Micro, Diffuser, Nozzle, Microfluidics, Static, Total, Pressure, Loss, Recovery, Separation


The field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS soft lithography including 38 diffuser/nozzle channels a piece. Each nozzle and diffuser consisted of a throat dimension of 100µm x 50µm, leg lengths of 142µm, and half angles varying from 0o - 90o in increments of 5o. The flow speeds tested included throat Reynolds numbers of 8.9 -“ 89 in increments of 8.9 using distilled water as the fluid. The static pressure difference was measured from the entrance to the exit of both the diffusers and the nozzles and the collected data was plotted against a fully attached macro theory as well as Idelchik's approximations. Data for diffusers and nozzles up to HA = 50o hints at the idea that the flow is neither separating nor creating a vena contracta. In this region, static pressure recovery within diffuser flow is observed as less than macro theory would predict and the losses that occur within a nozzle are also less than macro theory would predict. Approaching a 50o HA and beyond shows evidence of unstable separation and vena contracta formation. In general, it appears that there is a micro scaled phenomenon happening in which flow gains available energy when the flow area is increased and looses available energy when the flow area decreases. These new micro scaled phenomenon observations seem to lead to a larger and smaller magnitude of pressure loss respectively.


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Graduation Date



Chew, Larry


Master of Science (M.S.)


College of Engineering and Computer Science


Mechanical, Materials and Aerospace Engineering

Degree Program

Mechanical Engineering








Release Date

September 2009

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)