Effects of Joule heating on the stability of time-modulated electro-osmotic flow

Effects of Joule heating and the induced variable viscosity are considered for time-modulated electro-osmotic flow in a two-dimensional microchannel confined between two infinitely parallel plates. Analytical expressions for both temperature and velocity profiles are obtained through asymptotic expansions for thin Debye layers, providing expressions for both the velocity and temperature slip outside these layers, and perturbation techniques for small viscosity variation. The amplitude variation of the temperature due to Joule heating is quite significant at low frequency electric fields, and decays gradually with increasing frequency. The induced variable viscosity effect changes the phase angle between velocity and harmonic electric field in comparison with the constant viscosity case, and reduces the shearing in the velocity profile. Results for the electrokinetic stability problem show that Joule heating generally exhibits a stabilizing effect. (c) 2005 American Institute of Physics.