Using LiveLink™ for Excel® with Microsoft® Visual Basic® for Applications

LiveLink™ for Excel® is an interfacing product that enables you to connect your Excel data to COMSOL Multiphysics simulations. If you are a new user of LiveLink™ for Excel®, you can get started by reading the following documentation (accessible after installing the software):

• Introduction to LiveLink™ for Excel®
• LiveLink™ for Excel® User’s Guide

The Excel® spreadsheet software also provides the functionality to define and run VBA (Microsoft® Visual Basic® for Applications) from within an Excel workbook. Although we can write the VBA scripts manually, it is also possible to generate them from an existing model using the COMSOL Multiphysics user interface. As we will see with the help of some examples, it is easy to implement the use of VBA with LiveLink™ for Excel®. We will look into a common application to retrieve and update parameters in a COMSOL Multiphysics model.

Although this functionality is useful, VBA and LiveLink™ for Excel® can be used for a lot more. We will, for example, see how it is possible to build a COMSOL Multiphysics model and define the model geometry with some basic shapes inserted in the Excel workbook.

Note: The examples discussed here are shown with Excel® version 2010, but the process is the same in other versions.

With VBA, it is possible to interface Component Object Model (COM) components. When LiveLink™ for Excel® is installed, it also installs a COM interface component that can be used to interface with COMSOL Multiphysics®. Two essential COM objects for interfacing between the COMSOL Multiphysics Server and COMSOL Multiphysics models are:

comsolcom.comsolutil
comsolcom.modelutil

By using comsolcom.comsolutil, it is possible to start a COMSOL Multiphysics Server, connect, and disconnect from the server. With comsolcom.modelutil, we can interface with COMSOL Multiphysics models.

Using the VBA Editor

We can write and edit VBA scripts in Excel workbooks with the help of the editor that is installed with the Excel® spreadsheet software. The editor window can be accessed in a couple of different ways. For example, the editor is shown if we right-click an Excel worksheet tab and select View Code. The editor is also displayed if we create or edit a macro. It is also possible to enable a Developer tab in the toolbar in Excel® spreadsheet software that contains buttons for accessing the editor and other development-related functionality.

Accessing COM Components in VBA

We can create dynamic instances of the comsolcom.comsolutil and comsolcom.modelutil objects in VBA with the following declaration.

Set comsolutil = CreateObject("comsolcom.comsolutil")
Set modelutil = CreateObject("comsolcom.modelutil")

The advantage with this declaration is version independence. The latest installed versions of comsolcom.comsolutil and comsolcom.modelutil are used at runtime.

It is also possible to declare comsolcom.comsolutil and comsolcom.modelutil with a static COM reference using

Dim comsolutil As comsolutil
Set comsolutil = CreateObject("comsolcom.comsolutil")
Dim modelutil As  modelutil
Set modelutil = CreateObject("comsolcom.modelutil")

An advantage of using this declaration is that help will be available in VBA when using the defined types.

In order to be able to define static types for comsolutil and modelutil, we must add a COM reference to ComsolCom. We can do so by opening the VBA editor in the Excel® spreadsheet software, selecting the Tools menu, selecting References, and selecting ComsolCom for the installed version.

Start a COMSOL Multiphysics Server, Connect, and Disconnect with VBA

The following short VBA script illustrates how to start a COMSOL Multiphysics Server, connect to the started server, and then disconnect from the server. The line call comsolutil.TimeOutHandle(True) applies a timeout handler that tells Excel® spreadsheet software to wait for long-running commands to return.

Set comsolutil = CreateObject("comsolcom.comsolutil")
Set modelutil = CreateObject("comsolcom.modelutil")
Call comsolutil.TimeOuthandler(True)
Call comsolutil.StartComsolServer(True)
Call modelutil.connect
Call modelutil.Disconnect

Migrating from COMSOL API for Use with Java® and Application Methods

If you have experience with the COMSOL API for use with Java® or writing code in application methods, there is a syntax difference that is good to know about. When retrieving a list of model features, for example, the syntax is similar for studies in the model. Thus, for retrieving studies in a model, the following syntax works:

model.study()

However, when accessing a specific study, the syntax is different. For example, when retrieving a study with the study tag std1 with the COMSOL API for use with Java® or code in applications, the syntax model.study("std1") works. However, with VBA® and LiveLink™ for Excel®, the following syntax must be used instead:

model.get_study("std1")

Interface Parameters in COMSOL Multiphysics® Models

A common application of VBA and LiveLink™ for Excel® is to retrieve and update parameters in a COMSOL Multiphysics® model. Here, we will see how easily this can be achieved.

