Numerical and experimental investigation of microchannel flows with rough surfaces

T. C. Lilly, J. A. Duncan, S. L. Nothnagel, S. F. Gimelshein, N. E. Gimelshein, A. D. Ketsdever, I. J. Wysong
2007 Physics of Fluids  
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more » ... ters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution unlimited (PA #07386A). SUPPLEMENTARY NOTES A conical surface roughness model applicable to particle simulations has been developed. The model has been experimentally validated for channel flows using helium and nitrogen gases at Reynolds numbers from 0.01 to 10 based on inlet conditions. To efficiently simulate gas-surface interaction, molecular collisions with the actual rough surface are simulated by collisions with a randomly positioned conical hole having a fixed opening angle. This model requires only one surface parameter, average surface roughness angle. This model has also been linked to the Cercignani-Lampis scattering kernel as a required reference for use in deterministic kinetic solvers. Experiments were conducted on transitional flows through a 150μm tall, 1cm wide, 1.5cm long microchannel where the mean free path is on the order of the roughness size. The channel walls were made of silicon with: (i) polished smooth surfaces, (ii) regular triangular roughness, and (iii) regular square roughness with characteristic roughness scales of <1μm, 11μm, and 29μm respectively. For the triangular roughness, mass flow reductions ranged from 6% at the higher stagnation pressures tested to 25% at the lower stagnation pressures tested when compared to the smooth channel. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON Dr. Ingrid Wysong a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified SAR 10 19b. TELEPHONE NUMBER (include area code) N/A Standard Form 298 (Rev. 8-98) A conical surface roughness model applicable to particle simulations has been developed. The model has been experimentally validated for channel flows using helium and nitrogen gases at Reynolds numbers from 0.01 to 10 based on inlet conditions. To efficiently simulate gas-surface interaction, molecular collisions with the actual rough surface are simulated by collisions with a randomly positioned conical hole having a fixed opening angle. This model requires only one surface parameter, average surface roughness angle. This model has also been linked to the Cercignani-Lampis scattering kernel as a required reference for use in deterministic kinetic solvers. Experiments were conducted on transitional flows through a 150 m tall, 1 cm wide, 1.5 cm long microchannel where the mean free path is on the order of the roughness size. The channel walls were made of silicon with: ͑i͒ polished smooth surfaces, ͑ii͒ regular triangular roughness, and ͑iii͒ regular square roughness with characteristic roughness scales of Ͻ1 m, 11 m, and 29 m, respectively. For the triangular roughness, mass flow reductions ranged from 6% at the higher stagnation pressures tested to 25% at the lower stagnation pressures tested when compared to the smooth channel.
doi:10.1063/1.2775977 fatcat:t4xjcokjzna6vlscqe5nmwsa6a