Investigation of the interacting flow of nonsymmetric jets in crossflow

Jiang, Wu; Vakili, Ahmad; Yu, Feiyan

doi:10.2514/3.9994

Cited by 68 publications

(34 citation statements)

References 8 publications

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“…In fact, those far-field wake experiments in part motivated the present investigation of the near-field wake. More recently, Wu, Vakili & Yu (1988) visualized coherent wake vortices behind asymmetric jets in crossflow, referring to them as 'spin-off' vortices. Those vortices were visualized by placing the dye port in the wake just downstream of the jet.…”

Section: : Fricmentioning

confidence: 99%

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Vortical structure in the wake of a transverse jet

1994

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Structural features resulting from the interaction of a turbulent jet issuing transversely into a uniform stream are described with the help of flow visualization and hot-wire anemometry. Jet-to-crossflow velocity ratios from 2 to 10 were investigated at crossflow Reynolds numbers from 3800 to 11400. In particular, the origin and formation of the vortices in the wake are described and shown to be fundamentally different from the well-known phenomenon of vortex shedding from solid bluff bodies. The flow around a transverse jet does not separate from the jet and does not shed vorticity into the wake. Instead, the wake vortices have their origins in the laminar boundary layer of the wall from which the jet issues. It is argued that the closed flow around the jet imposes an adverse pressure gradient on the wall, on the downstream lateral sides of the jet, provoking 'separation events' in the wall boundary layer on each side. These result in eruptions of boundary-layer fluid and formation of wake vortices that are convected downstream. The measured wake Strouhal frequencies, which depend on the jet-crossflow velocity ratio, match the measured frequencies of the separation events. The wake structure is most orderly and the corresponding wake Strouhal number (0.13) is most sharply defined for velocity ratios near the value 4. Measured wake profiles show deficits of both momentum and total pressure.

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Section: : Fricmentioning

confidence: 99%

“…Those vortices were visualized by placing the dye port in the wake just downstream of the jet. Wu et al (1988) did not report wake (or 'spin-off') vortices for symmetric jets.…”

Section: : Fricmentioning

confidence: 99%

Vortical structure in the wake of a transverse jet

1994

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“…Wake vortices are variously referred to in the literature as 'fire devils ' (McMahon et al 1971), 'spin-off vortices' (Wu et al 1988), 'fingers' (Lozano et al 1994), 'upright' (Kelso et al 1996), 'zipper' (Morton & Ibbetson, 1996), 'tornado-like' or Fric's vortices (Rivero et al 2001), and the 'wall-normal' vortices (Gopalan et al 2004). Although the wake vortices of the JICF have been investigated since the 1970s (e.g., McMahon et al, 1971), the question of their origin, statistics, and potential technological applications still persists.…”

Section: Introductionmentioning

confidence: 99%

Unsteady wake vortices in jets in cross-flow

Milanović

Zaman²,

Bencic³

2011

J Vis

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The current flow visualization study investigates unsteady wake vortices of jets in cross-flow in order to (1) advance the understanding of their origin and characteristics and (2) explore various excitation techniques for organizing and accentuating them. An isolated circular jet passed through a nozzle and entered the cross-flow normal to the wall. Free stream velocities up to 5 m/s and jet-to-cross-flow velocity ratio range between 1 and 10 were covered. While mechanical perturbation did not result in any significant periodic organization of the wake vortices, the database obtained for the unperturbed flow provided further insight into their behavior. The key finding was that the wake vortices always originated from the lee-side of the jet where the jet efflux boundary layer and the wall boundary layer intersected. In no case these vortices were seen to form either from the wall boundary layer or the jet shear layer at downstream locations. After formation the wake vortex twists and stretches as it convects downstream with the base still attached to the near-wall region on the jet's lee side. The top remains connected to the underside of the jet where the tracer particles dissipate due to high turbulence in the shear layer.

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“…Wu et a l. [2] documented the fl ow topo logy of normal j ets with di ffe rent cross-sectio nal shape and I ::; VR ::; 9 using fl ow visuali zati on techniques. ote that fo r incompressible flo w, the velocity ratio VR is the squ are root of the mome ntum-flu x ratio J.…”

Section: Introductionmentioning

confidence: 99%

“…In Ref. 2, co mpa ri son of fl ow fi elds was made in an attempt to identify conditi ons that enJl ance asym metry. Jo hn sto n and Ni shi [3] studied j et pitched at 45° and yawed at 90° and 180° over a range of velocity rati os, 0 .4::; VR ::; I.…”

Section: Introductionmentioning

confidence: 99%

Pitched and Yawed Circular Jets in Cross-Flow

Milanović

Zaman

2002

Volume 1: Fora, Parts a and B

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Results from an experimental in vesti gation of flow fie ld generated by pitched and yawed j ets di schargin g from a fl at plate into a cross-flow are presented. The circul ar j et was pitched at a = 20° and 4 5° and yawed between f3 = 0° and 90° in increments of IS O. The measurements were performed with two X-wires prov iding a ll three components of velocity and turbul ence intensity. These data were obta ined at down trea m locati ons of x = 3, 5, 10 and 20, where the distance x, normali zed by the j et di ameter, is measured from th e center of the ori fice . D ata fo r a ll configurati ons were acquired at a momentum-flux rati o J = 8. Additionall y, for selected angles and locations, surveys were conducted for J = 1.5, 4, and 20.As expected, the jet p enetration is found to be hi gher at larger a. With increasing f3 the j et spreads more. The rate of reducti on of peak streamwise vo rti city, (Oxma.n with th e downstream d istance is significantl y lessened at hi gher f3 but is found to be practica lly independent of a. Thus, at th e fa rth est measurement station x = 20, w'tmax is about fi ve times large r for f3 = 75° compared to the leve ls at f3 = 0°. Strea mwise ve locity within the j et-vortex stru cture is fo un d to depend on the parameter J. A t J = 1. 5 and 4, 'wake-li ke' velocity profi les are observed. In compari son, a 'j et-like' overshoot is present at hi gher J. NOMENCLAT URE

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Investigation of the interacting flow of nonsymmetric jets in crossflow

Cited by 68 publications

References 8 publications

Vortical structure in the wake of a transverse jet

Vortical structure in the wake of a transverse jet

Unsteady wake vortices in jets in cross-flow

Pitched and Yawed Circular Jets in Cross-Flow

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