Virtual Disk Model Reference

The Virtual Disk model uses approximation methods to model the fluid dynamical effect of rotating disks without discretizing the real disk geometry such as propellers, rotors, fans and so on. The properties of this model are as follows:

Virtual Disk Common Properties

The following nodes located within the Virtual Disk > Virtual Disks node are common for all four types of virtual disk model:


Object	Properties
[virtual disk]	Method Specifies the method used to define the virtual disk. The options are: None 1D Momentum Method Blade Element Method Body Force Propeller Method User Defined Method Display Source Term Makes the field function Virtual Disk Source Term of [Virtual Disk] available (see Virtual Disk Field Functions) Verbosity Activates the outputs of additional information on the respective methods. All values are given at the current iteration. The options are: None: No additional information is written to the output window. Low High For more information, see Verbosity Outputs.
Disk Geometry	Number of Blades Specify the number of blades on the rotor. Inner Radius Specify the inner radius of the disk. This radius corresponds to the hub radius of the propeller or the wind turbine Outer Radius Specify the outer radius of the disk. This radius corresponds to the tip radius of the propeller or wind turbine. Thickness Specify the thickness of the propeller or wind turbine. Origin Specify the coordinates of the origin of the disk. The origin is defined in terms of the coordinates and the coordinate system with respect to which the coordinates are specified. Here, the choice of coordinate system is dictated by the selection you make for the Orientation Specification property: For the option Disk Normal and Coordinate System, the coordinates of the origin are specified with respect to the coordinate system that is selected in that node. For the option Pitch Angle and Lateral Angle, the coordinates of the origin are always with respect to the laboratory coordinate system. Local Coordinate System Reference to the local coordinate system of the disk (read only). Orientation Specification Specify the disk orientation by selecting this option. The disk orientation defines in which direction the thrust is produced. The options are: Disk Normal and Coordinate System Pitch Angle and Lateral Angle
Normal and Coordinate System Only visible when Orientation Specification is set to Disk Normal and Coordinate System.	Coordinate System Specify the coordinate system in regards to which the normal of the virtual disk is defined. You can also use a user-defined local Cartesian coordinate system to define the disk normal. Disk Normal Specify the direction that is normal to the plane of the disk.
Lateral and Pitch Angle Only visible when Orientation Specification is set to Pitch Angle and Lateral Angle .	Pitch Angle To rotate the local disk coordinate system, you specify a pitch angle. The pitch angle rotates the x-z plane around the y-axis. Lateral Angle To rotate the local disk coordinate system, you specify a lateral angle. The lateral angle rotates the y-z plane around the x-axis.

Verbosity Outputs

For each virtual disk method, there are different outputs which correspond to the verbosity settings specified.


Virtual Disk Method	Verbosity Output
Body Force Propeller Method	Low Outputs the value of the velocity at the inflow plane. Can be interpreted as the advance velocity with respect to propeller terminology. High Outputs the following values: Velocity at the inflow plane Selected operation point input options Advance ratio
Blade Element Method	Low Outputs the following values: rotation rate user-specified rotation rate rotation rate ramping status residuals and convergence status of the source term computation residuals and convergence status of the trimming algorithm High Outputs the following values: rotation rate user-specified rotation rate rotation rate ramping status residuals and convergence status of the source term computation residuals and convergence status of the trimming algorithm perturbation used to calculate the Jacobian number of iterations of the Newton-Raphson algorithm with convergence tolerace under-relaxation factor for the trim angles update disk stick state before and after the update
1D Momentum Method	Low Outputs the value of the velocity at the inflow plane. High Outputs the following values: velocity at the inflow plane power curve limits (cut-in and cut-out velocity)