Compressible turbulent mixing: Effects of Schmidt number

doi:10.1103/PhysRevE.91.053020

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	Compressible turbulent mixing: Effects of Schmidt number
	Ni, Qionglin
刊名	PHYSICAL REVIEW E
	2015
关键词	QUANTITIES LIKE TEMPERATURE AIR-POLLUTANT TRANSPORT SMALL-SCALE VARIATION PASSIVE SCALAR NUMERICAL SIMULATIONS COASTAL ENVIRONMENT STATISTICS RESOLUTION CONDUCTIVITY SPECTRUM
DOI	10.1103/PhysRevE.91.053020
英文摘要	We investigated by numerical simulations the effects of Schmidt number on passive scalar transport in forced compressible turbulence. The range of Schmidt number (Sc) was 1/25 similar to 25. In the inertial-convective range the scalar spectrum seemed to obey the k(-5/3) power law. For Sc >> 1, there appeared a k(-1) power law in the viscous-convective range, while for Sc << 1, a k(-17/3) power law was identified in the inertial-diffusive range. The scaling constant computed by the mixed third-order structure function of the velocity-scalar increment showed that it grew over Sc, and the effect of compressibility made it smaller than the 4 3 value from incompressible turbulence. At small amplitudes, the probability distribution function (PDF) of scalar fluctuations collapsed to the Gaussian distribution whereas, at large amplitudes, it decayed more quickly than Gaussian. At large scales, the PDF of scalar increment behaved similarly to that of scalar fluctuation. In contrast, at small scales it resembled the PDF of scalar gradient. Furthermore, the scalar dissipation occurring at large magnitudes was found to grow with Sc. Due to low molecular diffusivity, in the Sc >> 1 flow the scalar field rolled up and got mixed sufficiently. However, in the Sc << 1 flow the scalar field lost the small-scale structures by high molecular diffusivity and retained only the large-scale, cloudlike structures. The spectral analysis found that the spectral densities of scalar advection and dissipation in both Sc >> 1 and Sc << 1 flows probably followed the k-(5/3) scaling. This indicated that in compressible turbulence the processes of advection and dissipation except that of scalar-dilatation coupling might deferring to the Kolmogorov picture. It then showed that at high wave numbers, the magnitudes of spectral coherency in both Sc >> 1 and Sc << 1 flows decayed faster than the theoretical prediction of k-(2/3) for incompressible flows. Finally, the comparison with incompressible results showed that the scalar in compressible turbulence with Sc = 1 lacked a conspicuous bump structure in its spectrum, but was more intermittent in the dissipative range.; SCI(E); EI; PubMed; ARTICLE; niql.pku@gmail.com; 5; 053020; 91
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/419362]
专题	工学院
推荐引用方式 GB/T 7714	Ni, Qionglin. Compressible turbulent mixing: Effects of Schmidt number[J]. PHYSICAL REVIEW E,2015.
APA	Ni, Qionglin.(2015).Compressible turbulent mixing: Effects of Schmidt number.PHYSICAL REVIEW E.
MLA	Ni, Qionglin."Compressible turbulent mixing: Effects of Schmidt number".PHYSICAL REVIEW E (2015).