# Mixture and Decay of a tracer in a Water Tank

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 June 23, 2012, 10:14 Mixture and Decay of a tracer in a Water Tank #1 New Member   Jeffrey Join Date: Jun 2012 Posts: 1 Rep Power: 0 Hello I have a problem that i cannot answer yet. My simulation is a water tank, circular, with Diameter of 10m and a inlet at a center-bottom, with diameter of 0.125m. There is a mixture of water+tracer entering at inlet, with concentration of 3mg/l. (MixtureInlet) But, in the water tank, there is another mixture of water+tracer, with a concentration of 4mg/l. (MixtureInside) Initially, the water lever of the mixture that was alredy in the tank was 9,85m (my tank has 10m high), the water rises until 10m, and then, water goes out until the water level is 3,75m. The two mixtures will mix, and i will analyse the decay of the tracer with time. My problem is, the mass fraction of inlet mixture is constant,so, I created a mixture fixed values (Mass fraction of tracer = 2x10^-6). The mixture INSIDE the tank will mix and decay, so, i created a mixture with variable values. The Mass fraction, initialy at the tank, before entering any water, is 3x10^-6. So, i will create a equation that simulates the decay. But, for that , i will use C= Co. e^-kt I am trying now, to put the initial value of mass fraction of mixture in tank, 3x10^-6, PLUS the mass fraction of water entering in the water tank. But it is not working ;/ I tried (Tracer.MixtureInlet.Volume Fraction + 3x10^-6).e^-kt, but it is not working. Any ideas?

 June 24, 2012, 07:49 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,732 Rep Power: 143 I do not completely understand your question - do you want the mass fraction of the incoming material to decay over time? This sounds straight forward. Please post the output file which shows the error.

 July 27, 2012, 13:31 #3 Member     Felipe Gobbi Join Date: Apr 2012 Location: Brazil Posts: 76 Rep Power: 14 Hello, First of all, are you familiar with the CEL language? Do you know the variables you're allowed to use? Do you know how to write them properly? Shouldn't you use Mass Fraction instead of Volume Fraction? Describe how your materials are set! Do you have water + tracer as a variable composition mixture? Is water set as constraint? Give us more details of how did you set your parameters, so help will come easier. Good luck, Felipe.

 Tags cfd, decay, mixture and liquid, tracer