Experiments on the Influence of Active Walls on the Initial Amplitudes and Growths of Instability Waves.
Abstract
An active-wall device was developed to determine those characteristics of traveling surface waves which are important in drag reduction with compliant coatings. Feasibility of an active wall was demonstrated with a Kelvin-Helmholtz solution for flow over a semi-infinite surface with traveling surface waves. Analysis indicated that freestream disturbances and the secondary flow generated by the leading edge could be modified or eliminated. An all solid-state electromechanical device was built which produces short-wavelength traveling surface waves. The active wall nominally designed to cancel Tollmien-Schlichting waves in a laminar boundary layer. Wave form, wave speed, frequency, and amplitude were independently selectable. The electronic subsystem was a hybrid analog/digital device, and wall motion was produced by piezoelectric ceramic elements. Surface displacement was measured with an electro-optical instrument developed for this research. Measurements of sinusoidal wall motion ranged in amplitude from 0.6 - 13 microns over a frequency span of 10-150 Hz. Maximum phase speed was 166 cm/s. A low turbulence water tunnel was designed and assembled for the active-wall experiments. Design velocity was 10 m/s in a test section. Longitudinal relative turbulence intensity in the test section was estimated to be less than 0.2%. Keywords: Fluid dynamics; Fluid mechanics; Hydrodynamics; Hydromechanics; Incompressible flow; Uniform flow.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1985
- Accession Number
- ADA154630
Entities
People
- H. L. Rogler
- H. S. Silvus Jr.
- J. T. Park
- S. A. Cerwin
Organizations
- Southwest Research Institute