Accession Number:

ADA065666

Title:

The Structure of Turbulent Velocity Fields.

Descriptive Note:

Final rept.,

Corporate Author:

CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF APPLIED MECHANICS AND ENGINEERING SCIENCES

Personal Author(s):

Report Date:

1978-11-26

Pagination or Media Count:

10.0

Abstract:

An experimental investigation of relaminarization of turbulent pipe flow subjected to a large decrease in Reynolds number was continued. A considerable amount of data on the downstream development of the flow field using both single wires and x-wires was obtained. For Re 2000 the turbulence cannot sustain itself and the flow relaminarizes with the rate of relaminarization being greater the lower the Reynolds number. The mean velocity profiles exhibit a gradual trend towards a parabolic profile with increasing xd. The nature of the flow field for 1900 Re 2800 was shown to be particularly interesting as puffs or incipient puffs exist in the flow for xd 40. Detection of puffs imbedded in the decaying turbulent flow is difficult so an iterative puff waveform eduction program was developed. Valuable results from the program include the average incipient waveform in an incipient puff, the average length of puffs, the mean time puffs, and other structural features of the puffs at various downstream locations. This information is useful in understanding the origin and evolution of puffs in transitional pipe flow. The existence of puffs in the present study as well as a previous transition study indicates that they play a fundamental role in the transition and reverse transition process.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE