Aeroacoustics Simulation User Guide
If you are wondering how to run an aeroacoustics simulation within bramble, welcome! Were here to guide you through the fascinating process of predicting broadband noise using state-of-the-art computational methods. Our journey begins with a RANS solve in OpenFOAM, setting the foundation for our acoustic analysis. From there, we’ll harness the power of the Fast Random Particle Mesh (FRPM) method to generate synthetic turbulent velocity fields, creating our aeroacoustics mesh from a RANS ‘donor’ attitude. Finally, we’ll bring it all together using Zenotech’s DGCAA aeroacoustic solver to reveal the acoustic characteristics of your design.
This guide outline the following new features:
- Setting up: Template Case
- Setting up: Model Viewer
- Run an aeroacoustic simulation
- CFD checks
- View results
How to run an aeroacoustics simulation
First Run an acoustic case
To start an acoustic solve, it is required to have a completed OpenFOAM RANS case, acting as a ‘donor’.
Please be aware only 1 RANS attitude is allowed within one Run, but multiple attitudes can be set.
To do this, we will use a Map to add new attitudes and create template cases to change settings
Step 1
Step 2
Create a template case
Most acoustic settings can be set from the new Acoustics tab in the template case.
Mesh Settings:
- ZCFD Domain
- ZCFD Refinement Boxes
- ZCFD Mesh Refinement
Solve Settings:
- FRPM
- Simulation Settings
PostPro:
- Export Microphones
- Export Iso-Volumes
- Export Movies
An acoustic case will also take these parameters from the Domain tab.
- Velocity
- Temperature
- Location In Mesh
- Domain
Template case settings
Please ensure you configure your template case with these essential settings:
FRPMs
- Regions of FRPM source generation
- Set up FRPM boxes by defining the translation (x, y, z), rotation (x, y, z) and length (x, y, z)
Refinement Boxes
- Regions of increased refinement for the acoustic mesh
- Provide the refinement level, minimum bounds (x, y, z) and maximum bounds (x, y, z)
Domain
- Set the acoustic mesh domain
- Provide the base point (x, y, z) and the lengths (x, y, z)
STL Refinement
-
Target cell size for the geometry in the acoustic mesh
Global Spacing
-
Largest cell size in the mesh
Sponge Layer Damping:
- Apply damping in regions approaching the farfield
Distance:
- Distance from farfield where damping starts to apply
Factor:
- The sponge layer damping factor
Simulation Order
CFL number:
- Courant-Friedrichs-Lewy number which controls the local pseudo time-step
Microphones
-
Acoustic Data will be measured at the given point, which will be processed after the simulation.
Isovolumes
- Set a lower and upper bounds with a given field to reveal the field volume with the geometry.
Movies
- Slice in x, y or z axes from the start to end positions at the given timestep.
Model viewer with acoustics
Step 1.
Select Acoustic in Additional Data Types to show aeroacoustics options.
FRPM Domains + zMesh Refinement Boxes
FRPM Domains
Aeroacoustic simulation checks
Pre-checks
-
Check the theoretical maximum frequency allowed by cell sizes
-
Acoustic mesh plots
-
FRPM plots
-
Microphone plots
Post-checks
-
Check for end time based on the desired minimum frequency of the case.
-
Check for the theoretical maximum frequency based on timesteps, and compare against the desired maximum frequency.
Aeroacoustic simulation solve results
Step 1.
Just select the attitudes from the table and then you will find the post-pros are available in the Results page once generated.
Step 2.
Step 3.
Then, select a graph from the Available Graphs dropdown, this can be either:
- Sound Pressure Level (SPL)
- Power Spectral Density (PSD)
Aeroacoustics post processing
Isovolume Plots
- Plot a volume with field values between a lower and upper bound
Movies
- Movies of slices across the x, y and z axes of the geometry.
- Acoustic Pressure
- Velocity (x, y, z)
Visit out Aeroacoustics page to discover more