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