1,032 research outputs found

    Stereoscopic PIV measurement in laminar rotating plane Couette flow

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    Plane Couette flow with spanwise system rotation shows structures of streamwise-oriented roll cells that arise due to the instability by the Coriolis force when the system rotation is in the opposite direction to the mean flow vorticity. The momentum transport caused by such roll cell structures makes the flow tend to exhibit zero absolute vorticity. In the present study, stereoscopic PIV measurements in the rotating plane Couette flow were carried out in order to further illuminate the vortex structures and transport phenomena in this flow. The Reynolds stresses and some terms of its transport equation were evaluated to discuss the transport phenomena caused by the coherent structure. Furthermore, the wall shear stress was evaluated based on the measurement results of the Reynolds and viscous shear stresses and its variation with the system rotation rate is also presented

    Application of decolourised hsian-tsao leaf gum to low-fat salad dressing model emulsions: a rheological study

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    The effects of mixed gums, including decolourised hsian-tsao leaf gum (dHG) mixed with propylene glycol alginate (PGA) or xanthan gum (XG), and egg yolk concentration on the rheological properties of low-fat salad dressing model emulsions were studied. All model emulsions showed pseudoplastic flow behaviour. Model emulsions with PGA addition showed the lowest pseudoplasticity, followed by those with dHG and then XG addition. Increasing the PGA level in the dHG/PGA system reduced the pseudoplasticity. Increasing the XG level in the dHG/XG system did not change the pseudoplasticity significantly but imparted a significant increase in viscosity. Dynamic viscoelasticity measurements indicated that model emulsions with dHG or XG addition could be classified as elastic gels. However, model emulsions with PGA addition essentially belonged to the class of either dilute or concentrated solutions rheologically, depending on the egg yolk concentration. The rheological characteristics of individual gums were found to be confounded in generating the rheological characteristics of model emulsions containing them. (C) 2004 Society of Chemical Industry

    Generalized diagnostic scaling for high-order moments in turbulent boundary layers

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    The present work builds upon the diagnostic plot for the streamwise turbulence intensity [Alfredsson & Örlü, 2010] and generalises it for higher-order (even and odd) moments providing a general description of the probability density distribution of streamwise velocity fluctuations. Turbulent boundary layers (up to a friction Reynolds number of 20'000) are employed and demonstrate its feasibility to scale data throughout the overlap and outer region

    PV architectures for DC microgrids using buck or boost exclusive microconverters

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    DC microgrids can connect directly dc renewable energy sources with increasing amount of dc loads. In this paper it is looked for possible architectures for integrating PV panels into dc microgrids, by means of microconverter strings. Three topologies are considered, featuring only buck microconverters and only boost microconverters, since they promise higher efficiency due to fewer semiconductors in the current path. The topologies under exam are tested with a perturb and observe MPPT, in the cases of abrupt local shading and uneven shading over a solar panels' array. Among the three, the best topology by response time and control ease is found.Accepted Author ManuscriptOld - EWI-ESE-DC&S DC systems & StorageElectrical Power Processin

    Matching PV array output with residential load by optimisation of array orientation

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    Currently PV modules are positioned to receive the highest amount of incident radiation in a year. Therefore, the generation pattern is independent of the consumption and a large storage is required to compensate for the same. This paper studies the possibility of orienting the modules differently in order to match the consumption more efficiently.Accepted Author ManuscriptOld - EWI-ESE-DC&S DC systems & Storag
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