Auto-oscillations of planar colliding jets

Денщиков, В. А.; Кондратьев, В. Н.; Romashov, A. N.; Чубаров, В. М.

doi:10.1007/bf01090570

Cited by 48 publications

(45 citation statements)

References 1 publication

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“…A low frequency bulk motion in the axial direction has been reported by Rolon et al [9], Deshchikov et al [32,33] and Mounaïm-Rousselle and Gökalp [34] among others. In the current work the effect was noticeable and could not be fully eliminated by the use of a co-flowing stream of air.…”

Section: Mean Velocities and Normal Stressesmentioning

confidence: 82%

Fractal-Generated Turbulence in Opposed Jet Flows

Geipel

Goh

Lindstedt

2010

Flow Turbulence Combust

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The opposed jet configuration presents a canonical geometry suitable for the evaluation of calculation methods seeking to reproduce the impact of strain and re-distribution on turbulent transport in reacting and non-reacting flows. The geometry has the advantage of good optical access and, in principle, an absence of complex boundary conditions. Disadvantages include low frequency flow motion at high nozzle separations and comparatively low turbulence levels causing bulk strain to exceed the turbulent contribution at small nozzle separations. In the current work, fractal generated turbulence has been used to increase the turbulent strain and velocity measurements for isothermal flows are reported with an emphasis on the axis, stagnation plane and the distribution of mean and instantaneous strain rates. Energy spectra were also determined. The instrumentation comprised hotwire anemometry and particle image velocimetry with the flows to both nozzles seeded with 1 μm silicon oil droplets providing a relaxation time of 3 μs. It is shown that fractal grids increase the turbulent Reynolds number range from 48-125 to 109-220 for bulk velocities from 4 to 8 m/s as compared to conventional perforated plate turbulence generators. Low frequency motion of the order 10 Hz could not be completely eliminated and probability density functions were determined for the location of the stagnation plane. Results show that the fluctuation in the position of the stagnation plane is of the order of the integral length scale, which was determined to be 3.1±0.1 mm at the nozzle exits through the use of hot-wire anemometry. Flow statistics close to the fractal plate located upstream of the nozzle exit were also determined using a transparent glass nozzle.

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Section: Mean Velocities and Normal Stressesmentioning

confidence: 82%

Fractal-Generated Turbulence in Opposed Jet Flows

Geipel

Goh

Lindstedt

2010

Flow Turbulence Combust

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“…Moreover, the experimental results of the planar opposed jets with acoustic excitation in our lately published paper show that the planar opposed jets exhibit a selfsustained deflecting oscillation and the impinging plane do not synchronize with the excitation until the excitation amplitude is larger than 30%, which proves once again the flow regimes of planar opposed jets and axisymmetric opposed jets are different in nature. [21][22][23]35 As discussed in the introduction, the stagnation point offset or the three stable states are the inborn instability regimes of axisymmetric opposed jets, [3][4][5][6][7][8][9][10][11][12] which are the prerequisites of the excited oscillation in current article. But the excitation of modulated airflow is the direct cause of the periodic oscillation of the impinging plane of axisymmetric opposed jets under excitations, and current experimental results indicate that the excitation frequency, excitation amplitude, turbulence intensity, and nozzle separation have important influence on the periodic oscillation of opposed jets with excitations.…”

Section: Discussionmentioning

confidence: 98%

“…It can be seen that the oscillation regimes of unrestricted axisymmetric opposed jets are basically different to the self-sustained oscillation in RIM and the periodic deflecting oscillation of planar opposed jets. [21][22][23] The excitation of modulated inflow has been widely used in the fluid mixing, 24,25 particle dispersion, 26 and liquid breakup. 27 However, the study of the flow regime of axisymmeric opposed jets with excitation is very rare, although it is important to fundamental fluid dynamics and applications.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of oscillation of axisymmetric turbulent opposed jets with modulated airflow

Guo-Feng

et al. 2013

AIChE Journal

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Oscillation behaviors of axisymmetric opposed jets with modulated airflow were experimentally studied. The oscillation frequency, the oscillation amplitude, and the movement velocity of the impingement plane at various nozzle separations, excitation frequencies, and exit turbulence intensities have been investigated by a hot-wire anemometer and flow visualization technique combined with a high-speed camera. Results show that the oscillation frequency of the impingement plane is nearly equal to the excitation frequency, whereas the oscillation amplitude decreases with the increase of the excitation frequency. The full-scale amplitude oscillation occurs at low excitation frequencies and 2 L/D 8 (where L is the nozzle separation and D is the diameter of the nozzle exit). With the increase of the exit turbulence intensity caused by a turbulence generating plate, the oscillation amplitude decreases remarkably. Flow regimes of axisymmetric opposed jets with excitations are analyzed and discussed based on the experimental results.

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“…The instability regime observed in current study is similar to Rolon et al 23 and Pawlowski et al, 25 though the flows in their work are laminar. But current instability regime is different to the deflecting oscillation instability in RIM and planar opposed jets, [8][9][10][11][12]17,18 which may be due to the influences of the wall or the nozzle geometry.…”

Section: Flow Pattern Of Turbulent Opposed Jetsmentioning

confidence: 91%

“…The oscillation in their experiment is a deflecting oscillation from the symmetric axis and the two opposed jets are deflected in the opposite directions from each other and switches directions periodically. 17,18 For two unrestricted turbulent opposed jets, however, several researchers have observed various kinds of stagnation point offset in their experiments. Kostiuk et al studied turbulent opposed jets using LDA at L ¼ 2D and observed the stagnation point offset along the symmetric axis.…”

Section: Introductionmentioning

confidence: 98%

Study on factors influencing stagnation point offset of turbulent opposed jets

Yao

Wang

2010

AIChE Journal

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in Wiley Online Library (wileyonlinelibrary.com).Turbulent opposed jets were experimentally studied by the hot-wire anemometer measurement, the smoke-wire flow visualization, and the CFD simulation at L ¼ 1À20D (where L is the nozzle separation and D is the nozzle diameter) and Re [ 4500. The instability pattern of turbulent opposed jets was identified by investigating the smoke-wire photos recorded by a high-speed camera. The factors affecting stagnation point offset, such as the bulk velocity, the velocity profile, and the turbulence intensity at the nozzle exits were investigated. Results show that the stagnation point offset is the main instability regime of turbulent opposed jets. Uniform exit velocity profile and increasing exit turbulence intensity will decrease the stagnation point offset of turbulent opposed jets.

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Auto-oscillations of planar colliding jets

Cited by 48 publications

References 1 publication

Fractal-Generated Turbulence in Opposed Jet Flows

Fractal-Generated Turbulence in Opposed Jet Flows

Experimental study of oscillation of axisymmetric turbulent opposed jets with modulated airflow

Study on factors influencing stagnation point offset of turbulent opposed jets

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