SimWorks Advanced Introduction

Introduction to SimWorks (advanced features)

This tutorial introduced some new functionalities of SimWorks and expands what has been already described in the SimWorks introduction tutorial.

If you have not done it yet, we strongly recommend reading the introduction tutorial before proceeding futher.

Create a new simulation

Create a single simulation within a Geometry
In the Setup tab of the Simulation editor, click on button to Find the geometry file and select the glider.igs file from the tutorials folder within the SimWorks installation folder
Then, click on the Load geometry button
The Geometry entry in the Simulation editor will show the path to the file and the Geometry viewer will display the loaded geometry with the outer domain which is automatically created by SimWorks

The outer domain (OD) is shown with transparency so that it is possible to see the geometry inside it. Please read the article about how to define a computational domain, which offers guidelines about the correct size to use. Here we want to modify its dimensions and position for the purposes of this exercise

Select the Regions tab in the Simulation editor window and under Outer Domain set the Size to 60 40 8
Change the Origin of the OD to -12 0 0 in order to have a longer distance behind the glider than in front of it

While editing the size and position of the OD the Geometry viewer is updated automatically.

Meshing parameters

In order to define the meshing parameters for the simulation, select the Mesh tab in the Simulation manager window:

Under Global Mesh Parameters, set the Cell base size of 0.5 m (the unit was set to m when loading the geometry). This will define the global base size of the mesh cells and represents the larger characteristic length of the mesh
Define a Point in mesh positioned at 5 0 0 and with size 0.5m. This point indicates the volume that will be meshed. For an external aerodynamics simulation this must be inside the OD but outside the geometry
The individual surfaces defined from CAD in the IGES file are automatically recognised by SimWorks and arranged in Surface Mesh Options by name. In the case of the glider, all the surface patches called Fuselage will be grouped in one Surface Mesh Option. This is the way SimWorks parses the geometry file, therefore we recommend that the original CAD file has the different surfaces labelled as required. As we want to have a finer mesh on the wings, it is possible to create a new Surface Mesh Option group by selecting the LHSWing and RHSWing parts from the Parts dropdown menu
Once the parts are selected. a new group can be created pressing the Create new part group button from the Simulation editor toolbar. This creates a new entry in the tree where we can apply specific mesh parameters on this group of parts
On the newly created group, we will apply an Edge level of 5 and a Surface level of 5 5. The first number is the minimum refinement level and the second the maximum. By setting both the minimum and maximum refinement levels to the Surface level, we are enforcing the mesher to refine the region and its boundary (by defining an Edge level of 5) to the same mesh size. A level of 5 means that the base cell size will be divided in two 5 times, so if we have a base cell of 0.5m this will be divided by 2^5 = 32 times, meaning that the local cell size on the airplane wings will be 0.5m/32=1.56cm. This resolution is required to correctly capture the geometric features of the glider wings and guaranteed an acceptable quality of the results
It is also possible to define prism layers on the surface to improve the near wall resolution. The prism layer mesh is activated by setting the First cell height, the Number of layers and the Expansion ratio. In this example, we request 3 layers with expansion ratio of 1.2 and a first cell height of 1 cm, therefore the mesh will have three layers of 1 cm, 1.2cm and 1.44cm respectively

The pre-processor is a useful tool to visualise graphically the settings we have just specified.

The first step is to select the Refinement levels from the drop-down layering menu of the Geometry viewer
It is convenient to hide the OD from the Geometry viewer to have a better view of settings on the glider surface

The legend on the Geometry viewer now shows the refinement levels with different colours. The wings of the glider are coloured differently from the fusolage and tail wings as they have a refinement level of 5 while the remaining of the surface has a level of 3.

Boundary conditions

In the pre-processor, it is possible to define the boundary conditions. In this case, we want to set a velocity of 25 m/s at the inlet of the OD. This corresponds to 90 km/h, which representative average cruise speed for a glider. Also we assume a constant relative pressure of 0 Pa at the outlet face of the OD.

Select the Boundary condition types in the layering menu
Select the Part Group containing the inlet face and set a Velocity Normal with a value of 25 m/s
Similarly, select the Part Group containing the outlet face and set Pressure Outlet with a value of 0 Pa

Run the simulation

It is now time to actually run the simulation by executing the Setup, Meshing phase and Run phases. Each phase is described in more detail in the SimWorks introduction tutorial.

Duplicate simulations

One of the main features of SimWorks is the possibility to duplicate a simulation and automatically re-apply all the parameters and boundary conditions to a new simulation even if the geometry has changed. This way it is possible to carry out an aerodynamic scan just by duplicating a simulation and importing a different geometry iteration.

To duplicate a simulation, select in the Simulation manager tree, right click on the simulation and click on Simulation manager → duplicate. A new simulation will appear below the original one
Select the new simulation and the Simulation editor window will be populated with the data of the new simulation
Now the new geometry can be loaded in the new simulation. Find the geometry file Glider_extended_wings.igs in the tutorials folder and load it
In the layering menu of the Geometry viewer, select the Boundary condition types to check that the new simulation has the same parameters and boundary condition of the original one. This is because SimWorks automatically recognises the named surfaces in the CAD file and when it finds surfaces with same name as the original simulation, it re-applies the same parameters to Part Groups and Surface Mesh Options. New surfaces (e.g. with different names) will be automatically added with default settings. Similarly, geometrical parts that no longer exists, will be automatically deleted.

Now that the new simulation has been defined, it is possible to rename it by just changing the name in the text box next to the new simulation in the Simulation manager window. Finally, to complete the simulation, please execute the Setup, Mesh and Run phases

Post-processing

The duplication functionality and the capability of automatically reapplying the simulation parameters to new imported geometries opens the possibility of quickly run through different design iterations without spending any time in redefining any simulation parameter for the newly imported geometries. SimWorks has the functionality to compare and show differences between the results of several simulations concurrently. This enables the user to assess the individual effect of each design iteration. The Fields viewer of SimWorks has been expanded with the capability of loading multiple simulations at the same time, calculate and display the difference of all the results.

Once both simulations are completed, in the Simulation manager window right click on the first simulation and and select Fields –> Load. Repeat the same on the second simulation
The Fields viewer loads the results of both simulations and splits the window in two, with the first simulation on the left hand side and the second on the right
In the menu, select the variable p (pressure) in the Plot variable drop-down list. Set a range of -100 100 and click Update legend

Maximise the Fields viewer window and click the Show/Hide delta button
Define a range for the Delta of -10 10 and click the Update delta legend button
You can see that a new sub window will be added in the Fields viewer window showing the difference (or delta) of the selected variable between the simulations loaded. The delta is calculated subtracting the values of the second simulation from the first one

We have seen how to plot a delta of two simulations, but it is possible to load multiple simulations in the same Fields viewer window. For instance, if we load in two additional simulations in the existing Fields viewer, we will have a total of 4 simulations loaded and 3 deltas on the bottom row showing the difference of the results of each simulation with respect to the first simulation.

In SimWorks it is also possible to have more than one Fields viewer window. To load a simulation in a new Fields viewer, right clicking on a simulation from the Simulation manager and select Fields → Load in new. The results of a simulation can be added to any of the existing Fields viewer windows by first clicking on the desired Fields viewer window to activate it, and then right click on Fields → Load to load the selected simulation.

Please note that the original Fields viewer window cannot be closed but only minimised (hidden) and then reinstated clicking on the relevant button in the Task bar, as already shown in the SimWorks introduction. Any additional Fields viewer window can instead be closed clicking on the x icon in the top right corner.

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