Inlet Boundary Condition

athar786 · May 23, 2011, 14:26

Dear All,

i am doing a small project on gas turbine using fluent, but i am facing problems with boundary conditions at inlet...
working fluid is simply air. What BCs should I use at inlet?
Please guide me in this regard?

Secondly, is it possible to apply two boundary conditions on one face? (e.g. pressure and velocity)

Thanks

L. Hamid · May 24, 2011, 02:33

Hi athar786

1- you can set the pressure inlet or velocity inlet in inlet Boundary condition. with the velocity B.C you can converge your model easier than Pressure outlet.

2- you can't set two B.C on one face. if you want do this you should create two face and then set two B.C on face.

athar786 · May 24, 2011, 08:06

Thanks Hamid...

please clear one more thing reagrding two BCs on one face i.e. at inlet...
should I split the face and apply one BC on each face (i.e. pressure inlet at one and velocity inlet at other)? or something else?

L. Hamid · May 24, 2011, 23:45

Hi athar786

you can't split the one face in two or several parts and then apply the different B.C for each parts. if you want check the velocity and pressure on one face, do the following procedure:

1- set the velocity inlet B.C for your desired face.
2- go to "Solve\Monitor\Surface" in fluent and in the "Surface Monitors" window increase the 0 to 1. then in the Name:monitor-1 click define and from the "report of" select "pressure: total pressure" and in the "surface" section, select your velocity inlet B.C then set 1 to the "plot window" click OK. you should click the Plot button in "Surface Monitors" window then click OK.

3- you can check your face pressure in each iteration.
4- when the pressure of the face reaches to your desired value your solution in done.

inform me if you do this process
i hope this explanation would help you

athar786 · May 25, 2011, 14:24

Thanx dear.

i,ve tried every thing you mentiond in your last post but this opens up a window which shows convergence of pressure......
let me clear my problem........

I want to apply pressure and velocity at inlet of the gas turbine....
velocity=100 m/s and pressure=1.96e5

but according to your procedure, i can only give velocity=100 m/s, and there is no option for pressure input at all........ the thing is, i want to put both velocity and pressure value at inlet.....

i think its more clear now....
so please help me......and i sorry for bothering you again and again....

thanx alot dear....

L. Hamid · May 26, 2011, 01:18

Hi athar786

i know what you say. according to the process i explained, you can check the pressure convergence and your pressure should reach to the near value 1.96e5

if you did not accept the last procedure, you can set the ''pressure=1.96e5'' in fluent according to the bellow way:
Fluent: Define\operating pressure then you set the operating pressure to your desired value.
in fact, you set velocity inlet at inlet boundary and set the pressure at inlet B.C

good luck

athar786 · May 26, 2011, 11:07

thanx alot dear........i'll try it soon.....
what does "operating pressure" mean? isn't it the pressure at which your entire system operates? or it dictates something else.?

L. Hamid · May 27, 2011, 23:58

Hi

the operating pressure means that your system pressure start to work at P = ...
it means that your Fluid or gas inters to the inlet at this specific pressure. the pressure of other sections varies with this pressure. in fact in your problem you should transfer your coordinate in Gambit to the inlet B.C and now your reference point is (0,0,0)

May 23, 2011, 14:26	Inlet Boundary Condition	#1
athar786 New Member Join Date: May 2011 Posts: 4 Rep Power: 14	Dear All, i am doing a small project on gas turbine using fluent, but i am facing problems with boundary conditions at inlet... working fluid is simply air. What BCs should I use at inlet? Please guide me in this regard? Secondly, is it possible to apply two boundary conditions on one face? (e.g. pressure and velocity) Thanks

May 24, 2011, 08:06	Boundary conditions at inlet	#3
athar786 New Member Join Date: May 2011 Posts: 4 Rep Power: 14	Thanks Hamid... please clear one more thing reagrding two BCs on one face i.e. at inlet... should I split the face and apply one BC on each face (i.e. pressure inlet at one and velocity inlet at other)? or something else?

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May 24, 2011, 02:33		#2
L. Hamid Member Hamid Join Date: Dec 2010 Location: Iran Posts: 30 Rep Power: 15	Hi athar786 1- you can set the pressure inlet or velocity inlet in inlet Boundary condition. with the velocity B.C you can converge your model easier than Pressure outlet. 2- you can't set two B.C on one face. if you want do this you should create two face and then set two B.C on face.

May 24, 2011, 23:45		#4
L. Hamid Member Hamid Join Date: Dec 2010 Location: Iran Posts: 30 Rep Power: 15	Hi athar786 you can't split the one face in two or several parts and then apply the different B.C for each parts. if you want check the velocity and pressure on one face, do the following procedure: 1- set the velocity inlet B.C for your desired face. 2- go to "Solve\Monitor\Surface" in fluent and in the "Surface Monitors" window increase the 0 to 1. then in the Name:monitor-1 click define and from the "report of" select "pressure: total pressure" and in the "surface" section, select your velocity inlet B.C then set 1 to the "plot window" click OK. you should click the Plot button in "Surface Monitors" window then click OK. 3- you can check your face pressure in each iteration. 4- when the pressure of the face reaches to your desired value your solution in done. inform me if you do this process i hope this explanation would help you

May 25, 2011, 14:24		#5
athar786 New Member Join Date: May 2011 Posts: 4 Rep Power: 14	Thanx dear. i,ve tried every thing you mentiond in your last post but this opens up a window which shows convergence of pressure...... let me clear my problem........ I want to apply pressure and velocity at inlet of the gas turbine.... velocity=100 m/s and pressure=1.96e5 but according to your procedure, i can only give velocity=100 m/s, and there is no option for pressure input at all........ the thing is, i want to put both velocity and pressure value at inlet..... i think its more clear now.... so please help me......and i sorry for bothering you again and again.... thanx alot dear....

May 26, 2011, 01:18		#6
L. Hamid Member Hamid Join Date: Dec 2010 Location: Iran Posts: 30 Rep Power: 15	Hi athar786 i know what you say. according to the process i explained, you can check the pressure convergence and your pressure should reach to the near value 1.96e5 if you did not accept the last procedure, you can set the ''pressure=1.96e5'' in fluent according to the bellow way: Fluent: Define\operating pressure then you set the operating pressure to your desired value. in fact, you set velocity inlet at inlet boundary and set the pressure at inlet B.C good luck

May 26, 2011, 11:07		#7
athar786 New Member Join Date: May 2011 Posts: 4 Rep Power: 14	thanx alot dear........i'll try it soon..... what does "operating pressure" mean? isn't it the pressure at which your entire system operates? or it dictates something else.?

May 27, 2011, 23:58		#8
L. Hamid Member Hamid Join Date: Dec 2010 Location: Iran Posts: 30 Rep Power: 15	Hi the operating pressure means that your system pressure start to work at P = ... it means that your Fluid or gas inters to the inlet at this specific pressure. the pressure of other sections varies with this pressure. in fact in your problem you should transfer your coordinate in Gambit to the inlet B.C and now your reference point is (0,0,0)