DPM concentration in Fluent.
The DPM concentration is defined as:
DPM concentration = (Avg. particle mass in cell * Part resi. Time * Strength of particle) / Cell volume ...1
Strength of particle = number in parcel / dt_flow ...2a
= total particle flow rate / mass of single particle in the stream ....2b
From equation 1 and equation 2b,
DPM conc. = (Avg. particle mass in cell * Part resi. Time * Total particle flow rate) / (mass of single particle in stream * cell volume) .....3
Consider the following example to make things more clear.
a. A simple channel flow with constant velocity of 1m/s is used.
b. The top and bottom surface are defined as symmetry to ensure the plug flow condition.
c. The particles with total mass of 0.1 Kg/s and velocity of 1m/s are injected as single injection at the center of inlet.
d. This ensures that DPM concentration is non-zero only at the center line and is zero everywhere else.
A single stream of particle is modelled, hence,
Average particle mass in cell = Average mass of particles in particle stream ...4
From equations 3 and 4,
DPM conc. = Part resi. Time * Total particle flow rate / Cell volume
For the test case, Part resi. Time = 0.002 s, Total particle flow rate = 0.1 Kg/s, Cell volume = 2.08e-6 m3
DPM conc. = 0.002 * 0.1 / 2.081 e-6 = 95 Kg / m3