Measurement of Friction Coefficient on a Powder Layer and Fluid Dynamic Study

Cross sections of the flour layer was made by cutting the powder layer across the color line, formed with starch colored by a food color, at right angles (Fig. 13). Examples of the cross section are shown in Fig. 14. They show different features with  distance from the center of the track. Fig. 14c is positioned outside of the track, therefore it can be regard as showing the initial state before the sliding.

From observation of  these sections, it was found that a shear motion in the powder layer is larger as when the distance from the center was smaller. Moreover,  it was also larger in the  upper part  than in the  lower part of the layer. However we could not observe them correctly because of a defect in the preparation method; colored powder clung onto the cutter blade and was displaced downward.

Fig. 13. Preparation of  the cross section. Line a, b and c show the position of the cross section of Fig. 14.

a
b
c
Fig. 14. Cross sections of the powder layer.

Measurement of Friction Coefficient on a Powder Layer and Fluid Dynamic Study