Using SOLIDWORKS Flow Simulation for Noise Prediction

You’ve seen us here at CADimensions talk about how cool SOLIDWORKS Flow Simulation is and how we’ve used it to simulate a wide variety of problems, from sizing a fuse to cooling a room with a box fan. But did you know that Flow Simulation also has the ability to predict how loud your model will be?

Have you ever been driving down the highway and accidentally opened one of your windows and heard that unpleasant buffering sound? It actually has a name: Helmholtz Resonance. The air in the car interacts with the air moving past the open window and it creates a swirling vortex between the two different masses of fluids. To take a look at this phenomenon, I’ve got a rough outline of a truck model here in SOLIDWORKS:

Truck Model

The blue arrow in the image above is the air velocity I’ve applied in SOLIDWORKS Flow Simulation, which was taken to be 45 MPH for this example. Since we’re just looking at the interaction of the air over the truck model, all I needed to do was mesh and run our flow study and look at the velocity plots to make sure we’re on the right track.

Flow Velocity

That looks like I’m expecting, so now let’s dive deeper into the noise issue we might see here. In SOLIDWORKS Flow Simulation, there is a parameter we can ask for called Acoustic Power Level:

Power Level

Which will measure the sound level in decibels throughout the flow field. In this example, we can see the noise level in the cabin is somewhere between 50-60 dB right around the middle of the cabin. That’s not too loud, but how does it compare to the windows closed? I ran this study again, but this time I closed up the window on the driver's side so the air wouldn’t interact with the cabin. One of the neat new features in SW Flow Simulation is the ability to compare plots across different Flow Simulation projects as a difference plot so you can see exactly where things change between projects. To access this feature, right click on your Results folder and hit “Compare”, then set up your comparison as normal. Here, I’m comparing the Cut Plot I set up between the open-door configuration and the closed-door configuration:

Flow Simulation compare

My closed-door configuration is my “Control” group, and my open window configuration is the difference between that data set and the Control Group. If we take a deeper look at the open window configuration, we can see it’s over 30 dB louder in some spots!

Difference Plot

The difference plot is a great new tool introduced in SW Flow Simulation 2024 and makes direct comparison like this easier than ever. We’d love to see how you are using SW Flow Simulation in your projects, so give us a call and let us know!