Adding force fluid in comsol 5.1
![adding force fluid in comsol 5.1 adding force fluid in comsol 5.1](https://i.ytimg.com/vi/Lhn4dlWFmR4/maxresdefault.jpg)
It was only possible to obtain an exact solution because of all of the simplifying assumptions involved, most notably that the fluid velocity u was zero everywhere. In the previous section, we were quite lucky that Eq. In contrast, smaller particles will match the fluid velocity much sooner when they spread out, it is more likely due to turbulent diffusion of the surrounding fluid.
![adding force fluid in comsol 5.1 adding force fluid in comsol 5.1](https://i.ytimg.com/vi/KKqsPrqcLDU/maxresdefault.jpg)
![adding force fluid in comsol 5.1 adding force fluid in comsol 5.1](https://cdn.comsol.com/wordpress/sites/1/2020/12/solver-settings-small-steps.png)
In the figure below, the dimensionless position and velocity are plotted as functions of the dimensionless time t‘.