期刊
EXPERIMENTAL THERMAL AND FLUID SCIENCE
卷 123, 期 -, 页码 -出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.expthermflusci.2020.110293
关键词
Jets; Nozzles; Turbulence
资金
- Department of Mechanical Science and Engineering at the University of Illinois Urbana-Champaign
In this experimental study, the effects of various axisymmetric orifice geometries on jet characteristics at Reynolds number of approximately 10^5 were explored. The thickness and divergence angle of the orifices were found to impact velocity profiles and mixing rates in the near region, highlighting the influence of geometry on turbulent structures and flow behavior.
We experimentally explored the distinct effects induced by the geometry of various axisymmetric orifices in the near and intermediate regions of jets at a Reynolds number of Re approximate to 10(5) based on the diameter, d = 10 mm, of the orifices. The orifices inspected had thicknesses of is an element of/d = 0.2, 1 and 2 and divergence angles of theta = 0 degrees, 20 degrees and 45 degrees. High-speed planar particle image velocimetry (PIV) was used to characterize the instantaneous flow field, high-order statistics, and dominant coherent motions at the jets symmetry plane within a streamwise distance of x/ d is an element of (0, 10]. Time-averaged flow fields reveal the effects of each orifice; velocity profiles in the near region exhibited saddle-backed, top-hat, and developing flow profiles with the short (sharp-edged), medium (contraction) and long (pipe-like) nozzles, which are modulated by is an element of/d. The mixing rate was also affected by the orifices; differences between the cases are associated with the formation of distinct turbulent structures. Instantaneous vorticity fields, velocity spectra, and modal decomposition revealed relatively strong vortices and large scale meandering shed at relatively high frequency. The divergence angle strongly modulated the onset of large-scale oscillations.
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