Week 11- Broadband Noise modelling over Ahmed body
Aim: To study acoustic behavior of flow over an Ahmed Body
Ahmed's body is very much useful in predicting the most aerodynamic features that act on the automobile. The Ahmed body is a model very useful in the automotive industry for validating simulation tools. The Ahmed body shape is a simple model while maintaining car-like geometry features. This is a bluff body though we can't be able to predict the flow separation effects in a useful way. Many factors affect the Drag forces Viscosity, velocity, and shape of the body. So to study and perform experiments on the behavior of air on Automobiles Ahmed's body is developed. The real-world simulations are performed on the Ahmed body it is a similar replica of the cars. As it is difficult to perform simulations on Realworld cars In the late 80's Ahmed body is developed. Advancements in CFD led to Acoustic modeling. It is a generic car model to validate wind tunnel tests.
Case Set-up & Boundary Conditions:
Domain:
Mesh:
By providing a body of influence around the Ahmed Body with a size of 35 mm and providing inflation around the Ahmed Body and on the road for capturing the acoustic details.
A total cell count of 4 Lakh was created for the simulation.
Boundary Conditions.
Pressure Based Solvae steady-state solver.
energy equations are turned on and the viscous model is K-e realizable
Inlet is velocity inlet at 31 m/s
The outlet is a pressure outlet at 0 gauge Pressure.
Symmetry plan is provided to the side so the enclosure and wall with no-slip for the car body
The road is given with moving wall BC with a translational velocity of 31 m/s.
First, run the simulation for 300 iterations, and then Broadband Noise Modelling is turned on.
Results:
Residuals, Cd & Cl plots are shown for convergence.
The Numerical Value of Cd & Cl were computed as 0.15408133 & 0.15242997 respectively.
Contours of Acoustic Analysis.
Noise can be seen to produced atmost in the wake region.
Conclusions:
Noise has mainly been produced due to wake region & boundary layer interactions.
Any sudden change in the Area of the body is also seen to aid to the noise generated.