Application of the Ultrasound Doppler Velocimetry in a Czochralski crystal growth model experiment


Application of the Ultrasound Doppler Velocimetry in a Czochralski crystal growth model experiment

Cramer, A.; Pal, J.; Gerbeth, G.

The present work is concerned with ultrasound and temperature measurements in a Czochralski crystal growth model experiment. In the Czochralski growth, primary strong horizontal temperature gradients are present at the solidification front, which should lead to an axisymmetric flow pattern in the melt volume. To study the flow structure a modified Rayleigh-Bénard configuration was built up in which the upper thermal boundary condition in a Czochralski system is accounted for by a partially cooled surface. The measurements show, that rather a large scale flow pattern develops known as wind in real Rayleigh–Bénard configurations. The wind was always found as the only stable flow pattern for all performed Grashof numbers. Applying a rotating magnetic field (RMF) to the melt volume, the wind starts to co-rotate with the RMF. By analogue with the superposition of the primary and the secondary flow in an RMF, the swirl evoked by the RMF is also superimposed to the wind without any remarkable interaction. Not until the weaker secondary flow produced by the RMF becomes similar in vigour to the buoyant wind does the flow structure in the modified Rayleigh-Bénard system change basically. The results show the applicability of the Ultrasound Doppler Velocimetry (UDV) in the detection and identification of complex flow patterns.

Keywords: Ultrasound Doppler Velocimetry; Temperature gradients; Czochralski crystal growth; Fluid flow

  • Contribution to proceedings
    The 7th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 07.-09.04.2010, Göteborg, Sweden
    Proceedings of the 7th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 978-91-7290-292-3, 57-60
  • Lecture (Conference)
    The 7th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 07.-09.04.2010, Göteborg, Sweden

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Publ.-Id: 13887