Mixing Processes in a Coaxial Geometry with a Central Lobed Mixer-Nozzle

Belovich, Vincent; Samimy, Mo

doi:10.2514/2.7455

Cited by 51 publications

(13 citation statements)

References 94 publications

(168 reference statements)

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“…McCormick and Bennett (17) further investigated experimentally the mixing mechanism downstream of the lobed mixer in detail and concluded that the intense small-scale turbulence mixing was mainly due to the formation of the pinchedoff structures which is unstable. Similar conclusions were obtained by the Belovich et al (24) , Hu et al (25)(26)(27)(28) and Yu et al (29) . More recently, the K-H vortex rolling-up mechanisms in the enhanced mixing processes has been partly revealed (30)(31)(32)(33)(34) .…”

Section: Introductionsupporting

confidence: 88%

Experimental and numerical study of mixing characteristics of a rectangular lobed mixer in supersonic flow

Feng¹,

Shen²,

Wang

et al. 2015

Aeronaut.j.

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A combined experimental and computational study on a rectangular lobed mixer is performed. A series of simulations based on a steady Reynolds-averaged Navier-Stokes Simulation (RANS) are conducted to analyse the mixing mechanisms of large-scale streamwise structure shed by the trailing edge of lobed mixer, with emphasis being placed on the effect of turbulence modeling and inflow conditions. The simulations are validated in respect of velocity and scalar distribution against the data obtained through Particle Image Velocimetry (PIV) and Nanoparticle-based Planar Laser Scattering (NPLS) technique. The computational results predicted by the SST k -ω turbulence model show better agreement with the experimental data. But the small-scale turbulence structures are not captured accurately by these turbulence models. The convoluted shear layer shed from trailing edge is stretched and rotated by the large-scale streamwise vortices, forming an unstable 'pinching-off' structure, which increases the interfacial area. And at the interface of two streams, a large number of small-scale turbulence structures are formed, which contribute a lot to the mixing enhancement along with the increased interfacial area. The streamwise vorticity decays more rapidly with the decrease of velocity ratio and total pressure ratio of two streams. The scalar thickness which reflects the mixing rate of two streams increases with the decreasing velocity ratio and total pressure ratio.

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Section: Introductionsupporting

confidence: 88%

Experimental and numerical study of mixing characteristics of a rectangular lobed mixer in supersonic flow

Feng¹,

Shen²,

Wang

et al. 2015

Aeronaut.j.

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“…The large-scale streamwise vortices generated by lobed nozzles and azimuthal vortices due to the Kelvin-Helmholtz instability have been suggested to play important roles in the mixing processes of lobed mixing flows. 11,12 Since most of previous studies on lobed mixing flows were conducted by using conventional measurement techniques like Pitot probes, hot film anemometer and laser doppler velocimetry, instantaneous, quantitative whole-field velocity and vorticity distributions in lobed mixing flows have never been obtained until the recent work of the authors. 13,14 In the earlier work of the authors, planar laser induced fluorescence ͑PLIF͒ and ''classical'' PIV techniques 13 and conventional ''singleplane'' stereoscopic PIV technique 14 were used to study lobed jet mixing flows.…”

Section: Lobed Jet Flow and Experimental Apparatusmentioning

confidence: 99%

Simultaneous measurements of all three components of velocity and vorticity vectors in a lobed jet flow by means of dual-plane stereoscopic particle image velocimetry

Saga

Kobayashi

et al. 2002

Physics of Fluids

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Results from an advanced particle image velocimetry ͑PIV͒ technique, named as dual-plane stereoscopic PIV technique, for making simultaneous measurements of all three components of velocity and vorticity vectors are presented for a lobed jet flow. The dual-plane stereoscopic PIV technique uses polarization conservation characteristic of Mie scattering to achieve simultaneous stereoscopic PIV measurements at two spatially separated planes. Unlike ''classical'' PIV systems or conventional stereoscopic PIV systems, which can only get one component of vorticity vectors, the present dual-plane stereoscopic PIV system can provide all three components of velocity and vorticity distributions in fluid flows instantaneously and simultaneously. The evolution and interaction characteristics of the large-scale streamwise vortices and azimuthal Kelvin-Helmholtz vortices in the lobed jet flow are revealed very clearly and quantitatively from the simultaneous measurement results of the dual-plane stereoscopic PIV system. A discussion about the satisfaction of the measurement results of the present dual-plane stereoscopic PIV system to mass conservation equation is also conducted in the present paper to evaluate the error levels of the measurement results.

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“…First type of geometry represents a baseline that is used nowadays in air terminals devices, which has a circular shape ("O"). The second geometry, named lobed ("+"),is used more in a specific field, aeronautics and combustion [13][14][15]. Both shapes with their dimensions can be seen in the The 3D geometries were made in SolidWorks and imported to DesignModeler from Ansys Workbench.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

et al. 2019

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In order to achieve more realistic boundary conditions on the inlet of a ventilation system it is necessary to study the influences of the air diffuser orifices geometry on the airflow distribution in the enclosure. Integrating these orifices directly in a real scale air diffuser for a numerical study will result in a huge computational grid which will translate in huge computational resources and a much larger calculation time. The solution, in this case, was the numerical simulation of the airflow through small parts of the studied air diffuser. Later, the numerical results will be implemented as boundary conditions in the unidirectional diffuser of a numerical simulation that represents a real scale operating room (OR). In the current study two diffusers with different orifices were studied, one having circular („O”) and the other one lobbed („+”) orifices. The initial numerical model had 25 orifices on the diffuser, but because of the very large numerical grid resulted for the initial meshes (>35 million tetrahedral cells), a solution with only 4 orifices was chosen for this study. A mesh independency study was made for these two types of air diffusers. The numerical studies were made using RANS method, with SST k-ω turbulence model in steady state conditions. The numerical results obtained with the first step models showed very good agreement with the PIV stereoscopic experimental measurements.

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Mixing Processes in a Coaxial Geometry with a Central Lobed Mixer-Nozzle

Cited by 51 publications

References 94 publications

Experimental and numerical study of mixing characteristics of a rectangular lobed mixer in supersonic flow

Experimental and numerical study of mixing characteristics of a rectangular lobed mixer in supersonic flow

Simultaneous measurements of all three components of velocity and vorticity vectors in a lobed jet flow by means of dual-plane stereoscopic particle image velocimetry

Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

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