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Problem Definition

The problem is to simulate a Rotary Air-Lock Valve. The external diameter of rotor is about 21 cm. There is one type of particle in this simulation. Particles are inserted into the inlet of the valve from t=0 s.

28000 particles with 5 mm diameter are inserted into the valve with the rate of 4000 particles/s.
The rotor starts its ortation at t = 1.25 s at the rate of 2.1 rad/s.

<html>

a view of the Rotary Air-Lock Valve while rotating

particles are colored according to their id

</html>

Setting up the Case

As it has been explained in the previous simulations, the simulation case setup is based on text-based scripts. Here, the simulation case setup files are stored into three folders: caseSetup, setting, and stl (see the above folders). See next the section for more information on how we can setup the geometry and its rotation.

Geometry

Defining rotation axis

In file settings/geometryDict the information of rotating axis of rotor and its speed of rotation are defined. The rotation starts at t = 1.25 s and ends at t = 7 s.

// information for rotatingAxisMotion motion model 
rotatingAxisMotionInfo
{
	rotAxis 
	{

		// first point for the axis of rotation
		p1 (0.561547 0.372714 0.000);

		// second point for the axis of rotation
		p2 (0.561547 0.372714 0.010);

		// rotation speed (rad/s)
		omega 2.1;

		// Start time of Geometry Rotating (s)
		startTime 1.25;
		
		// End time of Geometry Rotating (s)
		endTime 7;
	}
}

Surfaces

In settings/geometryDict file, the surfaces component are defined to form a Rotating Air-Lock Valve. All surface components are supplied in stl file format. All stl files should be stored under 'stl' folder.

surfaces
{
	gear
	{
		// type of the wall
		type 	 stlWall;

		// file name in stl folder
		file 	 gear.stl;

		// material name of this wall
		material wallMat;

		// motion component name 
		motion 	 rotAxis;
	}
	surfaces
	{
		// type of the wall
		type 	 stlWall;

		// file name in stl folder
		file 	 surfaces.stl;

		// material name of this wall
		material wallMat;

		// motion component name 
		motion 	 none;
}

Defining particles

Diameter and material of spheres

In the caseSetup/sphereShape the diameter and the material name of the particles are defined.

in caseSetup/sphereShape file

// names of shapes
names 		(sphere);

// diameter of shapes 
diameters 	(0.005);

// material names for shapes 
materials	(sphereMat);

Insertion of Particles

Insertion of particles starts from t = 0 s and ends at t = 7 s. A box is defined for the port from which particles are being inderted. The rate of insertion is 4000 particles per second.

in settings/particleInsertion file

topRegion
{

	// type of insertion region
	type  boxRegion;

	// insertion rate (particles/s)
	rate 	  4000;

	// Start time of Particles insertion (s)
	startTime 	  0;

	// End time of Particles insertion (s)	
	endTime   	  7;

	// Time interval between each insertion (s)
	interval       0.025;

	// Coordinates of BoxRegion (m,m,m)
	boxRegionInfo 
	{
		min ( 0.48 0.58 0.01 ); // (m,m,m)
		max ( 0.64 0.59 0.05 ); // (m,m,m)
	}

	setFields
	{
		// initial velocity of inserted particles
		velocity    realx3 (0.0 -0.6 0.0);  
	}

	mixture
	{
		sphere 1;  
	}
}

Interaction between particles

In caseSetup/interaction file, material names and properties and interaction parameters are defined. Since we are defining 1 material type in the simulation, the interaction matrix is 2x2 (interactions are symmetric).

// a list of materials names
materials   (sphereMat  wallMat);

// density of materials [kg/m3]
densities   (1000    2500);

contactListType   sortedContactList;

model
{
   contactForceModel nonLinearNonLimited;

   rollingFrictionModel normal;
  
   /*
   Property (sphereMat-sphereMat  sphereMat-wallMat
                                 wallMat-wallMat);
   */
  
   // Young modulus [Pa]
   Yeff  (1.0e6 1.0e6
                1.0e6);

   // Shear modulus [Pa]
   Geff  (0.8e6 0.8e6
                0.8e6);

   // Poisson's ratio [-]
   nu    (0.25 0.25
               0.25);

   // coefficient of normal restitution
   en    (0.7  0.8
               1.0);

   // coefficient of tangential restitution
  et    (1.0   1.0
               1.0);

   // dynamic friction
   mu    (0.3  0.35
               0.35);

   // rolling friction
   mur   (0.1  0.1
               0.1);     
}

Performing simulation and seeing the results

To perform simulations, enter the following commands one after another in the terminal.

Enter $ particlesPhasicFlow command to create the initial fields for particles (here the simulaiton has no particle at the beginning).
Enter $ geometryPhasicFlow command to create the geometry.
At last, enter $ sphereGranFlow command to start the simulation.
After finishing the simulation, you can use $ pFlowtoVTK to convert the results into vtk format stored in ./VTK folder.

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