stationary plate

Report

Report PDF Author: United States. National Bureau of Standards
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ISBN:
Category : Hydraulic engineering
Languages : en
Pages : 844

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DTNSRDC. PDF Author: David W. Taylor Naval Ship Research and Development Center
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Category : Shipbuilding
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Category : Hydraulic engineering
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Languages : en
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Languages : en
Pages : 840

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