Fluent UDF shows number of hits more than particles injected

syedabdullah · April 23, 2021, 04:21

I am injecting particles in the form a group in fluent. Under number of streams i give the value 7200.
The console shows 1504 particles trapped, 5696 escaped.
I am also using a UDF that records the number of particles colliding with the boundary of my airfoil.
When i add all the values of that data variable (the output i get from the udf, i get a number like 15000 or 17000 in some cases.
If i am injecting 7200 particles then how is it possible??

pakk · April 23, 2021, 07:42

It could be that your UDF does not return the number of particles that collide. Maybe your UDF counts the number of insects in your garden. It's hard to tell for us without seeing your UDF.

syedabdullah · April 23, 2021, 08:18

So i checked.
Fluent is injecting 7200 particles from -1 to 1 (y axis) with the flow rate mentioned, continuously until the simulation is finished. So even though the console shows only the particles in the current injection, the UDF records the number of collisions as they keep on happening one after the other until the flow simulation converges. Thats what i think is happening

Is there any way to just make injection one time? not a continuous injection

April 23, 2021, 04:21	Fluent UDF shows number of hits more than particles injected	#1
syedabdullah New Member Syed Muhammad Abdullah Join Date: Jul 2015 Posts: 6 Rep Power: 10	I am injecting particles in the form a group in fluent. Under number of streams i give the value 7200. The console shows 1504 particles trapped, 5696 escaped. I am also using a UDF that records the number of particles colliding with the boundary of my airfoil. When i add all the values of that data variable (the output i get from the udf, i get a number like 15000 or 17000 in some cases. If i am injecting 7200 particles then how is it possible??

April 23, 2021, 07:42		#2
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	It could be that your UDF does not return the number of particles that collide. Maybe your UDF counts the number of insects in your garden. It's hard to tell for us without seeing your UDF. __________________ "The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform" is NOT the error after compiling. It is the error after loading. To see compiler errors, look at your screen after you click "build".

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April 23, 2021, 08:18		#3
syedabdullah New Member Syed Muhammad Abdullah Join Date: Jul 2015 Posts: 6 Rep Power: 10	So i checked. Fluent is injecting 7200 particles from -1 to 1 (y axis) with the flow rate mentioned, continuously until the simulation is finished. So even though the console shows only the particles in the current injection, the UDF records the number of collisions as they keep on happening one after the other until the flow simulation converges. Thats what i think is happening Is there any way to just make injection one time? not a continuous injection