Experiments on Transitional Oscillatory Pipe Flow,
Abstract
Fully developed oil flow in a smooth circular pipe at a mean Reynolds number of about 2100 was subjected to a nominally sinusoidal flow modulation at frequencies ranging from 0.05 - 1.75 Hz. It was observed that flow oscillation increased the critical Reynolds number and, under certain conditions, even brought about laminarization of the flow, which would be intermittently turbulent at the mean Reynolds number under quasi-steady (infinitely small oscillation frequency) conditions. The occurrence and extent of laminarization was, however, found to depend on factors such as the intermittency of turbulent puffs in the mean quasi-steady flow, frequency of oscillation, etc. Two series of experiments were performed. In one series, the oscillatory flow was almost completely laminarized. In the other series, the oscillatory flow was fully turbulent. In both the cases, instantaneous velocities in the flow were measured using Laser Doppler anemometry. The instantaneous velocity was decomposed into time-mean, periodic and random components employing ensemble averaging techniques. The experiments indicated that the laminarized oscillatory flow behaves very similar to laminar oscillatory flow at either end of the Strouhal number range studied. The oscillatory turbulent flow was found to depend on both the Strouhal number and the ratio of the oscillation frequency to some characteristic frequency of turbulence in the flow in the flow. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1979
- Accession Number
- ADA081180
Entities
People
- B. R. Ramaprian
- S. W. Tu
Organizations
- University of Iowa