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22.12 Setting Initial Conditions for the Discrete Phase

For liquid sprays, a convenient representation of the droplet size distribution is the Rosin-Rammler expression. The complete range of sizes is divided into an adequate number of discrete intervals; each represented by a mean diameter for which trajectory calculations are performed. If the size distribution is of the Rosin-Rammler type, the mass fraction of droplets of diameter greater than $d$ is given by


 Y_d = e^{-(d/\bar{d})^n} (22.12-1)

where $\bar{d}$ is the size constant and $n$ is the size distribution parameter. Use of the Rosin-Rammler size distribution is detailed in Section  22.12.1.

The primary inputs that you must provide for the discrete phase calculations in FLUENT are the initial conditions that define the starting positions, velocities, and other parameters for each particle stream. These initial conditions provide the starting values for all of the dependent discrete phase variables that describe the instantaneous conditions of an individual particle, and include the following:

These dependent variables are updated according to the equations of motion
(Section  22.2) and according to the heat/mass transfer relations applied (Section  22.9) as the particle/droplet moves along its trajectory. You can define any number of different sets of initial conditions for discrete phase particles/droplets provided that your computer has sufficient memory.




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