Backward facing step

Table of Contents

• Overview
• Mesh
• Boundary conditions
  • Common fields
  • Turbulence fields
    • kOmega SST
• Results

Overview

• Solver: simpleFoam
• Experimental case described by Driver and Seegmiller [15]
• CFD case based on https://turbmodels.larc.nasa.gov/backstep_val.html
• Reynolds number based on the step height of \( Re_h \) 36000
• Reattachment at 6.26+-0.1 x/h
• $FOAM_TUTORIALS/incompressible/simpleFoam/backwardFacingStep2D

Case description

Mesh

• 2D structured mesh created using blockMesh

Mesh

Close-up around the step

Boundary conditions

• \( U \) 44.2 m/s
• \( h \) 1.27 cm

Common fields

Velocity: U

Patch	condition	value
Inlet	fixedValue	44.2 m/s in x
Outlet	zeroGradient
Walls	noSlip

Pressure: p

Patch	condition	value
Inlet	zeroGradient
Outlet	fixedValue	0 Pa (static)
Walls	zeroGradient

Turbulence fields

• turbulence model: k-omega Shear Stress Transport (SST)

Turbulence viscosity: nut

Patch	condition	value
Inlet	calculated
Outlet	calculated
Walls	nutUSpaldingWallFunction

kOmega SST

Turbulence kinetic energy: k

Patch	condition	value
Inlet	fixedValue	based on 0.061% intensity
Outlet	zeroGradient
Walls	kqRWallFunction

Turbulence specific dissipation rate: omega

Patch	condition	value
Inlet	fixedValue	based on nut/nu = 0.009
Outlet	zeroGradient
Walls	omegaWallFunction

Results

Predictions are comapared against the measurements by Driver and Seegmiller [15] below

Skin friction	Pressure coefficient - lower
	Shear stress
	Shear stress

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