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Title of Journal: Exp Fluids

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Abbravation: Experiments in Fluids

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Springer-Verlag

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DOI

10.1002/pssa.2210190148

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1432-1114

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Vortex dynamics and mass entrainment in turbulent

Authors: Ilinca Nastase Amina Meslem
Publish Date: 2009/10/25
Volume: 48, Issue: 4, Pages: 693-714
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Abstract

Passive control of jet flows in order to enhance mixing and entrainment is of wide applicative interest Our purpose is to develop new air diffusers for HVAC systems by using lobed geometry nozzles in order to ameliorate users the thermal comfort Two turbulent 6lobed air jets with and without lobe deflection angles were studied experimentally and compared with a reference circular jet having the same initial Reynolds number The main objective was to analyze the modifications occurring in the vortex dynamics of the flow firstly by replacing a circular tube with a straight lobed tube and secondly by a lobed tube having a double inclination of the lobes Rapid visualizations of the flows and hotwire measurements of the streamwise velocity spectra allow understanding the vortex rollup mechanisms Unlike the circular jet where the primary rings are continuous the Kelvin–Helmholtz vortices in the lobed jet flows were found to be discontinuous The resulting “ring segments” detach at different frequencies whether they are shed in the lobe troughs or at the lobe sides One explanation relies on the strong variation of the exit plane curvature Additionally a speculative scenario of the vortical dynamics is advanced by the authors The discontinuous nature of the K–H vortices enables the development of secondary streamwise structures noninfluenced by the passage of the primary structures as in the case of the circular jet Thus the momentum flux transport role played by the streamwise structures is rendered more efficient and leads to a spectacular increase in the entrainment rate in the initial region The amount of fluid being entrained in the lobed jet by the streamwise structures is drastically amplified by the double inclination of the nozzle exit boundary


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  1. Passive mixing control of plane parallel jets
  2. Planar fluorescence for round bubble imaging and its application for the study of an axisymmetric two-phase jet
  3. Imaging diffusion in a microfluidic device by third harmonic microscopy
  4. Two- and three-dimensional flows in nearly rectangular cavities driven by collinear motion of two facing walls
  5. Using stereo multigrid DPIV (SMDPIV) measurements to investigate the vortical skeleton behind a finite-span flapping wing
  6. Influence of a wavy boundary on turbulence.
  7. A novel data reduction technique for single slanted hot-wire measurements used to study incompressible compressor tip leakage flows
  8. Digital holography for micro-droplet diagnostics
  9. Kriging regression of PIV data using a local error estimate
  10. Active control of an axisymmetric jet with distributed electromagnetic flap actuators
  11. Experimental investigations on steady wake effects in a high-lift turbine cascade
  12. Simultaneous droplet and vapour-phase measurements in an evaporative spray by combined ILIDS and PLIF techniques
  13. Simultaneous droplet and vapour-phase measurements in an evaporative spray by combined ILIDS and PLIF techniques
  14. Experimental study of liquid–vapor phase distribution in a single tube capillary evaporator
  15. Analysis of the impact of impeller geometry on the turbulent statistics inside a fan-stirred, cylindrical flame speed vessel using PIV
  16. Detection of microorganismic flows by linear and nonlinear optical methods and automatic correction of erroneous images artefacts and moving boundaries in image generating methods by a neuronumerical hybrid implementing the Taylor’s hypothesis as a priori knowledge
  17. Hot-wire spatial resolution effects in measurements of grid-generated turbulence
  18. Effect of experimental parameters and image noise on the error levels in simultaneous velocity and temperature measurements using molecular tagging velocimetry/thermometry (MTV/T)
  19. Turbulence measurements in pipe flow using a nano-scale thermal anemometry probe
  20. The pinch-off process in a starting buoyant plume
  21. Defining the roughness sublayer and its turbulence statistics
  22. Evolution of a forced counter rotating vortex pair for two selected forcing frequencies
  23. Optically efficient fluorescent tracers for multi-constituent PIV
  24. Intermittent corner separation in a linear compressor cascade
  25. A novel architecture for a super-resolution PIV algorithm developed for the improvement of the resolution of large velocity gradient measurements
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  28. High-speed roll coating with complex rheology fluids
  29. Wing–vortex interaction: unraveling the flowfield of a hovering rotor
  30. Near-surface velocimetry using evanescent wave illumination
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  32. Characterizing the lower log region of the atmospheric surface layer via large-scale particle tracking velocimetry
  33. Development and characterization of high-frequency resonance-enhanced microjet actuators for control of high-speed jets
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  41. Polymer-induced turbulence modifications in an impinging jet
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