“…The influence of non-Dirichlet boundary conditions on either the velocity field or the temperature field is also an area which has attracted much recent attention in thermal convection in porous media, see e.g. Barletta et al [44], Barletta [45], Barletta [46], Barletta and Celli [47], Barletta and Rees [48], Celli and Kuznetsov [49], Mohammad and Rees [50], Nield and Kuznetsov [51], Rees and Barletta [52], Rees and Mojtabi [53,54], Brandao et al [55].…”