de Groot G, Sargeant A, Geysel J
Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
Med Sci Sports Exerc. 1995 Jul;27(7):1090-5. doi: 10.1249/00005768-199507000-00020.
To calculate the power output during actual cycling, the air friction force Fa and rolling resistance Fr have to be known. Instead of wind tunnel experiments or towing experiments at steady speed, in this study these friction forces were measured by coasting down experiments. Towing experiments at constant acceleration (increasing velocity) were also done for comparison. From the equation of motion, the velocity-time curve v(t) was obtained. Curve-fitting procedures on experimental data of the velocity v yielded values of the rolling resistance force Fr and of the air friction coefficient k = Fa/v2. For the coasting down experiments, the group mean values per body mass m (N = 7) were km = k/m = (2.15 +/- 0.32) x 10(-3)m-1 and ar = Fr/m = (3.76 +/- 0.18) x 10(-2)ms-2, close to other values from the literature. The curves in the phase plane (velocity vs acceleration) and the small residual sum of squares indicated the validity of the theory. The towing experiments were not congruent with the coasting down experiments. Higher values of the air friction were found, probably due to turbulence of the air.
为了计算实际骑行过程中的功率输出，必须知道空气摩擦力(F_a)和滚动阻力(F_r)。本研究没有采用风洞实验或稳定速度下的牵引实验，而是通过下坡滑行实验来测量这些摩擦力。还进行了恒加速度（速度增加）的牵引实验以作比较。根据运动方程，得到了速度 - 时间曲线(v(t))。对速度(v)的实验数据进行曲线拟合，得出了滚动阻力(F_r)和空气摩擦系数(k = F_a/v^2)的值。对于下坡滑行实验，每单位体重(m)的组均值（(N = 7)）为(km = k/m = (2.15 ± 0.32)×10^{-3}m^{-1})，(ar = F_r/m = (3.76 ± 0.18)×10^{-2}ms^{-2})，与文献中的其他值相近。相平面（速度与加速度）中的曲线以及较小的残差平方和表明了该理论的有效性。牵引实验与下坡滑行实验不一致。发现空气摩擦力的值较高，可能是由于空气湍流所致。
