Cross-helicity in rotating homogeneous shear-stratified turbulence

Area of Science:

• Fluid dynamics
• Turbulence research
• Statistical mechanics

Background:

• Turbulence exhibits complex nonlinear dynamics, particularly in rotating and stratified systems.
• Understanding the relative orientation of coupled fluctuating fields is key to analyzing turbulence dynamics.

Purpose of the Study:

• To investigate the alignment properties of velocity and gravity fields with the potential vorticity gradient in rotating, shear-stratified turbulence.
• To define and analyze a cross-helicity vector field analogous to that in magnetohydrodynamics.

Main Methods:

• Utilizing statistical mechanics to define a novel vector field.
• Performing high-resolution direct numerical simulations of developed homogeneous baroclinic turbulence.
• Analyzing probability density functions for the defined cross-helicity.

Main Results:

• A net preference for positive cross-helicity was observed.
• A new alignment mechanism contributing to this preference was identified.
• The study provides detailed probability density functions for cross-helicity.

Conclusions:

• The analysis of cross-helicity is essential for comprehending the dynamics of buoyancy-driven flows.
• The identified alignment mechanism offers new insights into rotating, stratified turbulence.
• Cross-helicity serves as a critical parameter in understanding complex fluid dynamics.