Two-way coupled simulations are conducted to investigate the interaction between quantum turbulence and normal fluid turbulence in superfluid helium-4. At less than 2.17 K, superfluid helium-4 comprises an inviscid superfluid component and a viscous normal fluid component. The circulation of the superfluid velocity is quantized, so that the superfluid exists as quantized vortex lines. The tangled vortex lines are referred to as quantum turbulence. Our numerical results exhibit that normal fluid turbulence enhances quantum turbulence due to internal mutual friction in thermal counterflows. The square root of vortex line density is proportional to the relative velocity between normal fluid and superfluid, and its proportionality constant is called a response parameter. The response parameter obtained from our numerical simulations agrees well with experimental results. In our two-way coupled simulation, we observed that the energy in the decaying superfluid turbulence obeys a power law consistent with Kolmogorov spectra. In contrast, in a one-way simulation, the energy profile deviates from the power law associated with Kolmogorov spectra.

Helium-4