# how to measure the additional variable at outlet

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 January 28, 2008, 01:17 how to measure the additional variable at outlet #1 sherkhan Guest   Posts: n/a I am using CFX11. Can anybody help me that how to find the additional variable %mass(kg) which leave the outlet at a specific time in a transient solution

 January 28, 2008, 05:03 Re: how to measure the additional variable at outl #2 Rikio Guest   Posts: n/a Some functions can be obtained from the function calculator. Is the %mass mean mass fraction? If so, you can obtain the massflow of outlet for each component, and then calculate manually or using customer defined variable.

 January 28, 2008, 07:49 Re: how to measure the additional variable at outl #3 sherkhan Guest   Posts: n/a Thanks Rikio, My problem is that i run the simulation 1st for steady state and then use these results for transient rum. I selected monitor points at inlet and outlet to monitor the concentration of additional variable (kg m^-3. But when I output data from solver the conc. at monitor pt1(inlet) is 0.98 (kg m^-3) but at outlet the conc. is only 0.06(kg m^-3). Is something wrong with my setting?? How can I take the X percent(any percent) of additional variable at outlet. Please any body help

 January 30, 2008, 04:34 Re: how to measure the additional variable at outl #4 Andreas Guest   Posts: n/a At first you should check your imbalances, i.e. whether (especially in your steady-state simulation) the amount of your additional variable coming in at inlet is also coming out; otherwise you still need more iterations. Then, is concentration is in kg/m^3 it is a concentration density, and you can directly compare this with fluid density. Take the function calculator in CFX-Post and calculate areaAve of concentration at outlet divided by areaAve of density at outlet, then you have the ratio; multiply with 100, then you have percentage.

 January 30, 2008, 21:39 Re: how to measure the additional variable at outl #5 sherkhan Guest   Posts: n/a Thanks andreas, But there is still problem that i can not see in CFX post the function variable Concentration. Please have a detail look The tracer at the inlet was added by the following eq. ExpFunction= fc*(1/(1+exp(-alpha*(t-sher ))))*(1-1/(1+exp(-alpha*(t-sher )))), alpha= 0.5[s^-1], fc = 1[kg m^-3], sher = 15[s], mass flow rate at inlet = 0.005kg s^-1, mass flow rate at outlet = 0.005kg s^-1, The solution was run for 20000s as transient and convergence level is 10^-6. but i can not get the percentage of mass flowing away the outlet. please help

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