Learning Forum

[ccmhaekal]

Hi, I am currently modeling slurry multiphase flow through a 2D pipe. The pipe has a drop tube in the middle to capture the sand (secondary phase). To analyze the result, I need to know how much sand enter the intersection (before_dt), fall into the drop tube (into_dt), and exit the intersection (after_dt) in order to understand the efficiency of the system in capturing sand. 

I used Surface Integrals -> Mass Flow Rate on sand phase to extract the result, however I doubt the values are correct. The Mass Flow Rate is showing negative values for before_dt and into_dt lines, and also the magnitude of into_dt is larger than before_dt, is it possible? The volume fraction countour somehow is looking fine.

Did I do anything wrong on extracting the sand amount? I am sorry if the question and data provided are not clear enough.

 

[Rob]

There are a few things to check. 

• The interior zones don't have a normal so need to be oriented so all facets are aligned. That may or may not alter the +/- sign but more critically means all of the facets on the surface are +/- and can't cancel each other out. 
• Convergence - has the model been converging? Does the total mass in the domain add up to the injection?
• As there's a position difference in the 3 lines, are you seeing a lag effect in the values. Look at the upstream section to see why that might be occuring.