A function of time boundary condition

stewie · April 19, 2023, 14:12

Hello everyone,

i'm trying to set a boundary condition to simulate a speaker, therefore the following equation is used for the pressure field: pm+pa*cos(2*pi*F*T)

so i'm trying to set this function as a boundary condition for the pressure field, tried the BC type waveTransmissive but it's tricky to use.

according to Chat gpt this is the way it's used:
inlet { type waveTransmissive; waveType function; functionObjectLibs ("libsampling.so"); functionObjectDict { type genericFunctionObject; outputControl timeStep; enabled true; function "0.5*sin(2*pi*2*time)"; fields (U); } }
but it's not working

so how to set a function of time as a boundary condition (any desired function).

thank you'all

olesen · April 20, 2023, 03:51

Probably the easier is use a uniformFixedValue boundary condition, which takes a PatchFunction1 to describe the value. The name 'uniform fixed value' (historical name) is definitely very misleading, since in the meantime it can be also be spatially and temporally varying.

With the PatchFunction1 for the uniformValue, you have a variety of functions available, ranging from constant, table, sin, coded etc. For you, the expression function is probably the most convenient.

stewie · April 20, 2023, 07:32

thank you a lot sir, it works, appreciated .

olesen · April 20, 2023, 10:24

For a nice followup, could you also post your solution. There will inevitably be someone coming in 1-3 years and asking about how you managed to solve it.

April 19, 2023, 14:12	A function of time boundary condition	#1
stewie New Member abdellah Join Date: Apr 2023 Posts: 2 Rep Power: 0	Hello everyone, i'm trying to set a boundary condition to simulate a speaker, therefore the following equation is used for the pressure field: pm+pacos(2piFT) so i'm trying to set this function as a boundary condition for the pressure field, tried the BC type waveTransmissive but it's tricky to use. according to Chat gpt this is the way it's used: inlet { type waveTransmissive; waveType function; functionObjectLibs ("libsampling.so"); functionObjectDict { type genericFunctionObject; outputControl timeStep; enabled true; function "0.5sin(2pi2time)"; fields (U); } } but it's not working so how to set a function of time as a boundary condition (any desired function). thank you'all

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April 20, 2023, 03:51		#2
olesen Senior Member Mark Olesen Join Date: Mar 2009 Location: https://olesenm.github.io/ Posts: 1,695 Rep Power: 40	Probably the easier is use a uniformFixedValue boundary condition, which takes a PatchFunction1 to describe the value. The name 'uniform fixed value' (historical name) is definitely very misleading, since in the meantime it can be also be spatially and temporally varying. With the PatchFunction1 for the uniformValue, you have a variety of functions available, ranging from constant, table, sin, coded etc. For you, the expression function is probably the most convenient.

April 20, 2023, 07:32		#3
stewie New Member abdellah Join Date: Apr 2023 Posts: 2 Rep Power: 0	thank you a lot sir, it works, appreciated .

April 20, 2023, 10:24		#4
olesen Senior Member Mark Olesen Join Date: Mar 2009 Location: https://olesenm.github.io/ Posts: 1,695 Rep Power: 40	For a nice followup, could you also post your solution. There will inevitably be someone coming in 1-3 years and asking about how you managed to solve it.