Constant mass flux in a collisional cascade

In a steady collisional cascade supplied at large sizes and depleted only at small sizes, mass conservation makes the downward mass flux across every intermediate size threshold equal. With self-similar fragmentation and comparable transfer between logarithmic bins, the mass removed per bin per unit time is consequently independent of size. Nonlocal or size-dependent fragmentation, additional sources, and proximity to the cutoffs can invalidate the simplified bin-by-bin relation.