# How to get desired flow rate with pressure inlet and zero pressure outlet BC

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 November 15, 2016, 15:53 How to get desired flow rate with pressure inlet and zero pressure outlet BC #1 Member   saurabh kumar gupta Join Date: Jul 2016 Location: kanpur,india Posts: 53 Rep Power: 8 Hi all, i am doing a 2-D simulation where i need to get some fixed mass flow and my inlet and outlet BC's are pressure inlet and zero pressure outlet. From one of the paper i got to know that i need to keep on changing my inlet pressure to get desired mass flow but it is getting almost to close to zero at inlet. How should i proceed? Any help will be great. Thanks in advance. regards saurabh

 November 15, 2016, 23:58 #2 Senior Member   Behrooz Jamshidi Join Date: Apr 2013 Posts: 110 Rep Power: 11 Hi Your inlet pressure is gauge pressure. If your operating pressure is 101325Pa then you can also give negative values for inlet pressure to find your desired mass flow rate. Another way is checking the box target mass flow rate on pressure outlet boundary.

 November 16, 2016, 06:02 #3 Member   saurabh kumar gupta Join Date: Jul 2016 Location: kanpur,india Posts: 53 Rep Power: 8 Hi, i have total pressure at inlet and zero static pressure at outlet. and my pressure range is 80-120mm Hg. here i am confuse with operating pressure. should i give it atmospheric or 80 mm Hg. Thanks for your kind reply. regards saurabh

 November 16, 2016, 07:24 #4 Senior Member   Behrooz Jamshidi Join Date: Apr 2013 Posts: 110 Rep Power: 11 Hi This is a basic fluid mechanics question, not cfd. While you dont have phase change or pressure dependent material properties, then value of operating pressure is not imprtant. If you choose any value for it, then other static pressure values are relative to that value. The answer which software gives you is the pressure drop from inlet to outlet.

 November 16, 2016, 07:32 #5 Member   saurabh kumar gupta Join Date: Jul 2016 Location: kanpur,india Posts: 53 Rep Power: 8 i am taking zero as operating pressure, 100 at inlet as total pressure and zero static pressure at outlet. is this correct or need some changes here. and my desired flow rate is 5 litre/minute. so in Kg/s=.08333

 Tags boundary conditon, mass flow rate, pressure inlet