title: Preconditions and limitations of the postulate of scalar-dissipation-conductivity independence in a variable conductivity medium.
abstract: Classical turbulent mixing paradigm--ingrained in scaling laws and closure models--is revisited in a variable-conductivity inhomogeneous medium. We perform direct numerical simulations to study the evolution of a passive scalar (temperature) field in a fluid with large conductivity gradients and investigate the behavior of scalar dissipation, conditional scalar dissipation, and velocity-to-scalar time scale ratio. Subject to the conditions of the investigation, it is found that these mixing characteristics become reasonably insensitive to conductivity after about one-third eddy turnover time. While the results support the classical paradigm, important preconditions and limitations are clearly identified.
authors.affiliation: Department of Aerospace Engineering, Texas A&M University, College Station, Texas 77843-3141, USA.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Kumar
authors.forename: Sharath S
authors.initials: SS
authors.lastname: Girimaji
authors.forename: Johannes
authors.initials: J
authors.lastname: Kerimo