fluid rotational velocity

Module: fluid

Category: bc

Type string: "fluid rotational velocity"

Parameters

Name	Description	Default	Units
relative	relative	false	[]
angular_speed	angular_speed	0	[]
axis	axis	{0,0,1}	[]
origin	origin	{0,0,0}	[]

Description

This boundary condition prescribes a rotational velocity on an axisymmetric surface. It is the user's responsibility to ensure that the surface is axisymmetric. The angular velocity \(\boldsymbol{\omega}=\omega\mathbf{n}\) is prescribed by specifying the angular speed \(\omega\) and the unit vector along the axis of rotation (axis of symmetry) \(\mathbf{n}\). The user-defined vector \(\mathbf{n}\) is automatically normalized. If the axis does not pass through the origin, the user may specify any point \(\mathbf{p}\) on the axis. The fluid velocity relative to the mesh, \(\mathbf{w}\), for nodes on the selected surface is evaluated from \(\mathbf{w}=\boldsymbol{\omega}\times\mathbf{r}\), where \(\mathbf{r}=\left(\mathbf{I}-\mathbf{n}\otimes\mathbf{n}\right)\cdot\left(\mathbf{x}-\mathbf{p}\right)\) is the shortest vector from the axis to the node and \(\mathbf{x}\) is the nodal position.

<surface_load type="fluid rotational velocity" surface="FluidRotationalVelocity01">
    <angular_speed lc="1">1</angular_speed>
    <axis>0,0,1</axis>
    <origin>0,0,0</origin>
</surface_load>

Though this boundary condition may be used in fluid-FSI analyses, it is most relevant for standard fluid analyses where the mesh is stationary.