Acoustic Emissions from Unsteady Transitional Boundary Layer Flow Structures
Abstract
The research described critically examines the popular approaches to modeling the radiation mechanisms and attempts to bring some degree of closure to the physical and practical significance of noise and pseudo-noise originating in the laminar-to-turbulent transition zone within a natural boundary layer. Several refinements were made to theoretical models for directly radiated noise based upon the Liepmann analogy for fluctuating displacement thickness including the incorporation of a semi-empirically derived space-time correlation function for the intermittency indicator. A quiet airflow facility was developed to measure the direct acoustic radiation from a naturally transitioning boundary layer. Real-time acoustic intensity measurement instrumentation was developed if measurements of isolated spots in otherwise laminar flow had been necessary. This technique uses a hot film signal from the transition structure to obtain the coherent output intensity (COI). Model predictions are compared to the measured acoustic radiation from a naturally transitioning boundary layer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2000
- Accession Number
- ADA384537
Entities
People
- G. C. Lauchle
- R. C. Marboe
Organizations
- Pennsylvania State University