Under low flow-rate conditions, a Francis turbine exhibits precession of vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration performance as manifested by torque and power output fluctuations. In order suppress swirl component tube, use anti-swirl fins was investigated previous study. However, generation still occurred near cone th...

With economical energy market strategies based on instantaneous pricings of electricity as function of the demand or the predictions, operators harness more hydroelectric facilities to off-design operating points to cover the variations of the electricity production. Under these operating conditions, Francis turbines develop a cavitating swirling flow at the runner outlet which induces pressure...

We report the production of electron vortex beams carrying large orbital angular momentum (OAM) using micro-fabricated spiral zone plates. A series of the spherical waves, focussing onto different positions along the propagating direction of the electron beam, were observed. The nth order vortex beam has an OAM n times larger than that of the first-order vortex beam. We observed an electron vor...

A thin-tube vortex method is developed to investigate the intrinsic instability within a counter-rotating vortex pair system and the e ects from the core size and the wavenumbers (or wavelengths). The numerical accuracy and the advantages of the scheme are theoretically estimated. A nearest-neighbour-image method is employed in this three-dimensional vortex simulation. Agreement with Crow’s ins...

Two theorems on the Riemannian geometrical constraints on vortex magnetic filaments acting as dynamos in (MHD) flows are presented. The use of Gauss-Mainard-Codazzi equations allows us to investigate in detail the influence of curvature and torsion of vortex filaments in the MHD dynamos. This application follows closely previous applications to Heisenberg spin equation to the investigations in ...

The present study considers of the water and air flow and Micro-Bubble production inside the venturi tube, by the use of dimensional analysis. Numerical analysis of Micro-Bubble creation in venturi tube requires fast computers and large amounts of storage space. Up to now, there has been no numerical analysis concerning Micro-Bubble creation and all other existing studies are experimental. To s...

The physics of compressible vortex loops generated due to the rolling up of the shear layer upon the diffraction of a shock wave from a shock tube is far from being understood, especially when shock-vortex interactions are involved. This is mainly due to the lack of global quantitative data available which characterizes the flow. The present study involves the usage of the PIV technique to char...

Fully developed turbulence is analised with the lattice model employing vortex tube representation which is introduced recently by the authors. Several characteric features observed in experiments and direct numeric integrations are reproduced. Not only Kolmogorov’s inertial range is observed, but also several local probability distribution functions are obtained as well. Those of the local vel...

This paper illustrates the mechanism of U-shaped vortex formation which is found both by experiment and DNS. The main goal of this paper is to explain how the U-shaped vortex is formed and further develops. According to the results obtained by our direct numerical simulation with high order accuracy, the U-shaped vortex is part of the coherent vortex structure and is actually the tertiary strea...

Meso-scale turbulence is an innate phenomenon, distinct from inertial turbulence, that spontaneously occurs at low Reynolds number in fluidized biological systems. This spatiotemporal disordered flow radically changes nutrient and molecular transport in living fluids and can strongly affect the collective behaviour in prominent biological processes, including biofilm formation, morphogenesis an...