Week 3 - External flow simulation over an Ahmed body.

• External flow simulation over an Ahmed body.
• Objective - To perform external flow simulation over an Ahmed body ,by considering the only half body.
• Also Run the simulation for the velocity of 25 m/sec with the default air properties in fluent.
• Describe Ahmed's body and its importance.

• Explain the reason for the negative pressure in the wake region.

• Explain the significance of the point of separation.

• Ahmed's body and its importance.
• Ahmed body is a generic body (simplified car model).
• The airflow around the Ahmed body captures the essential flow characteristics around a car.
• Because the Ahmed body is easy to model, various properties such as turbulence, drag coefficient, wake area, lift, magnitude of velocity in different regions of the car, magnitude of pressure around the car, etc. can be examined.
• A wake is a region of turbulent flow downstream of solids moving through a liquid caused by the flow of liquid around the object.
• Sharp corners usually produce segregation flows, but they are not the only cause of segregation. For example, a flow over a cylinder can create a large area of ​​separation flow downstream of the cylinder. This area is called wake.

• Procedure for Ahmed body setup
• Ahmed body model

• Creating an enclosure across Ahmed body

• Creating a plane section on the origin

• Simulating with a default mesh size of Ansys-Fluent

• Simulation procedure

Setup

Boundaries

inlet - inlet

outlet - pressure outlet

wall-car - wall (no-slip)

back, top and bottom - symmetry

symmetry zplane - symmetry

A separate boundary was created for the symmetry plane to make post processing easier.

Reference Values

The most important values here are: Area, Density, Length and Velocity.

• Simulation of the base setup
• Velocity contour