Application of a Biot-Savart Solver to Predict Axis Switching Phenomenon in Finite-Span Vortices Expelled from a Synthetic Jet

2017 ◽  
Author(s):  
Joseph C. Straccia ◽  
John A. Farnsworth
Keyword(s):  
Synthetic Jet ◽  
Finite Span ◽  
Switching Phenomenon ◽  
Axis Switching

Comparative study on interfacial oscillations of rectangular and elliptical liquid jets

2020 ◽  
Vol 234 (7) ◽  
pp. 1272-1286 ◽  
Author(s):  
Amin Jaberi ◽  
Mehran Tadjfar
Keyword(s):  
Aspect Ratio ◽  
Weber Number ◽  
High Speed ◽  
Nozzle Geometry ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Aspect Ratios ◽  
Water Jets ◽  
Switching Phenomenon ◽  
Axis Switching

The instability characteristics and flow structures of water jets injected from rectangular and elliptical nozzles with aspect ratios varying from 2 to 6 were experimentally studied and compared. Shadowgraph technique was employed for flow visualization, and structures on the liquid jet surface were captured using high speed photography. It was found that disturbances originating from the nozzle geometry initially perturbed the liquid column, and then, at high jet velocities, disturbances generated within the flow dominated the jet surface. It was also found that rectangular nozzles introduced more disturbances into the flow than the elliptical ones. The characteristic parameters of axis-switching phenomenon including wavelength, frequency, and amplitude were measured and compared. Axis-switching wavelength was found to increase linearly with Weber number. Also, the wavelengths of rectangular jets were longer than the elliptical jets. Further, the frequency of axis-switching was shown to be reduced with increase of both Weber number and aspect ratio. It was observed that the axis-switching amplitude increased monotonically, reached a peak, and then decreased gradually. It was also found that the axis-switching amplitude varied with Weber number. At lower values of Weber number, the rectangular nozzles had higher amplitude than the elliptical nozzles. However, at higher values of Weber number, this relation was reversed, and the elliptical nozzles had the higher axis-switching amplitudes. This reversal Weber number decreased with the orifice aspect ratio. The reversal Weber number for aspect ratio of 4 was about 289, and it had decreased to 144 for the aspect ratio of 6.

Interaction of a finite-span synthetic jet near the tip of a sweptback wing

2015 ◽  
Vol 27 (6) ◽  
pp. 067102 ◽  
Author(s):  
Joseph D. Vasile ◽  
Michael Amitay
Keyword(s):  
Synthetic Jet ◽  
Finite Span

Studies of magnetic axis switching phenomenon in magnetite

2007 ◽  
Vol 442 (1-2) ◽  
pp. 83-85 ◽  
Author(s):  
G. Król ◽  
J. Kusz ◽  
Z. Tarnawski ◽  
Z. Kąkol ◽  
A. Kozłowski ◽  
...  
Keyword(s):  
Magnetic Axis ◽  
Switching Phenomenon ◽  
Axis Switching

Numerical Simulation of Breakup of Elliptical Liquid Jet in Still Air

2012 ◽  
Author(s):  
Ehsan Farvardin ◽  
Ali Dolatabadi
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Breakup Length ◽  
Aspect Ratios ◽  
Switching Phenomenon ◽  
Dimensional Simulation ◽  
Axis Switching ◽  
Recent Experimental Work

Numerical simulation of liquid jets ejecting from a set of elliptical jets with different aspect ratios between 1 (circular) to 3.85 is performed for several Weber numbers ranging 15 to 330. The axis-switching phenomenon and breakup length of the jets are characterized by means of a Volume of Fluid (VOF) method together with a dynamic mesh refinement model. This three dimensional simulation is compared with a recent experimental work and the results agree well. It is concluded that at Weber numbers less than 100, the breakup length of the liquid jet increases, reaches a peak and then decreases suddenly.

Three-dimensional interactions between a finite-span synthetic jet and a crossflow

2011 ◽  
Vol 671 ◽  
pp. 254-287 ◽  
Author(s):  
ONKAR SAHNI ◽  
JOSHUA WOOD ◽  
KENNETH E. JANSEN ◽  
MICHAEL AMITAY
Keyword(s):  
Three Dimensional ◽  
Particle Image Velocimetry Data ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Physical Parameters ◽  
Mean Flow ◽  
Cross Sectional ◽  
Finite Span ◽  
Blowing Ratio ◽  
Ratio Range

A complementary experimental and numerical investigation was performed to study the three-dimensional flow structures and interactions of a finite-span synthetic jet in a crossflow at a chord-based Reynolds number of 100,000 and a 0° angle of attack. Six blowing ratios in the range of 0.2–1.2 were considered. Experiments were conducted on a finite wing with a cross-sectional profile of NACA 4421, where particle-image velocimetry data were collected at the centre jet. To complement the experiments, three-dimensional numerical simulations were performed, where the numerical set-up matched not only the physical parameters (e.g. free stream) but also the physical dimensions (e.g. orientation and location of the jet. For the low blowing ratio cases, spatial non-uniformities developed, due to the finite span of the slit, which led to the formation of small and organized secondary structures or a streak-like pattern in the mean flow. On the other hand, for the high blowing ratio range, turbulent vortical structures were dominant, leading to larger spanwise structures, with a larger spanwise wavelength. Moreover, the phase-locked flow fields exhibited a train of counter-rotating coherent vortices that lifted off the surface as they advected downstream. In the mid-blowing ratio range, combined features of the low range (near the slit) and high range (in downstream locations) were found, where a pair of counter-rotating vortices issued in the same jet cycle collided with each other. In all cases, the spanwise extent of the secondary coherent structures reduced with downstream distance with a larger decrease at higher blowing ratios. Similar observations were made in earlier studies on finite-span synthetic jets in quiescent conditions.

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