How large should the far-field region be?

Paulni · October 7, 2010, 09:57

I am currently doing my master thesis where I am going to perform CFD calculations on the above water portion of a 228 meter long PCTC vessel equipped with vertical bow wing sails (or rather spoilers).

I need to find a reference on how large the far-field region should be. Any suggestions?

njenkins360 · October 7, 2010, 11:44

Not familiar with that application, but are you asking how big of a computational region you need to mesh? Like when can you assume potential flow (irrotational,incompressible)?

Paulni · October 7, 2010, 12:22

Precisely.

njenkins360 · October 7, 2010, 12:43

I would look at my Reynolds number, and determine the width of my boundary layer. As long as there are no other walls/boundaries to create vorticity, then potential flow should be valid as l,r --> inifinity. Where r,l are the distance from your object.

I think.

agarzon · October 21, 2010, 19:28

That usually depends on the CFD code you use. For subsonic flow usually somewhere between 10-20 times the body's longest dimension.

And as it may sound too big, you can let the elements grow big as they go out into the far filed. That way you wont get a ridiculously big grid.

I hope is not too late for the reply...

October 7, 2010, 09:57	How large should the far-field region be?	#1
Paulni New Member Paul Nielsen Join Date: Oct 2010 Posts: 2 Rep Power: 0	I am currently doing my master thesis where I am going to perform CFD calculations on the above water portion of a 228 meter long PCTC vessel equipped with vertical bow wing sails (or rather spoilers). I need to find a reference on how large the far-field region should be. Any suggestions?

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October 7, 2010, 11:44		#2
njenkins360 New Member Join Date: Oct 2010 Posts: 10 Rep Power: 15	Not familiar with that application, but are you asking how big of a computational region you need to mesh? Like when can you assume potential flow (irrotational,incompressible)?

October 7, 2010, 12:22		#3
Paulni New Member Paul Nielsen Join Date: Oct 2010 Posts: 2 Rep Power: 0	Precisely.

October 7, 2010, 12:43		#4
njenkins360 New Member Join Date: Oct 2010 Posts: 10 Rep Power: 15	I would look at my Reynolds number, and determine the width of my boundary layer. As long as there are no other walls/boundaries to create vorticity, then potential flow should be valid as l,r --> inifinity. Where r,l are the distance from your object. I think.

October 21, 2010, 19:28		#5
agarzon New Member agar Join Date: Oct 2010 Posts: 1 Rep Power: 0	That usually depends on the CFD code you use. For subsonic flow usually somewhere between 10-20 times the body's longest dimension. And as it may sound too big, you can let the elements grow big as they go out into the far filed. That way you wont get a ridiculously big grid. I hope is not too late for the reply...