Project

Flow over a Backward Facing Step using CONVERGE CFD

Project Objectives:

(1) To simulate air flow through a Backward-facing step using CONVERGE Studio and Post-process using ParaView.

(2) To conduct a grid independent test and study the Pressure and Velocity contour.

Geometry:

length along x-axis = 0.27 m

length along y-axis = 0.02 m

length along z-axis = 0.025 m

Mesh Sizes:

mesh sizes were considered for the project -

Fixed embedding option was enabled at the top and bottom wall.

Boundary and Initial Conditions:

Base Mesh:

(1) 0.0008 m

Cell count = 9450

(2) 0.001 m

Cell count = 7429

(3) 0.002 m

Cell count = 2606

Velocity and Pressure Contour:

(1) 0.0008 m

(2) 0.001 m

(3) 0.002 m

Velocity profile at x=0.25 m

(1) 0.0008 m

(2) 0.001 m

(3) 0.002 m

As we can observe, finer mesh gives a smoother plot than compared to others.

Mass Flow Rate:

Glyph Plot:

Pressure plot along the x-direction:

Conclusion:

As the base mesh size is increased, the total cell count is increased.
The contours obtained are more smooth when a finer mesh is used for simulation. A coarse mesh can give results which can be hard to interpret.
The flow gets separated after the step as it can be seen from the velocity contour.
From the Glyph plot, it is seen that there is a region of recirculation just after the step. This happens due to the increase in pressure as there is sudden expansion in area and the flow separation.
Reason for flow separation - From the pressure plot shown above, pressure suddenly starts to increase after the step. So the pressure gradient becomes greater than zero. Hence, the potential energy of fluid increases and the kinetic energy reduces leading to deceleration of the fluid. This is the reason that flow is separated from the boundary layer.

Ship work like this
in your own course.