Passive and reactive scalar measurements in a transient high-Schmidt-number Rayleigh–Taylor mixing layer

• Published in: Experiments in fluids Vol. 53; no. 3; pp. 717 - 729
• Main Authors: Banerjee, Arindam, Mutnuri, Lakshmi Ayyappa Raghu
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2012; Springer
• Subjects: Asymptotic properties; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Exact sciences and technology; Fluid dynamics; Fluid flow; Fluid- and Aerodynamics; Fluids; Fundamental areas of phenomenology (including applications); Heat and Mass Transfer; Hydrodynamic stability; Instability; Instrumentation for fluid dynamics; Interfacial instability; Physics; Research Article; Scalars; Scandium; Stability; USA, Texas; Mixture Fraction; Phenolphthalein; Equivalence Ratio; Shear Layer; Reactive Scalar; Interfaces; Test facilities; Rayleigh-Taylor instability; Chemical reactions; Optical systems; Calibration; Experimental study; Mixing layer
• ISSN: 0723-4864; 1432-1114
• DOI: 10.1007/s00348-012-1328-y

An experimental study of mixing induced by Rayleigh–Taylor (RT) instability at an Atwood number ( A t ) ~7.5 × 10 −4 and Schmidt number (Sc) ~1,000 has been performed. A new transient experimental facility developed on the working principles of the draw-tank facility at Cambridge (Dalziel et al. in J Fluid Mech, 399:1–48, 1999 ) has been established and enhanced to observe a higher (2×) Reynolds number regime. Water and brine were used to produce the RT density stratification. The evolution of the instability was studied using passive and reactive scalar techniques and quantified using optical diagnostic methods. The data were combined to estimate local and global mixing metrics representative of the mixing mechanism across the mixing layer. In comparison with parameters reported from analogous experiments, the mixing phenomenon at a high Sc shows a strong dependency on the initial conditions prevailing at the onset of the instability and the evidence of a delay in the mixing transition. Values of global and integral mixing parameters did not reach late-time asymptotic values that have been reported previously from steady-state experiments (Texas A&M Water Channel) and may be attributed to the effect of the barrier pull and the overturning mechanism that is thought to hinder the progress of the mixing layer.