Piston-effect-induced thermal jets in near-critical fluids.
In very compressible fluids, such as fluids near their critical point, the bulk fluid is adiabatically thermalized by the expansion of a hot boundary layer. Thanks to this thermomechanical process (the so-called piston effect) the fluid velocity at the edge of the boundary layer can become very high when the heating power is concentrated in a fissure. Spectacular jets are then observed in SF6 and CO2. Data obtained under weightlessness (in order to remove convection) and data obtained under earth gravity are compared and analyzed. They emphasize the key role of the boundary layer expansion for thermal phenomena in compressible fluids and the hydrodynamic nature of the piston effect.
Fröhlich
T
T
European Aeronautic Defence and Space Company, 37 boulevard de Montmorency, 75016, Paris, France.
Beysens
D
D
Garrabos
Y
Y