Processes occuring in a pressure-driven shock tube

Author

Michael Steven Smith

Date of Award

8-1984

Degree Type

Thesis

Degree Name

Master of Science

Major

Physics

Major Professor

James L. Lewis

Committee Members

Arthur A. Mason, Horace Crater

Abstract

Calculations involving the processes occurring within a pressure-driven shock tube are described in this work. Ideal incident and reflected shock-wave theory are reviewed. Nonequilibrium vibrational relaxation and laminar boundary layer theory are discussed.

A numerical integration of the incident and reflected shock conservation equations is performed. Results are presented for diatomic nitrogen (N₂) gas over the incident shock Mach number range of 3≤M_s≤6 and over the temperature range of 800≤T≤4000 K. It is shown that, as a result of the rapid vibrational excitation in the reflected shock region, the reflected shock front, once fully excited, accelerates as it propagates into the oncoming incident shock-wave of fractional vibrational excitation.

This analysis was accompanied by a shock tube experiment which was performed prior to the completion of these calculations. The shock tube system was designed and constructed to provide a high-temperature, local-thermal-equilibrium gas sample for the determination of Raman scattering cross sections. The shock tube was designed for operation over the temperature range of 800≤T≤4000 K and the fabri-the number density range of 0.2≤n≤2.1 amagat. The fabricated steel shock tube was 6.98-m long with a 6.35-cm inner diameter; the driven/driver section length ratio was 1.88. The initial demonstration of a laser Raman shock tube system for high-temperature cross section and calibration measurements was accomplished. The incident Mach number range of 4 to 5 was studied with the He driver gas and N₂ as the driven species using a seamless steel shock tube. The Raman spectra obtained with the seamless steel tube revealed excessively high contributions to the scattering signal due to effects of rust particles which had been scrubbed from the tube wall. To minimize this problem a tube, and these effects were reduced to small corrections to the Raman signal. Vibrational Raman spectra of shock-heated N₂ were acquired using a frequency-doubled ruby laser, spectrometric dispersion, and a single photomultiplier tube (PMT) detection channel. The results were acquired on separate shots at two wavelengths of the vibrational Raman Stokes band, and T_V was determined. The results of the measurements yielded a mean vibrational temperature TV = 2,110±220 K. Heat-transfer gauges were used to determine the shock speed u_s and incident Mach number M₁, which was found to be 4.96±0.04. The incident gas temperature corresponding to M₁ = 4.96 was approximately T_{2,/sub> = 1, 600 K, and the discrepancy between T2 and TV} is attributed to observation in the early portion of the reflected shock region rather than the latter phase of the incident shock.

Recommended Citation

Smith, Michael Steven, "Processes occuring in a pressure-driven shock tube. " Master's Thesis, University of Tennessee, 1984.
https://trace.tennessee.edu/utk_gradthes/14719