On the scaling of propagation of periodically generated vortex rings Academic Article uri icon

abstract

  • The propagation of periodically generated vortex rings (period$T$) is numerically investigated by imposing pulsed jets of velocity$U_{jet}$and duration$T_{s}$(no flow between pulses) at the inlet of a cylinder of diameter$D$exiting into a tank. Because of the step-like nature of pulsed jet waveforms, the average jet velocity during a cycle is$U_{ave}=U_{jet}T_{s}/T$. By using$U_{ave}$in the definition of the Reynolds number ($Re=U_{ave}D/unicode[STIX]{x1D708}$,$unicode[STIX]{x1D708}$: kinematic viscosity of fluid) and non-dimensional period ($T^{ast }=TU_{ave}/D=T_{s}U_{jet}/D$, i.e.equivalent to formation time), then based on the results, the vortex ring velocity$U_{v}/U_{jet}$becomes approximately independent of the stroke ratio$T_{s}/T$. The results also show that$U_{v}/U_{jet}$increases by reducing$Re$or increasing$T^{ast }$(more sensitive to$T^{ast }$) according to a power law of the form$U_{v}/U_{jet}=0.27T^{ast 1.31Re^{-0.2}}$. An empirical relation, therefore, for the location of vortex ring core centres ($S$) over time ($t$) is proposed ($S/D=0.27T^{ast 1+1.31Re^{-0.2}}t/T_{s}$

published proceedings

  • JOURNAL OF FLUID MECHANICS

altmetric score

  • 0.25

author list (cited authors)

  • Asadi, H., Asgharzadeh, H., & Borazjani, I.

citation count

  • 25

complete list of authors

  • Asadi, H||Asgharzadeh, H||Borazjani, I

publication date

  • October 2018