Natural convective flow oscillations in isosceles trapezoids are considered for three vertex angles, 22 degrees, 45 degrees, and 67 degrees. Simulations for smaller angles show periodicity that was superimposed with significant perturbations. For the largest angle, 67 degrees, periodicity was observed which was similar to previous calculation of periodic flow oscillations in rectangles and squares in the second critical Rayleigh number regime. Additionally, the observed oscillations for the 67 degrees case was fractal in nature, with periodicity maintained at different time scales. (C) 2012 Elsevier Ltd. All rights reserved.