Observation and Measurements of Flow Structures in the Stagnation Region of a Wing-Body Junction
Abstract
Behavior of a junction vortex formed around an obstacle in a boundary layer flow was studied experimentally in a water tunnel for two low speed cases. A wing consisting of a 3:2 elliptical nose and an NACA 0020 tail was used to simulate the junction vortex. A flow visualization study, using a hydrogen bubble technique, was conducted to investigate flow structures in the stagnation region of the wing. A multiple vortex system showing an acyclic flow pattern was observed. LDV measurements were performed in the plane of symmetry upstream of the wing. The general flow agrees with an earlier wind tunnel test conducted at higher speed. A low frequency, bistable flow structure was observed as in the wind tunnel measurements. The switching between two flow modes (a backflow mode and a zero flow mode) was analyzed using LDV signals in the zone of a bimodal structure. A dimensionless frequency group was found to represent the average frequency of successive switches from one mode to the other. Visual evidence of an acyclic flow pattern was consistent with LDV measurements and revealed that aperiodic stretching of the junction vortex appears responsible for the bimodal (double-peaked) structure in the velocity histograms. An attempt to measure the three-dimensional instantaneous velocity field in this region was made. A particle image displacement velocimetry technique was developed using a multiple wire hydrogen bubble method and a high speed video system.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1991
- Accession Number
- ADA243403
Entities
People
- D. A. Walker
- R. L. Simpson
- Seungchan Kim
Organizations
- Virginia Tech