Boundary Layer Response to an Unsteady Turbulent Environment
Abstract
An experimental investigation of a wing boundary layer subjected to periodic turbulent flow at a Reynolds number of 500,000 was conducted. Non- thrusting turbulence pulses were generated at a rate of 50 pulses/s with a turbulence intensity near 10%. Time-varying velocity measurements were made at representative chord locations (laminar, transitional/turbulent, fully turbulent) at one angle of attack using single-element hot-wire anemometry. Characteristics of the boundary layer velocity profiles, turbulence intensity profiles, and velocity spectra and total spectral power were documented. The time-varying boundary layer response could be characterized by undisturbed flow, turbulence pulse, and recovery period. The boundary layer exhibited a cyclic transition response varying from the undisturbed flow regime to the turbulence pulse regime back to the undisturbed flow regime. The turbulence pulse penetrated into the entire boundary layer. The turbulence pulse prompted flow laminarization during the recovery period. Laminarization apparently resulted from rapid acceleration of near-surface flow within the boundary layer due to turbulence induced momentum transfer down through the boundary layer and local flow acceleration following velocity deficit of the turbulence pulse. Effects of the periodic turbulence pulse were most noticeable in the recovery period at the transitional/turbulent and fully turbulent regions of the wing. Recovery was generally characterized by lowered turbulence levels and reduction in boundary layer thickness, indicating a stabilizing effect of the external turbulence pulse. Low Reynolds number; Unsteady aerodynamics; Experimental data; Computer programs. Theses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1988
- Accession Number
- ADA206578
Entities
People
- Robert W. Renoud
Organizations
- Naval Postgraduate School