Turbulent heat transfer in a ribbed square duct of three different blockage ratios are investigated using direct numerical simulation (DNS). The results of ribbed duct cases are compared with those of a heated smooth duct flow. It is observed that owing to the existence of the ribs and confinement of the duct, organized secondary flows appear as large streamwise-elongated vortices, which intensely interact with the rib elements and four sidewalls and have profound influences on the transport of momentum and thermal energy. This study also shows that the drag and heat transfer coefficients are highly sensitive to the rib height. It is observed that as the rib height increases, the impinging effect of the flow on the windward face of the rib strengthens, leading to enhanced rates of turbulent mixing and heat transfer. The influence of sidewalls and rib height on the turbulence structures associated with temperature fluctuations are analyzed based on multiple tools such as vortex swirling strengths, temporal auto-correlations, spatial two-point cross-correlations, joint probability density functions (JPDF) between the temperature and velocity fluctuations, statistical moments of different orders, and temperature spectra.

使用直接数值模拟（DNS）研究了三种不同堵塞率的带肋方管中的湍流传热。将带肋风管箱的结果与加热的光滑风管流的结果进行比较。可以看到，由于肋的存在和管道的限制，有组织的二次流表现为大的沿流向伸长的涡流，这些涡流与肋元件和四个侧壁强烈相互作用，并对动量和热能的传输产生深远的影响。 。这项研究还表明，阻力和传热系数对肋骨高度高度敏感。可以看出，随着肋骨高度的增加，气流对肋骨迎风面的冲击作用增强，导致湍流混合和传热的速率增加。