An Experimental Investigation Into the Effects of Turbulence on Vortex Shedding PDF Download

Author: Richard W. Nanes
Publisher:
ISBN:
Category :
Languages : en
Pages : 106

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 65

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An experimental investigation of the effects of Mach number and Reynolds number on the side forces induced on a slender body of revolution at high angles of attack was conducted. The tests were carried out in the Air Force Flight Dynamics Laboratory's Trisonic Gasdynamic Facility.

Author: Peter J. Brown
Publisher:
ISBN: 9781423510697
Category :
Languages : en
Pages : 105

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An investigation of vortex shedding downstream of a cascade of second-generation, controlled-diffusion, compressor stator blades, at off-design inlet-flow angles of 31, 33 and 35 degrees and Reynolds numbers, based on chord length, of 280,000, 380,000 and 640,000 is reported. The objective of the study was to characterize the flow and shedding through various complementary methods. Blade surface pressure measurements were taken from a fully instrumented blade, and distributions of pressure coefficients were determined. Five-hole probe wake surveys were performed at midspan, and the total pressure loss coefficients and axial velocity ratios were calculated. Upstream inlet-flow angle was set, and further characterized through two-component laser- Doppler velocimetry (LDV). Hot-wire anemometry measurements were performed at midspan, in the wake, and the reduced data were compared with two-component LDV surveys of the same regions. Plots of hot-wire vs. LDV turbulence data are reported in addition to power spectra documenting the shedding events. Vortex shedding was determined to be a leading edge phenomenon as periodic shedding was only detected on the pressure side of the wake. The frequency and magnitude of shedding were found to be independent of incidence angle, and to increase with Reynolds number at constant incidence angle. The Strouhal number, based on leading edge diameter, was found to be in the range of 0.23-0.26, which is comparable to that of vortex shedding behind a circular cylinder in the Reynolds number range tested.

Author: Alexander Vladimir Lisin
Publisher:
ISBN:
Category : Boundary layer
Languages : en
Pages : 164

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Author: Jerome Francis Jaminet
Publisher:
ISBN:
Category : Cylinders
Languages : en
Pages : 110

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Vortex shedding has been identified as a potential major source of loading on the Ocean Thermal Energy Conversion (OTEC) Plant Cold Water Pipe (CWP). To gain a better understanding of the vortex shedding phenomena, a series of model tests has been conducted. The results of this investigation are presented. The effects of current shear on vortex shedding patterns in high Reynolds number (R/sub e/) flow around a circular cylinder used to model the OTEC CWP are addressed. Tests were conducted in a wind tunnel on a 56-inch long, 6-inch diameter circular cylinder for various flow and shear conditions. Measurements were conducted to describe the frequencies of the eddies shed from the cylinder and to investigate the fluctuating surface pressure on the cylinder. From these tests it was determined that shedding for high R/sub e/ sheared flow is characterized by the formation of distinct cells of eddies with constant frequency, that pressure fluctuations on the surface of the cylinder are greater for sheared flow than unsheared flow, and that the mean surface pressures are generally independent of the magnitude of shear.

Author: Jeffry William Ely
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 290

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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721940462
Category :
Languages : en
Pages : 254

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Experimental results from a study of the effects of passing wakes upon laminar-to-turbulent transition in a low-pressure turbine passage are presented. The test section geometry is designed to simulate the effects of unsteady wakes resulting from rotor-stator interaction upon laminar-to-turbulent transition in turbine blade boundary layers and separated flow regions over suction surfaces. Single-wire, thermal anemometry techniques were used to measure time-resolved and phase-averaged, wall-normal profiles of velocity, turbulence intensity, and intermittency at multiple streamwise locations over the turbine airfoil suction surface. These data are compared to steady state, wake-free data collected in the same geometry to identify the effects of wakes upon laminar-to-turbulent transition. Results are presented for flows with a Reynolds number based on suction surface length and exit velocity of 50,000 and an approach flow turbulence intensity of 2.5 percent. From these data, the effects of passing wakes and associated increased turbulence levels and varying pressure gradients on transition and separation in the near-wall flow are presented. The results show that the wakes affect transition both by virtue of their difference in turbulence level from that of the free-stream but also by virtue of their velocity deficit relative to the freestream velocity, and the concomitant change in angle of attack and temporal pressure gradients. The results of this study seem to support the theory that bypass transition is a response of the near-wall viscous layer to pressure fluctuations imposed upon it from the free-stream flow. The data also show a significant lag between when the wake is present over the surface and when transition begins. The accompanying CD-ROM includes tabulated data, animations, higher resolution plots, and an electronic copy of this report. Kaszeta, Richard W. and Simon, Terrence W. and Ashpis, David (Technical Monitor) Glenn Research Center NCC3-652; RTOP 71

Author: Victor Zakkay
Publisher:
ISBN:
Category : Turbulent boundary layer
Languages : en
Pages : 52

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Author: Sammy Khalil
Publisher:
ISBN:
Category : Axial flow
Languages : en
Pages : 598

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