Question:

How can I accumulate two different functions of HMMT (for example, Wind +
Turning).



Answer:

You can load a particular heeling moment value into a variable and add it to
another value.  For example,

  VARIABLE x
  HMMT OFF
  SOLVE `<- finds equilibrium without heeling moment
  HMMT TURN radius speed /C1
  SET x = {HMMT}
  HMMT WIND /C1
  SET x = {x} PLUS {HMMT}
  HMMT {x} /C1

The limitation of this is that it can only provide a constant or sinusoidal
HMMT function of heel.  However by using more variables you could "capture"
the values at several heel angles and then use the form of the HMMT command
where you specify a value at each heel angle.