diff --git a/m_fdm_calc.f90 b/m_fdm_calc.f90
index 9057e86..a5518a8 100644
--- a/m_fdm_calc.f90
+++ b/m_fdm_calc.f90
@@ -289,11 +289,12 @@ module m_fdm_calc
         write(St_data,'(f10.5,10e25.15)')fdmtime,dummyu_,sum_wrate,fl_location/(REAL(nx-1)*hx)*100.
 
 ! Control the inflow mean velocity, dummyu_
+        write(*,'(a20,2f12.8)') ' ** oldsumc, sumc = ',oldsumc,sumc
         if(swadtv.ne.0.and.mod((fdmcyc+1),swadtv).eq.0) then
           time_int=fdmtime-time_int
-          delu=(oldsumc-sumc)/time_int
+          delu=(sumc-oldsumc)/time_int
           if ((fdmtime).gt.startad.and.oldsumc.ne.0.) then
-            dummyu_=dummyu_-delu
+            dummyu_=dummyu_+delu
           endif
           time_int=fdmtime
         endif