Entropy generation analysis for grooved structure plate flow

Abstract Currently, bionic drag reduction is a popular research topic, particularly the drag reduction effect of a grooved structure. To investigate entropy generation caused by the effect of a grooved structure on flow, this study used Fluent software and large eddy simulation (LES) technology to analyze entropy generation in flow over a plate with a grooved structure. The purpose of this work is to provide a theoretical basis for reducing drag on such a structure. The study showed that a grooved structure was able to reduce entropy generation in the flow process. At 30 m/s, the total entropy generation in the near-wall region decreased by approximately 25%, and at 40 m/s, it decreased by approximately 19%. However, the grooved structure did not have a sustained effect on the subsequent flow. Moreover, as the distance from the wall in the normal direction increased, the effect gradually decreased. The secondary vortex that formed within the grooved structure changed the velocity gradient in the normal direction in the near-wall region and weakened the shearing action between flow layers, thereby reducing the entropy generation caused by viscous dissipation. Moreover, the reduction in entropy generation in the near-wall region was significant, decreasing by 49% and 58% at y+=5 when the flow rate was 30 and 40 m/s, respectively. Since the grooved structure was unable to inhibit the velocity fluctuations in turbulent flow, the magnitude of the entropy generation caused by the turbulence did not decrease. However, the distribution of the entropy generation caused by turbulent dissipation was more uniform in the region with the grooved structure than in the region with the smooth structure. The entropy generation at the tip of the grooved structure was one order of magnitude larger than the entropy generation at the near-wall region in the flow field. Even though the entropy generation caused by turbulent dissipation was predominant in that region, the entropy generation caused by viscous dissipation should not be ignored.