Related Experiment Video
Updated: May 26, 2026

The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Preconditions and limitations of the postulate of scalar-dissipation-conductivity independence in a variable
Gaurav Kumar1, Sharath S Girimaji, Johannes Kerimo
1Department of Aerospace Engineering, Texas A&M University, College Station, Texas 77843-3141, USA.
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.
Related Concept Videos
Boundary Conditions for Current Density
Electrical Conductivity
In a practical conductor, an applied electric field may be sustained, causing a flow of electrons, which produce a current. The differential form of the current, the current density, is related to the electric field.
More generally, it is related to the force per unit charge, which involves the...
Magnetostatic Boundary Conditions
Theory of Metallic Conduction
In this theory, Newton's second law of motion is used to determine the acceleration of an electron in the presence of an applied electric field. Then, its velocity is expressed via this acceleration.
An electron moves through the crystal, containing positive ions,...
Electrostatic Boundary Conditions in Dielectrics
Consider a case where both the mediums across a boundary are two different dielectric materials. Recall that the electric field and electric displacement are proportional and related through the material's permittivity.
Second Uniqueness Theorem
In contrast, consider that the electric field is non-unique and apply Gauss's law in divergence form in the region between the conductors and the integral form to the surface...