The following VBA script starts a COMSOL Multiphysics Server, connects to the started server, loads the Electrical Heating in a Busbar Using the LiveLink™ for Excel® model from the same directory as the active Excel® workbook, solves the model with an updated length parameter, and saves the updated model with another file name.

The following VBA script extracts parameter data for parameters in the model and inserts them into the Excel workbook.

How to Build COMSOL Multiphysics® Models with Excel® and Visual Basic®

In the next example, we create a COMSOL Multiphysics model and solve a 2D simulation using the Heat Transfer in Solids interface. The process involves defining geometry within Excel® spreadsheet software by adding a text box with some instructions, an outer temperature boundary, an inner temperature boundary, and a button for solving the simulation. When the model is solved, a results plot is inserted in the Excel® workbook. Let’s go through these steps in detail.

1. First, we create a text box with instructional text and insert it into the Excel workbook.

2. Then, we define a region for the simulation. We select a freeform shape and insert it in the Excel® workbook. Then, we select SimulationRegion as the name for the shape. We make the polygon editable by right-clicking on the shape and selecting Edit Polygon. Then, we edit the shape as shown below.

3. We create an inner boundary with a higher temperature. To do so, we use an oval shape, create a circle, and insert it inside the freeform. We select HeatSource as the name for the shape. The oval shape must reside inside the SimulationRegion shape.

4. We then add a text box shape with the text Solve to use as a button. We right-click on the button, select Assign Macro, and create a new macro named Solve_Click.

5. Next, we open the assigned macro in the VBA® editor and replace the content with the following script:

Expand or collapse VBA code…

Option Explicit
 
Sub Solve_Click()
 
Dim node
Dim coordinates
Dim index
Dim newPolygonTable() As Double
Dim newHeatSource(1 To 2) As Double
Dim model As ModelImpl
 
newHeatSource(1) = Sheets("Sheet1").Shapes("HeatSource").DrawingObject.Left + (Sheets("Sheet1").Shapes("HeatSource").DrawingObject.Width / 2)
newHeatSource(2) = Sheets("Sheet1").Application.Height - (Sheets("Sheet1").Shapes("HeatSource").DrawingObject.Top + (Sheets("Sheet1").Shapes("HeatSource").DrawingObject.Height / 2))
 
Dim nNodes As Long
nNodes = Sheets("Sheet1").Shapes("SimulationRegion").Nodes.Count
ReDim Preserve newPolygonTable(1 To nNodes, 1 To 2)
 
For Each node In Sheets("Sheet1").Shapes("SimulationRegion").Nodes
    coordinates = node.points
    index = index + 1
    newPolygonTable(index, 1) = coordinates(1, 1)
    newPolygonTable(index, 2) = Sheets("Sheet1").Application.Height - coordinates(1, 2)
Next
 
Set model = SetModel(newPolygonTable, newHeatSource)
 
Call model.get_study("std1").Run
 
If Not ContainsTag(model.result().tags(), "pg1") Then
    Call model.result().Create("pg1", "PlotGroup2D")
   Call model.get_result("pg1").feature().Create("surf1", "Surface")
    Call model.get_result("pg1").Label("Temperature (ht)")
    Call model.get_result("pg1").set("data", "dset1")
   Call model.get_result("pg1").get_feature("surf1").Label("Surface")
    Call model.get_result("pg1").get_feature("surf1").set("colortable", "ThermalLight")
    Call model.get_result("pg1").get_feature("surf1").set("data", "parent")
    Call model.get_result("pg1").get_feature("surf1").Run
End If
Call model.get_result("pg1").Run
 
Call Range("J10").Select
Dim tempPng As String
tempPng = Environ("Temp") & "\PolygonHeat" & Format(Now(), "yyyymmddhhmmss") & ".png"
 
Dim exportTag As String
exportTag = model.result().Export.uniquetag("export")
Call model.result().Export().Create(exportTag, "Image2D")
Call model.result().get_export(exportTag).set("plotgroup", "pg1")
Call model.result().get_export(exportTag).set("pngfilename", tempPng)
Call model.result().get_export(exportTag).Run
 
If Dir(tempPng)  "" Then
   Call Application.ActiveSheet.Pictures.Insert(tempPng)
    SetAttr tempPng, vbNormal
    Kill tempPng
End If
 
Call model.result().Export().Remove(exportTag)
 
