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274 lines
11 KiB
Markdown
274 lines
11 KiB
Markdown
# Simulating a small rotating drum {#rotatingDrumSmall}
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## Problem definition
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The problem is to simulate a rotating drum with a diameter of 0.24 m and a length of 0.1 m, rotating at 11.6 rpm. It is filled with 30,000 spherical particles with a diameter of 4 mm. The time step for integration is 0.00001 s.
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<div align="center"><b>
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a view of rotating drum
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</b></div>
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***
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## Setting up the case
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The PhasicFlow simulation case setup is based on the text-based scripts that we provide in two folders located in the simulation case folder: `settings` and `caseSetup` (You can find the case setup files in the above mentioned folders.
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All commands should be entered in the terminal with the current working directory being the simulation case folder (at the top of the `caseSetup` and `settings` folders).
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### Creating particles
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Open the file `settings/particlesDict`. Two dictionaries, `positionParticles` and `setFields` position particles and set the field values for the particles.
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In dictionary `setFields`, dictionary `defaultValue` defines the initial value for particle fields (here, `velocity`, `acceleration`, `rotVelocity`, and `shapeName`). Note that `shapeName` field should be consistent with the name of shape that you later set for shapes (here one shape with name `sphere1`).
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<div align="center">
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in <b>settings/particlesDict</b> file
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</div>
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```C++
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setFields
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{
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defaultValue
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{
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velocity realx3 (0 0 0); // linear velocity (m/s)
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acceleration realx3 (0 0 0); // linear acceleration (m/s2)
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rotVelocity realx3 (0 0 0); // rotational velocity (rad/s)
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shapeName word sphere1; // name of the particle shape
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}
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selectors
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{
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shapeAssigne
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{
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selector stridedRange; // other options: box, cylinder, sphere, randomPoints
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stridedRangeInfo
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{
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begin 0; // begin index of points
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end 30000; // end index of points
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stride 3; // stride for selector
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}
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fieldValue // fields that the selector is applied to
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{
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shapeName word sphere1; // sets shapeName of the selected points to largeSphere
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}
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}
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}
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}
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In dictionary `positionParticles`, the positioning `method` is `ordered`, which position particles in order in the space defined by `box`. `box` space is defined by two corner points `min` and `max`. In dictionary `orderedInfo`, `numPoints` defines number of particles; `diameter`, the distance between two adjacent particles, and `axisOrder` defines the axis order for filling the space by particles.
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<div align="center">
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in <b>settings/particlesDict</b> file
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</div>
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```C++
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positionParticles
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{
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method ordered; // other options: random and empty
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mortonSorting Yes; // perform initial sorting based on morton code
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orderedInfo
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{
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diameter 0.004; // minimum space between centers of particles
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numPoints 30000; // number of particles in the simulation
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axisOrder (z y x); // axis order for filling the space with particles
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}
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regionType box; // other options: cylinder and sphere
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boxInfo // box information for positioning particles
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{
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min (-0.08 -0.08 0.015); // lower corner point of the box
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max ( 0.08 0.08 0.098); // upper corner point of the box
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}
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```
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In dictionary `setFields`, dictionary `defaultValue` defines the initial value for particle fields (here, `velocity`, `acceleration`, `rotVelocity`, and `shapeName`). Note that `shapeName` field should be consistent with the name of shape that you later set for shapes (here one shape with name `sphere1`).
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<div align="center">
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in <b>settings/particlesDict</b> file
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</div>
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```C++
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setFields
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{
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defaultValue
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{
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velocity realx3 (0 0 0); // linear velocity (m/s)
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acceleration realx3 (0 0 0); // linear acceleration (m/s2)
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rotVelocity realx3 (0 0 0); // rotational velocity (rad/s)
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shapeName word sphere1; // name of the particle shape
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}
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selectors
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{}
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}
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```
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Enter the following command in the terminal to create the particles and store them in `0` folder.
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`> particlesPhasicFlow`
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### Creating geometry
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In file `settings/geometryDict` , you can provide information for creating geometry. Each simulation should have a `motionModel` that defines a model for moving the surfaces in the simulation. `rotatingAxis` model defines a fixed axis which rotates around itself. The dictionary `rotAxis` defines an motion component with `p1` and `p2` as the end points of the axis and `omega` as the rotation speed in rad/s. You can define more than one motion component in a simulation.
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<div align="center">
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in <b>settings/geometryDict</b> file
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</div>
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```C++
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motionModel rotatingAxis;
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.
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.
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rotatingAxisInfo
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{
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rotAxis
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{
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p1 (0.0 0.0 0.0); // first point for the axis of rotation
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p2 (0.0 0.0 1.0); // second point for the axis of rotation
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omega 1.214; // rotation speed (rad/s)
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}
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}
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```
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In the dictionary `surfaces` you can define all the surfaces (walls) in the simulation. Two main options are available: built-in geometries in PhasicFlow, and providing surfaces with stl file. Here we use built-in geometries. In `cylinder` dictionary, a cylindrical shell with end radii, `radius1` and `radius2`, axis end points `p1` and `p2`, `material` name `prop1`, `motion` component `rotAxis` is defined. `resolution` sets number of division for the cylinder shell. `wall1` and `wall2` define two plane walls at two ends of cylindrical shell with coplanar corner points `p1`, `p2`, `p3`, and `p4`, `material` name `prop1` and `motion` component `rotAxis`.
