Search results for " Transition to turbulence"

showing 3 items of 3 documents

Analysis of complex singularities in high-Reynolds-number Navier-Stokes solutions

2013

AbstractNumerical solutions of the laminar Prandtl boundary-layer and Navier–Stokes equations are considered for the case of the two-dimensional uniform flow past an impulsively-started circular cylinder. The various viscous–inviscid interactions that occur during the unsteady separation process are investigated by applying complex singularity analysis to the wall shear and streamwise velocity component of the two solutions. This is carried out using two different methodologies, namely a singularity-tracking method and the Padé approximation. It is shown how the van Dommelen and Shen singularity that occurs in solutions of the Prandtl boundary-layer equations evolves in the complex plane be…

Prandtl numberMathematics::Analysis of PDEsFOS: Physical sciencesPhysics::Fluid Dynamicssymbols.namesakeFlow separationSingularityboundary layer separation Navier–Stokes equations transition to turbulenceFOS: MathematicsMathematics - Numerical AnalysisComplex Variables (math.CV)Navier–Stokes equationsSettore MAT/07 - Fisica MatematicaMathematical PhysicsPhysicsMathematics - Complex VariablesMechanical EngineeringMathematical analysisFluid Dynamics (physics.flu-dyn)Reynolds numberLaminar flowPhysics - Fluid DynamicsMathematical Physics (math-ph)Numerical Analysis (math.NA)Condensed Matter PhysicsMechanics of MaterialssymbolsGravitational singularityPotential flow
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Route to chaos in the weakly stratified Kolmogorov flow

2019

We consider a two-dimensional fluid exposed to Kolmogorov’s forcing cos(ny) and heated from above. The stabilizing effects of temperature are taken into account using the Boussinesq approximation. The fluid with no temperature stratification has been widely studied and, although relying on strong simplifications, it is considered an important tool for the theoretical and experimental study of transition to turbulence. In this paper, we are interested in the set of transitions leading the temperature stratified fluid from the laminar solution [U∝cos(ny),0, T ∝ y] to more complex states until the onset of chaotic states. We will consider Reynolds numbers 0 < Re ≤ 30, while the Richardson numb…

Fluid Flow and Transfer ProcessesPhysicsRichardson numberTurbulenceMechanical EngineeringMathematical analysisComputational MechanicsReynolds numberLaminar flowCondensed Matter Physics01 natural sciences010305 fluids & plasmasPhysics::Fluid Dynamicssymbols.namesakeTemperature gradientMechanics of Materials0103 physical sciencessymbolsBifurcation Computational complexity Reynolds number Boussinesq approximations Chaotic solutions Richardson number Stabilizing effects Stratified fluid Temperature stratification Transition to turbulence Weak stratificationStratified flowBoussinesq approximation (water waves)010306 general physicsSettore MAT/07 - Fisica MatematicaBifurcation
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Numerical simulation of reciprocating turbulent flow in a plane channel

2009

Direct numerical simulation results were obtained for oscillatory flow with zero time mean (reciprocating flow) in a plane channel using a finite volume method, Crank-Nicolson time stepping and central approximation of the advection terms. A pressure gradient varying co-sinusoidally in time was imposed as the forcing term, and its frequency and amplitude were made to vary so as to span a range of regimes from purely laminar to fully turbulent. For the limiting cases of reciprocating laminar flow and steady-state turbulent flow, numerical results were validated against analytical solutions and classic experimental literature data, respectively. For general reciprocating flows, predictions we…

Fluid Flow and Transfer ProcessesPhysicsChézy formulaTurbulenceMechanical EngineeringComputational MechanicsDirect numerical simulationThermodynamicsLaminar sublayerLaminar flowMechanicsReciprocating Flow Channel flow transition to turbulence Direct Numerical SimulationCondensed Matter PhysicsPipe flowOpen-channel flowPhysics::Fluid DynamicsFlow separationMechanics of MaterialsSettore ING-IND/19 - Impianti NucleariPhysics of Fluids
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