End Sub
 
Private Function SetModel(ByRef newPolygonTable() As Double, ByRef newHeatSource() As Double) As Variant
 
Dim comsolutil As comsolutil
Set comsolutil = CreateObject("comsolcom.comsolutil")
Dim modelutil As modelutil
Set modelutil = CreateObject("comsolcom.modelutil")
Dim model As ModelImpl
 
If Not IsConnected(modelutil) Then
    Call ConnectServer(comsolutil, modelutil)
End If
 
If Not ContainsTag(modelutil.tags(), "PolygonHeatModel") Then
    Set SetModel = CreateModel(modelutil, "PolygonHeatModel", newPolygonTable, newHeatSource)
    Exit Function
End If
 
Set model = modelutil.model("PolygonHeatModel")
Call model.get_geom("geom1").get_feature("pol1").set("table", newPolygonTable)
 
Call model.get_geom("geom1").get_feature("c1").set("x", newHeatSource(1))
Call model.get_geom("geom1").get_feature("c1").set("y", newHeatSource(2))
Call model.get_geom("geom1").runAll
 
Set SetModel = model
 
End Function
 
Private Function CreateModel(ByRef modelutil As modelutil, ByRef modelTag As String, ByRef newPolygonTable() As Double, ByRef newHeatSource() As Double) As Variant
Dim model As ModelImpl
Set model = modelutil.Create(modelTag)
 
Call model.ModelNode().Create("comp1")
 
Call model.geom().Create("geom1", 2)
Call model.mesh().Create("mesh1", "geom1")
 
Call model.get_geom("geom1").Create("pol1", "Polygon")
Call model.get_geom("geom1").get_feature("pol1").set("source", "table")
Call model.get_geom("geom1").get_feature("pol1").set("table", newPolygonTable)
Call model.get_geom("geom1").Selection().Create("csel1", "CumulativeSelection")
Call model.get_geom("geom1").get_feature("pol1").set("contributeto", "csel1")
Call model.get_geom("geom1").get_run("pol1")
 
Call model.get_geom("geom1").Create("c1", "Circle")
Call model.get_geom("geom1").get_feature("c1").set("r", 0.01)
Call model.get_geom("geom1").get_feature("c1").set("x", newHeatSource(1))
Call model.get_geom("geom1").get_feature("c1").set("y", newHeatSource(2))
Call model.get_geom("geom1").Selection().Create("csel2", "CumulativeSelection")
Call model.get_geom("geom1").get_feature("c1").set("contributeto", "csel2")
 
Call model.get_geom("geom1").Run
Call model.get_geom("geom1").get_run("fin")
 
Call model.Material().Create("mat1", "Common", "comp1")
Call model.get_material("mat1").set("family", "copper")
Call model.get_material("mat1").get_propertyGroup("def").set("heatcapacity", "385[J/(kg*K)]")
Call model.get_material("mat1").get_propertyGroup("def").set("density", "8960[kg/m^3]")
Call model.get_material("mat1").get_propertyGroup("def").set("thermalconductivity", "400[W/(m*K)]")
 
Call model.Physics().Create("ht", "HeatTransfer", "geom1")
Call model.get_physics("ht").Create("temp1", "TemperatureBoundary", 1)
Call model.get_physics("ht").Create("temp2", "TemperatureBoundary", 1)
Call model.get_physics("ht").get_feature("temp2").set("T0", "293.15[K]+20")
Call model.get_physics("ht").get_feature("temp1").Selection().named("geom1_csel1_bnd")
Call model.get_physics("ht").get_feature("temp2").Selection().named("geom1_csel2_bnd")
 
Call model.study().Create("std1")
Call model.get_study("std1").Create("stat", "Stationary")
Call model.get_study("std1").Run
 
Call model.result().Create("pg1", "PlotGroup2D")
Call model.get_result("pg1").Label("Temperature (ht)")
Call model.get_result("pg1").set("data", "dset1")
Call model.get_result("pg1").feature().Create("surf1", "Surface")
Call model.get_result("pg1").get_feature("surf1").Label("Surface")
Call model.get_result("pg1").get_feature("surf1").set("colortable", "ThermalLight")
Call model.get_result("pg1").get_feature("surf1").set("data", "parent")
 
Set CreateModel = model
 
End Function
 
Private Function IsConnected(modelutil As modelutil) As Boolean
 
'Try to access model tags. If not connected to a server this will throw an error.
On Error GoTo ErrorHandler
Call modelutil.tags
IsConnected = True
Exit Function
 
