A brass Vortex Tube (VT) with interchangeable parts is used to determine the optimum cold end orifice diameter, main tube length and diameter. Experim...

A straight tube with a smooth axisymmetric constriction is an idealised representation of a stenosed artery. We examine the three-dimensional instability of steady flow plus an oscillatory component in a tube with a smooth 75% stenosis using both linear stability analysis and direct numerical simulation. These flows become unstable through a subcritical period-doubling bifurcation involving alt...

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...

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...

In this paper free convection from a horizontal isothermal elliptic tube placed in a micropolar fluid with its major axis vertical is investigated. The governing equations are based on the conservation of mass, linear momentum, angular momentum and energy. The full governing equations written in stream function-vorticity formulation are solved numerically using the Spectral method based on Four...

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 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...

Using theoretical and computational methods we obtain these findings: 1) In micro-confined high-pressure transcritical turbulence, higher than typical levels of vorticity are observed in the viscous sublayer; 2) Flow topologies from far-wall regions vicinity supercritical gas-like wall; 3) Tube-like flow motions favored at scales comparable to density-gradient scale, resulting a smaller number ...