Effect of Chamber Wall Proximity on Radiometer Force Production (Preprint)
Abstract
The impact of chamber wall location on a radiometric device has been studied experimentally and numerically in chambers from 0.2m to 1.8m in diameter with background pressure ranging from 0.006 to 1Pa. The range of pressures investigated is broad enough to observe the impact of the chamber walls on a given radiometer configuration in both the free molecule and transitional regimes. The contribution of the chamber walls to both the flowfield structure and radiometric force production were examined for helium, argon, and nitrogen test gases. Various radiometer geometries were experimentally tested on a force balance, with nano- Newton resolution, placed in a stagnant gas. The computational results were obtained using the solution of the model kinetic equations and by the direct simulation Monte Carlo method. The simulations compliment the experimental work by varying the chamber dimensions to a degree not practically attainable, demonstrating both the decreasing temperature gradient of the flowfield and the reduced force production of the radiometer as the physical dimensions of the chamber increase. It is concluded that chamber wall location has a dramatic effect on the force production of a radiometer, especially at higher pressures, where increasing the distance from the vane to the wall reduces both temperature gradient and the total force produced.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 02, 2008
- Accession Number
- ADA484881
Entities
People
- A. D. Ketsdever
- N. E. Gimelshein
- N. P. Selden
- S. F. Gimelshein
Organizations
- Air Force Research Laboratory