Multilayer Transducer Operating in a Water Load

In this tutorial, you will learn how to set up a simple 2D transducer model with a backing and matching layer and extract outputs such as impedance, directivity plots and transmit sensitivities.

You will learn:

• The Basic Simulation Workflow in OnScale Designer
• How to set up a 2D axi-symmetric model
• How to create a simple geometry
• How to simulate piezoelectric materials
• How to display and post-process your results
• How to use Extrapolation tool

Model Definition

Characteristics of the model

Material Data

Note: Material Data in OnScale are generally defined using the bulk velocity and the shear velocity parameters instead of the more traditional Elastic Modulus and Poisson's Ratio. You can check this page if you want to understand the relation between those parameters.

Why This Simulation?

Transducer sensors often are constructed using multiple layers to try maximize key performance indicators (KPIs) such as bandwidth. Common ways are to introduce a heavy backing layer and matching layers.

The full design is often tested under specific environmental conditions to measure real-world performance to validate the design.

Important: Make Sure that you select the correct Axis of Symmetry from the beginning in the New project window because it is impossible to change afterwards in the designer mode.

The Simulation Process

Let's go through the step by step tutorial and see how to simulate this in OnScale!

Step 1 - Create a New Project

1. Click New Project to open the New Project window.
2. Name the project Transducer_2D.
3. If desired, change the save location and/or project file name by clicking … beside Project File.
4. For Analysis, select Mechanical Dynamic.

5. For Model Type, select 2D Axi-Symmetric Model (Y).

   Warning: You can't change the axis of symmetry later, so be sure to select Y here and not X!

6. Select the Advanced checkbox.
7. For Distance, select mm.
8. Click OK.

Step 2 - Add the Materials from the Material DB

First we will add the materials needed from the material database. We will use pmt3 and water in this tutorial.

1. Click Project Materials to open the database
2. Expand Fluid and add watr to the Project Materials (double click)
3. Expand Epoxy and add hard and back20
4. Expand Piezoelectric and add pmt3
5. Expand pmt3 and change the poling direction to Y+
6. Click Done

Step 3 - Create Basic Geometry Shapes

Note: After making changes to X and Y right click the workspace and select Reset View

1. Click Rectangle
2. Change Material to watr
3. Set End (mm): X (mm) = 15
4. Set End (mm): Y (mm) = 15

1. Right click primitive_1 and select Duplicate Selection
2. Click primitive_2
3. Change material from watr to back20
4. Set End (mm): X(mm) = 10
5. Set End (mm): Y(mm) = 5

1. Right click primitive_2 and select Duplicate Selection
2. Click primitive_3
3. Change material from back20 to pmt3
4. Set Begin (mm): Y(mm) = 5
5. Set End (mm): Y(mm) = 7

1. Right click primitive_3 and select Duplicate Selection
2. Click primitive_4
3. Change material from pmt3 to hard
4. Set Begin (mm): Y(mm) = 7
5. Set End (mm): Y(mm) = 7.634

Step 4 - Define a Time Function

We will now add a Ricker Wavelet drive function for later use as out loads require a time function be set.

1. Click '+' to open the Define Input Time function window
2. Change to Ricker Wavelet
3. Click Insert to close the window. A record called timefunc_1 will be added to the window

Step 5 - Choose the right Mesh Size

We will now change the mesh settings to use 15 elements per wavelength

1. Select Configuration
2. Set Definitions to Wavelength Based
3. Set Elements Per Wavelength to 15

Step 6 - Create the two electrodes

We'll create two loads to represent the two electrodes. We'll drive the top electrode and ground the bottom electrode.

Create Electrode 1

1. In the Model Tree, expand Boundary Conditions and then, beside Loads, click +.
2. For Creation Mode, select Geometry Interface.
3. For Geometry, select primitive_3 (pmt3) or click it in the model.
4. For Interfacing Item, select primitive_4 (hard).
5. For Load Type, select Voltage.
6. For Termination, select timefunc_1.
7. Click Create Load.

Create Electrode 2

The Load Definition window should still be open.

1. For Geometry, select primitive_3 (pmt3) or click it in the model.
2. For Interfacing Item, select primitive_2 (back20).
3. For Termination, select Ground.
4. Click Create Load.

Step 7 - Define the Boundary Conditions

We will need to change the X minimum boundary condition to Symmetry as this model is symmetrical across that axis.

1. Click Domain Boundaries
2. Change the X Minimum boundary condition to Symmetry. All others will be absorbing
3. Change remaining boundary conditions to Absorbing

Step 8 - Define the Analysis Simulation Time

We will now set the model simulation time to be 5e-5 seconds

1. Click Analysis
2. Change Simulation Run Time (s) to 2e-05

Step 9 - Define the Output Results

We will now define 1 output, a extrapolation boundary to allow us to generate outputs using the Extrapolation tool

Output Result 1: Extrapolation Data

1. Click '+' this will create a new output
2. Change Output Type to  Extrapolation Data
3. Change Cutting Plane to Y
4. Change Cutting Point (mm) to 8.5

Step 10 - Run on the Cloud

At this point the model is completely set up and it can now be run on the cloud.

1. Click Run on Cloud
2. The option to rename your job. This is how it will appear in the storage
3. Click Estimate
4. Click Run

How to Get the Simulation Results?

The simulation results will need to be downloaded from the cloud storage in order to analyse the results in the post processor. More experience users may also be able to process Time Histories in Review.

1. Click Storage this opens the window shown above
2. Locate the job
3. Click Download
4. Click Download all

Choose an appropriate save location when the file explorer pops up and click Select Folder to close the window.

Step 11 - Check the Simulation Results

Switch to the Post Processor

1. Click this icon to access the Post Processor

Open Results, Calculate and Plot Conductance

1. In the File Explorer, Locate the Flex History File (.flxhst) & double Left Click
2. Select the Charge record on load1
3. Select Real/Imag from the drop down menu
4. Click Admittance
5. Two new records will appear, double click on Admt:load1.re to plot
6. The real part of Admittance (Conductance) will be plotted allowing you to analyze the transducer performance in greater detail.

Using the Extrapolation Tool

1. In the Tools tab, Select Extrapolation Tool
2. Click Open
3. Select the downloaded extrapolation file (.flxext)
4. Click Open

1. You will be prompted to open the flxmdl file. Click Yes

Directivity (Radial Plot)

1. Select Radial Plot
2. Change Y1 origin of directivity to 7.634e-3 m
3. Change Radius (m) to 1
4. Change Angular Spread to 180
5. Change No. of points on line to 181
6. Change Propagation Vector to Y
7. Change Drive Frequency (Hz) to 1e6
8. Click Start to calculate

Radial Plot Result

Transmit Sensitivity (TVR)

1. Select TVR Calculation
2. Select User Defined
3. Alter Y reference value to 7.634e-3 m
4. Change Propagation direction to Y
5. Click Start to calculate

TVR Response

Try For Yourself

Now that we have introduced you to the tutorial try have a play around with some of the settings, add some other outputs, or use this model as a starting point for your own.