Direct numerical simulations of two-phase laminar jet flows with different cross-section injection geometries

Creators: Abdel-Hameed, H.; Bellan, J.

Abstract

Direct numerical simulations are performed of spatial, three-dimensional, laminar jets of different inlet geometric configurations for the purpose of quantifying the characteristics of the flows; both single-phase (SP) and two-phase (TP) free jets are considered. The TP jets consist of gas laden with liquid drops randomly injected at the inlet. Drop evaporation ensues both due to the gaseous flow being initially unvitiated by the vapor species corresponding to the liquid drops, and to drop heating as the initial drop temperature is lower than that of the carrier gas. The conservation equations for the TP flow include complete couplings of mass, momentum, and energy based on thermodynamically self-consistent specification of the vapor enthalpy, internal energy, and latent heat of vaporization. Inlet geometries investigated are circular, elliptic, rectangular, square, and triangular. The results focus both on the different spreading achieved according to the inlet geometry, as well as on the considerable change in the flow field due to the presence of the drops. The most important consequence of the drop interaction with the flow is the production of streamwise vorticity that alters entrainment and species mixing according to the inlet geometry. Similar to their SP equivalent, TP jets are shown to reach steady-state entrainment; examination of the flows at this time station shows that the potential cores of TP jets are shorter by an order of magnitude than their SP counterpart. Moreover, whereas the TP circular jet exhibits a symmetric entrainment pattern well past the streamwise location of the potential core, noncircular jets display at the same location strong departures from symmetry. Furthermore, the SP-jet phenomenon of axis switching is no longer present in TP jets. The distributions of drop-number density, liquid mass, and evaporated species are compared for different inlet cross sections and recommendations are made regarding the optimal choice for different applications.

Additional Information

© 2002 American Institute of Physics. Received 8 November 2001; accepted 15 June 2002; published 5 September 2002. This investigation was performed at the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech), and sponsored by the Department of Energy, the Hydrogen Program, under an interagency agreement with the National Aeronautics and Space Administration, with Neil Rossmeissl and Douglas Hooker as contract monitors. One of the authors (H.A-H.) would like to acknowledge financial support from the Egyptian Ministry of Education, through a graduate student scholarship during his stay at Caltech as a Special Graduate Student, covering the period of this investigation. The authors would like to thank Dr. Kenneth Harstad and Dr. Nora Okong'o of JPL for many helpful discussions on boundary condition treatments and coding aspects, respectively. The JPL supercomputer facility was used in the course of this study.

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