Investigating Isotropy in Atmospheric Turbulence Using Large Eddy Simulations

Abstract

Turbulence plays a key role in many atmospheric and engineering flows, but understanding how it becomes isotropic under different conditions is still a challenge. In this thesis, we use the WRF model in idealized mode to explore how turbulence evolves in four setups: two driven by buoyancy (convective boundary layer and plume) and two by shear (random and bubble-perturbed Shear). We analyze anisotropy of the eddy dissipation using eddy-viscosity-based metrics, comparing how different forcing mechanisms and spatial resolutions affect the development and isotropization of turbulence. Buoyancy-driven cases showed smoother, more gradual transitions to isotropy, while shear-driven cases featured stronger bursts, persistent anisotropy, and slower convergence in time, especially at low resolution. It can also be understood that vertical velocity is more anisotropic in buoyancy-driven cases, while vertical shear dominates in shear-driven cases. These results highlight how both physical forcing and resolution shape the anisotropy of turbulence and point to important considerations for model setup in future turbulence studies.