ErrorHandler:
IsConnected = False
 
End Function
 
Private Function ConnectServer(comsolutil As comsolutil, modelutil As modelutil)
 
On Error GoTo ErrorHandler
Call modelutil.connect
If Not comsolutil.isGraphicsServer() Then
    MsgBox prompt:="The running COMSOL Multiphysics Server is not a graphics server. Exporting results will not work.", Buttons:=vbOKOnly, Title:="COMSOL"
End If
Exit Function
 
ErrorHandler:
 
Call comsolutil.TimeOuthandler(True)
Call comsolutil.StartComsolServer(True)
Call modelutil.connect
 
End Function
 
Private Function ContainsTag(tags() As String, tag As String) As Boolean
 
ContainsTag = False
If (UBound(Filter(tags, tag)) > -1) Then
    ContainsTag = True
End If
 
End Function

6. After inputting the code, we click on the Solve button. This executes the VBA script defined in the macro and creates the model based on the shapes in the Excel workbook. The model is solved and the graphics are inserted into the worksheet.

If the SimulationRegion shape is changed and the HeatSource shape is moved to another location inside the SimulationRegion, the model and results will be different.

It is easy to imagine how we can control and program this model based on other shapes, charts, and data in an Excel workbook. It is also possible to extract numerical results from the COMSOL Multiphysics model and generate Excel workbook content such as for reporting purposes, for example.

This blog post just scratches the surface with regard to what you can do using VBA and Excel® spreadsheet software. As a user, you have access to the entire COMSOL API, which gives access to all model settings and parameters. This makes it possible for you to define any type of model and extracts its data after having solved it using COMSOL Multiphysics.

Microsoft, Excel, and Visual Basic are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries.

Oracle and Java are registered trademarks of Oracle and/or its affiliates.

Using Spreadsheets for Handling and Storing Data

We often use spreadsheets to store numerical data originating from various sources. Since spreadsheet tools, such as Excel®, are used by most everyone in an organization, the data can be collected, stored, and transferred between people and departments without special regard for programs that must be used to process and utilize it. The data may originally have been obtained from online sources, in-house or external databases imported from other file formats, or simply entered directly into the spreadsheet when the measurement was obtained.

Spreadsheets are perfect for handling data, since you can easily sort and filter it. You are also able to validate the data by visualizing it graphically before using it in your models. While spreadsheets are geared more towards handling a variety of data sources, COMSOL Multiphysics® allows you to enter material data either directly in your models or in user-created material libraries that can be used by many models.

LiveLink™ for Excel®

When we introduced LiveLink™ for Excel®, we opened up the possibilities for collaboration across teams and departments. Now, your own or your colleague’s model data can be edited immediately in Excel®, and these edits can then be transferred back to COMSOL Multiphysics simply by pressing a button.

LiveLink™ for Excel® also includes a few features for exporting spreadsheet data into COMSOL software material data files, which can be used directly for subsequent modeling. The material data can even depend on field values, such as pressure and temperature.

Exporting Data

As mentioned previously, data can come from many sources. Here I’ll show an example using some data from Wikipedia. It’s from a table that contains values for the density of water for different temperatures, listed in descending order.

We copy and paste the data directly into Excel® and it’s ready for exporting into a COMSOL Material Database file.

Used with permission from Microsoft.

Now, we have to specify both where the field variable (temperature) and the property (density) are defined in the spreadsheet as well as what their units are. In COMSOL Multiphysics, you can define your data in almost any combination of units, but it’s important to specify which units you are using when you import the data. You do this by first clicking on the Settings button.

Settings button.

A large dialog box will open that is used to define the data ranges for the inputs. The field variable and material properties are defined on two different tabs in the dialog box, as you can see below.

Field Dependent Data tab in the Settings window.

Material Properties tab in the Settings window.

Finally, we are ready to export the data and click “OK”. We export the data by clicking on the “New” or “Append” buttons where we can also provide a file name for the Material Library. The next time we start up COMSOL Multiphysics and open the Material Browser, we’ll see the new library in the list of Material Libraries, ready for use.

Fitting Expressions to Data

When you import data using the method shown above, the data is interpolated automatically by COMSOL Multiphysics when solving the model. This is vital when the data varies a lot and an analytical expression cannot be fitted to the data.

Next up, I’ll show you a simple example using the thermal conductivity of copper’s dependency on temperature, using data from this source. Since there is only a small amount of data, the easiest way to import the values for copper is simply to write them in the spreadsheet. I then plot the data as a scatter plot, which allows me to fit a second order polynomial to the data. Since there are only three data points, I achieve a perfect fit, which looks reasonable in the given data range. Extrapolating outside the range can, however, be very dangerous.

