These granular flow equations were never derived to consider these things, but after calculating it, what came out is an apparent coefficient of friction that is negative.” ...

Yousuf AH Fudol, Yanchao Zhao, Hongping Liu, Sibin Zhou, Yinglian Li, Xiaoming Li, Origin and reservoir properties of deep-water gravity flow sediments in the Upper Triassic Ch6–Ch7 members of the ...