In this paper, a numerical model was established for incompressible, fully developed laminar deionized water flow in microchannels with trapezoidal cross section.

The traditional methods for computing critical water depth of open channel with trapezoid section (h k) are trial and error method, graphic method, approximate solution method and iteration method, whose shortcomings are rough precision, large computation amount and complex resolving problem.

Based on the knowledge of lotus leaves,a new pattern surface with gradient surface energy was designed ,and the water flow process on such surfaces was analyzed.