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TheRouse number (P orZ) is anon-dimensional number influid dynamics which is used to define a concentration profile ofsuspended sediment and which also determines howsediment will be transported in a flowing fluid. It is a ratio between the sedimentfall velocity and the upwards velocity on the grain as a product of thevon Kármán constant and theshear velocity.[1]
Occasionally the factor β is included before the von Kármán constant in the equation, which is a constant which correlates eddy viscosity to eddy diffusivity. This is generally taken to be equal to 1, and therefore is ignored in actual calculation. However, it should not be ignored when considering the full equation.
It is named after theAmerican fluid dynamicistHunter Rouse. It is a characteristic scale parameter in theRouse Profile of suspended sediment concentration with depth in a flowing fluid. The concentration of suspended sediment with depth goes as the power of the negative Rouse number. It also is used to determine how the particles will move in the fluid. The required Rouse numbers for transport asbed load,suspended load, andwash load, are given below.
| Mode of Transport | Rouse Number |
|---|---|
| Bed load | >2.5 |
| Suspended load: 50% Suspended | >1.2, <2.5 |
| Suspended load: 100% Suspended | >0.8, <1.2 |
| Wash load | <0.8 |
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