Fluid drainage in erodible porous media

Drainage, in which a nonwetting fluid displaces a wetting fluid from a porous medium, is well studied for media with unchanging solid surfaces. However, many media can be eroded by drainage, with eroded material redeposited in pores downstream, altering further flow. Here we use theory and simulation to examine how these coupled processes both alter the overall fluid displacement pathway and help reshape the solid medium. We find two drainage behaviors with markedly different characteristics and quantitatively delineate the conditions under which they arise. Our results thereby help expand the current understanding of these rich physics, with implications for applications of drainage in industry and the environment.