Hi all,

This is my very first post here in SimScale and I hope anyone of you can help me with my issues.

Well, first I will introduce you to my case. I am simulating the flow around a loudspeaker which is symmetric, actually it is a revolution. In my first simulations the air flow comes from the front (**positive Y direction**). See the figure.

First I started simulating the half of it due to its symmetry, then I realised that it would also make sense to simulate only a quarter of it in order to do some fast tests while I was trying to find the proper mesh and simulation parameters. Besides that, since it is a very simple case, I decided to try to mesh the whole loudspeaker in order to compare the results obtanied before in the symmetrical approximations. And here comes the problemsâŚ

As I am interested in the forces generated due to te wind I used the Result Control Item âForces and momentsâ and I figured out that the software is not accounting for the symmetry boundary condition when it comes to compute the forces and moments. As you can see in the following extracts from the log files.

```
full case
forces forces10 output:
sum of forces:
pressure : (0.00825357707279 87.5149908496 -0.0124717628806)
viscous : (-0.000623983437007 -0.380113391217 8.91044105778e-05)
porous : (0 0 0)
sum of moments:
pressure : (0.00366623415021 9.70446114237e-08 0.00358251252754)
viscous : (-4.85506514759e-06 -1.54834589139e-06 2.53780385519e-05)
porous : (0 0 0)
----------------------------------------------------------------------------
half case
forces forces10 output:
sum of forces:
pressure : (0.063647549237 84.2962878434 -107.410562012)
viscous : (5.27459856009e-05 -0.310844783919 -0.058027945383)
porous : (0 0 0)
sum of moments:
pressure : (11.5147196512 0.00198231280144 0.011050221433)
viscous : (-0.010047362284 3.77202129623e-06 2.28325651371e-06)
porous : (0 0 0)
----------------------------------------------------------------------------
quarter case
forces forces10 output:
sum of forces:
pressure : (54.0351529408 43.4167688264 -54.0068510305)
viscous : (0.0347102611718 -0.15713904296 -0.0346544658095)
porous : (0 0 0)
```

I can understand that the forces in **X** and **Z** directions vary between cases since symmetry is not handled as such, but I donât understand the noticeable differences in the force in the **Y** direction (wind direction) in the three cases. Can anyone explain me where they come from? I also attach the pictures of the pressure distribution in all the cases, which is related to the resulting force.

Cananyone explain me why the max pressure in the full case is less than half the max pressure in the symmetry cases? Did I make any mistake defining the symmetry BCâs?

Any hint will be very much appreciated!

Best regards,

Alex