# Predicting vortex merging and ensuing turbulence characteristics in shear layers from initial conditions

## TL;DR

This paper demonstrates that vortex merging patterns in shear layers, which influence turbulence and mixing, can be predicted from initial linearized conditions, using a measure based on initial asymmetry, validated by simulations.

## Contribution

It introduces a novel measure derived from initial conditions to predict vortex merging patterns and turbulence characteristics in shear layers.

## Key findings

- Initial asymmetry measure predicts vortex merging patterns.
- Predictions are validated with direct numerical simulations.
- The measure influences understanding of turbulence development.

## Abstract

Unstable shear layers in environmental and industrial flows roll up into a series of vortices, which often form complex nonlinear merging patterns like pairs and triplets. These patterns crucially determine the subsequent turbulence, mixing and scalar transport. We show that the late-time, highly nonlinear merging patterns are predictable from the linearized initial state. The initial asymmetry between consecutive wavelengths of the vertical velocity field provides an effective measure of the strength and pattern of vortex merging. The predictions of this measure are substantiated using direct numerical simulations. We also show that this measure has significant implications in determining the route to turbulence and the ensuing turbulence characteristics.