OPTIMIZED DESIGN OF SYSTEMS FOR MEASURING LOW PRESSURES IN SUPERSONIC WIND TUNNELS,
Abstract
A quantitative expression is derived for the stabilization or lag time which depends on dimensions of tubing system, manometer volume, and magnitude of pressure to be measured. It is assumed principally that the flow is isothermal, and that the flow is Poiseuille (Reynolds Number based on radius is less than 1000). When more than one size of tubing is used, a procedure for obtaining optimized dimensions of tubing is given. For the measurement of pressures varying with time, a procedure is given for determining maximum permissible time rate of variation for a given accuracy. Finally the effects of outgassing (evolution of gas from plastic tube walls) in causing an error in the pressure measurement are evaluated. The effects of outgassing are particularly insidious, since they introduce errors difficult to detect. Furthermore, in the measurement of low pressures, these errors may not be just small tolerable errors, but can easily amount to 50 per cent or more. Ready reference charts are given to aid in making computations for each of the conditions mentioned. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1958
- Accession Number
- AD0661937
Entities
People
- J. M. Kendall
Organizations
- AGARD