Noise modelling over Ahmed body
Introduction
The Ahmed body is a very generic and simplified model of a car. It was first developed by Ahmed and hence the name Ahmed body. A lot of work has been done on the Ahmed body, both computationally and experimentally. A wide variety and range of data for the Ahmed body are present in the form of literature. For this reason, and its simplicity, the Ahmed body is used as a basic test case to validate CFD codes.
For more information of Ahemed body, y+ - please check the below article
External Flow over Ahemed Body
Broadband Noise modelling over Ahmed body
Meshing
Mesh settings are taken from the article mentioned above.
Set-up
- Steady state simulation
- Pressure based
- K-Omega SST viscous model
- Inlet boundary condition = 31m/s
- Symmetry plane used to simulate only half of the ahemed body
- Road = moving wall with velocity 31m/s
From Residuals point of view, the solution seems convereged.
The drag coefficient has also atained stability.
The lift coefficent though not stable, gives an approximate range of C_L, which is in between 0.47 to 0.49.
Velocity contours show a wake region behind the Ahmed body, this meanse that the flow is turbluent in nature in this region.
- Switch ON - Aucostics frrom the Model.
Create necessary conoturs.
Inference
- Noice is higher in the Leading Edge region where the geometry curves. We must remember that this curve was added in the model in the first place to make the flow streamlined and thus reduce Drag.
It is note worthy that, One has to choose his priorities carefully while modelling. Trying to change one parameter can have adverse effects on others. - Noice can be seen in the Trailing Edge section also, where the flow seperates and slowly turns into wake-Turbluent Region which again generates Noice.
- Considerable Noice is also generated due to Boundary layer phenomenon, this can be observed on the top part of the Ahmed body.