Effect of Orifice Geometry on the Development of Slightly Heated Turbulent Jets

Abstract

Passive scalar (temperature) mixing with different orifice geometries is considered at low Reynolds number. The kinetic energy dissipation rate shows that the three jets achieve a selfsimilar state quickly compared to a nozzle jet. Scalar dissipation evolves faster to the selfpreserving state than kinetic energy dissipation and the asymptotic value of the normalized kinetic and scalar dissipation on the jet centerline can be predicted. Taylor and Corrsin microscales start evolving linearly with x/D as early as x/D = 10. Normalized spectra using these length scales continue to evolve for the circular jet and collapse faster for the sixlobe jet, when Rخ» reach a constant value. The scaling factor and range for the velocity and the scalar suggest that the scaling region “similar to the inertial rangeâ€‌ reaches equilibrium before small scales reach complete equilibrium. The use of multilobe jets promotes the development toward a complete selfpreserving state for the scalar field.