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In this study, a novel valveless impedance pump is applied, for the first time, in the thermal management of high performance electronic systems. This small pump comprises an amber latex rubber tube, connected at both ends to rigid copper tubes of different acoustic impedance, and a simple, economic, quiet and energy-efficient actuation mechanism, which combines a small DC motor and a cam. The motor activated cam periodically compresses the elastic tube at a position asymmetric from the tube ends.Traveling waves, emitted from the compression, combine with reflected waves, at the impedance-mismatched positions (rubber tube/copper tube interfaces). The resulting wave interference creates a pressure gradient, with the potential to generate a net flow. Several experimental set-ups for performance tests, using a single impedance pump, open system, with isothermal flow, and a closed liquid cooling system were designed and implemented.The performance of the impedance pump was affected significantly by the actuation This is the Pre-Published Version.

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A pebble/cobble passing a head drop tends to carry a large impact momentum when it hits a groundsill; the heavy impact may result in the breakage of concrete. This study explores the mechanics and the principles of this issue by computational fluid dynamics with particle tracking. The results reveal that the kinematics of a single particle passing a head drop is primarily affected by the size of particles. A small particle tends to travel along the flow lines and brings relatively low impact energy. A large particle is more affected by gravity; saltation is more likely and will carry relatively high impact energy. The major role of the discharge magnitude is just to enable the transportation of larger particles to the downstream. With the simulation, it is possible to evaluate the impact position, load and kinetic energy. The locations prone to damage and failure potential can then be identified.