organized by the Institute of Thermomechanics of the CAS, v. v. i.,
every first Wednesday of the month at 10:00
in the Conference Room B in the main building of the Institute of Thermomechanics of the CAS, v. v. i. (see directions)
 

Contact persons: Dr. Radek Kolman, Dr. Hanuš Seiner

 

Thursday, September 15, 2016, 10:00
 

 

Lecture outline:
The main motivation of the research effort reported here was passive protection of airplanes against an enemy’s heat seeking missiles. The stated goal was to reduce the temperature of a jet engine exit flow by means of the hot-jet rapid mixing with the ambient air, and no penalty of the jet engine thrust was allowed. The focus of the first phase of this project was to explore the properties of high-speed free jets and demonstrate that it is possible to enhance jet flow mixing by flow excitation. Inconsistencies in hot-jet responses to flow excitations were investigated in the second phase of this project. It was shown that the jet receptivity to flow excitation is strongly dependent on a character of the nozzle exit boundary layer. Finally, it was proven that the decisive factor controlling the jet receptivity is the velocity gradient across the exit boundary layer. There were also side byproducts of this research effort. First, it was an improvement in the high-frequency stroboscopic visualization of large-scale turbulent structures in free jet flows. The second innovation was the development of a new methodology for conditional sampling of random laser velocimeter data.