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Emanuele July 7, 2006 10:33

I intend simulate with Vectis the exhaust gas flow from cylinder both in steady and unsteady way. During calculation I encountered in some problems. They are described below: To calculate HTC and heat flux on valve surface I need of an high precision in the boundary layer. To ensure a correct calculation I monitored y+ value on the valve surface and I noticed that they are too low (< 30 on the majority of the surface). So I decreased the mesh by increasing cells' dimension: y+ values increased, but their values are still lower than 30 somewhere on surface. What can I do to control y+ as an alternative to reduce mesh resolution?In fact I think that calculation accuracy could be compromise in this way. To decrease calculation time I intend apply in-cylinder pressure and temperature at one boundary and pressure, temperature or mass mass flow at the other side. Pressure and temperature data were calculated by Wave at any crank angle. So for unsteady calculation I had to change boundary condition at any time region: do you think this could be a wrong solution? If not, in which format we have to write a file to assign boundary conditions? Can you send us an example of this file? We tried to make a calculation in this way, but at a point it stops giving this error: "negative temperature found in subroutine calch". What does it mean? Thank'you everybody for attention and collaboration.

mohsenfjs May 23, 2010 10:46

hi emanuele

I'm just doing the same project as you did but using AVL FIRE and i'm having my own difficulties and I just wanted to know how did you setup your cases. would you please email me on

thanks a lot

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