The effect of Prandtl number on decaying stratified turbulence

IF 1.5 4区工程技术 Q3 MECHANICS

Journal of Turbulence Pub Date : 2023-02-15 DOI:10.1080/14685248.2023.2178654

J. Riley, M. Couchman, S. M. de Bruyn Kops

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引用次数: 6

Abstract

The effects of the variation in the Prandtl number on turbulence in a stably-stratified fluid is investigated by direct numerical simulation. The results of simulations are presented of the homogeneous decay of turbulence for a given initial Froude number and three different initial Reynolds numbers of increasing values. For each of these cases results for two different Prandtl numbers, 1 and 7, are shown. Various statistics are put forward, including kinetic and potential energy decay rates, kinetic and potential energy dissipation rates, buoyancy fluxes, energy spectra, and statistics conditioned on the local value of the vertical density gradient. It is found that the effect of increasing the Prandtl number is to increase the kinetic energy dissipation rate, while decreasing the potential energy dissipation rate. There is a notable transfer of potential to kinetic energy for the higher Prandtl number case. Finally there is evidence, based upon the analysis of vertical planes and statistics conditional on the local density gradient, that most irreversible mixing of both density and momentum occurs in regions of stronger static stability.

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普朗特数对衰减分层湍流的影响

采用直接数值模拟的方法研究了稳定分层流体中普朗特数的变化对湍流的影响。给出了给定初始弗劳德数和三种不同初始雷诺数递增时湍流均匀衰减的模拟结果。对于每种情况，显示了两个不同普朗特数1和7的结果。提出了各种统计数据，包括动能和势能衰减率、动能和势能耗散率、浮力通量、能谱以及以垂直密度梯度局域值为条件的统计数据。发现增加普朗特数的作用是增加动能耗散率，而降低势能耗散率。在较高普朗特数的情况下，有一个显著的势能到动能的转移。最后，根据垂直平面的分析和局部密度梯度条件下的统计数据，有证据表明，密度和动量的最不可逆混合发生在静态稳定性较强的区域。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Turbulence 物理-力学

CiteScore

3.90

自引率

5.30%

发文量

审稿时长

6-12 weeks

期刊介绍： Turbulence is a physical phenomenon occurring in most fluid flows, and is a major research topic at the cutting edge of science and technology. Journal of Turbulence ( JoT) is a digital forum for disseminating new theoretical, numerical and experimental knowledge aimed at understanding, predicting and controlling fluid turbulence. JoT provides a common venue for communicating advances of fundamental and applied character across the many disciplines in which turbulence plays a vital role. Examples include turbulence arising in engineering fluid dynamics (aerodynamics and hydrodynamics, particulate and multi-phase flows, acoustics, hydraulics, combustion, aeroelasticity, transitional flows, turbo-machinery, heat transfer), geophysical fluid dynamics (environmental flows, oceanography, meteorology), in physics (magnetohydrodynamics and fusion, astrophysics, cryogenic and quantum fluids), and mathematics (turbulence from PDE’s, model systems). The multimedia capabilities offered by this electronic journal (including free colour images and video movies), provide a unique opportunity for disseminating turbulence research in visually impressive ways.