The predictability of skin-friction line topology on a rolled delta wing

The aim of the present study is to evaluate the efficiency of a boundary layer suction technique in case of a centrifugal compressor stage in order to extend its stable operating range. First, an analysis of the flow pattern within the radial vaned diffuser is presented. It highlights the stall of the diffuser vanes when reaching a low massflow. A boundary layer separation in the hub-suction side corner grows when decreasing the massflow from the nominal operating point to the surge and finally leads to a massive stall. An aspiration strategy is investigated in order to control the stall. The suction slot is put in the vicinity of the saddle that originates the main separating skin-friction line, identified thanks to the analysis of the skin-friction pattern. Several aspiration massflow rates are tested, and two different modelings of the aspiration are evaluated. Finally, an efficient control is reached with a removal of only 0,1% of the global massflow and leads—from a steady-state calculations point of view—to an increase by 40% of the compressor operating range extent.

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Study on delta wing skin friction measurement based on liquid crystal coatings in hypersonic wind tunnel

33rd AIAA Aerodynamic Measurement Technology and Ground Testing Conference ◽

10.2514/6.2017-3736 ◽

2017 ◽

Author(s):

Xing Chen ◽

Shuai Wen ◽

Junjie Pan ◽

Dapeng Yao

Keyword(s):

Liquid Crystal ◽

Wind Tunnel ◽

Skin Friction ◽

Delta Wing ◽

Friction Measurement ◽

Hypersonic Wind Tunnel ◽

Wing Skin

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Skin Friction Fields and Surface Dye Patterns on Delta Wings in Water Flows

Journal of Fluids Engineering ◽

10.1115/1.4030041 ◽

2015 ◽

Vol 137 (7) ◽

Cited By ~ 6

Author(s):

Tianshu Liu ◽

M. H. M. Makhmalbaf ◽

RS Vewen Ramasamy ◽

S. Kode ◽

P. Merati

Keyword(s):

Optical Flow ◽

Skin Friction ◽

Delta Wing ◽

Flow Equation ◽

Delta Wings ◽

Error Sources ◽

Water Flows ◽

Image Velocimetry ◽

Intensity Images ◽

The Relationship

This paper discusses the relationship between skin friction fields and surface dye patterns in surface luminescent dye visualizations in water flows, providing a theoretical foundation for extraction of high-resolution skin friction fields. The limiting form of the mass diffusion equation at a wall is recast as an optical flow equation connecting skin friction with the luminescent dye intensity. Snapshot solutions are obtained from a time sequence of luminescent intensity images by solving the optical flow equation via the variational method, and then a normalized skin friction field is reconstructed by averaging the snapshot solutions. An error analysis is given to identify the major error sources and the limitations of the technique. To evaluate the feasibility of this technique, surface luminescent dye visualizations on a 65 deg delta wing and a 76/40 deg double-delta wing are conducted in a water tunnel. The extracted skin friction topology on the delta wings and the velocity fields obtained by using particle image velocimetry (PIV) are discussed.

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