[ktron]

Hi,


I have a problem with the "massFlowRate" output of the facePostProcessing function object. I am using facePostProcessing to measure the massflow through a plane in my geometry. I am using the solver MPPICFoam in OpenFOAM v8, so I basically want to know how many particles pass said plane.


Here is some of the output I got:

# Source : facePostProcessing
# Face zone : midPlaneFaceZone
# Faces : 400
# Area : 0.0366643
# Time mass massFlowRate
80.1 0.0115611 0.115611
80.2 0.0212791 0.0709302
80.3 0.0320024 0.0533373
80.4 0.0423906 0.0423906
80.5 0.0541192 0.0360794
80.6 0.063167 0.0300795
80.7 0.0738903 0.0263894
80.8 0.0856189 0.023783
80.9 0.0978501 0.0217445
81 0.110417 0.0200757
81.1 0.121056 0.0183418
81.2 0.133622 0.0171311
81.3 0.142419 0.0156504
81.4 0.153477 0.0146169
81.5 0.164619 0.0137183
81.6 0.174505 0.0128312
81.7 0.187239 0.0122378
81.8 0.200224 0.011709
81.9 0.215388 0.0113362
82 0.224519 0.0106914
82.1 0.235745 0.0102054
82.2 0.248479 0.00982131
82.3 0.259956 0.00941871
82.4 0.271517 0.00905058
82.5 0.283078 0.00871011
82.6 0.297069 0.0084635
82.7 0.309552 0.0081892
82.8 0.319688 0.0078741
82.9 0.330412 0.00759567
83 0.341973 0.00735425
83.1 0.351858 0.00709392
83.2 0.363001 0.00687501
83.3 0.372132 0.00663337
83.4 0.384866 0.00646834
83.5 0.397349 0.00630712
83.6 0.409412 0.00614733
83.7 0.419298 0.00596441
83.8 0.431529 0.00582361
83.9 0.443928 0.00569138
84 0.457751 0.00558233
84.1 0.468893 0.00544591
84.2 0.477941 0.00529281
84.3 0.487073 0.00514876
84.4 0.495115 0.00500116

According to "mass", the flow has reached a relatively steady state of roughly 0.1 kg/s. The first entry of "mass flow rate" therefore makes sense to me. However, all the other entries continuously decrease. According to my concept of a mass flow rate, it should stay at around 0.1. Can somebody tell me, if I am missing something here? Any experiences?