Dear Community, I would like to know more about how to implement damping-zones in detail. Of course I already found the example with the following structure, but no other information about the mathematical background of this "Absorption-Forcing" and the definitions of RefFields and SpongeCoeffizient : <!-- Define reference fields /--> <FUNCTION NAME="RefFields"> <E VAR="u" VALUE="-y*y+1" /> <E VAR="v" VALUE="0" /> <E VAR="p" VALUE="0" /> </FUNCTION> <FUNCTION NAME="SpongeCoefficient"> <E VAR="u" VALUE="-100*(x>2.5)" /> <E VAR="v" VALUE="-100*(x>2.5)" /> </FUNCTION> </CONDITIONS> <FORCING> <FORCE TYPE="Absorption"> <COEFF> SpongeCoefficient </COEFF> <REFFLOW> RefFields </REFFLOW> </FORCE> </FORCING> With the SpongeCoefficient function I define the space where my sponge zone starts, am I right? So in this example it starts from x>2.5, but what about the -100? Is it some kind of function like u _damp = -100*u*(-y*y+1)? I'm not sure about that and there are no information in the user-guide. Can somebody explain that in more detail? And do I have to care any other modifications? Thanks for any answer! Best regards Fabian