An Experimental Study of the Time-Dependent Behavior of the Appendage-Body Junction Vortex
Abstract
The three dimensional flow in the region where a turbulent boundary layer encounters an appendage is characterized by the formation of a junction root vortex. The formation of this vortex can be attributed to the adverse pressure gradient upstream of the appendage. One major area of concern is the temporal behavior of the vortex. Fluctuations in the size and/or location of the vortex can cause degradation of downstream components or excitation of local structures. Recent studies in wind tunnels have identified a bi-modal characteristic in the structure of the vortex. An experimental investigation of the time-dependent behavior of the junction root vortex was conducted using MIT's variable pressure water tunnel and laser doppler anemometry system. Data was collected at various points forward of a modified NACA 0020 section appendage mounted on a splitter plate and analyzed using off-line DFT analysis. The data was gathered at tunnel speeds of 10 and 20 ft/sec using an analog-to-digital acquisition system. Velocity probability distributions using a fully digital acquisition system were also plotted to identify the bi-modal structure. The spectra generated from the DFT analysis were inconclusive. No distinct frequencies or pattern of frequencies attributable to the flow could be identified. Fluctuations within the spectra made their accuracy questionable. The existence of the bi-modal structure was confirmed by the velocity probability distributions. Theses. (jhd)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1989
- Accession Number
- ADA213465
Entities
People
- Joseph F. Fallone
Organizations
- Massachusetts Institute of Technology