Documentation

1.User Guide

1.1.Solver Control

In the solver control section you can setup the basic parameters of your simulation. These include:

  • Start time
  • End time
  • Time step size
  • Write interval of your simulation results
  • The size of your discretization points
  • The pressure on a free surface
  • The Magnitude and direction of gravity
  • A 2D offset in case you want to do a 2 dimensional simulation
  • The dimensions you want to include in your simulation
  • If you want to employ a turbulence model
  • If you want to include radiation heat transfer to the outside in your simulation

1.2.Particle Regions

To create a new particle region you can select the type of region you want to create. You can choose between:

Isothermal Fluid

For an isothermal fluid, like water without heat transfer.

Solidification Fluid

For a fluid that can undergo phase change from liquid to solid. This is suitable for the simulation of liquid metals.

Isothermal Fixed Wall 

You can choose this particle region to act as a wall boundary condition. This region can be chosen together with isothermal fluid as no heat transfer is simulated.

Free Motion Body

This type of particle region can be applied to moving bodies, like free floating or falling objects. The spacial and angular position of this region is tracked through out the simulation and can be later used in the post processing environment to analyze the movement of the body.

Fixed Motion Body

This particle region prescribes a fixed velocity to a solid object. It is suitable for rotation objects like the impeller of a pump or to specify the movement of a sloshing container.

1.2.1.Geometry import

You can import any STL file in ASCII format. Your geometry must be a closed volume for any type of particle region chosen. The discretization points will be created inside this volume. This means that you also need a closed volume for a wall. We recommend to dimension the volume of the geometry, so that at least three layers of discretization points can be created inside. 

1.2.3.Boundary Conditions

In shonDy you can set inlet and outlet boundary conditions. In contrast to traditional CFD methods, wall boundary conditions are imposed through real objects acting as a wall. The cool thing about it is, that these walls can now easily be moved around during a simulation in ways that is very difficult to achieve with traditional CFD methods.  

1.2.3.1.Inlet

You can add an inlet boundary condition by clicking on the plus sign next to “Flow Inlets”. Your inlet will appear in the 3D view as a green circle. Now you can give your inlet a name, choose the type of fluid you want to have flow through the inlet and set its material properties.

You can choose between an isothermal fluid and a solidification fluid as the fluid type of your inlet. Next you specify the center point of your inlet, its flow direction, the radius of your inlet circle and most important you specify the velocity of the fluid entering your domain.

 

1.2.3.2.Outlet

To add an outlet boundary condition to your simulation you click the plus sign next to “Flow Outlets”. Now your outlet will appear as a red circle in the 3D viewer of your project. At first you can give your outlet a name, then specify its position and dimensions. As a last step you can set the pressure to be applied at the outlet.

1.2.3.3.Wall

A wall boundary condition in shonDy is a little different from traditional CFD methods. A wall boundary condition is imposed through a real particle region with a particle region type of:

  • Isothermal Fixed Wall
  • Solidification Fixed Wall
  • Free Motion Body
  • Fixed Motion Body

For more details on these particle region types, please read on here.

1.2.3.4.Post Processing

You can either download your simulation results in the VTK format and use Paraview to analyze your results or you can use our build in post processing environment directly in the cloud. 

2.Tutorials

2.1.Dambreak 2D

2.1.1.Target

In this tutorial we want to simulate the impact of a water wave on an fixed object.

2.1.2.Setup the simulation

To setup a simulation with shonCloud, you login at cloud.shondynamics.com with your email and password:

After login, you are greeted with an overview of your current projects in shonCloud. Then you create a new simulation project by giving it a name:

This will take you to your simulation control view:

This window is separated into three parts:

  1. The solver control and component overview
  2. The edit area for the selected component
  3. A 3D representation of your current simulation setup

Now you add the particle region for the wall and the fluid regions.

Here you can select the type of particle region you want and give the region its material properties. For the liquid part you choose “isothermalFluid”. Next we import the geometry by clicking on the pencil icon. You can import any geometry in the STL ASCII file format here. Remember to import a closed volume.

