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Piston-effect-induced thermal jets in near-critical fluids
T Fröhlich1, D Beysens, Y Garrabos
1European Aeronautic Defence and Space Company, 37 boulevard de Montmorency, 75016, Paris, France.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 13, 2006
Summary
Highly compressible fluids near critical points exhibit a piston effect, where boundary layer expansion creates high velocities and spectacular jets in SF6 and CO2. This thermomechanical process is key to thermal phenomena in these fluids.
Area of Science:
- Fluid dynamics
- Thermodynamics
- Physics of compressible fluids
Background:
- Compressible fluids near their critical point exhibit unique thermal behavior.
- Boundary layer expansion significantly impacts fluid thermalization.
- The piston effect is a thermomechanical process observed in such fluids.
Purpose of the Study:
- To investigate the piston effect in highly compressible fluids.
- To analyze the role of boundary layer expansion in fluid thermalization.
- To compare phenomena under weightlessness and Earth gravity.
Main Methods:
- Experimental analysis of fluid behavior in SF6 and CO2.
- Utilizing weightlessness to isolate thermal effects from convection.
- Comparing data obtained under varying gravitational conditions.
Main Results:
- Observed high fluid velocities at the boundary layer edge due to concentrated heating.
- Demonstrated spectacular jet formation in SF6 and CO2.
- Confirmed the significant role of boundary layer expansion in thermal phenomena.
Conclusions:
- The piston effect is a crucial hydrodynamic phenomenon in compressible fluids.
- Boundary layer expansion is a primary driver of thermal phenomena in these fluids.
- Experimental data highlights the importance of this effect under different gravity conditions.
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