Modified pressure0 to be converted from positive to negative from the input...

Modified pressure0 to be converted from positive to negative from the input file, consistent with the DOUAR pressure sign convention

src/define_ov.f90

@@ -120,10 +120,10 @@ if (params%irestart.eq.0) then
    ov%wnode=0.d0
    ov%wnodeiso=0.d0
    !ov%pressure=0.d0 
-   ov%pressure=params%pressure0
+   ov%pressure=-params%pressure0
    ov%spressure=0.d0
    !ov%temporary_nodal_pressure=0.d0
-   ov%temporary_nodal_pressure=params%pressure0
+   ov%temporary_nodal_pressure=-params%pressure0
    call initialize_temperature (ov,params%ztemp)
    if (iproc.eq.0) write(8,*) ov%nnode,' nodes in initial velocity octree'