0000000000930647

AUTHOR

Paolo Luchini

showing 3 related works from this author

Turbulent Superfluid Profiles in a Counterflow Channel

2010

We have developed a two-dimensional model of quantised vortices in helium II moving under the influence of applied normal fluid and superfluid in a counterflow channel. We predict superfluid and vortex-line density profiles which could be experimentally tested using recently developed visualization techniques.

Condensed Matter::Quantum GasesPhysicsNormal fluidCondensed Matter::OtherTurbulenceFOS: Physical scienceschemistry.chemical_elementSuperfluid helium; Turbulence; VorticesVorticesMechanicsCondensed Matter PhysicsAtomic and Molecular Physics and OpticsVortexTurbulenceCondensed Matter - Other Condensed MatterSuperfluiditychemistryGeneral Materials ScienceSuperfluid heliumSettore MAT/07 - Fisica MatematicaHeliumOther Condensed Matter (cond-mat.other)Communication channelJournal of Low Temperature Physics
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Towards a quantitative comparison between global and local stability analysis

2017

A methodology is proposed here to estimate the stability characteristics of bluff-body wakes using local analysis under the assumption of weakly non-parallel flows. In this connection, a generalisation of the classic spatio-temporal stability analysis for fully three-dimensional flows is first described. Secondly, an additional higher-order correction term with respect to the common saddle-point global frequency estimation is included in the analysis. The proposed method is first validated for the case of the flow past a circular cylinder and then applied to two fully three-dimensional flows: the boundary layer flow over a wall-mounted hemispherical body and the wake flow past a fixed spher…

PhysicsMechanical Engineeringabsolute/convective instabilityMechanicsinstability; Key words absolute/convective instability; wakes; Condensed Matter Physics; Mechanics of Materials; Mechanical EngineeringKey words absolute/convective instabilityCondensed Matter Physics01 natural sciencesStability (probability)Instabilitywakes010305 fluids & plasmasTerm (time)Boundary layerinstabilityFlow (mathematics)Local analysisMechanics of Materials0103 physical sciencesApplied mathematics010306 general physicsabsolute/convective instability; instability; wakesEigenvalues and eigenvectorsSaddle
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Boundary-layer Flows Past an Hemispherical Roughness Element: DNS, Global Stability and Sensitivity Analysis

2015

Abstract We investigate the full three-dimensional instability mechanism arising in the wake of an hemispherical roughness element immersed in a laminar Blasius boundary layer. The inherent three-dimensional flow pattern beyond the critical Reynolds number is characterized by coherent vortical structures called hairpin vortices. Direct numerical simulation is used to analyze the formation and the shedding of hairpin packets inside the shear layer. The first bifurcation characteristics are investigated by global stability tools. We show the spatial structure of the linear direct and adjoint global eigenmodes of the linearized Navier-Stokes operator and use structural sensitivity analysis to …

TriGlobal Linear StabilityDirect numerical simulation02 engineering and technologyWake01 natural sciencesInstability010305 fluids & plasmasPhysics::Fluid Dynamicssymbols.namesake0203 mechanical engineeringHairpin vortices0103 physical sciencesPhysics020301 aerospace & aeronauticsRoughness ElementHairpin vortices; Roughness Element; TriGlobal Linear Stability; Mechanical EngineeringMechanical EngineeringReynolds numberLaminar flowGeneral MedicineMechanicsVortexBoundary layerClassical mechanicsBlasius boundary layersymbolsProcedia IUTAM
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