Used with permission from Microsoft.

The following fitted polynomial can be used directly from within COMSOL Multiphysics:

where is the thermal conductivity of copper and is the temperature in Celsius. The easiest way to use this expression in COMSOL Multiphysics is to define some expressions for these two variables.

COMSOL Multiphysics will then automatically interpret these expressions and symbolically calculate any derivatives that may be needed during the solution process. The idea of being able to enter expressions anywhere a setting can be defined in the COMSOL user interface is important since it allows you to customize the built-in models and parameter data without having to resort to writing external libraries.

Additional Resources

• Archived Webinar: LiveLink™ for Excel® Streamlines Simulation in COMSOL Multiphysics®
• Video Tutorial: Importing Excel® Data into a COMSOL® Model
• Blog posts:
  • Extend Your Modeling Capacity with LiveLink™ for Excel®
  • How Spreadsheets Are Used in Engineering

Excel is a registered trademark of Microsoft Corporation in the United States and/or other countries.

And a great piece of news is that all current subscription holders of COMSOL Multiphysics will get it for free!

The Excel® ribbon contains a COMSOL Multiphysics tab and specialized toolbar for changing parameter values, meshing or running a simulation.

What can LiveLink™ for Excel® do for you?

LiveLink™ for Excel® will let you immediately access variables and parameter values in Excel that have been previously modeled in COMSOL. Changing them on-the-fly in Excel automatically synchronizes them to your COMSOL model, and you can even run the meshing and solving from the spreadsheet environment.

As noted in the previous blog post, one major advantage with making COMSOL “Excel-friendly” is that the COMSOL user can now communicate far more effectively with other engineers and scientists, and operators, in his or her organization. Rather than having to send Excel files back and forth within your organization, and converting them to text files to get them in and out of COMSOL, the workflow is streamlined by the integration provided by LiveLink™ for Excel®.

No More “Back and Forth”

One scenario is that the simulations engineer provides a custom model that the Excel user can then utilize to collate by controlling a select and familiar set of input data, calibrate and optimize the material properties they are working with. No need for sending files back and forth anymore. LiveLink™ for Excel® provides an interactive COMSOL graphics window that updates immediately when the “Solve” button is clicked in Excel’s COMSOL toolbar. And when the final report is to be presented, the corresponding COMSOL 3D images can be embedded into the spreadsheet with a single click of the mouse.

Excel is a registered trademark of Microsoft Corporation.

Using Spreadsheets to Find the Answer

Take this structural mechanics example of a rubber part. What happens when you pull on it; how much does it stretch, when does it weaken, when does it break…? What would the physical model for stretching the rubber part be? When utilizing spreadsheets to figure out the answer to this, one would start by running experiments to see how the part reacts to different scenarios. These are then stored in the spreadsheet where they can be analyzed, and maybe parameters like material properties be extracted, often as an averaged value.

But, what is the optimal design of this component? Up until now, we’ve been working within the Excel environment, but in order to find out what the best design would be, each scenario needs to be solved for and compared to the experiment.

Cue: The Simulations Engineer

He or she is the go-to person for building a useful model. The engineer receives the Excel file with the material property data from his colleague and imports these into COMSOL Multiphysics. Interpolation functions in the software allow for better and more localized determination of the material property, and these are used to model the different scenarios.

The results from the simulations can then be given in a table, which can be further exported to Excel, and the engineer can now send the file back to his colleague who set up the different scenarios. The COMSOL software results are then compared to the original scenarios in Excel to see how these values compare to the values for the variables in the initial studies.

As far as we’ve seen, spreadsheets are mostly used for mechanical, magnetic, and chemical applications. Experiment is often required to provide the material data for materials, as well chemical reaction kinetics. But, if you work in another area that uses Excel as part of the simulation process, tell us about it in the comments section below!

Spreadsheets, a Widely Used Application

One of the great aspects of incorporating spreadsheets into the world of multiphysics modeling is that someone within the organization can enter data into Excel (a widely used application) and then use that in a simulation. Conversely, that simulations engineer can later export the results data into a spreadsheet format and send that back to the experimentalist — who can then use the results from the simulation in a familiar environment. The downside is, of course, that because these scenarios are run manually, and the processes are separated across different employees, it can take weeks or months to run through the project workflow. Wouldn’t it be great if at least parts of this process could be automated? Food for thought.