Effects of rapid spanwise rotation on turbulent channel flow with a passive scalar
2011 (English)In: Proc. 7th International Symposium on Turbulence and Shear Flow Phenomena, 2011Conference paper (Refereed)
Direct numerical simulations of fully developed turbulentchannel flow including a passive scalar rotating about thespanwise axis have been performed. The mean bulk Reynoldsnumber, Reb = Ubh/n ≥ 20000, where Ub is the bulk meanvelocity and h the channel half width, is higher than in previoussimulations and the rotation rate covers a wide range.At moderate rotation rates, turbulence on the stable channelside is significantly less damped than in DNS at lower Reb. Athigh rotation rates we observe re-occurring, quasi-periodic instabilitieson the stable channel side. Between these events theturbulence is weak, but during the instability events the wallshear stress and turbulence intensity are much stronger. Theinstabilities are caused by structures resembling Tollmien-Schlichting (TS) waves that at some instant rapidly grow, thenbecome unstable and finally break down into intense turbulence.After some time the TS waves form again and the processrepeats itself in a periodic-like manner.Mean scalar profiles are also strongly affected by rotationand large scalar fluctuations are found on the border of the stableand unstable channel side. The turbulent Prandtl/Schmidtnumber of the scalar is much less than unity if there is rotation.Predicting scalar transport in rotating channel flow willtherefore pose a challenge to turbulence models.
Place, publisher, year, edition, pages
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-86818OAI: oai:DiVA.org:kth-86818DiVA: diva2:501047
7th International Symposium on Turbulence and Shear Flow Phenomena. 28-31 July 2011. Ottawa, Canada
QC 201204102012-02-132012-02-132012-04-10Bibliographically approved