FORCING: Normalize the injection power by the volume size.

Signed-off-by: Grzegorz Kowal <grzegorz@amuncode.org>

sources/forcing.F90

@@ -173,7 +173,7 @@ module forcing
   subroutine initialize_forcing(verbose, status)
 
     use constants  , only : pi2
-    use coordinates, only : xlen, ylen, zlen
+    use coordinates, only : xlen, ylen, zlen, vol
     use helpers    , only : print_message
     use parameters , only : get_parameter
     use random     , only : randuni, randnorz
@@ -732,6 +732,10 @@ module forcing
 
           end select
 
+! normalize the injection power by the volume size
+!
+          fmodes(:) = fmodes(:) / sqrt(vol)
+
 ! === Ornstein–Uhlenbeck driving ===
 !
           if (injection_method == injection_oh) then