Visualization Study of Turbulent Spots.
Abstract
An investigation of turbulent spots evolving in a laminar boundary layer has been conducted during the period 1 May 1978 - 30 April 1980. A flat plate was towed through an 18 m water channel. The plate was mounted under a carriage that was towed at a constant velocity. The carriage rides on a continuously replenished oil film giving a vibrationless tow. Turbulent spots were initiated by a solenoid valve that ejected a small amount of water through a hole located downstream from the leading edge. A novel visualization technique has been employed that utilizes fluorescent dye excited by a sheet of laser. Some aspects of entrainment and structure of turbulent spots were inferred from the present experiments. In particular, the present results strongly suggest that another mechanism, in addition to entrainment, is needed to explain the lateral growth characteristics of the turbulent zone defining the spot. This mechanism, termed growth by destabilization', appears to be a result of the turbulence in the spot destabilizing the unstable laminar boundary layer in the neighborhood of the spot. Two additional tasks were carried out as part of this investigation. The first, a theoretical study of three-dimensional wave packets; and the second an investigation of the effects of drag reducing polymers and stratification on turbulent spots. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1980
- Accession Number
- ADA086831
Entities
People
- James J. Riley
- Mohamed Gad-el-hak