VELOCITY RECOVERY AND SHEAR REDUCTION IN JET-DRIVEN VORTEX TUBES
AEROSPACE CORP EL SEGUNDO CA
Pagination or Media Count:
The laminar, two-dimensional flow of a viscous vortex, driven by tangential fluid injection in a porous cylindrical container, is considered. The jets are idealized as sources of mass and momentum. The tangential velocity profile in the annular region between the jet input radius of the cylinder is found analytically as a solution of the tangential momentum equation. The peripheral wall shear is evaluated with and without radial fluid injection through the cylinder wall. For a given tangential velocity in the vortex, radial fluid injection through the porous wall substantially reduces the shear. The effect of radial fluid injection on the fraction of the jet velocity that is recovered in the vortex is found by means of a torque balance, including the torque required to accelerate the radially injected fluid to the peripheral vortex velocity. For a given total mass flow through the center of the vortex, radial fluid injection is always detrimental to the velocity recovery in the vortex that is, for a given jet velocity, diversion of a fraction of the mass flow from tangential to radial injection always results in a reduced vortex strength. The results for zero radial fluid injection are compared with experimental data for which the flow was turbulent. The theory predicts the recovery accurately even for turbulent flow, provided an appropriate turbulent eddy viscosity is included in the evaluation of the Reynolds number.
- Fluid Mechanics
- Nuclear Propulsion