Oscillatory Flow Mixer Flow Field Simulation Study

Oscillatory Flow Mixer (OFM) is a new type of devices in Chemical Engineering Process, which has a good performance in heat and mass transport. And the process in an OFM is very convenient to control. It has wide potential usages in many Chemical Engineering Processes, such as particle suspension and separation, flocculation process and chemical reactor. Quite a few researchers have showed great interest in it and many significant results have been achieved.With the rapid development of computer technology, numerical simulation technique becomes an efficient method for scientific research. Computational Fluid Dynamics (CFD) simulation has been widely used in many fields of Chemical engineering and has contributed a lot to the R&D work. In this paper, numerical simulation technique was used to study the oscillatory velocity fields in OFM. The work focus on the influence of two crucial factors梠scillatory Reynolds number and St number on the behavior of OFM.In the study, a series of cases of two-dimensional and three-dimensional velocity field in an OFM was simulated under the conditions of laminar flow and zero net flow were studied. When the oscillatory Reynolds number is very low. the velocity field distribution is axis-symmetric. So the two-dimensional simulation is used to simplify the simulation and to decrease the calculating time. With the increase of oscillator} Reynolds number, the field distribution becomes asymmetric. In this situation, the correct results cannot be obtained by two-dimensional simulation and the three-dimensional simulation must be applied.In the two-dimensional simulation, the work focus on the evolution of velocity field in an OFM. It is found that eddies exist with geometric scale changing continuously even at small Re0 which make OFM excellent in the radial mixing. In the situation of axis-symmetric velocity field, the velocity distributions are periodically similar at the same phase position of different cycles.It is first time that the three-dimensional simulation of OFM velocitv field wasimplemented and that the transition of velocity distribution from an axis-symmetric pattern to an asymmetric one was successfully simulated. By tracing of the variation of the three-dimensional velocity field with Re0, it was found that at St=l, the transition occurs as Re0 is about 200. This result was consistent with the experiment observations reported by others. In situation of asymmetric flow field, the velocity distribution shows obvious different at the same phase position of different cycles. The work presented here will be essentially helpful to the further research.