negative mass flow rate in pressure outlet

piyusharas · June 29, 2015, 15:05

I am modeling a multiphase system of water and air in which only water is leaving from my pressure outlets . .
I have getting negative mass flowrates at my pressure outlets.
Is it correct that it is treating mass flow rate as vector quantity or something and I should take the magnitude or it is conceptually wrong and water is instead entering through my outlet.

pakk · June 30, 2015, 09:05

Fluent uses the inward normal.
So a negative mass flow at a boundary means that mass is leaving your system, and a positive mass flow means that mass is entering your system.

piyusharas · June 30, 2015, 11:41

Yeah that's what my doubt was.
thank you for clearing my doubt.

esha · December 9, 2018, 07:06

hi, I am simulating a channel flow having the periodic inlet in fluent and mass flux rate is negative, is that right answer? and is there any effect of this on Reynolds number?

June 29, 2015, 15:05	negative mass flow rate in pressure outlet	#1
piyusharas Member Piyush Aras Join Date: Jun 2015 Posts: 34 Rep Power: 10	I am modeling a multiphase system of water and air in which only water is leaving from my pressure outlets . . I have getting negative mass flowrates at my pressure outlets. Is it correct that it is treating mass flow rate as vector quantity or something and I should take the magnitude or it is conceptually wrong and water is instead entering through my outlet.

June 30, 2015, 09:05		#2
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	Fluent uses the inward normal. So a negative mass flow at a boundary means that mass is leaving your system, and a positive mass flow means that mass is entering your system. ayhan515, dhiraj.lote@gmail.com, prasa and 1 others like this.

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June 30, 2015, 11:41		#3
piyusharas Member Piyush Aras Join Date: Jun 2015 Posts: 34 Rep Power: 10	Yeah that's what my doubt was. thank you for clearing my doubt.

December 9, 2018, 07:06		#4
esha Member Join Date: Aug 2018 Posts: 85 Rep Power: 7	hi, I am simulating a channel flow having the periodic inlet in fluent and mass flux rate is negative, is that right answer? and is there any effect of this on Reynolds number?