MEASUREMENTS OF FLUID FRICTION WITH STEADY AND UNSTEADY MOTION
Abstract
A pilot model tunnel of the blow-down type is described which employs 2 tanks mounted vertically and connected by a tube, or working section. Flow from the upper tank passes through guide vanes and an entrance nozzle, through a 1-in. tube which extends inside the lower tank, and through a quick- opening valve. High-frequency-response electronic cells for measuring differential water pressures directly were used to determine loss of head along the test section and for measuring the instantaneous average velocity. The flow velocity and acceleration were governed by the difference in air pressure above the water surfaces in the upper and lower-tanks. The loss of head due to fluid friction in turbulent flow was determined for steady and unsteady flow in a 1- in. -diam smooth brass tube 9 ft long. Measurements were made in a section where the boundary layer was fully developed. Unsteady flow runs were made with average velocities of 15 to 72 ft/sec and average accelerations from 0 to 35 ft/sec sq. No appreciable difference was observed between the friction factors referred to the instantaneous velocity for steady and unsteady flow as long as the rate of acceleration was constant of changed slowly. For sudden impulses from steady flow to accelerated flow, the measured values of the wall shearing stress were below those for steady flow at the same instantaneous average velocities. This indicated a change in the distribution of internal shear stresses and velocity distribution from the steady flow distributions at the same velocity
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1952
- Accession Number
- AD0004804
Entities
People
- James W. Daily
- Kenneth C. Deemer
Organizations
- Massachusetts Institute of Technology