# Strong anisotropy of superfluid $^4$He counterflow turbulence

## TL;DR

This study combines theory and simulations to reveal that superfluid helium counterflow turbulence exhibits strong anisotropy in velocity fluctuations, with energy concentrated in a plane orthogonal to the flow direction, especially at higher temperatures.

## Contribution

It provides new insights into the anisotropic nature of superfluid helium turbulence and highlights the role of temperature and component coupling in this phenomenon.

## Key findings

- Velocity fluctuations are strongly anisotropic.
- Energy concentrates in a plane orthogonal to counterflow.
- Anisotropy increases with temperature.

## Abstract

We report on a combined theoretical and numerical study of counterflow turbulence in superfluid $^{4}$He in a wide range of parameters. The energy spectra of the velocity fluctuations of both the normal-fluid and superfluid components are strongly anisotropic. The angular dependence of the correlation between velocity fluctuations of the two components plays the key role. A selective energy dissipation intensifies as scales decrease, with the streamwise velocity fluctuations becoming dominant. Most of the flow energy is concentrated in a wavevector plane which is orthogonal to the direction of the counterflow. The phenomenon becomes more prominent at higher temperatures as the coupling between the components depends on the temperature and the direction with respect to the counterflow velocity.