Re: [ESPResSo-users] OIF - background_errors

[Iveta Jancigova]

Hi,

it also depends on the size of your object. If it is small, it  
basically "flows with the fluid" and as the fluid flows past the  
obstacle, so does the object.

However, if your object is large - let's say, half of the object is in  
the flow that goes above the obstacle and the other half in the flow  
that goes below the obstacle, then the object hits the obstacle and  
the soft-sphere potential is not strong enough to prevent particles  
from entering.

If you send the complete script together with obstacles and the  
mesh-files you are using for your object, we could take a look.

Regards,
Iva

> Message: 1
> Date: Tue, 8 Apr 2014 11:21:12 +0000
> From: "Wink, Markus" <address@hidden>
> To: "address@hidden" <address@hidden>
> Subject: [ESPResSo-users] OIF - background_errors 0
> Message-ID:
>         <address@hidden>
> Content-Type: text/plain; charset="us-ascii"
>
> Dear ESPResSo-community,
>
> I have got a question concerning the OIF implementation. In my case  
> I have put an object (a sphere) in a microfluidic channel that has a  
> rhomboid as a barrier inside. I applied a constant force density to  
> achieve a fluid flow. I want to investigate the trajectory of the  
> object inside the channel. As it reaches the rhomboid, the object is  
> deflected by it. Nevertheless, I get an error message after some  
> time the object is in contact with the rhomboid:
>
> background_errors 0 {063 rhomboid constraint 4 violated by particle 376}
>
> My interpretation is, that one node of my object (particle 376)  
> tries to enters the rhomboid. That of cause should not be the case.
>
> The rhomboid was defined by the command:
>
> constraint rhomboid corner $corX $corY $corZ a $aX $aY $aZ b $bX $bY  
> $bZ c $cX $cY $cZ direction 1 type 10
> lbboundary rhomboid corner $corX $corY $corZ a $aX $aY $aZ b $bX $bY  
> $bZ c $cX $cY $cZ direction 1
>
>
> The object is defined by:
>
> oif_add_object object-id 0 template-id 0 origin 125 85 9 part-type 0 mass 1
>
> The object-rhomboid interaction is implemented by:
>
> inter 0 10 soft-sphere 0.0001 1.2 0.1 0.0
>
> How can I avoid the error message mentioned above? Is there any  
> mistake in my script? Does it help to lower the time step (so far, I  
> chose time_step 0.1)?
>
> Thanks for your help?
>
> Greetings
>
> Markus Wink

Iveta Jancigova, PhD student
Department of Information Networks
Faculty of Management Science and Informatics
University of Zilina
E-mail: address@hidden
Office: B352
Work Phone: +421-41-5134313