Performance of Double-step Savonius Rotor for Environmentally Friendly Hydraulic Turbine

The aim of this investigation is to develop an environmentally friendly nano-hydraulic turbine. Three type models of Savonius rotor are constructed and tested in a water tunnel to improve and clarify the power performance. Flow field around the rotor is examined visually to reveal the enhancement mechanisms of power coefficient using the double-step rotor. Flow visualization showed the difference of flow patterns at the central section between the standard (single-step) rotor and the double-step one. A meandering flow in the axial direction of the rotor was observed only for the double-step rotor. This flow had the pressure restoration effect at the returning blade's concave side and the torque strengthened effect at the advancing blade's convex side. As a consequence, the power coefficient was 10% improved.ArticleJournal of Fluid Science and Technology. 3(3):410-419 (2008)journal articl

Performance of Savonius Rotor for Environmentally Friendly Hydraulic Turbine

The aim of this investigation was to develop an environmentally friendly nano-hydraulic turbine. A model of a two-bucket Savonius type hydraulic turbine was constructed and tested in a water tunnel to arrive at an optimum installation condition. Effects of two installation parameters, namely a distance between a rotor and a bottom wall of the tunnel, a rotation direction of the rotor, on the power performance were studied. A flow field around the rotor was examined visually to clarify influences of installation conditions on the flow field. The flow visualization showed differences of flow pattern around the rotor by the change of these parameters. From this study it was found that the power performances of Savonius hydraulic turbine were changed with the distance between the rotor and the bottom wall of the tunnel and with a rotation direction of the rotor.ArticleJournal of Fluid Science and Technology. 3(3):420-429 (2008)journal articl

Acoustic Control of an Impinging Planar Jet upon a Wedge

Active control of an impinging jet upon a wedge has been attempted using a sinusoidal excitation of blowing and sucking at the jet exit. The excitation sufficiently enables 'phase-lock', which is synchronization between self-oscillating flow and the excitation, so that hot-wire measurements directly provide phase averaged flow fields and they illustrate appearance of the jet swing in front of the wedge and collision of the jet on one of side of the wedge. It was demonstrated that this control set up is practical not only for illustration of the phase averaged flow field but also for reduction of the edge tone due to the flow oscillation with inverse phase excitation in half of the jet.ArticleJournal of Fluid Science and Technology. 3(2):274-281 (2008)journal articl

Optical evidence for symmetry changes above the Neel temperature in KCuF3

We report on optical measurements of the 1D Heisenberg antiferromagnet KCuF3. The crystal-field excitations of the Cu2+ ions have been observed and their temperature dependence can be understood in terms of magnetic and exchange-induced dipole mechanisms and vibronic interactions. Above T_N we observe a new temperature scale T_S characterized by the emergence of narrow absorption features that correlate with changes of the orbital ordering as observed by Paolasini et al. [Phys. Rev. Lett. 88, 106403 (2002)]. The appearance of these optical transitions provides evidence for a symmetry change above the Neel temperature that affects the orbital ordering and paves the way for the antiferromagnetic ordering.Comment: 4 pages, 2 figure