Angle of repose

When a pile of powder or granular material is made, this is the angle between the slope and the horizontal plane. This has long been used as a simple way of expressing the frictional properties of powder or granular material, but the value varies depending on the measurement method and conditions. Common measurement methods are the injection method (see figure), in which the powder or granular material is gently dropped onto a horizontal surface and the slope angle of the resulting piled layer is measured, and the discharge method, in which the powder or granular material is allowed to flow out of a hole in the bottom of a cylindrical container held horizontally and the slope angle of the resulting residual layer is measured.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

粉粒体の堆積をつくった場合，その斜面と水平面のなす角をいう．これは粉粒体の摩擦特性の簡単な表現の一つとして古くから用いられているが，値は測定法や測定条件により変化する．測定法としては，水平面上に粉粒体を静かに落下させて生じた堆積層の傾斜角を測定する注入法(図)と，水平に保った円筒容器の底面の孔より粉粒体を流出させ，生じた残留層の傾斜角を測定する排出法とがよく用いられる．

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