ensure_projection_workspace Subroutine

   subroutine ensure_projection_workspace(mesh)
      type(mesh_t), intent(in) :: mesh

      if (projection_work%initialized) then
         if (projection_work%ncells == mesh%ncells .and. &
             projection_work%nfaces == mesh%nfaces) return

         call finalize_flow_projection_workspace()
      end if

      projection_work%ncells = mesh%ncells
      projection_work%nfaces = mesh%nfaces

      allocate(projection_work%local_vec(3, mesh%ncells))
      allocate(projection_work%local_vec_star(3, mesh%ncells))
      allocate(projection_work%local_scalar(mesh%ncells))
      allocate(projection_work%rhs_poisson(mesh%ncells))
      allocate(projection_work%local_face_flux(mesh%nfaces))
      allocate(projection_work%predicted_face_flux(mesh%nfaces))

      allocate(projection_work%r(mesh%ncells))
      allocate(projection_work%z(mesh%ncells))
      allocate(projection_work%pvec(mesh%ncells))
      allocate(projection_work%ap(mesh%ncells))
      allocate(projection_work%local_ap(mesh%ncells))

      projection_work%local_vec = zero
      projection_work%local_vec_star = zero
      projection_work%local_scalar = zero
      projection_work%rhs_poisson = zero
      projection_work%local_face_flux = zero
      projection_work%predicted_face_flux = zero

      projection_work%r = zero
      projection_work%z = zero
      projection_work%pvec = zero
      projection_work%ap = zero
      projection_work%local_ap = zero

      projection_work%initialized = .true.
   end subroutine ensure_projection_workspace