$FOAM_TUTORIALS/incompressible/boundaryFoam/boundaryWallFunctionsProfile

We calculate the flow with the kinematic viscosity ν which is changed to 1e-2, 1e-3, 1e-4, 1e-5, 1e-6, 1e-7, and 1e-8 (in m2/s), respectively, and from the results, get the dimensionless distance and the dimensionless velocity from the cell adjacent to the wall. Then we compare them with the Spalding's law. The dimensionless distance y^{+}, the dimensionless velocity u^{+}, and the Spalding's law are defined as follows.

- The dimensionless distance from wall:
- the dimensionless velocity:
- Spalding's law:

where u_{τ} is the wall friction velocity (= (wall shear stress/fluid density)1/2), y is the distance between the center of the cell adjacent to the wall and the wall, u is the flow velocity at the center of the cell adjacent to the wall, and ν is the kinematic viscosity. And, κ = 0.41 and E = 9.8 are used.

Periodic boundary conditions are set for the inflow region "front" and the outflow region "back", and no-slip wall conditions are set for the channel wall regions "lowerWall" and "upperWall". The mesh is created only in the Y direction and the calculation is performed as a 2-dimensional model.

The target mean velocity of 10 m/s for each kinematic viscosity is specified in the file constant/transportProperties as follows.

Ubar [0 1 -1 0 0 0 0] (10 0 0);

The meshes are as follows.

Meshes

The calculation result is as follows.

y+ vs. u+ (The circular marker is the calculated value and the line is the Spalding's law)

The calculated values are approximately consistent with the Spalding's law.

cp -r $FOAM_TUTORIALS/incompressible/boundaryFoam/boundaryWallFunctionsProfile boundaryWallFunctionsProfile

cd boundaryWallFunctionsProfile

blockMesh

echo "# yPlus vs uPlus" > yPlus_vs_uPlus

# Calculation with nu = 1e-2

sed "s/XXX/2/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.2

foamLog log.boundaryFoam.2

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-3

sed "s/XXX/3/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.3

foamLog log.boundaryFoam.3

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-4

sed "s/XXX/4/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.4

foamLog log.boundaryFoam.4

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-5

sed "s/XXX/5/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.5

foamLog log.boundaryFoam.5

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-6

sed "s/XXX/6/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.6

foamLog log.boundaryFoam.6

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-7

sed "s/XXX/7/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.7

foamLog log.boundaryFoam.7

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-8

sed "s/XXX/8/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.8

foamLog log.boundaryFoam.8

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

gnuplot

gnuplot>set grid

gnuplot>set xlabel "y+"

gnuplot>set ylabel "u+"

gnuplot>set key top left

gnuplot>set size 0.75, 0.75

gnuplot>set parametric

gnuplot># u+ range

gnuplot>set trange [0:35]

gnuplot># Spaldings law

gnuplot>k=0.41

gnuplot>E=9.8

gnuplot>f(t) = t + 1/E*(exp(k*t) - 1 - k*t*(1 + 0.5*k*t) - 1/6*k*t**3)

gnuplot>set logscale x

gnuplot>set format x "10^{%T}"

gnuplot>plot f(t),t title "Spalding" with lines linetype -1, "yPlus_vs_uPlus" title "OpenFOAM" with points lt 1 pt 6

cd boundaryWallFunctionsProfile

blockMesh

echo "# yPlus vs uPlus" > yPlus_vs_uPlus

# Calculation with nu = 1e-2

sed "s/XXX/2/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.2

foamLog log.boundaryFoam.2

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-3

sed "s/XXX/3/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.3

foamLog log.boundaryFoam.3

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-4

sed "s/XXX/4/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.4

foamLog log.boundaryFoam.4

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-5

sed "s/XXX/5/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.5

foamLog log.boundaryFoam.5

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-6

sed "s/XXX/6/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.6

foamLog log.boundaryFoam.6

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-7

sed "s/XXX/7/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.7

foamLog log.boundaryFoam.7

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

# Calculation with nu = 1e-8

sed "s/XXX/8/g" constant/transportProperties.template > constant/transportProperties

boundaryFoam > log.boundaryFoam.8

foamLog log.boundaryFoam.8

yPlus=`awk < logs/yPlus_0 'END{print $2}'`

uPlus=`awk < logs/uPlus_0 'END{print $2}'`

echo "$yPlus $uPlus" >> yPlus_vs_uPlus

rm -rf logs

gnuplot

gnuplot>set grid

gnuplot>set xlabel "y+"

gnuplot>set ylabel "u+"

gnuplot>set key top left

gnuplot>set size 0.75, 0.75

gnuplot>set parametric

gnuplot># u+ range

gnuplot>set trange [0:35]

gnuplot># Spaldings law

gnuplot>k=0.41

gnuplot>E=9.8

gnuplot>f(t) = t + 1/E*(exp(k*t) - 1 - k*t*(1 + 0.5*k*t) - 1/6*k*t**3)

gnuplot>set logscale x

gnuplot>set format x "10^{%T}"

gnuplot>plot f(t),t title "Spalding" with lines linetype -1, "yPlus_vs_uPlus" title "OpenFOAM" with points lt 1 pt 6

(y+, u+) are obtained from each calculation result with the foamLog utility.

10.61 seconds *Single, Inter(R) Core(TM) i7-2600 CPU @ 3.40GHz 3.40GHz

- OpenFOAMの壁関数, Fumiya Nozaki
- boundaryFoam:平行平板間の発達した境界層の壁関数プロファイル
- The Potential of Large Eddy Simulation for the Modeling of Wall Bounded Flows, p.81, Eugene de Villiers, 2006/7/25