[mohamed samy]

Hi there,
I am trying to simulate 2D piston movement i searched online and i got that i can make it with profile file so i wrote this file
*the moving wall called piston

piston 2 11 0
time x
0 0
1 -0.01
2 -0.02
3 -0.03
4 -0.04
5 -0.05
6 -0.06
7 -0.07
8 -0.08
9 -0.09
10 -0.1


but when i read it in fluent it not added to profiles and it says
"Reading profile file..."
and not doing anything so what is the error is it in profile file or on how i add it or what ??!

[mohamed samy]

I found a solution the right way to make it work

piston 11 2 0
time x
1 0.1
2 0.09
3 0.08
4 0.07
5 0.06
6 0.05
7 0.04
8 0.03
9 0.02
10 0.01
11 0.0

but i have another problem after starting the solution before any iteration it gives error
"Update-Dynamic-Mesh failed. Negative cell volume detected."
so what should i do ?!

[`e`]

It's likely you're moving the piston too far in each time step (causing a negative volume in a single cell). Try reducing the time step of the moving/deforming mesh and/or increase the number of mesh updates per time step.

[mohamed samy]

Originally Posted by `e`

It's likely you're moving the piston too far in each time step (causing a negative volume in a single cell). Try reducing the time step of the moving/deforming mesh and/or increase the number of mesh updates per time step.

yes at first it was moves to far 10 cell at each time step i tried and made the movement one cell at a time break the hole simulation into 100 time step but it gives the same error
"Update-Dynamic-Mesh failed. Negative cell volume detected."
when i press calculate or when click on preview mesh motion

how to increase updates per mesh ?! sorry i'm new in CFD

[mohamed samy]

i believe the problem may be wrong in profile file or in the way i setup the dynamic mesh settings

the motion of the line is working right but i want to ask in a thing in profile file i just wrote the position of the left line (piston) at each time step only
should i change the length of wall and axis (upper and lower line) too or the program understand that or what ?

[mohamed samy]

the white vertical line is piston so with its movement the horizontal lines (wall and axis) length not change is that what causes the negative volume problem if so how to overcome this problem should i wrote that in profile file or what please anyone help