Modeling the Rotor by Using the Virtual Disk Model

For this simulation, you model the effects of the rotor on the helicopter fuselage using the blade element method. This method belongs to the virtual disk model.

To model the rotor:

Right-click the Continua > Physics 1 > Models > Virtual Disk > Virtual Disks node and select New.
Select the Virtual Disks > Virtual Disk node and set Method to Blade Element Method.

Before you can define the airfoil sections and the twist distribution, you must import two table data files (here in .csv format) into Simcenter STAR-CCM+.

Note	Simcenter STAR-CCM+ internally processes the provided angle data for the airfoil sections and the twist distribution in SI units, that is, in radians. In this context, it is important that you specify the tabular angle data correctly with respect to units.

First, you verify the preferred unit settings for angle data:

Select the Tools > Units > radian node and make sure that Preferred is activated.
Radian is the preferred unit for angle data for this simulation.

Next, you verify the unit specification in your table data for twist distribution and the airfoil sections.

Using a text editor of you choice, open NACA_0012.csv and twistTable.csv in the motion folder of the downloaded tutorial files.
You can see that the angles in twistTable.csv are specified in radians. This specification corresponds to the preferred units settings and no further changes are required. In NACA_0012.csv, you can see that the angles are specified in degrees. In order to let Simcenter STAR-CCM+ know that this angle data is specified in degrees and must be converted to radians, a unit specification is added to the column header of the table data file:
```
"AoA (deg)","Cl","Cd","Mach"
-16,0,0,0
-16,-1.218,0.09183,0.2
-16,-1.316,0.08124,0.4
-16,-1.521,0.07389,0.6
...
```
Right-click Tools > Tables and select New Table > File Table.
Navigate to NACA_0012.csv in the motion folder of the downloaded tutorial files and click Open.
Create another file table and import twistTable.csv from the same directory.

You can now proceed to set up the virtual disk.

Right-click the Virtual Disk > Airfoil Sections node and select New.

Edit the Virtual Disk node and set the following properties:


Node	Property	Setting
Airfoil Sections > Airfoil Section 1
Cl (AoA, Mach)	Input Table	NACA_0012
	Table: Mach Number	Mach
	Table: Angle of Attack	AoA
	Table: Cl	Cl
Cd (AoA, Mach)	Input Table	NACA_0012
	Table: Mach Number	Mach
	Table: Angle of Attack	AoA
	Table: Cd	Cd
Chord Distribution > Constant	Value	0.066294 m
Twist Distibution	Method	Table (r/R)
Table (r/R) > Table (r/R)	Input Table	twistTable
	Table: Data	twist
	Table: Normalized Span	r/R
Disk Geometry	Number of Blades	4
	Inner Radius	0.207 m
	Outer Radius	0.860552 m
	Thickness	0.02 m
	Origin	[0.696, 0.051, 0.322] m, m, m
	Orientation Specification	Pitch Angle and Lateral Angle
Lateral and Pitch Angle	Pitch Angle	-3 deg
Rotation Rate	Rotation Rate	$Omega
Rotation Rate	Ramp Method	Linear Ramp
Linear Ramp	Start Counter	1
	Stop Counter	100
	Initial Value	1.0
Disk Stick Specification	Collective Pitch	7.7 deg
	Cyclic Pitch: Cosine Component	-1.8 deg
	Cyclic Pitch: Sine Component	2.3 deg
	Virtual Disk Trim Option	Trim Thrust Only
Virtual Disk Resolution	Radial Resolution	30
	Azimuthal Resolution	30
Target Thrust	Target Rotor Thrust	$Thrust

Based on the Origin and the Pitch Angle that you provided, Simcenter STAR-CCM+ creates a local virtual disk coordinate system. The thrust produced by the virtual disk acts in the Z direction of this coordinate system.

You can visualize the local virtual disk coordinate system and the virtual disk.

Expand the Tools > Coordinate Systems > Laboratory > Local Coordinate Systems and drag and drop the Virtual Disk-CSys 1 node into the currently active Geometry scene 1.
Select the Virtual Disk node within Physics 1 continuum and zoom in on the virtual disk.

You can see the dimensions, location, and the orientation of the virtual disk. The orientation determines the direction of the thrust that is produced by the virtual disk. This thrust acts in the Z direction of the local virtual disk coordinate system.
Save the simulation.