Experiments on Turbulent Flow Through Channels Having Porous Rough Surfaces With or Without Air Injection
Abstract
Transpiration cooling, obtained by injecting a coolant through a porous surface, is receiving increased consideration as an effective means of maintaining walls exposed to a hot gas stream at temperatures that can be tolerated by the material. Applications for which this cooling method is considered are the cooling of different structural elements such as turbine blades or the walls of combustion chambers in jet engines and parts of the skin of missiles. In some of these applications the surf ace roughness inherently connected with a porous material may exceed the limit for which such a surface is considered as hydraulically smooth. In order to obtain information on friction and flow characteristics of rough surfaces under the condition of fluid injection, an investigation with turbulent air flow was made in a rectangular channel. Provisions were made so that porous samples with varying degrees of roughness could be installed in the lower wall. Velocity profiles and friction factors for these surfaces are presented for ratios of air-injection velocity to mainstream velocity ranging from 0 to approximately 0.0170. For zero injection velocity the friction data compared favorably with available data on impermeable rough surfaces. It was found that the shape of the velocity profile is decidedly influenced by the fluid injection. The results also indicate in a qualitative manner the expected decrease in friction with increase in fluid injection.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1955
- Accession Number
- ADA377051
Entities
People
- Anthony J. Diaguila
- E. R. Eckert
- Patrick L. Donoughe
Organizations
- National Aeronautics and Space Administration