Turbulent Vortices in Stratified Fluids

Hecht, Anne‐Marie; Bilanin, Alan J.; Hirsh, Joel E.; Snedeker, Richard S.

doi:10.2514/3.50814

Cited by 19 publications

(7 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After the wake vortices have decayed, the dispersion process of the aircraft emissions in the middle atmosphere is usually subject to weak ambient turbulence, resulting in a vertical eddy diffusion coefficient of the order 10 -2 m 2 s -x. Nevertheless, it can be influenced by sporadically occurring strong turbulence produced by dynamical (Kelvin-Helmholtz) instabilities [Schilling and Janssen, 1992] or breaking gravity waves [Fritts and Rastogi, 1985;Schilling and Etling, 1996 nomenon of wake vortices in the free atmosphere was studied numerically [Hill, 1975;Hecht et al, 1980Hecht et al, , 1981 Most of the previous studies are concerned with vortex dynamics only, while investigations on dispersion of aircraft emissions and contrails [see, e.g., Scorer and Davenport, 1970;Holdeman, 1974;Nielsen et al, 1974;Schumann, 1995] could not take into account the influence of the wake vortex system. Therefore we are investigating the combined problem of wake vortex dynamics and dispersion of aircraft emissions influenced by coexisting stratification and vertical wind shear.…”

Section: Introductionmentioning

confidence: 99%

Dispersion of aircraft emissions due to wake vortices in stratified shear flows: A two‐dimensional numerical study

Schilling¹,

Siano²,

Etling³

1996

J. Geophys. Res

View full text Add to dashboard Cite

The development of the wake vortex system behind an airplane (B-747) at cruising altitude (8-15 km) and the dispersion of the aircraft emissions due to this vortex system have been studied by means of a two-dimensional numerical model. Simulation experiments are presented which examine the influence of atmospheric stratification and vertical wind shear on the combined vortex-emission system. Although the development of the vortex wake system can be influenced by three-dimensional effects (e.g., Crow instabilities), the undisturbed process can be approximated as a two-dimensional phenomenon, which allows the study of details of the vortex structures at small scales (length L • i m) and the dispersion of engine exhausts at larger scales (L • 100 m). The results of simulation experiments show that the maximum lifetime of the wake vortices (120 s _< T• • 300 s) as well as the descending rate (1.2 m s -1 _< w• _< 2.4 m s -1) and the dispersion of the emitted substances depend on the atmospheric stratification as well as verticM wind shear, but buoyancy forces seem to dominate over shear forces. The overall dispersion of aircraft emissions due to the wake vortex system can be quantified by a vertical standard deviation for the entire process of about rr• _< 70 m. first 1 or 2 s after the exhaust components have left the engines, the diffusion of the plume is nearly similar to that of free turbulent jets ("jet regime"), where the effective cross section grows from A0 • 3 m 2 to a few hundred square meters [Miake-Lye et al., 1993]. At the end of the jet regime, corresponding to a distance of about 1 km from the engines, the temperature as well as the momentum excess of the exhaust plumes are reduced by mixing and entrainment of ambient air, and the aircraft emissions can be approximated as cold and passive scalars subject to the further dispersion process [e.g., KSrcher, 1994].The second phase is characterized by the influence of the wake vortex system ("vortex regime"), which is formed from the wing vortex sheets due to the pressure differences at the respective wings. In this study we assume, as a simple case, that only one pair of counterrotating trailing vortices is formed in the wake of 20,965 20,966 SCHILL•G ET AL.' DISPERSION OF AIRCRAFT EMISSIONS

show abstract

Section: Introductionmentioning

confidence: 99%

Dispersion of aircraft emissions due to wake vortices in stratified shear flows: A two‐dimensional numerical study

Schilling¹,

Siano²,

Etling³

1996

J. Geophys. Res

View full text Add to dashboard Cite

show abstract

“…For example, Saffman (1972) describes the motion of a vortex pair in a weakly stratified fluid, for which Hill (1975) presents numerical calculations using vortex elements. Hecht et al (1980Hecht et al ( , 1981 give computational results based on closure modelling of turbulent vortex pairs and rings propagating through various stratification conditions. Sarpkaya (1983) describes experiments which include the propagation of trailing vortex pairs through a stratified medium, and Maxworthy (1977) presents results from an experiment on the motion of a turbulent vortex ring propagating through a fluid with a very weak uniform density gradient.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of vortex interaction with a density interface

1989

View full text Add to dashboard Cite

We present results from an experimental and numerical investigation into the dynamics of the interaction between a planar vortex pair or axisymmetric vortex ring with lengthscale a and circulation Γ encountering a planar interface of thickness δ across which the fluid density increases from ρ1 to ρ2. Similarity considerations indicate that baroclinic generation of vorticity and its subsequent interaction with the original vortex is governed by two dimensionless parameters, namely (a/δ) A and R, where A ≡ (ρρ2 − ρ1)/(ρ2 + ρ1) and R ≡ (a3g/Γ2). For thin interfaces (δ [Lt ] a), the interaction is governed only by the parameters A and R. Furthermore, in the Boussinesq limit (A → 0), the dynamics are governed solely by the product AR and the interaction is entirely invertible with respect to the initial locations and direction of propagation of the vortices. We document details of the interaction dynamics in the Boussinesq limit over a range of the parameter AR. Results show that, for relatively small values of AR, rather than the vortex simply rebounding at the interface, its outermost layers are instead successively ‘peeled’ away by baroclinically generated vorticity and form a topologically complex backflow in which the ring fluid, the light fluid and the heavy fluid are intertwined. For larger values of AR the vortex barely penetrates the interface, and our results suggest that in the limit AR → ∞ the interaction with a density interface becomes similar to the interaction at a solid wall. We also present results for thick interfaces in the Boussinesq limit, as well as larger density jumps for which the density parameter A enters as a second similarity quantity. Comparison of the experimental and numerical results demonstrate that many of the features of such interactions can be understood within the context of inviscid fluids, and that inviscid vortex methods can be used to accurately simulate the dynamics of such interactions.

show abstract

“…The majority of the experimental data have been obtained in large-scale atmospheric tests using aircraft (Burnham et al 1978) or from vortex rings (Hecht et al 1980). Flight tests are usually limited in both the quantity and quality of information that can be extracted because of the vagaries of atmospheric flow conditions.…”

Section: Introductionmentioning

confidence: 99%

Trailing vortices in homogeneous and density-stratified media

Sarpkaya

1983

J. Fluid Mech.

104

View full text Add to dashboard Cite

Experiments were conducted with three delta wings and two rectangular wings to investigate the evolution of trailing vortices in stratified and unstratified water. The vortex trajectories were determined as a function of the normalized time V0t/b0, stratification parameter Nb0/V0 and an effective vortex-core size re/b0. The results have shown that the vortices rise only to a finite height as they decay gradually at first and rapidly thereafter under the influence of turbulence, sinusoidal instability, and core bursting. The effect of stratification is to reduce the lifespan of vortices and the maximum height attained by them.

show abstract

Turbulent Vortices in Stratified Fluids

Cited by 19 publications

References 19 publications

Dispersion of aircraft emissions due to wake vortices in stratified shear flows: A two‐dimensional numerical study

Dispersion of aircraft emissions due to wake vortices in stratified shear flows: A two‐dimensional numerical study

Dynamics of vortex interaction with a density interface

Trailing vortices in homogeneous and density-stratified media

Contact Info

Product

Resources

About