Flow Visualization and Wake Analysis for Standard and Modified Configurations of the AN/ALQ-78 Antenna Pod
Abstract
A low-speed wind tunnel investigation was conducted to compare the aerodynamic flow field characteristics for standard and modified configurations of a 20 percent scale model of the AN/ALQ-78 electronic support measures system antenna pod. The modification consisted of replacing the standard quasi- conically shaped radome with a cylindrical radome and adapter collar. The research was requested by the Naval Air Systems Command (NAVAIRSYSCOM) as part of a risk and feasibility assessment in preparation for possible full-scale flight tests of the modified configuration. Wake flow visualization was conducted to determine the general characteristics of the flow field. Base pressure measurements were made to assess three-dimensional effects. The presence of coherent vortex shedding in the wake was investigated using a cross- probe constant temperature hot-film anemometer and spectrum analyzer. The Reynolds number varied from 40,000 to 6 times 10 to the 5th power with the upper value approximately equal to one-eighth that of the full-scale pod in flight. Asymmetric vortex shedding was visualized in the wakes of both configurations at subcritical Reynolds numbers. The modified configuration exhibited a pronounced region of quasi-two-dimensional flow during wake visualization and base pressure tests, indicating a significant increase in the aerodynamic forces acting on the pod structure. Spectral analysis of the hot-film output confirmed the presence of coherent vortex shedding in the wakes of both models at subcritical Reynolds numbers. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1991
- Accession Number
- ADA243552
Entities
People
- James F. Small
Organizations
- Naval Postgraduate School