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4.1. One-dimensional Evaporating Water Spray in Nitrogen 65
3E+08
2.5E+08
Experiment - 293 K
Evaporation - 293 K
Evaporation and Coalescence - 293 K
Evaporation - 313 K
Evaporation and Coalescence - 313 K
Number density [m -3 ]
2E+08
1.5E+08
1E+08
5E+07
0.14 0.28 0.42 0.56 0.7 0.84
Position [m]
Fig. 4.12: Profiles of droplet number density computed with and without coalescence
at surrounding gas temperatures of 293 K and 313 K.
of coalescence affects the calculation of droplet number density significantly as it can
be inferred through comparison of the numerical results with experimental data. This
may be understood by the fact that only coalescence is considered in the present work
and processes of breakup, reflexive and stretching separation along with formation of
satellite droplets is neglected in the present simulations, which leads to a lower droplet
number density at any given position. This may be improved by including a more
advanced droplet–droplet interaction model [184]. Moreover, in these computations
the evaporating flux at zero droplet size is computed through the ratio constraints of
weights, radii and velocities given by Eqs. (2.33)– (2.34), which are derived based on
a smooth and continuous density function [60]. This approach is prone to errors and
may be rectified by implementing an maximum entropy model [66] explained in Section
2.3.4, which is done in the case of two-dimensional water and PVP/water in air
spray flows.
The successful implementation of DQMOM in studying the one-dimensional water
spray flow in nitrogen and the good agreement with experimental data has led to the
extension of DQMOM to two dimensions in order to model the evaporating water
spray in air in two-dimensional configuration. The DQMOM extension is outlined in
Section 2.3.4. The next section presents the results of two-dimensional water spray in
air in axisymmetric configuration.