There has been a growing interest in understanding the flow behaviour inside diffuserozzle elements in order to identify performance characteristics of these elements for micropump applications. Flat-walled diffuserozzle element is the most commonly used type for valveless micropump applications due to its ease of fabrication and compact design. In this paper, we study generic flat-walled diffuserozzle elements and apply optimization techniques to explore how the pumping efficiency can be improved by changing geometry to provide higher rectification efficiency and lower pressure drop in rectification valveless micropumps. The primary motivation for this study is to evaluate the performance of flat-walled diffuserozzle elements based on geometry variations under several Reynolds numbers (Re). In this study we employ a design methodology for diffuserozzle elements that incorporates computational fluid dynamics (CFD) within an optimization methodology. To start the process a series of geometric parameters are selected including element neck width, depth, divergence angle, and entrance fillet radius. Then, the pressure drop and rectification property of an element are calculated as performance parameters, i.e., by varying the geometry it is desirable to maximise pressure rise and the rectification property of the element. Design of experiments (DOE) is employed to generate the experimental table which corresponds to different geometries representing the design space. These limited numbers of geometries generated by DOE are evaluated by using CFD to obtain corresponding performance parameters. By preparing all the design and performance parameters, Surrogate model (SM) technique is applied to obtain the relationship (approximation function) between design and performance parameters. Eventually, based on the developed approximation functions or response surfaces,a multi-objective genetic algorithm (MOGA) is employed to maximise pressure rise and rectification property of diffuserozzle element. This design methodology is a very powerful tool to design and optimise flat-walled diffuserozzle elements for micropump applications and can speed up the micropump design process significantly.
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