“…An analogous problem in Newtonian fluid-saturated porous media is now well investigated (see the monographs by Bejan (2004) , Nield and Bejan (2006), Vafai (2000) and Alloui et al (2010), and references therein). Some aspects of the problem involving a viscoelastic liquid were studied by Sharma and Sunil (1994), Haro et al (1996), Srikrishna (2001), Srikrishna (2001)-(2003), Kim et al (2003), Kumar and Singh (2006), Fu et al (2007) , Shivakumara and Sureshkumar (2008), Long et al ((2009Long et al (( )-(2008), Malshetty et al (2009), Malashetty and Kulkarni (2009),Tan and Masuoka (2007, Wang and Tan (2008), and Awad et al (2010). The main result that can be conjured up from these works focusing on the onset of convection is that Maxwell fluids are generally more unstable than Jeffreys liquids while Rivlin-Ericksen and Newtonian liquids are comparatively more stable.…”