Multiscale Fluid Flow Studies with Molecular Tagging Diagnostics

Manoochehr Koochesfahani ProfessorDepartment of Mechanical Engineering Michigan State University East Lansing, MI A brief overview of molecular tagging diagnostics will be presented, along with results from studies in three different flow fields. Molecular tagging methods take advantage of molecules that can be turned into long lifetime tracers upon excitation by photons of an appropriate wavelength. Typically a pulsed laser is used to "tag" the regions of interest, and those tagged regions are interrogated at successive times within the lifetime of the tracer. This approach has been utilized for the measurement of velocity and temperature fields. The first study presented here considers unsteady flow separation from a pitching airfoil. Boundary-layer resolved measurements of this phenomenon and comparison with complementary computations will be discussed. The second study involves in-cylinder measurements in a motored IC engine. Results from flow mapping of cycle-to-cycle variation in late compression will be presented. Preliminary observations on the possibility of flow control will be discussed. The final study addresses the flow inside a microchannel driven by either a pressure differential or electroosmosis. In-situ measurements of wall friction factor in pressure-driven flow will be compared with theoretical predictions in order to assess the large discrepancies that have been previously reported. Electroosmotically-driven flows involve additional complications, e.g. presence of an electric field and a time-varying temperature field caused by Joule heating. Results will be shown from simultaneous measurements of velocity and temperature within a microchannel for different applied potentials.

Location: Staufer Science Lecture Hall, Rm 102 (SLH)

Audiences: Everyone Is Invited

Contact: April Mundy