Effect of small roughness elements on thermal statistics of a turbulent boundary layer at moderate Reynolds number
Effect of small roughness elements on thermal statistics of a turbulent boundary layer at moderate Reynolds number
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DOI：
10.1017/jfm.2015.676
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发表时间：
2016-01-01
影响因子：
3.7
通讯作者：
Castillo, Luciano
中科院分区：
文献类型：
--
作者：
Doosttalab, Ali;Araya, Guillermo;Castillo, Luciano
用直接数值模拟方法研究了k(+)约为11，动量厚度雷诺数约为2400的过渡粗糙表面(24粒砂纸)上的零压力梯度湍流边界层。模拟了分子Prandtl数Pr=0.71的等温粗糙表面与湍流之间的换热。由Araya等人开发的动态多尺度方法。(J.Fluid Mech，Vol.670,2011，pp.581-605)被用来规定真实的随时间变化的热流入边界条件。一般而言，当Wang&Castillo(J.Turbu.，第4卷，2003,006)内/外标度归一化时，粗糙表面减少了相对于光滑表面流动的平均和波动的温度分布。结果表明，雷诺类比对y(+)和lt；9不成立。在这一区域内，湍流普朗特数的值基本上偏离了1。在这一区域以上，雷诺类比仅是近似有效的，对于粗糙和光滑的壁面，湍流普朗特数在边界层两端从1下降到0.7。与光壁情况相比，单位质量的湍流热输运，
A zero-pressure-gradient turbulent boundary layer flowing over a transitionally rough surface (24-grit sandpaper) with k(+) approximate to 11 and a momentum-thickness Reynolds number of approximately 2400 is studied using direct numerical simulation (DNS). Heat transfer between the isothermal rough surface and the turbulent flow with molecular Prandtl number Pr = 0.71 is simulated. The dynamic multiscale approach developed by Araya et al. (J. Fluid Mech., vol. 670, 2011, pp. 581-605) is employed to prescribe realistic time-dependent thermal inflow boundary conditions. In general, the rough surface reduces mean and fluctuating temperature profiles with respect to the smooth surface flow when normalized by Wang & Castillo (J. Turbul., vol. 4, 2003, 006) inner/outer scaling. It is shown that the Reynolds analogy does not hold for y(+) < 9. In this region the value of the turbulent Prandtl number departs substantially from unity. Above this region the Reynolds analogy is only approximately valid, with the turbulent Prandtl number decreasing from 1 to 0.7 across the boundary layer for rough and smooth walls. In comparison with the smooth-wall case, the turbulent transport of heat per unit mass,