Slip Flow Research In Microchannels With Superhydrophobic Surface By Experimental And Numerical Simulation Methods

Hundreds of years, the noslip boundary condition is well used in practical engineering, namely the velocity adhering to the wall is zero. However, more and more experiments have observed slip flow between gas-liquid interfaces in microscale field these years.We have made a review on the slip flow, containing the concepts, the types, the theory, the experiments and the impacts working on slip flow, especially for hydrophobic/super hydrophobic surfaces, and entirely explained the two mechanisms for slip flow advanced at present. Simultaneity, the basic theories of superhydrophobic surfaces has been reviewed briefly. All of these are the foundations of the superhydrophobic surface fabrication and slip flow experiment.In this article, we apply the dislocation etching then fluoroalkylsilane method to fabricate superhydrophobic surface on Aluminum, and use Flux-Pressure drop method to study the slip flow in microchannels. The ratio of width to height of the microchannel section is about 20, which likes flowing between two infinite parallel planes. The height of the microchannels is 0.15mm, 0.2mm and 0.3mm, respectively. The cover board of the microchannel is PMMA plane, and the upper is the superhydrophobic aluminum plane.In the research of the experiments, the relationship of the pressure drop reduction, slip length and slip velocity with the flux, the Renault number, the height of the microchanel and the contact angle have been studied by the numbers. We obtain that slip velocity will increase with increasing the flux, but the pressure drop reduction will be not changed. The pressure drop reduction will reduce with increasing the height of the microchannel. The slip length is only the function of the contact angle of the microchannel surfaces, not be affect by other factors. For the superhydrophobic surface with contact angle 157°, we obtain the slip length 3μm-4μm.In addition, we have computed the slip flow in microchannels with superhydrophobic surface of regular roughness (cavities) by numerical simulation. The two-dimensional model has been made which could be solved by VOF method. We have analyzed the results and obtained the relationship of the flux, the microchannel height, the dimension of the roughness and the immerge depth working on slip flow.