USING GROOVED SURFACES TO IMPROVE THE EFFICIENCY OF AIR INJECTION DRAG REDUCTION METHODS IN HYDRODYNAMIC FLOWS

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.

• Supplemental Notes:
  • J Ship Res, v 38 n 2, June 1994, p 133 [4 p, 8 ref, 3 fig]
• Authors:
  • Reed, J C
• Publication Date: 1994

Language

• English

Subject/Index Terms

• TRT Terms: Air injection systems; Drag; Flow visualization
• Old TRIS Terms: Air injection; Drag reduction; Grooved surfaces
• Subject Areas: Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00717480
• Record Type: Publication
• Source Agency: British Maritime Technology
• Files: TRIS
• Created Date: Mar 4 1996 12:00AM