Some Features of Tip Gap Flow Fields of a Linear Compressor Cascade
Abstract
This report presents results from an experimental study of three-dimensional turbulent tip gap flows in the linear cascade wind tunnel for two different tip gap clearances (t/c=1.65% and 3.3%). Three experimental techniques are used to measure the tip gap velocity field and static pressure field on the end-wall: a three-orthogonal-velocity-component fiber-optic laser Doppler anemometer (3D-LDA) system, surface oil flow visualization and a scani-valve pressure measurement system. The end-wall skin friction velocity is calculated from near-wall LDA data and pressure gradient data using the near-wall momentum equation. The statistics of Reynolds stresses and triple products in the two-dimensional turbulent boundary layer and three-dimensional turbulent boundary layer were examined using a velocity fluctuation octant analysis. The octant analysis for the two-dimensional turbulent boundary layer reveals that ejections and sweeps are the dominant coherent motions. The octant analysis for the three-dimensional turbulent boundary layer in the tip gap shows that the dominant octant events are partially different from those in the two-dimensional turbulent boundary layer, but ejections and sweeps are still the dominant coherent motions. For the three-dimensional turbulent boundary layer in the moving wall flow, the near-wall shear flow reinforces the sweep motion to the moving wall and weakens the outward ejection motion in the shear flow dominant region. Between the passage flow and the shear flow is the interaction region of the high speed streaks and the low speed streaks. This is the first time that the coherent structure of the three-dimensional turbulent boundary in the linear cascade tip gap has been studied.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 15, 2003
- Accession Number
- ADA419469
Entities
People
- Qing Tian
- Roger L. Simpson
Organizations
- Virginia Tech