Investigation on entrance length for electroosmotic flow in circular and noncircular cross section nanochannel

Abstract

Characteristics of bulk electroosmotic flow in nanochannel are different to microchannel because the electric double layer (EDL) becomes comparable to the channel height. This work presents a numerical investigation on the entrance length of pure electroosmotic flow inside 3D rectangular, cylinder and triangular nanochannel with same channel length. The electric field is fixed at 250 kV/cm for all models. A finite element analysis has been performed to solve the governing equation for laminar flow under the influenced of an electric field. The entry length estimation for fully developed electroosmotic laminar flow in a circular and noncircular cross sections are compared by evaluating the electroosmotic velocity magnitude and flow profiles at the centre line cut plane inside the nanochannel. The entrance length in nanochannel is found shorter in a smaller depth flow in rectangular, cylinder and triangular channels. While the triangular nanochannel has the shortest entry length for fully developed laminar flow compare to other cross section shape models. The effect of a step change in ζ-potential on the channel wall surface to the electroosmotic flow entrance length is also presented.