Numerical Modeling of Drag Reduction by Bionic Microstructures on High-speed Trains

Abstract

With the continuous increase in the operating speed of high-speed trains, aerodynamic performance plays an increasingly critical role in energy consumption, operational stability, and passenger comfort. Among various aerodynamic factors, drag has become a key constraint on train efficiency. As train-shape optimization aimed at reducing pressure drag approaches its practical limits, skin-friction drag remains a major contributor with considerable potential for further reduction. Inspired by the microscale surface structures of fast-swimming sharks, flow control using bionic microstructures has been demonstrated to achieve drag reduction in high-Reynolds-number turbulent boundary layers. In this study, an improved numerical modeling approach based on wall-function modification is employed to investigate the flow-control effects of V-shaped riblet microstructures for aerodynamic drag reduction in high-speed trains. The adopted approach builds on a previously validated improved wall-boundary-condition model and represents the aerodynamic effects of microscale riblets without explicitly resolving individual grooves. This enables the efficient evaluation of riblet dimensions ranging from tens to hundreds of micrometers on an engineering-scale three-car train configuration. Based on this approach, a 1:8-scale high-speed train model is employed to study V-shaped riblet microstructures with a fixed aspect ratio of s/h = 1, with particular emphasis on the effects of riblet size and spatial placement on aerodynamic drag reduction. The results show that an overall drag reduction of 3.26% can be achieved for the entire train. This study demonstrates the effectiveness of V-shaped riblet microstructures under representative operating conditions and provides guidance for the design and optimization of surface microstructures on high-speed trains.