Turbulent Flow Characteristics in an S-Shaped Diffusing Duct,
Abstract
Velocity characteristics of the flow in a round cross-sectional S-shaped shaped diffusing duct with an offset of 0.3 of the length (axial) of the duct were measured, using laser-Doppler anemometry and refractive index matching technique, with two inlet boundary layer thicknesses, corresponding to 0.5 and 0.2 of the inlet duct diameter at a fixed Reynolds number of 40,000. The duct had inlet and exit diameters of 48 mm and 56.8 mm respectively, a length of 170.4 mm and an offset between the centre-line of the inlet and exit of 51.1 mm and the dimensions corresponded to a scaled model of the Royal Aerospace Establishment 2129 duct used for jet aircraft initiates. The previously speculated incipient separation regions were confirmed and found to be larger with the thinner inlet boundary layer and, as a consequence, the exit mean flow distribution consisted of a large pair of contra-rotating vortices occupying almost half of the cross-section, with maximum second mean velocity 20% or the inlet bulk velocity, compared to a third of the cross-section in the thicker inlet boundary layer and with maximum secondary mean velocity 15% of the inlet bulk velocity. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 23, 1992
- Accession Number
- ADP008919
Entities
People
- J. H. Whitelaw
- S. C. Yu
Organizations
- Imperial College London