Vane Flow Direction Sensor for Blast Waves
Abstract
The objectives of this study were to review the use of vanes for sensing flow direction and to design a fieldable vane flow direction gage for use in experiments with precursed blast waves. Estimates of the requirements for a flow direction sensor were made from the results of an existing numerical calculation of a precursed blast wave. The precursed flow field contains two large vortices and mechanisms for generating smaller scale vortices near the surface. There are high speed flows (Mach 3) present in a jet near the ground, and the response time for a flow direction sensor must be short, 0/2 ms or less if possible. A rotating wind vane sensor has a response time that is too long. Alternative means of sensing flow direction, will be a gage was measuring the direction of bending of a cantilever beam protruding into the flow by use of strain gages. The gage has four cylindrical hollow cantilever beams in a cruciform configuration on the end of a supporting shaft. The four output signals describe the flow direction in the vertical plane containing the gage and ground zero, and the horizontal plane. Each cylinder has a natural frequency of about 8300 Hz. Because it is underdamped, the upper usable frequency is about 2080 Hz. Because it is underdamped, the upper usable frequency is about 2080 Hz, with a rise time of 0.12 ms. The test program recommended includes static calibration, tests of response versus flow angle in a 0.61 meter diameter shock tube at a shock overpressure of about 172 kPa (25 psi), supersonic wind tunnel tests at Mach 1.5, 2.0, and 2.5, and tests in the 0.43 meter shock tube at higher shock pressures with and without dust in flow.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 07, 1987
- Accession Number
- ADA208237
Entities
People
- G. T. Watson
- Noel H. Ethridge