Abstract: Turbulent
transport of a passive contaminant in rotating homogeneous turbulence with or
without mean shear is studied using linear theory. System rotation is around the
direction,
and the mean velocity is given by with
constant shear rate S. Passive
contaminant with mean gradients in each of the directions
is considered.
The fluctuating
(or disturbance) fields are expressed in terms of Fourier components (i.e., in
the form of plane waves with a time-dependent wave vector). Complete analytical
solutions for the linear response function are found. In the presence of shear,
the solutions are expressed in terms of the Legendre functions of imaginary
argument.
By using these
solutions, turbulence statistics (spectra, single-point correlations) are
determined for an initially isotropic turbulence in inviscid and non diffusive
fluid, and in viscous fluid with molecular Prandtl number equals to unity.
For the pure
rotating case, the three-dimensional spectra are integrated analytically over
wave space to obtain single-point correlations (i.e., scalar intensities and
fluxes), and similarities between the turbulent transport of the passive
contaminant and the turbulent diffusion are drawn.
In
the presence of shear, the three-dimensional spectra are integrated numerically
over wave space to obtain scalar intensities and fluxes. To elucidate the role
of the mode, the three-dimensional spectra
are integrated analytically over the waveplane The product of the integral length
scales in the direction by associated
single-point correlations (or equivalently, ‘two-dimensional’ energy
components) in terms of Bessel functions is then determined. When the flow is
unstable (i.e., the ratio of the Coriolis parameter f to the shear rate S
ranges between –1 and 0) the long-time behavior of some ratios such as the
normalized fluxes or the turbulent Prandtl number is well reproduced by that of
their counterparts formulated from the ‘two-dimensional’ energy components.