CFD analysis of the ahmed body using ANSYS FLUENT
The Ahmed Body is a simplified car, used in automotive field to investigate the flow
analysis and find the wake flow around the body. Its shape is simple enough to allow for accurate flow simulation but retains some important practical features relevant to automobile bodies. This model describes how to calculate the turbulent flow field around a simple car-like geometry using the Turbulent Flow, k-epsilon interface.
During the analysis of ahmed body, following steps are taken in the same order:
1. Geometry
2. Meshing
3. Setup
4. Solution
5. Result
Analysis of flow over an ahmed body in general mesh:
Geometry:
The enclosure around the ahmed body has been created to analyze the air flow around the ahmed body. Therefore, the geometry of ahmed body is also suppressed for physics.
Meshing:
No. of elements = 83886
Setup:
General: Density based solver
Steady state condition
Model: Energy
K-epsilon
Material: Fluid-air
Cell zone condition: Enclosure-fluid
Boundary condition: Inlet velocity = 50m/s
Symmetry - symmetry
Wall - wall
Outlet - pressure outlet
Initialization: Hybrid
Solution:
A cut plane is created through the center of the ahmed body to observe the velocity flow around the ahmed body. The calculation runs for 1000 iterations.
Result:
Velocity contour:
Pressure contour:
Analysis of flow over an ahmed body in refined mesh:
Geometry:
The enclosure around the ahmed body has been created to analyze the air flow around the ahmed body. Therefore, the geometry of ahmed body is also suppressed for physics.
Here, another enclosure is created inside the first enclosure.
Case 1:
Meshing:
No. of elements = 251190
In this case, we are adding 5 inflation layers to the geometry.
Setup:
General: Density based solver
Steady state condition
Model: Energy
K-epsilon
Material: Fluid-air
Cell zone condition: Enclosure-fluid
Boundary condition: Inlet velocity = 50m/s
Symmetry - symmetry
Wall - wall
Outlet - pressure outlet
Initialization: Hybrid
Solution:
A cut plane is created through the center of the ahmed body to observe the velocity flow around the ahmed body. The calculation runs for 1600 iterations.
Result:
Velocity contour:
Pressure contour:
Velocity vectors:
Case 2:
Meshing:
No. of elements = 326978
In this case, we are adding 5 inflation layers to the geometry.
Setup:
General: Density based solver
Steady state condition
Model: Energy
K-epsilon
Material: Fluid-air
Cell zone condition: Enclosure-fluid
Boundary condition: Inlet velocity = 50m/s
Symmetry - symmetry
Wall - wall
Outlet - pressure outlet
Initialization: Hybrid
Solution:
A cut plane is created through the center of the ahmed body to observe the velocity flow around the ahmed body. The calculation runs for 1000 iterations.
Result:
Velocity contour:
Pressure contour:
Velocity vectors:
Case 3:
Meshing:
No. of elements = 509084
In this case, we are adding 5 inflation layers to the geometry.
Setup:
General: Density based solver
Steady state condition
Model: Energy
K-epsilon
Material: Fluid-air
Cell zone condition: Enclosure-fluid
Boundary condition: Inlet velocity = 50m/s
Symmetry - symmetry
Wall - wall
Outlet - pressure outlet
Initialization: Hybrid
Solution:
A cut plane is created through the center of the ahmed body to observe the velocity flow around the ahmed body. The calculation runs for 1000 iterations.
Result:
Velocity contour:
Pressure contour:
Velocity vectors:
As the number of elements in the mesh increases, the accuracy of the results increases simultaneously. At some areas, there are negative pressures and velocities. This occurs where there is no air flow and the velocity of the boundary layer is zero.