Effect of ambient turbulence intensity on sphere wakes at intermediate Reynolds number

J.-S. Wu, G. M. Faeth
1995 AIAA Journal  
Separalioi Choking Eg. (21) 0.10 0.15 Fractional Mass Addition 0.20 0.25 Fig. 3 Combined effects of mass addition and wall friction, 4/(L/D) = 0 cases also appear in Fig. 1. Most importantly, the information of Fig. 3 shows that wall friction should not have a dominant effect on the qualitative and quantitative behavior of the flow in typical experiments. The fractional mass addition for choking and separation is changed by less than 25% over the range of expected values of 4/(L/D). Finally,
more » ... preceding equations Eq (24) may be combined with the definition of q to show that (25) which leads to the conclusion that, regardless of the value of the inlet Mach number, q e will always be at least about 0.8g/, and the average q, therefore, at least 0.9g/, thus supporting the earlier assertion that the local dynamic pressure does not vary much from inlet to exit. Conclusions This study has shown that there is a striking similarity between the influence of heat addition and mass addition on compressible flows. Most importantly, these results encourage the belief that relatively modest laboratory experiments employing mass addition can be devised that will reproduce the leading phenomena of heat addition, such as the axial variation of properties, choking, and wall boundary-layer separation. If so, the mass addition method could be further developed to explore and/or demonstrate the complex behavior of dual-mode ramjet/scramjet combustors. Meanwhile, the insights into both types of flows found here further extend the already generous benefits of classical onedimensional compressible flow analysis. Acknowledgments We are indebted to the U.S. Air Force Frank J, Seiler Research Laboratory for financial support and to the Department of Aeronautics of the U.S. Air Force Academy for its traditional hospitality and operational support of our work. The central concept for this research grew out of stimulating telephone discussions with Edward T. Curran, now Director of the Aero Propulsion and Power Directorate of the Wright Laboratory, that took place in 1992. His continuing interest in the project since then has also been of great value. Nomenclature = drag coefficient = sphere diameter, m t = characteristic wake width, Eq. (2), m Re, Re t = sphere and turbulence Reynolds numbers, dU^/v and radial position, m wake-scaling velocity, Eq. (2), m/s mean relative velocity of sphere, m/s mean and rms fluctuating streamwise velocities, m/s rms fluctuating cross-stream velocity, m/s streamwise distance from center of sphere, m molecular and turbulence kinematic viscosities, m 2 /s C d d Subscripts c = centerline value o -virtual origin condition oo = ambient condition
doi:10.2514/3.12353 fatcat:an54cgcvsneirpv6beyr3dutii