Showing 3 results for Electro-Osmotic Flow
Amer Alizadeh, Seyed Ali Mirbozorgi,
Volume 12, Issue 3 (8-2012)
Abstract
In this paper the effects of the inlet fluid temperature on the electro-osmotic flow pattern in a two-dimensional microchannel with constant walls temperature is investigated with solving the governing equations by the Lattice Boltzmann method. The main objective of this research is to study the effects of temperature variations on the distribution of ions and consequently internal electric potential and velocity field. For make possible to use the Boltzmann ion distribution equation, cup mean temperature for every cross section of the microchannel is used. At the used Lattice Boltzmann method, LBGK model for modeling the Boltzmann collision function and the Zou-He boundary conditions method for velocity field has been used. Wang model for solving the Poisson-Boltzmann and He-Chen model for solving the energy equation has been used. The results show that, with increase the temperature difference between the inlet flow and the walls, the electro-osmotic flow rate increases. Also, observed that with decrease the external electric potential and the electric double layer thickness and increase the temperature difference at the inlet zone of the microchannel, a region with return flow is formed which can be used for controlling the internal flow pattern.
Jafar Jamaati, Ali Reza Farahinia, Hamid Niazmand,
Volume 15, Issue 3 (5-2015)
Abstract
Numerical modeling of electro-osmotic flow in heterogeneous micro-channels using two different models is presented in this article. For the through modeling of such flows, the coupled equations of Navier-Stokes, Nernst-Planck and the Poisson-Boltzmann are solved for the flow field, electric charges transport and electric field, respectively. Numerical solution of these equations for the heterogeneous micro-channels is complicated and difficult. Therefore, simple and approximate models such as Helmholtz-Smoluchowski have been proposed in which the solution of Poisson-Boltzmann, Nernst-Planck are neglected and the effect of the electric field on the flow field is applied through a prescribed slip boundary condition at the walls of micro-channel. The electro-osmotic flow fields within the heterogeneous micro-channels are usually complex and contain the vortex region that is ideal for mixing purpose. Hence, in this paper, the micro-channels designed so that they are capable to serve as micro-mixers in the mixing applications. For the micro-channels proposed here, the flow fields are obtained both with approximate modeling and the full simulation of electro-osmotic flows so that a comparison can be made to discuss the accuracy of the approximate model. The results of this study can be used to model the electro-osmotic flow field within heterogeneous micro-channels.
Mohammad Gholizadeh, Mohsen Ghazikhani, Iman Khazaee,
Volume 16, Issue 3 (5-2016)
Abstract
In this study, the relative humidity of the gases in the PEM fuel cell was changed and its effect on electro-osmotic flow was investigated. By changing the humidity on both sides of the fuel cell and using the water balance equations, the values of the electro-osmotic flow, electro-osmotic coefficient and net drag in different humidity levels were found. Results showed that variations of the electro-osmotic flow changed linearly by anode and cathode humidity to the special humidity and after that not much variation was seen. In addition, the results revealed that humidity change at anode had more desirable effect than the cathode. For example, at 70% anode humidity and 35% cathode humidity with the current of 5A, the value of electro-osmotic flow was obtained as 2.66639E-06 mol/cm2.s, while in the former 35% and the latter 70% with the same current, this value was recorded as 2.56418E-06 mol/cm2.s. In addition, results showed that the variations of the electro-osmotic coefficient changed linearly by humidity. It was determined the current change of fuel cell has not so effect on the curves of electro-osmotic coefficient. The electro-osmotic coefficients varied between 0.636001 and 1.632476, which were in a good agreement with the values obtained in other related papers. In addition, the variations of the net drag in respect of humidity were investigated, too. It was determined that the net drag changed linearly by the cathode humidity with positive slope, but its variations by the anode humidity were linearly with negative slope.
