# Gas Mixing Measurements

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 April 21, 2015, 07:48 Gas Mixing Measurements #1 New Member   Rogaland Join Date: Mar 2014 Posts: 4 Rep Power: 5 Hi! I took the liberty of creating a new thread. My case is pretty straight forward. I have two parallel pipes. The smaller one located inside the bigger one. Eventually the smaller pipe ends and the mixing of nitrogen (bigger pipe) and helium (smaller pipe) begins. The flow rates are controlled by the inlet velocities (1% helium, 99% nitrogen). What I'm going to investigate is the level of mixing. I've been told that the CoV (Coefficient of Variation = standard deviation / mean) represents how well the mixture has blended. CoV = 1 means no mixing, while CoV = 0 indicates a perfect mix? With this being said I think I'm ready to define my problem. As you can see in the code below (functions output in controlDict), the CoV is greater than one. This means that the difference in concentration at a given measurement point is significantly higher or lower than the mean concentration of the cross section at the majority of measurement points? I.e. there is definitely not a uniform mix? Also, the flow rates given by my initial conditions doesn't seem right either (0.01-0.99). The inlet conditions have been verified several times. I could try changing from a velocity condition to a flow rate condition, although I can't see how this will change anything. The plane1/2 output is taken from a plane right before the outlet. the faceObje1/2 output is taken from my patch "outlet". Any thoughts? Code: ```faceSource plane1 output: areaAverage(sampledSurface) for He = 0.00162516212296 areaAverage(sampledSurface) for T = 352.574410291 areaAverage(sampledSurface) for N2 = 0.998374837877 faceSource plane2 output: CoV(sampledSurface) for He = 1.29855814792 CoV(sampledSurface) for T = 0.00170251695443 CoV(sampledSurface) for N2 = 0.00211380278868 faceSource faceObj1 output: areaAverage(outlet) for He = 0.00158949601069 areaAverage(outlet) for T = 352.583244014 areaAverage(outlet) for N2 = 0.998410503989 faceSource faceObj2 output: CoV(outlet) for He = 1.31250790071 CoV(outlet) for T = 0.00168238393736 CoV(outlet) for N2 = 0.00208954739943``` Last edited by Javell; April 21, 2015 at 14:09.

 April 22, 2015, 01:20 #2 Member   Join Date: May 2012 Posts: 55 Rep Power: 8 Which solver are you using?

 April 22, 2015, 02:15 #3 New Member   Rogaland Join Date: Mar 2014 Posts: 4 Rep Power: 5 reactingFoam with reactions turned off.

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