Ducasse Lauris, Pumir Alain
Institut Non Linéaire de Nice, CNRS, F-06560 Valbonne, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Jun;77(6 Pt 2):066304. doi: 10.1103/PhysRevE.77.066304. Epub 2008 Jun 10.
Tracer particles on the surface of a turbulent flow have a very intermittent distribution. This preferential concentration effect is studied in a two-dimensional synthetic compressible flow, both in the inertial (self-similar) and in the dissipative (smooth) range of scales, as a function of the compressibility C . The second moment of the concentration coarse grained over a scale r , n_{r};{2} , behaves as a power law in both the inertial and the dissipative ranges of scale, with two different exponents. The shapes of the probability distribution functions of the coarse-grained density n_{r} vary as a function of scale r and of compressibility C through the combination C/r;{kappa} (kappa approximately 0.5) , corresponding to the compressibility, coarse grained over a domain of scale r , averaged over Lagrangian trajectories.
湍流表面上的示踪粒子具有非常不均匀的分布。在二维合成可压缩流中，研究了这种优先浓度效应，该效应在尺度的惯性（自相似）和耗散（平滑）范围内，作为压缩性C的函数。在尺度r上粗粒化的浓度的二阶矩(n_{r}^{2})在尺度的惯性和耗散范围内均表现为幂律，具有两个不同的指数。粗粒化密度(n_{r})的概率分布函数的形状随尺度r和压缩性C的变化而变化，通过组合(C/r^{\kappa})（(\kappa)约为0.5），对应于在尺度r的域上粗粒化的压缩性，在拉格朗日轨迹上平均。
