The open source CFD toolbox
Bump (2D)

Case description

# Mesh

• 2D structured mesh created using blockMesh
• bump described

$y(x) = \begin{cases} 0.05 [\sin(\pi \frac{x}{0.9}-\frac{\pi}{3})]^4, & 0.3 \le x \le 1.2, \\ 0 , & 0 \le x \lt 0.3 \, \text{and} \, 1.2 \lt x \le 1.5. \end{cases}$

• this has been set in the blockMeshDict using a codeStream
Close-up around the bump

# Boundary conditions

• $$U$$ based on a Mach number of 0.2. Mach number, $$Ma$$, is defined as:

$Ma = \sqrt{\gamma R T}$

where $$\gamma$$ is the ratio of specific heats, $$R$$ the gas constant and $$T$$ the temperarture. Using values for air at 300K, the inflow velocity is given as:

$U = 0.2 Ma = 0.2 \sqrt{1.4 \times 287 \times 300} = 69.44 m/s$

• The laminar viscosity is derived from the Reynolds number, i.e.

$\nu_\infty = \frac{|\u| L}{Re} = \frac{69.44 \times 1}{3 \times 10^6} = 2.31 \times 10^{-5} m^2/s$

## Common fields

Velocity: U

Patch condition value
Inlet fixedValue 69.44 m/s in x
Bump noSlip
Walls symmetryPlane

Pressure: p

Patch condition value
Outlet fixedValue 0 Pa (static)
Walls symmetryPlane

## Turbulence fields

Turbulence viscosity: nut

Patch condition value
Inlet calculated
Outlet calculated
Bump nutUSpaldingWallFunction
Walls symmetryPlane

### Spalart-Allmaras

Modified turbulence viscosity: nuTilda

Patch condition value
Inlet fixedValue based on $$3 \nu_\infty$$
Bump fixedValue 0
Walls symmetryPlane

# Results

The NASA Turbulence Modelling Resource employs a code comparison to show that the FUN3D and CFL3D codes produce equivalent results for this case. OpenFOAM and CFL3D results are presented in the following series of images, showing that OpenFOAM results compare very favourably.

 Normalised turbulence viscosity Skin friction Pressure coefficient

 Would you like to suggest an improvement to this page? Create an issue