Vortex pairing in asymmetric stratified shear instabilities

Stratified turbulent mixing events play a key role in setting the distribution of heat, momentum, and nutrients in the ocean. Vortex pairing, an important process observed in experiments and simulations of stratified shear flows, can enhance the amount and details of turbulent mixing in the flows. Prior research has explored the effects and sensitivity of the pairing process in vertically-symmetric stratified shear flows; however, there is a relative lack of work connecting asymmetry in background flow profiles and their influence on pairing evolution. Using direct numerical simulations in both single- and double-wavelength domains, we investigate the role of pairing in two different flow configurations, the asymmetric Kelvin-Helmholtz and Holmboe instabilities. We observe that the greater offset of the initial background velocity profile facilitates the generation of pairing and mixing behaviors. Additionally, the different flow setups and parameters are compared using detailed energetics and mixing analyses, allowing us to quantify the importance of the pairing process for modelling turbulent fluxes in oceanic mixing events.