Citation

Wu Q, Sun Q. Med. Sci. Sports Exerc. 2011; 43(10): 1955-1963.

Affiliation

Department of Mechanical Engineering & Cellular Biomechanics and Sports Science Laboratory, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085, USA; Animation School, Communication University of China, No.1 East Ding Fuzhuang Street, Chao Yang District, Beijing 100024, China.

Copyright

(Copyright © 2011, Lippincott Williams and Wilkins)

DOI

10.1249/MSS.0b013e318219480c

PMID

21448088

Abstract

PURPOSE:: Lift mechanics of downhill skiing or snowboarding is a new theory developed by the corresponding author and colleagues in 2006 and published on Med. Sci. Sports Exerc. This theory, hereafter referred to as Wu-Weinbaum theory, captures the lift contributions due to both the transiently trapped air inside a snow layer and the solid phase (snow crystals) for the first time, and examines the stability and control of skiing/snowboarding. However, it has two major shortcomings. First, it only predictsa single equilibrium position for a given gliding condition due to its limitations on the numerical simulation. Second, it is only applicable to rectangular boards. In the current study, we shall treat these limitations by improving the numerical methods as well as extending the Wu-Weinbaum theory to more complex planar shapes. METHODS:: A modified mathematical model is developed where a width factor, f(x), which characterizes the variation of width from the leading to the trailing edge of a ski/snowboard, is introduced. RESULTS:: We have performed a thorough re-examination of the force and moment balance on a rectangular board based on an improved numerical scheme and obtained multiple equilibrium positions for a skier or snowboarder gliding over a compressed snow layer at a certain speed. Furthermore, the performance of a commercial ski/snowboard with a specified shape was studied based on our revised model, which revealed different pore pressure distribution underneath the sliding surface compared to a rectangular board. CONCLUSION:: This study, along with the Wu-Weinbaum theory, has laid the foundation for the optimization of a ski/snowboard from a lift generation point of view.

Language: en