The objective of this study was to determine the flow characteristics and thermal efficiency in various ducts geometries numerically and experimentally. The whole studies were conducted for Reynolds numbers in the range of 3 x 10(3) <= Re <= 6 x 10(3). Firstly, effects of the aspect ratio, S/H on flow structures and heat transfer enhancement were aimed to be examined. Therefore, the corrugated duct geometries were designed for three different aspect ratios such as S/H = 0.1, 0.2, 0.3. Thermal efficiency of these geometries were examined numerically in order to optimize the aspect ratio, S/H. By increasing the corrugation height, the rate of turbulence intensity on the axis of corrugated channel increases as expected. Heat transfer rate increases with the rise of the aspect ratio, S/H and shows a maximum value at S/H = 0.3 that corresponds to the highest aspect ratio. The highest friction factor, f occurs in the corrugated channel with aspect ratio of S/H = 0.3 and it is followed by S/H = 0.2, and 0.1, respectively. Afterwards, experimental studies were conducted in order to identify hydrodynamic structures and verify findings of numerical solution using the Particle Image Velocimetry (PIV) technique. Velocity distributions, patterns of streamline and corresponding turbulent statistics were determined experimentally and numerically in order to reveal hydrodynamics characteristics and thermal performance of the corrugated channel flow. (C) 2017 Elsevier Ltd. All rights reserved.