Pressure-inlet: controlling velocity

KeganLeckness · January 28, 2016, 16:13

I'm working with a cylindrical canal, with only one pressure-inlet BC and all other BCs are walls.

I have a pressure-vs-time profile of experimental data that I assign to the Gauge Total Pressure box in the Pressure Inlet task window. I understand that I can control the velocity through the inlet by defining static pressure in addition to total pressure. (This is achieved via Eq. 6-78 in section 6.3.3.3.2. of the Fluent User's Guide.) My issue is in defining the static pressure. I have created an additional pressure-vs-time profile of the desired static pressure profile, that I apply to the Supersonic/Initial Gauge Pressure box. This should, in my mind, define both total and static pressure, thereby governing inlet velocity. Monitors show that static pressure remains unchanged (as compared to runs with only total pressure defined). It's as if I didn't change the referenced profile in the Supersonic box.

I have two profiles (static pressure- and total pressure-vs-time); how do I define both profiles such that I may control the velocity through the inlet?

Thanks,
Kegan Leckness

LuckyTran · January 29, 2016, 15:04

Is your inlet supersonic or subsonic?

The Supersonic/Initial Gauge Pressure box does not directly control the static pressure. This cell is used only when you initialize your fields by computing from the inlet or if the flow is supersonic. In order to specify the velocity via the static pressure, the flow must be supersonic.

I don't think there is an (easy) way to specify the static pressure at the inlet in order to control the velocity for the subsonic case.

KeganLeckness · February 8, 2016, 17:15

My flow is subsonic. And you are correct.

I'm interested in how a certain parameter changes with increasing inlet velocity. I want inlet total pressure to remain the same (and be my control). Is there really no way to keep velocity the same to test pressure's effect, and visa-versa? I need to determine how to conduct these analyses, as these results would supply much-needed support to one of my conclusions. If the only way is hard- I'm still interested.

January 28, 2016, 16:13	Pressure-inlet: controlling velocity	#1
KeganLeckness Member Kegan Leckness Join Date: Mar 2015 Posts: 38 Rep Power: 11	I'm working with a cylindrical canal, with only one pressure-inlet BC and all other BCs are walls. I have a pressure-vs-time profile of experimental data that I assign to the Gauge Total Pressure box in the Pressure Inlet task window. I understand that I can control the velocity through the inlet by defining static pressure in addition to total pressure. (This is achieved via Eq. 6-78 in section 6.3.3.3.2. of the Fluent User's Guide.) My issue is in defining the static pressure. I have created an additional pressure-vs-time profile of the desired static pressure profile, that I apply to the Supersonic/Initial Gauge Pressure box. This should, in my mind, define both total and static pressure, thereby governing inlet velocity. Monitors show that static pressure remains unchanged (as compared to runs with only total pressure defined). It's as if I didn't change the referenced profile in the Supersonic box. I have two profiles (static pressure- and total pressure-vs-time); how do I define both profiles such that I may control the velocity through the inlet? Thanks, Kegan Leckness

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January 29, 2016, 15:04		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	Is your inlet supersonic or subsonic? The Supersonic/Initial Gauge Pressure box does not directly control the static pressure. This cell is used only when you initialize your fields by computing from the inlet or if the flow is supersonic. In order to specify the velocity via the static pressure, the flow must be supersonic. I don't think there is an (easy) way to specify the static pressure at the inlet in order to control the velocity for the subsonic case.

February 8, 2016, 17:15		#3
KeganLeckness Member Kegan Leckness Join Date: Mar 2015 Posts: 38 Rep Power: 11	My flow is subsonic. And you are correct. I'm interested in how a certain parameter changes with increasing inlet velocity. I want inlet total pressure to remain the same (and be my control). Is there really no way to keep velocity the same to test pressure's effect, and visa-versa? I need to determine how to conduct these analyses, as these results would supply much-needed support to one of my conclusions. If the only way is hard- I'm still interested.