Flow, Turbulence and Combustion ( IF 2.4 ) Pub Date : 2022-08-09 , DOI: 10.1007/s10494-022-00352-8 Angela Busse, Oleksandr Zhdanov
The influence of the orientation of ratchet-type rough surfaces on their fluid dynamic roughness effect is investigated using direct numerical simulations of turbulent channel flow at \(Re_{\tau }=395\). The ratchet length-to-height ratio is varied from \(\ell /k=2\) to 16 for a fixed ratchet height of \(k/\delta =0.1\) where \(\delta\) is the mean channel half-height. The results show that both roughness function and mean flow and turbulence statistics strongly depend on the ratchet orientation. Existing empirical formulae, which estimate the roughness function \(\Delta U^+\) or the equivalent sand-grain roughness \(k_s\) based on surface-slope related parameters such as the effective slope or the Sigal-Danberg parameter, fail to accurately predict the differences between ratchet surfaces with high windward slopes and ratchet surfaces with high leeward slopes.
中文翻译:
湍流通道流对棘轮粗糙度的直接数值模拟
使用\(Re_{\tau }=395\)处湍流通道流动的直接数值模拟研究了棘轮型粗糙表面的取向对其流体动力粗糙度效应的影响。对于固定的棘轮高度\(k/\delta =0.1\) ,棘轮长高比从\(\ell /k=2\)到 16 变化,其中\(\delta\)是平均通道半高。结果表明,粗糙度函数和平均流量和湍流统计在很大程度上取决于棘轮方向。现有经验公式,估计粗糙度函数\(\Delta U^+\)或等效砂粒粗糙度\(k_s\)基于有效坡度或Sigal-Danberg参数等表面坡度相关参数,无法准确预测具有高迎风坡度的棘齿表面和具有高背风坡度的棘齿表面之间的差异。