Direct numerical simulations of a planar jet laden with evaporating droplets Thomas G. Almeida 1 , Farhad A. Jaberi * Department of Mechanical Engineering, Michigan State University, 2240 Engineering Building, East Lansing, MI 48824-1226, USA Received 1 October 2005; received in revised form 23 November 2005 Available online 28 February 2006 Abstract A direct numerical simulation (DNS) study is conducted on the various aspects of phase interactions in a planar turbulent gas-jet laden with non-evaporative and evaporative liquid droplets. A compressible computational model utilizing a finite difference scheme for the carrier gas and a Lagrangian solver for the droplet phase is used to conduct the numerical experiments. The effects of droplet time constant, mass-loading and mass/momentum/energy coupling between phases on droplet and gas-jet fields are investigated. Signif- icant changes in velocity, temperature, density and turbulence production on account of the coupling between the liquid and gas phases are observed in non-isothermal jets with evaporating droplets. Most of these changes are attributed to the density stratification in the carrier gas that is caused by droplet momentum and heat transfer. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Droplet-laden turbulent jet; Two-phase planar jet; Droplet evaporation; DNS 1. Introduction Multiphase flows occur in a wide range of engineering applications. Ink jet printers, spray combustors, and fire prevention systems are obvious examples of physical situa- tions for which the understanding of multiphase transport phenomena are very important. This work is focused on a specific class of multiphase flows, that of dilute turbulent free shear flows laden with a dispersed medium, either solid particles or evaporating droplets. It is an effort to under- stand the complex mass/momentum/energy interactions between gas and droplet phases in a two-phase planar jet. The general features of the ‘‘developed’’ single-phase planar and round turbulent jets are well-established. Hinze [1], Pope [2], Bernard and Wallace [3] and others have dis- cussed these flows in detail, noting the general characteris- tics of the self-preserving portion of the flow. The near- fields of shear layers and jets are mainly controlled by the Kelvin–Helmholtz instabilities and are strongly dependent on the inlet flow conditions and external forcing [4]. Stan- ley and Sarkar [5] studied two-dimensional shear layers and jets, noting the impact that external forcing has on the jet development. They found that, although the downstream growth was nearly unaffected by forcing at the inlet, the near-field was modified. They reported some interesting results related to the symmetry of ‘weak’ and ‘strong’ jet flows due to forcing. The simulations performed herein would be classified as strong using their convention. The effects of temperature/density on the growth and stability of free jets were studied by Kennedy and Chen [6]. They found that ‘‘cold jets’’ tended to be significantly more stable than ‘‘hot jets’’. They also indicated a modifi- cation of the mean velocity profile, where the cold jets profile were ‘narrower’ and had a ‘‘more gradual taper of velocity’’ than their hot counterparts. These are explained by Colucci [7], who used the linear stability theory to show that with a lower density at the shear zone the jet is more 0017-9310/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijheatmasstransfer.2005.11.029 * Corresponding author. Tel.: +1 517 432 4678; fax: +1 517 353 1750. E-mail address: jaberi@egr.msu.edu (F.A. Jaberi). 1 Present address: General Dynamics-AIS, 1200 Joe Hall Drive, Ypsi- lanti, MI 48197, USA. www.elsevier.com/locate/ijhmt International Journal of Heat and Mass Transfer 49 (2006) 2113–2123