We now see a 3D representation of the geometry we imported. This represents the initial state of the water you want to simulate. You also see the discretization points used for the simulation. In this case, we want to make a two dimensional simulation, so the points form a plane inside the 3D geometry.

The next step is to add the geometry file for the wall:

Now you see the wall geometry added to the 3D view. As regionType we choose “isothermalFixedWall”.

As next step, we want to adjust the duration of the simulation and also review the position of the two dimensional plane. For this we open the tab solverControls:

Here we change the simulation duration to 3 seconds and change the position of the 2D plane to be in the center of our geometry.

As a last step we place sample probes inside the domain to watch for the pressure impact we are interested in.

You can see the position of your sample probe as a blue square in your 3D view. Be sure to place it in the right panel in case of a 2D simulation.

This is all that is needed to setup the simulation. The next step is to run the simulation on our high performance computers in the cloud.

2.1.3.Run the Simulation

To run the simulation, just click on the play icon of the project your want to run:

The status of your simulation will be updated automatically.

Here we can see progress of the simulation. The last step is to analyze our results.

2.1.4.Postprocess the simulation

To analyze our simulation result we open the postprocessing mode in shonCloud. For this you click on the magnify icon of the simulation you want to analyze:

As you can see, we can also analyze simulations, that have are not completely finished yet. This is handy to see if everything is going well with your simulation without having to wait until its finished.

 Here we select the particle region we want to visualize. Now we get a 3D representation of all time steps available. We can choose which simulation parameter is to be visualized. Here we chose the pressure field.

Now we can switch from the 3D view to the plot view, to visualize the sampled values of the probe we placed inside the domain.

Here we see exactly the time at which the impact of the water wave occurred. We also get an absolute value of the resulting pressure on the wall.

This concludes our analysis of the water wave impact on a fixed object.

3.Validation

All validation simulations are run on the following system:

Operating System: Fedora 27

CPU: Intel® Core™ i7-7820X CPU @ 3.60GHz × 16 

Memory: 32GB

3.1.Hydrostatic Pressure in a Water Column

The hydrostatic pressure in a water column can be calculated as: p = \rho * g * h . With the density \rho = 1000.0 \frac{kg}{m^3}, gravitational acceleration of g = -9.8 \frac{m}{s^2} and a column height of h = 0.2 m. The simulated pressure is plotted over time and compared to its analytical result at the elevations 0.01 m, 0.1 m and 0.15 m. The initial value of the pressure is set to 0 Pa uniformly.

3.2.Heat Conduction

The transient heat conduction in a two dimensional slab is simulated in this validation case. A constant temperature boundary condition on the left and right wall of 0 K is imposed on initial temperature field that follows the temperature distribution of T(x) = \sin( \frac{\pi * x}{L}). L is the length of the domain. In this simulation L is chosen as 0.1 m. The material constants used in this simulation are thermal conductivity of 1.0 \frac{K}{m} and a specific heat capacity of  1.0 \frac{J}{kg*K}. The simulated values are compared to their analytical result.

3.3.Solidification

The validation of the solidification capabilities of shonDy are performed by recalculation the Stefans-Problem. A two dimensional plate is initially in its liquid state (10 K above its liquidus temperature of 273.15 K). At the start of the simulation a cold wall (173.15 K) is placed on its left side. The analytical result to this problem is available in the form of the position of the melt front over time (moving from the cold wall to the center over time) and the temperature distribution in direction from cold wall to plate center at fixed time points.

3.4.Sloshing

Sloshing of water has be investigated experimentally by Delrome 2009*. In this validation simulation we compare the results obtained by shonDy to these experimental results.

*A set of canonical problems in sloshing, Part I: Pressure field in forced roll – comparison between experimental results and SPH L. Delorme, A. Colagrossi, A. Souto-Iglesias, R. Zamora-Rodrı́guez, E. Botı́a-Vera