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<div align="center">
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in <b>settings/geometryDict</b> file
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</div>
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```C++
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surfaces
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{
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cylinder
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{
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type cylinderWall; // type of the wall
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p1 (0.0 0.0 0.0); // begin point of cylinder axis
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p2 (0.0 0.0 0.1); // end point of cylinder axis
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radius1 0.12; // radius at p1
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radius2 0.12; // radius at p2
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resolution 24; // number of divisions
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material prop1; // material name of this wall
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motion rotAxis; // motion component name
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}
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wall1
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{
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type planeWall; // type of the wall
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p1 (-0.12 -0.12 0.0); // first point of the wall
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p2 ( 0.12 -0.12 0.0); // second point
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p3 ( 0.12 0.12 0.0); // third point
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p4 (-0.12 0.12 0.0); // fourth point
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material prop1; // material name of the wall
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motion rotAxis; // motion component name
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}
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wall2
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{
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type planeWall;
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p1 (-0.12 -0.12 0.1);
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p2 ( 0.12 -0.12 0.1);
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p3 ( 0.12 0.12 0.1);
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p4 (-0.12 0.12 0.1);
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material prop1;
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motion rotAxis;
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}
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}
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```
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Enter the following command in the terminal to create the geometry and store it in `0/geometry` folder.
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`> geometryPhasicFlow`
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### Defining properties and interactions
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In the file `caseSetup/interaction` , you find properties of materials. `materials` defines a list of material names in the simulation and `densities` sets the corresponding density of each material name. model dictionary defines the interaction model for particle-particle and particle-wall interactions. `contactForceModel` selects the model for mechanical contacts (here nonlinear model with limited tangential displacement) and `rollingFrictionModel` selects the model for calculating rolling friction. Other required Properties should be defined in this dictionary.
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<div align="center">
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in <b>caseSetup/interaction</b> file
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</div>
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```C++
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materials (prop1); // a list of materials names
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densities (1000.0); // density of materials [kg/m3]
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.
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model
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{
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contactForceModel nonLinearNonLimited;
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rollingFrictionModel normal;
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Yeff (1.0e6); // Young modulus [Pa]
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Geff (0.8e6); // Shear modulus [Pa]
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nu (0.25); // Poisson's ratio [-]
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en (0.7); // coefficient of normal restitution
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et (1.0); // coefficient of tangential restitution
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mu (0.3); // dynamic friction
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mur (0.1); // rolling friction
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}
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```
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Dictionary `contactSearch` sets the methods for particle-particle and particle-wall contact search. Larger `sizeRatio` include more particles in the neighbor list and you require to update it less frequent.
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<div align="center">
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in <b>caseSetup/interaction</b> file
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</div>
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```C++
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contactSearch
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{
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method NBS; // method for broad search
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updateInterval 10;
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sizeRatio 1.1;
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cellExtent 0.55;
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adjustableBox Yes;
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}
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```
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In the file `caseSetup/shapes`, you can define a list of `names` for shapes (`shapeName` in particle field), a list of diameters for shapes and their `properties` names.
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<div align="center">
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in <b>caseSetup/shapes</b> file
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</div>
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```C++
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names (sphere1); // names of shapes
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diameters (0.004); // diameter of shapes
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materials (prop1); // material names for shapes
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```
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Other settings for the simulation can be set in file `settings/settingsDict`.
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<div align="center">
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in <b>settings/settingsDict</b> file
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</div>
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```C++
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dt 0.00001; // time step for integration (s)
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startTime 0; // start time for simulation
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endTime 10; // end time for simulation
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saveInterval 0.1; // time interval for saving the simulation
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timePrecision 6; // maximum number of digits for time folder
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g (0 -9.8 0); // gravity vector (m/s2)
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includeObjects (diameter); // save necessary (i.e., required) data on disk
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// exclude unnecessary data from saving on disk
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excludeObjects (rVelocity.dy1 pStructPosition.dy1 pStructVelocity.dy1);
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integrationMethod AdamsBashforth2; // integration method
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writeFormat ascii; // data writting format (ascii or binary)
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timersReport Yes; // report timers (Yes or No)
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timersReportInterval 0.01; // time interval for reporting timers
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```
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## Running the case
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The solver for this simulation is `sphereGranFlow`. Type the following command in a terminal. Depending on your computer's computation power, it may take from a few minutes to a few hours to complete.
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`> sphereGranFlow`
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## Post processing
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When the simulation is finished, you can render the results in Paraview. To convert the results to VTK format, just type the following command in a terminal. This will convert all results (particles and geometry) to VTK format and save them in the folder `VTK/`.
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`> pFlowToVTK` |