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Unsteady Flow Characteristics in a 90 Degree Elbow Affected by Developed, Undeveloped and Swirling Inflow Conditions
- Source :
- Journal of Fluid Science and Technology, Vol 7, Iss 3, Pp 315-328 (2012)
- Publication Year :
- 2012
- Publisher :
- The Japan Society of Mechanical Engineers, 2012.
-
Abstract
- Laser Doppler Velocimetry (LDV) measurements in a 90 degree elbow of which the curvature radius coincides with its inner diameter were examined for the cases of inflow from a long pipe, short pipe and swirl generator. Ensemble averaged flow distribution at the Reynolds number of 320000 based on the inner pipe diameter and bulk velocity shows that shortening the upstream pipe length to 4.9D from 10D induces the flow separation downstream of the elbow. Detailed observation suggests that shortening upstream pipe weakens the Prandtl's secondary flow of the first kind. Our swirl generator induced a swirling inflow with the non-dimensional angular momentum of 0.12 based on the inner pipe diameter and bulk velocity. The circumferential velocity distribution formed a shape like a Rankine combined vortex at the elbow inlet, and the accelerated axial velocity was observed at the vortex center. The axial velocity distribution however was found to be almost the same as that of the non-swirl inflow case in the latter half of the elbow. Frequency analyses showed that the Strouhal number by vortex shedding from the boundary layer occurring at the inner side of the elbow become 0.5, except for 0.6 in the case of the long pipe. The change of the Strouhal number is probably related with the boundary layer width and the local flow velocity.
- Subjects :
- Fluid Flow and Transfer Processes
Technology
Science (General)
Meteorology
Mechanical Engineering
Elbow
education
flow induced vibration
swirling inflow
Inflow
Mechanics
elbow
Degree (temperature)
Unsteady flow
ldv
Q1-390
medicine.anatomical_structure
developed inflow
Vortex-induced vibration
medicine
undeveloped inflow
Geology
Subjects
Details
- Language :
- English
- ISSN :
- 18805558
- Volume :
- 7
- Issue :
- 3
- Database :
- OpenAIRE
- Journal :
- Journal of Fluid Science and Technology
- Accession number :
- edsair.doi.dedup.....0807f2c0874b63101e725eb46c985957