Research On The Flow Characteristics Of Circular And Elliptical Cross-Section Micro Column Group Channels Based On Micro PIV

As a kind of efficient micro heat dissipation structure,the micro column group channel has attracted many researchers’ attention in recent years.However,due to the relatively high internal resistance of fluid flowing around the micro column,it is difficult to play a role in the condition of no dynamic force,which seriously limits the application of micro column group channels.In order to solve the problem of high flow resistance in the microchannel group,we designed and manufactured the circular and elliptical cross-section microchannel group of PDMS,and built the microchannel flow visualization experimental platform.Using deionized water as the working medium,melamine formaldehyde resin microspheres as the tracer particles,we studied the single-phase flow mechanism in the circular and elliptical microchannel using micro PIV Experimental System,It provides a theoretical basis for flow drag reduction and heat transfer enhancement in microchannels.In this paper,we study the changes of streamline,vorticity and turbulent energy intensity around a micro cylinder at different Reynolds numbers.The results show that with the increase of Reynolds number,there are flow separation and twin vortices in the wake behind the cylinder,two large reverse symmetric vortices in the shoulder of the micro cylinder,and the turbulence intensity around the micro cylinder increases gradually.Based on the streamline distribution near the wall,the influence of the wall on the wake is analyzed.The results show that the streamline inclines to the wall at high Reynolds number.The influence of row number on the flow is studied by the change of dimensionless vortex length of different row of microcolumn.It is found that there is entrance section effect in the front row of microcolumn.The dimensionless velocity behind the micro cylinder is analyzed,and it is found that the velocity component in the direction of flow presents a "cross" distribution and the velocity component in the direction of transverse presents a "U" distribution.Through the study of the group of columns and the single column,it is found that the group of columns limits the growth of the vortex.The comparison between circular and elliptical cross-section microchannels is made in terms of streamline,vorticity,turbulence intensity,vortex length and flow resistance in microchannels.The results show that the flow resistance of elliptical section is smaller than that of circular section,and the flow is more stable.