An experimental study of unsteady turbulent flows
Abstract
In the wind tunnel, a fully-developed turbulent pipe flow is almost linearly accelerated or decelerated from one stationary stage to another stationary stage. The structure of unsteady turbulent boundary layer is characterized by the combined ensemble and short-time average estimates of the mean motion, the turbulent intensities and the Reynolds stress. The spectral structure of unsteady turbulence is presented with segment spectrum, physical spectrum, instantaneous spectrum and the evolutionary spectrum. Those spectral calculation schemes are first tested by a computer simulated nonstationary random process. It is found that the structures of unsteady turbulent flows (except the radical turbulent intensity) depend upon the history of nonstationary process characterized by the generalized Strouhal number. The longitudinal turbulent intensity and Reynolds stress generally increase with the absolute value of Strouhal number.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- February 1976
- Bibcode:
- 1976PhDT........61W
- Keywords:
-
- Strouhal Number;
- Turbulent Flow;
- Unsteady Flow;
- Wind Tunnel Tests;
- Computerized Simulation;
- Flow Characteristics;
- Pipe Flow;
- Turbulent Boundary Layer;
- Fluid Mechanics and Heat Transfer