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A study of the velocity and temperature boundary layers over a heated rotating disk

Author Document Type Year Download File size
Fredrik Lundell, A. Cederholm MSc thesis 1998 Download 1.2MB
Id
ISSN 0348-467X
ISRN KTH/MEK/TR--98/10--SE

Abstract

In the present work the velocity and temperature boundary layers over a heated rotating disk have been studied. For this purpose a rotating-disk apparatus with a possibility to heat the disk by radiation towards the bottom surface has been built. The temperature distribution of the air above the disk has been measured with constant current anemometry at different radial positions. A thermal video system and liquid crystals were used to measure the temperature on the disk surface. Velocity measurements have been conducted with hot-wire anemometry using a single hot wire oriented in different directions in order to measure two velocity components. The measured velocity and temperature profiles agree well with theory in the laminar region. As the radius is increased, the profiles indicate that Reynolds analogy is valid for this flow if no artificial disturbances are introduced. The disturbance distributions calculated from the measured temperature data do agree with the eigenfunctions obtained from the linear stability analysis. Investigations of the disturbance growth shows that the disturbances are more instationary with heating applied than in the case without heating. The visualizations of the disk temperature with the liquid crystals show that there is a rapid increase of heat transfer close to transition. The liquid crystals also provided a simple way to investigate the influence of different roughness elements on the heat transfer.