عنوان مقاله [English]
Micro-mixers are one of the important components of micro-fluid systems. Micro
mixers are small devices that are used to mix two different fluids which can be liquid or gas phases. Since the scale of these devices is very small and fluid
flows with very low Reynolds. At lower Reynolds numbers, the fluid's diffusivity is the dominant parameter to mix the fluids. If the flow is forced to create vortices, mixing phenomena will improve considerably. So using the appropriate geometries to create vortices and accelerate the mixing process along the channel is essential. In this study, two cylinders are used to enhance the mixing which is a passive method.Despite other mixing accelerators, cylinders are better because of their smaller drag coefficient. Rotating cylinders can help the mixing phenomena by means of fluid no-slip boundary condition. Since a rotating cylinder can change the path lines of fluid particles and help the mixing process, both cylinders is used geometry rotate clockwise or counter clockwise. Simulation of mixing and fluid flow, accomplished with numerical methods and finite element.
Governing equations are solved by means of COMSOL software and the results are shown as contours of pressure and concentration.Four different cases are considered base on the combination of rotation direction of cylinders. To verify the numerical method, simulation of a T-mixer is done by standard input data and compared with previous works, data. Results for a T-shaped mixer are in good agreement with reference data. Then, simulation of flow around stationary cylinders is done and results are compared with different rotating cases. It can be admitted that two rotating cylinders are better. However, two cases in which the rotational direction of cylinders are the same, improve mixing much better. In these two cases, cylinders force the fluid particles to enter the other fluids region and mix with each other.