The flowability of granular material is commonly determined from shear cell tests,but in the real world,the granular flow is quite different in many cases.For this paper,the flowabilities in a narrow channel of five different granular materials were investigated.The flow parameters of the granular flows were determined to classify the flowabilities.Granular flow surface velocities and flow heights and thicknesses were measured,and it was found that the mean shear rates in the linear portions of the velocity profiles increase with both flow rates and inclination.A universal parameter,the ratio of the sine of the inclination to the shear rate in the linear part of the velocity profile,is proposed as a constant.This constant is independent of particle properties.In addition,a flowability parameter,the ratio of the mean shear rate to the cosine of the inclination,is proposed to characterize the friction between the particles in the flowing granular material.