A Study of Transonic Drag Reduction of a Blunt Cylinder by a Cylinder Probe
Abstract
This thesis examines the reduction of the drag of a blunt cylinder by a cylindrical probe in the transonic regime, and determines characteristics of the flowfield from the experimental drag coefficient data. The experiment was conducted in the NASA-Ames Research Center 6 x 6 ft. supersonic wind tunnel. The model consisted of a blunt cylinder with diameter d2 and several extendable cylindrical probes, yielding probe-to-cylinder diameter ratios d1/d2 of 0.248, 0.368, an 0.45, an probe length-to-cylinder diameter ratios 1/d2 up to 2.0 (3.0 for the smallest probe). These configurations were tested at Mach numbers between 0.8 and 1.5. C sub D decreased as both 1/d2 and d1/d2 increased, due to the fact that the cylinder face was immersed in a wake of reduced stagnation pressure created by the probe. After reaching a minimum, C sub D increased as 1/ d2 increased, indicating a transition of the flow over the probe from a lower- drag open cavity mode to a higher-drag open cavity mode to a higher-drag closed cavity mode. This change was rather abrupt, and there was also hysteresis in the supersonic tests in agreement with previous experiments. C sub D also reached a minimum and increased as d1/d2 approached 1. C sub D usually increased with Mach number due to the increase in stagnation pressure with M. For a particular range of length and diameter ratios, C sub D decreased with increasing M for 0.8 < M < 0.95. This was attributed to the transition of the flow over the probe from the higher-drag closed mode to the lower-drag open mode as M increased.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1988
- Accession Number
- ADA202557
Entities
People
- David H. Bridgesxc