Compressibility Effect in Vortex Identification

Kolář, V.

doi:10.2514/1.40131

Cited by 51 publications

(23 citation statements)

References 19 publications

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“…The inflow RMS values are taken from the DNS results of Schlatter and Orlu [27] for a similar Reynolds number. Fig.4 shows the iso-surface of compressible Q-criterion on the flat plate upstream of the jet orifice colored by the local wall-normal distance, which is a vortex-identification scheme for compressible flow [28] , i.e., [29,28] . downstream of the inlet, the position 60mm downstream of the inlet corresponds to x=-15mm (x/D=-7.5).…”

Section: Numerical Methods and Validationmentioning

confidence: 99%

Generation of Upper Trailing Counter-Rotating Vortices of a Sonic Jet in a Supersonic Crossflow

Sun

2018

AIAA Journal

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Direct numerical simulations were conducted to investigate physical structures of a transverse sonic air jet injected into a supersonic air crossflow at a Mach number of 2.7. Simulations were run for two different jet-to-crossflow momentum flux ratios (J) of 1.85 and 5.5. The main averaged flow features around the transverse jet, such as major counter rotating vortices (CRVs) and trailing CRVs (TCRVs) were captured. The major CRVs form in the lateral portion of the jet plume and absorb other induced trailing vortices downstream of the jet plume. Upper trailing CRVs form above the major CRVs downstream of the jet barrel shock. The streamline analysis indicates that the upper trailing CRVs are related to the Mach disk. As the streamlines penetrate the lateral side of Mach disk where a strong shear condition exists, the baroclinic torque induces upper vorticities in the opposite rotating direction against the major CRVs. Downstream of the Mach disk, the baroclinic vorticity production along the streamlines tends to approach zero, which means no more torque is pumped into the farfield and the upper TCRVs are merged into the major CRVs by their suction. Keywords: supersonic flow; transverse jet; direct numerical simulation; counter rotating vortices; upper trailing counter rotating vortices Nomenclature J =jet-to-crossflow momentum flux ratio BVP = baroclinic vorticity production CRV = counter rotating vortices DNS =direct numerical simulation JISC =jet interaction with supersonic crossflow LES =large eddy simulation STBL =supersonic turbulent boundary layer TCRV =trailing counter rotating vortices

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Section: Numerical Methods and Validationmentioning

confidence: 99%

Generation of Upper Trailing Counter-Rotating Vortices of a Sonic Jet in a Supersonic Crossflow

Sun

2018

AIAA Journal

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“…In the case of rigid rotation, the value of τ s 2π/λ ci gives the revolution period of the rotating flow. Unlike many other methods for vortex detection, the λ ci criterion is applicable also in the case of compressible hydrodynamics (Kolář 2009).…”

Section: Vortex Identificationmentioning

confidence: 99%

Vortices in simulations of solar surface convection

Moll

Cameron

Schüßler

2011

A&A

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We report on the occurrence of small-scale vortices in simulations of the convective solar surface. Using an eigenanalysis of the velocity gradient tensor, we find the subset of high-vorticity regions in which the plasma is swirling. The swirling regions form an unsteady, tangled network of filaments in the turbulent downflow lanes. Near-surface vertical vortices are underdense and cause a local depression of the optical surface. They are potentially observable as bright points in the dark intergranular lanes. Vortex features typically exist for a few minutes, during which they are moved and twisted by the motion of the ambient plasma. The bigger vortices found in the simulations are possibly, but not necessarily, related to observations of granular-scale spiraling pathlines in "cork animations" or feature tracking.

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“…Regarding compressibility aspects and other well-known schemes, it can be noted that the closely related Δ and λ ci criteria [5] are extendable to compressible flows as shown in [7] while the λ 2 -method [2] is not according to [3]. Haller [9] provides an objective frame-independent definition of a vortex based on Lagrangian stability considerations.…”

Section: Mamentioning

confidence: 98%

“…In view of relation (2), there is either the possibility to adopt the positive II ∇u or the positive kΩk 2 − kSk 2 ∕2. Moreover, both these alternatives fail as a correct candidate for vortex identification in compressible flows [7]. If a nonzero divergence u i;i enters the vortex-identification scheme, then the impact of compression is -on dynamic considerations -expected opposite than that of expansion similarly as in the pirouette effect (angular momentum conservation).…”

Section: Mamentioning

confidence: 98%

“…However, quadratic forms of nondeviatoric strain rate contradict these expectations. Consequently, it was proposed in [7] that the Q-criterion should be redefined by the deviatoric part of S, S D ≡ S − 1∕3 · trS · I, where I denotes identity matrix, to read Q D kΩk 2 − kS D k 2 ∕2 (the subscript D denotes a deviatoric quantity or a derived quantity based on deviatoric ones). The measure Q D is unambiguous and applicable to compressible flows.…”

Section: Mamentioning

confidence: 99%

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Corotational and Compressibility Aspects Leading to a Modification of the Vortex-Identification Q-Criterion

Kolář

Šístek

2015

AIAA Journal

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Nomenclature Ma= Mach number Q = vortex-identification criterion Q D = measure based on the deviatoric part of ∇u Q M = modification of the vortex-identification Q-criterion Re = Reynolds number S = strain-rate tensor, symmetric part of ∇u S D = deviatoric part of the strain-rate tensor S u, u i = velocity vector, components of u u i;j = spatial partial derivatives of components of u II = second invariant of an arbitrary second-order tensor A is defined by II A equals trA 2 − trA 2 =2 II S = second invariant of (the strain-rate tensor) S II SD = second invariant of (the deviatoric part of the strain-rate tensor) S D II ∇u = second invariant (see the definition of II above) of ∇u λ 2 = second-largest eigenvalue of S 2 Ω 2 , vortexidentification criterion σ = principal strain-rate difference vector,= deviatoric principal strain rates Ω = vorticity tensor, antisymmetric part of ∇u ω, ω 1 , ω 2 , ω 3 = vorticity vector, vorticity vector components ∇u = velocity-gradient tensor ∇ × u = curl of velocity vector

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Compressibility Effect in Vortex Identification

Cited by 51 publications

References 19 publications

Generation of Upper Trailing Counter-Rotating Vortices of a Sonic Jet in a Supersonic Crossflow

Generation of Upper Trailing Counter-Rotating Vortices of a Sonic Jet in a Supersonic Crossflow

Vortices in simulations of solar surface convection

Corotational and Compressibility Aspects Leading to a Modification of the Vortex-Identification Q-Criterion

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