ライブラリ登録: Guest
TSFP DL Home アーカイブ 執行委員会
TSFP DIGITAL LIBRARY ONLINE


ISSN オンライン: 2642-0554

SCHMIDT NUMBER DEPENDENCE OF DECAYING PASSIVE SCALAR FLUCTUATIONS IN ISOTROPIC TURBULENCE

Paolo Orlandi
Department of Mechanics and Aeronautics, "Sapienza" University of Rome, Via Eudossiana 18, 00184 Rome, Italy

Robert Anthony Antonia
Discipline of Mechanical Engineering, University of Newcastle, Newcastle, 2308, NSW, AUSTRALIA

要約

Direct numerical simulations have been carried out for decaying turbulence in a periodic box over a relative Sc, at a Taylor microscale Reynolds number of about 50. Several small-scale statistics of the passive scalar have been evaluated and compared, when possible, with those from grid turbulence experiments and previous simulations of box turbulence. On the basis of the skewness of the scalar derivatives, the local isotropy of the scalar field appears to be more closely satisfied as Sc increases. The magnitude of the flatness of the scalar derivative is maximum near Sc ~ 1 and decreases rapidly as Sc increases. The extremum seems consistent with the greater dominance of scalar sheets, especially near Sc ~ 1, under the influence of the compressive strain rate. A good collapse of the scalar spectra is observed at sufficiently high wavenumbers when the normalization uses Batchelor scales. The spectra support a k1−1 behaviour, which is first observed when Sc exceeds 1.