Experimental Study of Heat Release Effects in Exothermically ReactingTurbulent Shear Flows.

Heat Release in Turbulent Shear Flows;Aerospace Engineering;Engineering;Aerospace Engineering

Nagel, Zachary WilliamDriscoll, James F. ;

University of Michigan

关键词: Heat Release in Turbulent Shear Flows;    Aerospace Engineering;    Engineering;    Aerospace Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/57637/nagelz_1.pdf?sequence=2&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Comparisons are presented from the firstinner-scaled measurements of velocity gradient quantities in reacting andnonreacting versions of otherwise identical turbulent shear flows. Distributionsof gradient quantities are obtained for outer-scale Reynolds numbersfrom 7200 to 200,000. The local outer length and velocity scales and associated innerscaling are used to identify the dominant physical mechanisms that produceheat release effects on the inner scales. In the nonreacting cases, classicalinner scaling with the viscosity and inner (viscous) length scaleremoves most differences in distributions measured at different Reynolds numbers, with remainingdifferences being due to incomplete resolution with increasing Reynolds number.Inertial and dissipation range spectra allow the measurement resolutionscale and the proper resolution-correctedinner scaling to be determined, with the resulting scaling verifying near-perfectsimilarity for all Reynolds numbers. In the reacting cases, departures from thissimilarity reveal the true inner-scale changes due to heat release. Resultsclearly show that when inertial and body force effects on the outer length and velocity scales are accountedfor via the equivalent density, and viscous effects are accountedfor via the mixture-fraction-averaged viscosity, the resolution-correctedinner scaling reveals remaining effects of heat release on turbulent shearflows to be remarkably small.Using the same resolution-corrected inner scaling, further experiments were conducted under conditions ofnonzero mean shear.Accounting for the effects of classical external intermittency, resultsfrom the velocity gradient distributions indicatea small effect of nonzero mean shear at the finest scales of the flow.Thisis corroborated by evaluation of the Corrsin-Uberoicriteria, where the present results satisfy thecondition for all of the measured reacting and nonreacting cases.Use of the resolution-corrected inner scaling permits direct comparison between otherwise identicalturbulent shear flows; the present results reveal that the combined effects of heat release and mean shear onthe inner-scales of turbulent shear flows are relatively small.