Application of Experimental Measurements in a Wind Tunnel to the Development of a Model for Aerodynamic Drag on Elite Slalom and Giant Slalom Alpine Skiers

Matej Majerič,Matej Supej,Jan Ogrin,Hans-Christer Holmberg,Nina Verdel

doi:10.3390/app12020902

Abstract

Aerodynamic drag is a major cause of energy losses during alpine ski racing. Here we developed two models for monitoring the aerodynamic drag on elite alpine skiers in the technical disciplines. While 10 skiers assumed standard positions (high, middle, tuck) with exposure to different wind speeds (40, 60, and 80 km/h) in a wind tunnel, aerodynamic drag was assessed with a force plate, shoulder height with video-based kinematics, and cross-sectional area with interactive image segmentation. The two regression models developed had 3.9–7.7% coefficients of variation and 4.5–16.5% relative limits of agreement. The first was based on the product of the coefficient of aerodynamic drag and cross-sectional area (Cd∙S) and the second on the coefficient of aerodynamic drag Cd and normalized cross-sectional area of the skier Sn, both expressed as a function of normalized shoulder height (hn). In addition, normative values for Cd (0.75 ± 0.09–1.17 ± 0.09), Sn (0.51 ± 0.03–0.99 ± 0.05), hn (0.48 ± 0.03–0.79 ± 0.02), and Cd∙S (0.23 ± 0.03–0.66 ± 0.09 m2) were determined for the three different positions and wind speeds. Since the uncertainty in the determination of energy losses due to aerodynamic drag relative to total energy loss with these models is expected to be <2.5%, they provide a valuable tool for analysis of skiing performance.

Highlights

IntroductionPublished: 17 January 2022The execution of turns in connection with the four major events of the Olympic sport of alpine skiing, i.e., slalom, giant slalom, super-G (super-giant slalom), and downhill [1], differs considerably, due to large differences in the placement of the gates, the length of each turn, the incline of the slope, and, above all, skiing speed [2]
Published: 17 January 2022The execution of turns in connection with the four major events of the Olympic sport of alpine skiing, i.e., slalom, giant slalom, super-G, and downhill [1], differs considerably, due to large differences in the placement of the gates, the length of each turn, the incline of the slope, and, above all, skiing speed [2]
In an attempt to maximize speed, skiers try to minimize the dissipation of mechanical energy [3,4], which is caused primarily by aerodynamic drag and ski–snow friction [1,5]

Summary

Introduction

Published: 17 January 2022The execution of turns in connection with the four major events of the Olympic sport of alpine skiing, i.e., slalom, giant slalom, super-G (super-giant slalom), and downhill [1], differs considerably, due to large differences in the placement of the gates, the length of each turn, the incline of the slope, and, above all, skiing speed [2]. The extent to which different skiers expose themselves to aerodynamic drag varies considerably [6], being the cause of almost 50% of the difference in race time between slower and faster skiers [7]. As early as 1983, Leino and colleagues [5] estimated that aerodynamic drag is responsible for 10–40% of energy losses associated with alpine skiing. This form of resistance exerts its most pronounced impact on performance in the speed disciplines (Super-G and downhill), as the speed increases [8], contributing to more than 80% of total resistive force [9]. Meyer, Pelley, and Borrani [10]

Results

Discussion

Conclusion