Rouse number
Encyclopedia
The Rouse number is a non-dimensional number in fluid dynamics
which is used to define a concentration profile of suspended sediment and which also determines how sediment
will be transported in a flowing fluid. It is a ratio between the sediment fall velocity
and the upwards velocity on the grain as a product of the von Kármán constant
and the shear velocity
.
Occasionally the term β is added 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 the America
n fluid dynamicist Hunter Rouse
. It is a characteristic scale parameter in the Rouse 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 as bed load
, suspended load
, and wash load
, are given below.
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
which is used to define a concentration profile of suspended sediment and which also determines how sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
will be transported in a flowing fluid. It is a ratio between the sediment fall velocity
Terminal velocity
In fluid dynamics an object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the fluid through which it is moving....
and the upwards velocity on the grain as a product of the von Kármán constantVon Kármán constant
In fluid dynamics, the Von Kármán constant , named for Theodore von Kármán, is a dimensionless constant describing the logarithmic velocity profile of a turbulent fluid flow near a boundary with a no-slip condition...
and the shear velocityShear velocity
Shear velocity, also called friction velocity, is a form by which a shear stress may be re-written in units of velocity. It is useful as a method in fluid mechanics to compare true velocities, such as the velocity of a flow in a stream, to a velocity that relates shear between layers of flow.Shear...
.Occasionally the term β is added before the von Kármán constant
Von Kármán constant
In fluid dynamics, the Von Kármán constant , named for Theodore von Kármán, is a dimensionless constant describing the logarithmic velocity profile of a turbulent fluid flow near a boundary with a no-slip condition...
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 the America
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
n fluid dynamicist Hunter Rouse
Hunter Rouse
Hunter Rouse was a hydraulician known for his research on the mechanics of fluid turbulence.Rouse was a faculty member at the Massachusetts Institute of Technology, Cambridge, from 1929 until 1933, when he moved to Columbia University...
. It is a characteristic scale parameter in the Rouse 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 as bed load
Bed load
The term bed load or bedload describes particles in a flowing fluid that are transported along the bed. Bed load is complementary to suspended load and wash load.Bed load moves by rolling, sliding, and/or saltating ....
, suspended load
Suspended load
Suspended load is the portion of the sediment that is carried by a fluid flow which settle slowly enough such that it almost never touches the bed...
, and wash load
Wash load
Wash load is the portion of sediment that is carried by a fluid flow, usually in a river, such that it always remains close the free surface . It is in near-permanent suspension and is transported without deposition, essentially passing straight through the stream...
, are given below.
| Mode of Transport | Rouse Number |
|---|---|
| Bed load Bed load The term bed load or bedload describes particles in a flowing fluid that are transported along the bed. Bed load is complementary to suspended load and wash load.Bed load moves by rolling, sliding, and/or saltating .... |
>2.5 |
| Suspended load Suspended load Suspended load is the portion of the sediment that is carried by a fluid flow which settle slowly enough such that it almost never touches the bed... : 50% Suspended |
>1.2, <2.5 |
| Suspended load Suspended load Suspended load is the portion of the sediment that is carried by a fluid flow which settle slowly enough such that it almost never touches the bed... : 100% Suspended |
>0.8, <1.2 |
| Wash load Wash load Wash load is the portion of sediment that is carried by a fluid flow, usually in a river, such that it always remains close the free surface . It is in near-permanent suspension and is transported without deposition, essentially passing straight through the stream... |
<0.8 |