nusselt_DBG_der_Re Function

    function nusselt_DBG_der_Re(c_pt,Re,Pra,Tother,T) result(nusselt_der_Re) bind(C)
        type(c_ptr), value :: c_pt
        real(dp), value :: Re,Pra,Tother,T
        real(dp) :: nusselt_der_Re,NuT
        type(DBG_cfg_t), pointer :: DBG_ptr
        call c_f_pointer(c_pt,DBG_ptr)      
     
        NuT=DBG_ptr%a*(Re**DBG_ptr%b)*(Pra**DBG_ptr%c)*((Tother/T)**DBG_ptr%d)
        if(Re<1.0e-12_dp) NuT=0.0_dp
  
        if(DBG_ptr%NuL>NuT) then
          nusselt_der_Re=0.0_dp
        else
          nusselt_der_Re=DBG_ptr%a*DBG_ptr%b*(Re**(DBG_ptr%b-1.0_dp))*(Pra**DBG_ptr%c)*((Tother/T)**DBG_ptr%d)
        endif
    end function nusselt_DBG_der_Re