HEAT TRANSPER IN COMPRESSIBLE TURBULENT BOUNDARY LAYER WITH AIR INJECTION

1970 ◽  
Author(s):  
B. P. Mironov ◽  
M.I. Smirnov ◽  
Nadezhda I. Yarygina
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Air Injection

Using Grooved Surfaces to Improve the Efficiency of Air Injection Drag Reduction Methods in Hydrodynamic Flows

1994 ◽  
Vol 38 (02) ◽  
pp. 133-136
Author(s):  
Jason C. Reed
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Drag Reduction ◽  
Channel Flow ◽  
Air Injection ◽  
Surface Coatings ◽  
Laminar Channel Flow ◽  
Reduction Methods ◽  
Low Volume ◽  
Near Wall

A summary of experiments using grooved surfaces to trap and hold (via surface tension forces) an injected airstream in a low-speed (1.25 to 5 m/s) water flow is presented. The purpose of creating a low-volume near-wall air sheet is to possibly enhance the efficiency of current air injection drag reduction methods in terms of unit gas volume per % drag reduction. Flow visualization and preliminary quantitative data are included for a laminar channel flow, a disturbed laminar channel flow, and a flat plate turbulent boundary-layer flow. A stable convecting low-volume, near-wall gas film is produced in several instances. Groove dimension and the presence of anti-wetting surface coatings are shown to greatly affect the formation and stability of the gas sheet. Deeper, narrower grooves, anti-wetting surface coatings, and shallow-angle gas injection increase the stability of the attached gas layer. Convected disturbances are shown to increase the interfacial instability of the attached sheet. It is not known if a gas sheet can be held under a turbulent boundary layer over 3 m/s, or if the groove sizes needed to do so would become too small to be of use in a practical high-speed hydrodynamic flow.

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