Modes in flow focusing and instability of coaxial liquid–gas jets

Abstract

Six flow modes are distinguished in the flow-focusing experiments of a liquid jet forced by a high-speed air stream. The domains of the modes are identified on the parameter space of the liquid flow rateQland the gas pressure drop Δpg. The disturbance wavelength λ and breakup lengthLof the jet are also measured. A theoretical model considering axisymmetric disturbances is proposed, and a basic velocity profile of hyperbolic-tangent function is utilized. The linear temporal and spatio-temporal instability analyses are carried out using the Chebyshev collocation method. The effects of the flow parameters and the velocity profile on the flow instability are discussed. The temporal instability analysis demonstrates that the interfacial shear causes the instability of short waves and retards the instability of long waves. Moreover, the spatio-temporal instability analysis gives the transition boundary between the absolute and convective instability (AI/CI). The most unstable wavelength predicted by the temporal instability analysis and the AI/CI boundary predicted by the spatio-temporal instability analysis are in good agreement with the experimental results.

Ceramic micro-injection molded nozzles for serial femtosecond crystallography sample delivery

“…The stability behavior of the assembled nozzle qualitatively agrees with other such diagrams presented elsewhere. 19,29 However, a careful distinction must be made when comparing our stability phase diagram to these results. In some cases, the authors were primarily concerned with the stability of the liquid meniscus, called local stability.…”

“…The difference being that in the GDVN case, the focusing gas changes the axial velocity gradient of the liquid in the jet. 29 For experiments performed with X-ray beams, the jet length is of importance as it determines the maximum distance of the nozzle from the X-ray interaction region to intercept a contiguous jet. Intercepting the jet before it breaks up into droplets generally optimizes data collection efficiency, as will be discussed later.…”

Jet delivery system for Raman scattering on bio-inorganic compounds

“…We used ceramic-based gas dynamic virtual nozzles 17 for generation of the micro jet. [18][19][20][21][22][23][24][25][26][27][28] To fit the nozzle to the jet chamber, we designed a special short nozzle with a 10-mm long ceramic piece. For the Raman measurements, we used a Millennia-Tsunami system (Spectra Physics) with a repetition rate of 80 MHz and a pulse energy of 15 nJ including flexible harmonic generation as a source for the photons incident on the sample and a UT-3 Raman spectrometer as analyzer of the scattered light.…”

“…In order to increase the original micro-jet diameter of 2-5 lm, 17 we systematically changed certain jetting parameters. The micro jet diameter D j is given by [17][18][19][20][21][22][23][24][25][26] …”

Experimental design and instability analysis of coaxial electrospray process for microencapsulation of drugs and imaging agents

“…13,14 The theory deals with the mathematical analysis of the flow response to disturbances with small amplitudes superposed on a laminar basic flow. If the flow returns to its original laminar state, it is recognized as stable.…”