nusselt_DBG Function

    function nusselt_DBG(c_pt,Re,Pra,Tother,T) result(nusselt) bind(C)
        type(c_ptr), value :: c_pt
        real(dp), value :: Re,Pra,Tother,T
        real(dp) :: nusselt,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 .or. Pra<0.0_dp) NuT=0.0_dp

        nusselt=max(DBG_ptr%NuL,NuT)
    end function nusselt_DBG