Dina Soltani Tehrani

Dina Soltani Tehrani

Future Fluid Dynamist!

Talks and presentations

Turbulence in Compressible Systems and Energy Transfer Across Scale

February 01, 2024

Talk, University of Rochester, Department of Physics and Astronomy, Astro Journal Club, Rochester, NY

In this talk, I began with the levels of describing a system of particles, arrived at the Navier-Stokes equation as the first-order approximation of the Chapman-Enskog expansion, and laid the foundation for the study of turbulence. I then began with the theory we have in incompressible turbulence, elaborated on coarse-graining as a direct application of the representation theory, and discussed the theory of scale dynamics in compressible systems.

Scale-Locality: Insights into the energy cascade across scales in a shock

November 21, 2023

Conference proceedings talk, 76th Annual Meeting of the Division of Fluid Dynamics, Washington, DC

Inter-scale energy transfer (or the cascade) is of relevance to both LES modeling and turbulence theory. In incompressible homogeneous isotropic turbulence, there has been compelling theoretical and empirical support that the scale-transfer of kinetic energy (KE) is local. Here, we analyze the locality of KE scale-transfer in compressible turbulence. There is a common notion that shocks and discontinuities that pervade compressible turbulence necessarily imply a non-local scale-transfer. We show this not to be the case by demonstrating rigorous proofs of scale-locality using two examples: (i) solution to the Burgers equation and (ii) the 1D normal shock solution. Proofs of scale-locality in compressible turbulence hold in broad generality, at any Mach number, for any equation of state, and without the requirement of homogeneity or isotropy. Rather, locality rests on assumptions about the scaling of velocity, pressure, and density structure functions, which are weak and enjoy broad empirical support.

Energy transfer across scales in a shock: is it a scale-local cascade?

October 30, 2023

Conference proceedings talk, APS Division of Plasma Physics Meeting, Denver, CO

It is commonly claimed that kinetic energy (KE) in the presence of a shock does not undergo an inertial scale-local cascade but that KE at a given scale must be dissipated directly into heat at the viscous (molecular) scales without passing through intermediate scales. Using rigorous mathematical analysis and physical arguments, we will explain why this widely held notion rests on flawed/unrefined intuition. We demonstrate rigorous proofs of scale-locality of the cascade due to shocks using two examples:(i) Burgers equation and (ii) exact 1D normal shock solution. Our analytical results hold in broad generality, for turbulence at any Mach number, for any equation of state, and without the requirement of homogeneity or isotropy. The assumptions we make in our proofs on the scaling of velocity, pressure, and density structure functions are weak and enjoy compelling empirical support.

Numerical modeling of dielectric barrier discharge actuators based on the properties of low-frequency plasmons

March 01, 2023

Conference proceedings talk, APS March Meeting 2023, Las Vegas, NV

Electrohydrodynamic flow control systems have proven to be among the most promising flow control strategies within previous decades. Several methods are available for efficient evaluation and description of such systems’ effects. Yet, due to these systems’ critical role in various applications, possible improvements are still being investigated. A new phenomenological model is presented for the simulation of the plasma actuators based on the electrodynamic properties of low-frequency plasmons. The model simulates the plasmonic region as a dispersive medium. This dissipated energy is added to the flow by introducing a high-pressure region, calculated in terms of local body force vectors, requiring the distribution of the electric field and the polarization field. The model determines the electric field for the computation of the body force vector based on the Poisson equation and implements the simplified Lorentz model for the polarization field. To fully explore the performance of the presented model, an experiment has been conducted, comparing the observed effect of plasma actuators on the fluid flow with the results predicted by the model. The model is then validated based on the results of other distinct experiments and exempted numerical models based on the exchanging momentum with the ambient neutrally charged fluid, demonstrating that the model has improved adaptability and self-adjusting capability compared to the available models.