FLUENT 6 - Calculation of DPM Concentration
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How is the DPM concentration calculated 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 Example: 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 modeled, hence, Avg. 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 The test case file shows the same value for the DPM concentration. Please view the contours of DPM Concentration while keeping the node value option off. You will see the value of 95 Kg/m3 at the cells in center and zero value elsewhere. <a target=_blank href="http://www.fluentusers.com/support/solutions/1474/dpm_test.zip">http://www.fluentusers.com/support/solutions/1474/dpm_test.zip</a>http://www.fluentusers.com/support/solutions/1474/dpm_test.zip |
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