Model help:FallVelocity
FallVelocity
This model is used to calculate Particle fall velocity.
Model introduction
This model calculate fall velocity for spheres. Uses formulation of Dietrich (1982).
Model parameters
Uses ports
This will be something that the CSDMS facility will add
Provides ports
This will be something that the CSDMS facility will add
Main equations
- Explicit particle Reynolds number
[math]\displaystyle{ Re_{p} = {\frac{\sqrt { R g D } D}{\nu}} }[/math] (1)
- Dimensionless fall velocity
[math]\displaystyle{ R_{f} = exp \left ( -b_{1} + b_{2} ln \left ( Re_{p} \right ) - b_{3} \left ( ln \left ( Re_{p} \right ) \right ) ^2 - b_{4} \left ( ln \left ( Re_{p} \right ) \right ) ^3 + b_{5} \left ( ln \left ( Re_{p} \right ) \right ) ^4 \right ) }[/math] (2)
- fall velocity
[math]\displaystyle{ R_{f} = {\frac{v_{s}}{\sqrt { R g D }}} }[/math] (3)
| Symbol | Description | Unit |
|---|---|---|
| g | gravitational acceleration | L / T2 |
| ν | kinematic viscosity of water | L2 / T |
| R | submerged specific gravity of sediment, defined as (ρs -ρ) /ρ | - |
| D | grain size | L |
| ρs | sediment density | M / L3 |
| ρ | water density | M / L3 |
Output
| Symbol | Description | Unit |
|---|---|---|
| vs | fall velocity | L / T |
| Rep | explicit particle Reynolds no. | - |
| Rf | dimensionless fall velocity | - |
Notes
b1, b2, b3, b4, b5 are all parameters from Dietrich(1982).
This formulation is only valid for Reynold’s numbers less than or equal to 2.5·106. If Rep is greater than this upper limit, the function will alert the user, and exit the program.
Examples
An example run with input parameters, BLD files, as well as a figure / movie of the output
Follow the next steps to include images / movies of simulations:
- Upload file: https://csdms.colorado.edu/wiki/Special:Upload
- Create link to the file on your page: [[Image:<file name>]].
See also: Help:Images or Help:Movies
Developer(s)
References
Dietrich, E. W., 1982, Settling velocity of natural particles, Water Resources Research, 18 (6), 1626-1982.
