POD modal analysis of pore 1. The left column illustrates the results of POD temporal modes, a(t), for the first three modes (i.e. sausage, kink, and fluting modes, corresponding to the azimuthal wave numbers, m = 0, 1, and 2). The right column presents their corresponding spatial modes, ϕ(x, y) in a Cartesian coordinate system, projected over a reference circle. The blue and red curves show the maximum positive and negative values of the perturbations, respectively.