Visualization study of thermal counterflow of superfluid helium in the proximity of the heat source by using solid deuterium hydride particles

Ubiquity of particle–vortex interactions in turbulent counterflow of superfluid helium

“…The outcome suggests therefore that the vortex tangle is likely not uniformly distributed in the considered flow region; this, by the way, is consistent with our current understanding of counterflow in vertical channels – see, for example, Švančara et al. (2018 b ) and Varga & Skrbek (2019). Note also that Kivotides (2008 b ) observed a similar depletion of particle–vortex interactions in relevant numerical simulations.…”

“…We can also compute the mean distance between quantized vortices from (1.4) by using the values listed in table 2, that is, those derived from the statistical distributions of the particle vertical velocity – relevant values were obtained following Švančara et al. (2018 b ). The scales estimated in such a way are also reported in table 2, together with the corresponding ratio .…”

“…Švančara et al. (2018 b ) and references therein for detailed descriptions. In brief, it consists of a low-loss helium cryostat with the experimental volume located at its bottom; the latter has a square cross-section, of 51 mm sides, and is 300 mm high.…”

“…Bertolaccini, Lévêque & Roche (2017) and Švančara et al. (2018 b ) for discussions on the role of the entrance length in thermal counterflow. Consequently, at the same heat flux, the actual values of the regions experimentally probed are not expected to be equal.…”

Vortices inside a single-stage axial air turbine captured by Particle Image Velocimetry

“…The airflow is driven by a powerful radial 12-stage ČKD compressor with input power of 1.3 MW [9]. We use the optical non-intrusive method Particle Image Velocimetry (PIV) [10,11,12]. We measure the area of size 28 × 28 mm just behind the rotor wheel, the area is oriented in axial × tangential direction, therefore the wake system is well observable, see Fig.…”