This work investigates the turbulent flow in a channel roughened by seven ribs of rectangular cross section disposed transversely. The flow configurations of identical ribs from the first one generate a large eddy spreading along the top of the two first ribs, trapping the flow of the first cavity. The widening of the first rib may solve this problem. Therefore, this flow configuration might be required in building structure applications necessitating regular structures from the first cavity. Streamlines contours indicates that the first rib behaves as a forward facing step when L₁ > 5h (L₁ is the first rib width), regular structures of the flow occurs from the first cavity. The effect of wider first rib is highlighted by friction and pressure coefficients profiles and those of the turbulent kinetic energy. Its effect also appears in the Darcy friction factor. The viscous and pressure forces applied on the first rib and the 5th pitch roughness indicate that the pressure force is dominant. Darcy friction factor characterizing the flow and pressure drag coefficient evaluated at the 5th pitch roughness remains independent of Reynolds number, while the drag force applied on the first rib increases when Reynolds number augments.

中文翻译：

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二维肋粗糙化的通道内湍流分析：第一肋宽度的影响

这项工作研究了由横向布置的七个矩形横截面肋所粗糙化的通道中的湍流。来自第一个肋的相同肋的流动结构产生沿两个第一肋的顶部扩展的大涡流，从而捕获了第一空腔的流动。第一肋的加宽可以解决这个问题。因此，在建筑结构应用中可能需要这种流动配置，从而需要来自第一腔的规则结构。流线轮廓表明，当L ₁ > 5 h（L ₁是第一肋的宽度），从第一腔开始出现规则的流动结构。摩擦系数和压力系数曲线以及湍动能曲线突出了更宽的第一肋的效果。其作用也出现在达西摩擦因数中。施加在第一肋和第五节距粗糙度上的粘性和压力表明压力是主要的。达西摩擦因数表征了在第5节距粗糙度下评估的流量和压力阻力系数，而与雷诺数无关，而当雷诺数增加时，施加在第一肋上的阻力增大。