PRESSURE PROBES IN FREE MOLECULE FLOW
Abstract
When the mean free path becomes a signifiant fraction of a chrcteristic dimension of a pressure probe, the uual continuum formulae relating the measured pressure to the free-stream pressure and Mach number are no longer valid. The present paper treats the ase where the mean free path is so large compared wth the probe diameter that intermolecular collisions may be neglected. This is the condition for free molecule flow. Theoretical expressions are given for the pressure measured in a flowing gas with an orifice probe and a long-tube presre probe. Expeimenal investigtions were conducted using a low-density wind tunnel and a rotating-arm apparatus. agreement between theory and experiment was quite satisfactory. Although the reported work was done primarily in connection with the flow of low density gases over models in the laboatory, the reslts are equally applicable to siuations encountered in upper atmospheric research. Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1961
- Accession Number
- AD0287928
Entities
People
- E.l. Harris
- G.n. Patterson
- K.r. Enkenhus
Organizations
- AGARD