Multiple surface arrangement
 

Hello community,

I am researching the flow behaviour for two wings in a close together arrangement. That mean´s, the second wing is from an equal size and only 0.3 times the chord length away from the front wing.

I set up a steady state case with SST model and local timescale factor to 4. The Boundary is captured with inflation layers and a refined body-of-influence box used near the wings.

The forces are fully converged after ~600 iterations, but the drag value for the front wing is negative at zero angle of attack. Moving the wings further apart from each other the drag becomes positive along the x-axis, which is defined positive in the direction of the flow. Therefore, a negative drag seems to be unrealistic, false.

Do you have any advice or ideas about how to handle this, maybe applying some local factors, changes in the mesh or separation issues?

Thank you all,
Flemming