Microscale Measurement and Simulations

J.C. Cheng, M.G. Olsen, and R.O. Fox, A microscale multi-inlet vortex nanoprecipitation reactor Turbulence measurement and simulation. Applied Physics Letters, 94 (20), 204104 (3 pp.), 2009. 

Microscale flow visualization has become an important tool for characterizing the performance of microchannels, micromixers and microreactors. Due to the rapid improvement in computer power and the great efforts in optical instrumentation, new measuring systems with high spatial and temporal resolution are available even for smaller companies and research institutes. In connection with the recent success in numerical simulation of microscale flow, a signiflcant acceleration in clariflcation of microscale phenomena and technical development can be expected. By ensuring the development of reliable systems, microscale flow visualization will provide an important contribution to the further spread of micro process engineering applications in the chemical and biochemical industries. 

Note that the order of these steps is important. Indeed, it is very rare for a successful mesoscale model to result from simply studying the results from a microscale simulation that is not specifically designed to test a particular assumption or hypothesis. In general, a microscale simulation will produce an enormous quantity of data if all flow variables are stored at every time step, and it is not realistic to expect that such data sets will reveal the correct form of the mesoscale models without some a priori understanding of the physics. On the other hand, microscale simulations offer an invaluable and often unique tool for sorting out the validity of a proposed mesoscale model because they contain all of the microscale variables, many of which are impossible to measure in laboratory experiments. 

As microscales typically hinder detailed measurements, there is a need of advanced numerical models for the simulation of both catalytic (heterogeneous) and gas-phase (homogeneous) microreactors. A number of computational tools has thus been developed, ranging from simple steady models for the performance assessment of methane-fueled catalytic microreactors without the inclusion of axial heat conduction in the channel walls [39], to transient models for the mapping of... 

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