Hydro Ball

Hydrodynamic sphere with gravity, buoyancy, drag, and external forces.

Collaboration diagram for Hydro Ball:

HydroBall is a SimObject that models a hydrodynamic ball completely submerged in water. The ball is under the influence of gravity, buoyancy, hydrodynamic drag, and external forces. The SimObject is primarily created to illustrate the use of KalmanObject in FhSim. The buoyancy and the drag are those of fhsim_environment's sphere law (environment::sphere_hydro) with its defaults: water density 1025 kg/m^3 and drag coefficient 0.5 (owner ruling 2026-10-21, BASE-0085). There is no added mass.

Author

Joakim Haugen

Example file input:

<Lib
  LibName    = "fhsim_base"
  SimObject  = "Example/HydroBall"
  Name       = "Ball"
  Radius     = "1"
  Density    = "2000"
/>
...
<Connection
  Ball.ExternForce = "Cable.ForceB"
  Ball.Current     = "Current.Out"
/>
...
<InitialCondition
  Ball.Position = "0,6.15,18.9"
  Ball.Velocity = "0,0,0"
/>

Input Ports

Name	Width	Description
ExternForce	3	External forces acting on the ball, e.g. from other SimObjects.
Current	3	The uniform current of the surrounding water.

Output Ports

Name	Width	Description
Position	3	The position of the centroid of the ball.
Velocity	3	The linear velocity of the ball.

Configuration parameters

Name	Width	Description
Radius	1	Radius of the ball [meter].
Density	1	Density of the ball [kg/m^3].

Initial conditions

Name	Width	Description
Position	3	-.
Velocity	3	-.

Full example file

<Contents>
  <OBJECTS>
    <Lib
      LibName = "fhsim_base"
      SimObject = "Example/HydroBall"
      Name = "Ball"
      Radius = "1.0"
      Density = "1100"
    />
    <Lib
      LibName = "fhsim_base"
      SimObject = "Example/HydroCable"
      Name = "Cable"
      Diameter = "0.02"
      Density = "2000"
      Modulus = "20"
      Length = "20"
      InternalPoints = "7"
    />
    <Lib
      LibName = "fhsim_base"
      SimObject = "Src/Sine"
      Name = "NorthCurrent"
      PortWidth = "1"
      PhaseRad = "0"
      PeriodS = "200"
      StartTime = "0"
      StopTime = "-1"
      Bias = "0.7"
      Amplitude = "0.3"
    />
    <Lib
      LibName = "fhsim_base"
      SimObject = "Signal/Mux"
      Name = "Current"
      NumInput = "3"
      PortWidth = "3"
      InPortWidth1 = "1"
      InPortWidth2 = "1"
      InPortWidth3 = "1"
  />
  </OBJECTS>
 
  <INTERCONNECTIONS>
    <Connection
      Ball.ExternForce = "Cable.ForceB"
      Ball.Current     = "Current.Out"
      Current.In1      = "NorthCurrent.Out"
      Current.In2      = "0.5"
      Current.In3     = "0.1"
    />
 
    <Connection
      Cable.PositionA = "0,0,0"
      Cable.PositionB = "Ball.Position"
      Cable.VelocityA = "0,0,0"
      Cable.VelocityB = "Ball.Velocity"
      Cable.Current   = "Current.Out"
    />
  </INTERCONNECTIONS>
 
  <INITIALIZATION>
    <InitialCondition
    Ball.Position = "0,6.15,18.9"
    Ball.Velocity = "0,0,0"
    />
  </INITIALIZATION>
 
  <SIMULATION>
    <Timing TStart="0" TEnd="1000"/>
    <Integrator Method="Euler_i" NumCores="1">
      <StepControl Step="2e-5"/>
    </Integrator>
    
  </SIMULATION>
</Contents>

This SimObject is referred to as Example/HydroBall