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EXPERIMENTAL STUDY OF RADIOMETRIC FORCES WITH
COMPARISON TO COMPUTATIONAL RESULTS
by
Nathaniel P. Selden
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Ful llment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(MECHANICAL ENGINEERING)
May 2009
Copyright 2009 Nathaniel P. Selden
Object Description
| Title | Experimental study of radiometric forces with comparison to computational results |
| Author | Selden, Nathaniel P. |
| Author email | selden@usc.edu; nate@qvessel.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Mechanical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2009-01-28 |
| Date submitted | 2009 |
| Restricted until | Unrestricted |
| Date published | 2009-04-22 |
| Advisor (committee chair) | Muntz, E. Phil |
| Advisor (committee member) |
Shiflett, Geoffrey R. Wang, Hai Domaradzki, Julian A. Gundersen, Martin A. |
| Abstract | A study of the radiometric forces on heated plates has been conducted both experimentally and computationally. The experiments were carried out at USC in two vacuum chambers up to a maximum pressure of 6 Pa for various gases. The computations were performed with both the DSMC and ES-BGK methods for a 2-D gas over a comparable range of pressures. It is shown that the radiometric devices provide maximum force at a Knudsen number approximating 0.1. Of the various gases tested, helium provides the largest peak force. Qualitatively, the experimental data and computational results are similar. A lack of experimental data on gas-surface accommodation and three-dimensionality yields up to a 40% difference in the magnitude of the measured and computed forces, but it is shown that this discrepancy can be used to predict accommodation values. Comparison of four geometric configurations has shown that the effect of the area is signficant at pressures up to where the force is maximum. It is also demonstrated that the size of the chamber in which the radiometer resides is of primary importance, where the chamber dimensions are inversely related to the generated force. Finally, simulation of multi-vane configurations have shown that the optimal spacing of vanes can be tailored for specfic uses; for maximum force production a tight spacing should be used, while maximum efficiency requires spacing on the order of a vane dimension. While the results so far are encouraging, they are far from complete. Further improvements would include: a new experimental setup to reduce uncertainty with highly accurate temperature control and measurement, an in situ way to prepare the surface as well as measure its cleanliness, and an in depth iterative computational study observing the impact of multiple radiometer vanes at numerous separations. |
| Keyword | radiometric forces; rarefied flow; Knudsen; thermal gradients; accommodation; gas surface interaction; radiometer; thermal transpiration; microfluidics; low density gas; Einstein |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m2107 |
| Contributing entity | University of Southern California |
| Rights | Selden, Nathaniel P. |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@dots.usc.edu |
| Filename | etd-Selden-2649 |
| Archival file | uscthesesreloadpub_Volume51/etd-Selden-2649.pdf |
Description
| Title | Page 1 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@dots.usc.edu |
| Full text | EXPERIMENTAL STUDY OF RADIOMETRIC FORCES WITH COMPARISON TO COMPUTATIONAL RESULTS by Nathaniel P. Selden A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Ful llment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (MECHANICAL ENGINEERING) May 2009 Copyright 2009 Nathaniel P. Selden |
