On the Relationship between Transitional and Fully Turbulent Shear Flow.
Abstract
Pulsating flow of air in a straight smooth pipe was investigated experimentally. The period of forcing ranged from 0.5 sec to 5 sec which resulted in the change in the non-dimensional frequency parameter alpha = r sq root of w/nu of 4.5 to 15. The introduction of periodic surging had no effect on the time mean quantities. The present data was compared in detail with the theory of Uchida (1956) in the laminar flow regime. The time dependent components at the forcing frequency were presented by the radial distribution of amplitude and phase. An integral momentum equation in a time dependent flow requires a force triangle to be maintained at any instant. The triad of forces are: pressure, inertia and shear. All terms of the force balance equation were measured independently providing a good check of data. The measured turbulent characteristics of the flow, including the RMS values of the velocity fluctuations, Reynolds stress and short-time power spectra are dependent on the phase of the forced oscillations. The radial distribution of the phase angle of velocity is qualitatively different in laminar and turbulent flows. In order to explain this difference the concept of a relaxation time of the turbulent flow was employed. Transitional flow in a boundary layer is also briefly discussed. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 31, 1981
- Accession Number
- ADA108367
Entities
People
- I. Wygnanski
Organizations
- Tel Aviv University