Finding the optimal solution to a design challenge almost always requires a complex coupling process. CoTherm, our coupling software, allows you to plan, control, and monitor multi-physics simulations for complex transient simulations like drive cycle scenarios. In order for advanced simulations to be worth your while, it is important to be familiar with the process and prerequisites so you can set yourself up for success. As we transition from discussing the importance of coupling as a whole to the necessity of accurate inputs, we will look at the specific things you must do well in CoTherm to get successful results from advanced simulations.

Moving Toward Advanced Simulations

Even the most common simulation scenarios can quickly become complex as you seek more robust results. One of the most common scenarios of this nature are transient drive cycles. To make the leap from simple simulations to complex coupling processes requires that you follow a few best practices. Simulating drive cycles allow teams to know how their vehicle will perform at different points during the driving cycle, including hill climbs or stop-and-go city driving cycles. Throughout each driving cycle, teams also consider the environmental effects that surround the vehicle. The combination of a transient drive cycle and the environmental factors is where the simulation turns complex. Using CoTherm, you can couple TAITherm and a CFD code to simulate a full transient drive cycle.

Follow Best Practices for Functional Results

Putting effort in early on, and adhering to best practices in model creation will pay dividends in your simulation results. If you are simulating a transient scenario, you will need to define the thermal mass effects, while still following the principals of a steady-state simulation. To ensure optimal simulation results, the models need to include:

1. Heat sources
2. Material properties
3. Proper meshing techniques

It’s important to keep in mind, the higher the fidelity in the inputs, the better the simulation results.

The 3 Steps to Better Models

Once your models are in place, you can set-up the simulation in CoTherm. We prefer using CoTherm because it enables complex coupling to be coordinated using a user-friendly GUI. There are three tasks you must perform adequately to obtain good results:

1. Import quality data

First, and most importantly—import your appropriate data from Excel as well as your base thermal and CFD models. Define the inputs from Excel, to tell CoTherm where to access the items it requires to perform the simulation. A drive cycle scenario will include exhaust flow, inlet temperature, and engine speed and time.

2. Simplify data to simulate faster

Choose to run either a low-pass filter or a critical frequency resource to simplify your inputs depending on the level of detail you need from the simulation. Applying a low-pass filter is less intensive and faster because you choose your desired frequency value early in the process, and CoTherm doesn’t have to analyze the model first to find the recommended value. The Critical Frequency Resource will tell you which low pass filter to run, but requires more detail and consequently, more time. This feature should be used to determine a low pass filter if your properties are well defined.

3. Characterize the Drive Cycle

At this point, your transient data is prepared and almost ready to be applied to the thermal model. Before applying the data to the model, select the steady state points that will be used to characterize the drive cycle. You can choose to characterize the points based on vehicle speed, exhaust rates or even fan speed. Define how many steady coupling points you need CoTherm to use to characterize the drive cycle. Be mindful that too many points will affect the simulation speed.

If you follow these three steps when building your drive cycle model in CoTherm, it will be able to deliver valuable simulation results. Knowing these pre-processing steps will prepare you to master advanced coupling simulations in the future.

Simulation is crucial to testing all types of scenarios, not just worst case. Reaching this level of analysis is much more efficient when you are proficient in the set-up process. As we continue the conversation around simulating complex scenarios, we will further discuss the specifics of modeling transient drive cycle simulations. Stay tuned for our upcoming blog on the next topic.