CFD Plugin

This section explains how to simulate Remotely Operated Vehicles (ROVs) and Unmanned Aerial Vehicles (UAVs) using the CFD Simulator.

Creating and Configuring the CFD Simulator

This feature uses Choreonoid's standard "AIST Simulator." To set it up: Select File > New > CFD Simulator from the main menu. Place the generated CFD Simulator as a child item of the AIST Simulator.

Creating and Configuring MultiCollider Items

The MultiCollider item is used to virtually define regions in the Choreonoid world that contain fluids such as water or air.

To create one, select File > New > MultiCollider and specify the type as "Fluid". Place it as a child of the World item. You can define complex environments by creating multiple MultiCollider items.

注釈

If target areas overlap, the settings of the MultiCollider item positioned lower in the Item Tree view will take precedence.

Fluid items can be toggled on or off using the checkboxes in the Item Tree. Note that hidden MultiCollider items are excluded from the simulation.

The parameters for the MultiCollider item are as follows:

Parameter	Default Value	Unit	Meaning
Density	0.0	kg/m³	Specifies the fluid density.
Viscosity	0.0	Pa·s	Specifies the fluid viscosity.
Steady Flow	0, 0, 0	N, N, N	Specifies external forces applied to objects within the region.
Shape	Box	-	Specifies the shape of the region (Box/Cylinder/Sphere).
Size	1.0, 1.0, 1.0	m	Specifies the XYZ size (only for Box).
Radius	1.0	m	Specifies the radius (only for Cylinder/Sphere).
Height	1.0	m	Specifies the height (only for Cylinder).
Position / RPY	0, 0, 0	m / deg	Specifies the location (XYZ) and orientation (Roll, Pitch, Yaw).
Diffuse Color / Transparency	0, 0, 0 / 0	-	Specifies the RGB color and transparency of the region.

Body Item Settings

The CFD Simulator calculates buoyancy and drag forces acting on each link of the robot. To enable these calculations, add the following parameters to each link in the body file:

density: 1000.0
centerOfBuoyancy: [ 0.0, 0.0, 0.0 ]
cdw: 1.0
cda: 1.0
cw: 0.2

Details for each key:

Parameter	Default Value	Unit	Meaning
density	0.0	kg/m³	Specifies the density of the link.
centerOfBuoyancy	0.0, 0.0, 0.0	m	Coordinates of the center of buoyancy.
cdw	0.0	-	Drag coefficient in water.
cda	0.0	-	Drag coefficient in air.
cv	0.0	m	Viscous force coefficient proportional to velocity.
cw	0.0	-	Drag coefficient proportional to angular velocity (opposes rotation).

Thruster Settings (for ROVs)

The CFD Simulator provides a Thruster device to power ROVs, applying thrust and torque. The default orientation is the +X axis of the link's local coordinate system. Define it under the elements of a link:

-
  type: Thruster
  name: Thruster
  forceOffset: 1.0
  torqueOffset: 0.1
  symbol: true

Rotor Settings (for UAVs)

The Rotor device provides power for UAVs. The default orientation is the +Z axis of the link's local coordinate system. Define it under the elements of a link:

-
  type: Rotor
  name: Rotor
  forceOffset: 1.0
  torqueOffset: 0.1
  symbol: true

Running the Simulation

Start the simulation from the Simulation Bar. If configured correctly, buoyancy, drag, and other fluid forces will be applied to the robot based on the MultiCollider settings.