TY - CONF
T1 - Dual-tracer PLIF measurements of entrainment and mixing in a driven axisymmetric jet
AU - Meyer, Terrence R.
AU - Lucht, Robert P.
AU - Dutton, J. Craig
N1 - This-work was supported by the National Science Foundation, Division of Chemical and Transport Systems, Grant No. CTS 94-23280, with Dr. R.E.A. Arndt as monitor. In addition, the authors would like to thank Gregory F. King for his helpful input on implementing the experimental and image processing procedures.
PY - 1998
Y1 - 1998
N2 - The time-dependent mixing state during vortex formation and merging is investigated in the near-field of a driven axisymmetric jet Acoustic forcing is used to obtain repeatable vortex pairing events, and simultaneous passive scalar and cold-chemistry PLIF are used to obtain instantaneous images of molecularly mixed jet fluid fraction. The time varying scalar dissipation field and area-averaged mixedness of the vortex core region are also used to investigate various stages of vortex interaction. These mixing properties are analyzed in conjunction with the observed vortex dynamics, such as unsteady vortex convection velocity. The results indicate that there are three phases of the pairing event with distinct mixing characteristics, including the vortex roll-up, approach of the trailing vortex, and co-rotation/homogenization. Vortex roll-up is nearly laminar with molecular diffusion between the layers of jet and co-flow fluid. The most dramatic change in the mixing state of the leading vortex, which includes the appearance of a uniformly mixed core region, occurs as the trailing vortex approaches and interferes with co-flow fluid entrainment. The co-rotation phase is marked by gross deformation and stretching of the trailing vortex, and rapid homogenization. These stages of vortex pairing coincide with the temporal evolution of vorticity observed in previous studies.
AB - The time-dependent mixing state during vortex formation and merging is investigated in the near-field of a driven axisymmetric jet Acoustic forcing is used to obtain repeatable vortex pairing events, and simultaneous passive scalar and cold-chemistry PLIF are used to obtain instantaneous images of molecularly mixed jet fluid fraction. The time varying scalar dissipation field and area-averaged mixedness of the vortex core region are also used to investigate various stages of vortex interaction. These mixing properties are analyzed in conjunction with the observed vortex dynamics, such as unsteady vortex convection velocity. The results indicate that there are three phases of the pairing event with distinct mixing characteristics, including the vortex roll-up, approach of the trailing vortex, and co-rotation/homogenization. Vortex roll-up is nearly laminar with molecular diffusion between the layers of jet and co-flow fluid. The most dramatic change in the mixing state of the leading vortex, which includes the appearance of a uniformly mixed core region, occurs as the trailing vortex approaches and interferes with co-flow fluid entrainment. The co-rotation phase is marked by gross deformation and stretching of the trailing vortex, and rapid homogenization. These stages of vortex pairing coincide with the temporal evolution of vorticity observed in previous studies.
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U2 - 10.2514/6.1998-3018
DO - 10.2514/6.1998-3018
M3 - Paper
AN - SCOPUS:84959322712
SP - 1
EP - 20
T2 - 29th AIAA Fluid Dynamics Conference
Y2 - 15 June 1998 through 18 June 1998
ER -