A numerical analysis of an active micromixer with the oscillating stirrer at the different aspect ratios by LBM

In the present paper, a numerical simulation is performed to analyze aspect ratio effects of a rectangular stirrer along with two other parameters, frequency and amplitude of stirrer on the mixing efficiency inside a straight microchannel by LBM. Results showed that in a low frequency amplitude, AR variations are not effective on the efficiency in low values of St, however, in the intermediate values, the efficiency increases with the increase of AR. Moreover, in high values of St, the rise in AR up to 0.5 leads to the efficiency reduction, but further increase of AR, increases the mixing efficiency too. In a larger amplitude than the previous case, in high values St, increasing AR up to 0.7 rises efficiency, but further increase of AR, decreases the mixing efficiency. In low and intermediate values of St, the mixing performance in low values of AR has been more efficient than high values of AR. Furthermore, it was shown that in a low frequency, the mixing efficiency decreases and then increases with rise in AR for all values of K so that the closer to 1 the AR, the better the mixing efficiency. In a higher frequency, the efficiency decreases and then increases with the growth in AR in small value of K, while this trend become inverse in large values of K. Generally, in intermediate values, the larger and nearer to 1 the AR, the larger the mixing efficiency.