Volume averaged-field

acalado · October 3, 2016, 11:29

Hey guys,

suppose I want to create a new field function for velocity or pressure where the local value is a volume average of a sphere around that point.

What is the easiest way to define such a thing?

Thanks in advance!!

Schwob77 · October 3, 2016, 12:27

Hi,
I would create a local spherical coordinate system in the point you want to observe. For that coordinate system you can create a cell set of the type "threshold". Use the r-coordinate as field function and specify a radius that you wnt to use.
Along with that cell set you get a field function e.g. "Cell Set 1" that has a value of 1 for the cells inside the sphere.
Now you create two field functions:

FF1: $FF*$Volume*$CellSetVar1
FF2: $Volume*$CellSetVar1

"$FF" is the Field Function that you want to average inside the sphere, e.g $Pressure or $$Velocity.mag().

Create two sum reports for FF1 and FF2.
Now you create a third Field Function or a expression report that devides the sum report of FF1 by the sum report of FF2. The result should be your searched value.

acalado · October 3, 2016, 12:38

Quote:

Originally Posted by Schwob77

Hi,
I would create a local spherical coordinate system in the point you want to observe. For that coordinate system you can create a cell set of the type "threshold". Use the r-coordinate as field function and specify a radius that you wnt to use.
Along with that cell set you get a field function e.g. "Cell Set 1" that has a value of 1 for the cells inside the sphere.
Now you create two field functions:

FF1: $FF*$Volume*$CellSetVar1
FF2: $Volume*$CellSetVar1

"$FF" is the Field Function that you want to average inside the sphere, e.g $Pressure or $$Velocity.mag().

Create two sum reports for FF1 and FF2.
Now you create a third Field Function or a expression report that devides the sum report of FF1 by the sum report of FF2. The result should be your searched value.

Yes, but that would be the average of that point.

I want to do the average for my whole domain.

Schwob77 · October 3, 2016, 16:51

Ok, I haven't understood that you want to get that value in every cell of the domain.
Sorry, but I'm not aware of any easy method outside of user coding to do that.

October 3, 2016, 11:29	Volume averaged-field	#1
acalado Senior Member André Join Date: Mar 2016 Posts: 133 Rep Power: 10	Hey guys, suppose I want to create a new field function for velocity or pressure where the local value is a volume average of a sphere around that point. What is the easiest way to define such a thing? Thanks in advance!! __________________ Sapere aude!

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October 3, 2016, 12:27		#2
Schwob77 Member Join Date: Nov 2015 Posts: 38 Rep Power: 11	Hi, I would create a local spherical coordinate system in the point you want to observe. For that coordinate system you can create a cell set of the type "threshold". Use the r-coordinate as field function and specify a radius that you wnt to use. Along with that cell set you get a field function e.g. "Cell Set 1" that has a value of 1 for the cells inside the sphere. Now you create two field functions: FF1: $FF$Volume$CellSetVar1 FF2: $Volume*$CellSetVar1 "$FF" is the Field Function that you want to average inside the sphere, e.g $Pressure or $$Velocity.mag(). Create two sum reports for FF1 and FF2. Now you create a third Field Function or a expression report that devides the sum report of FF1 by the sum report of FF2. The result should be your searched value.

October 3, 2016, 16:51		#4
Schwob77 Member Join Date: Nov 2015 Posts: 38 Rep Power: 11	Ok, I haven't understood that you want to get that value in every cell of the domain. Sorry, but I'm not aware of any easy method outside of user coding to do that.