Estimation of flow parameters of turbulent fluctuations and vortex motions based on randomly sampled velocity data in the near wake of a circular cylinder in a steady flow
- Christian Michelsen Research AS, Bergen (Norway). Dept. of Process and Safety
Turbulent near wake flow is one of the key subjects for solving fluid dynamics-related problems in industrial practice, e.g. numerical simulation of gas explosions on offshore oil/gas production platforms. Flow velocities measured in the near-wake of bluff bodies contain information of mean flow, turbulent fluctuations and vortex motions. Flow parameters like RMS values of velocity fluctuations, Reynolds shear stresses, and auto-/spatial correlation of velocity fluctuations, derived by direct averaging of measured data, will include the total contributions of the periodic vortex motions and the random turbulent fluctuations. In the case of near-wake flows behind a cylinder at sub-critical Reynolds numbers, a vortex-street is formed in the wake and the vortex-shedding frequency is well defined. This offers a possibility for simplifying the decomposition of regular vortex motions and the random turbulent fluctuations. Velocity profiles and cross-stream spatial correlation of streamwise velocity were measured by positioning a TSI`s two-component LDA system in the region 2d to 4d downstream of a circular cylinder at Re = 35,000. The randomly sampled data were first interpolated linearly, and then re-sampled with a pertinent sampling frequency. The optimal FIR filters, designed using the Remez exchange algorithm, were applied to reject the digital signals in a narrow band around the vortex-shedding frequency. Various flow parameters associated with random turbulence were computed. The integration of the auto- and spatial correlation, obtained based on the filtered data gave a physically adequate estimation of the integral time and length scales of the turbulent fluctuations. Errors due to linear interpolation and filtering were discussed.
- OSTI ID:
- 220742
- Report Number(s):
- CONF-950793-; ISBN 0-8194-1905-2; TRN: IM9620%%136
- Resource Relation:
- Conference: 40. annual meeting of the Society of Photo-Optical Instrumentation Engineers, San Diego, CA (United States), 9-14 Jul 1995; Other Information: PBD: 1995; Related Information: Is Part Of Optical techniques in fluid, thermal, and combustion flow; Cha, S.S.; Trolinger, J.D. [eds.]; PB: 601 p.; Proceedings/SPIE, Volume 2546
- Country of Publication:
- United States
- Language:
- English
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