Some useful links about OpenFOAM [Always update]

This post is about how to calculate yPlus in OpenFOAM. For RANS Note that yPlusRAS calculates y* and not y+ 1. With wall function; · type ‘yPlusRAS’ for incompressible flow · type ‘yPlusRAS’ –compressible for compressible flow 2. Without wall function; · type wallShearStress if it is incompressible. If not, add " -compressible " flag · calculate manually: sqrt(wallShearStress/rho) * y/nu y = the distance to first cell from the wall nu = kinematic viscosity Be careful: You should use the cell center (height of the cell devided by two) for y For LES type ‘ yPlusLES’ Note: Y-star = rho*Cmu^0.25*sqrt(k)*y/mu y-plus = rho*sqrt(tau_w/rho_w)*y/mu Y-star is related to the turbulent kinetic energy and y-plus to the wall shear ...

wallShearStress in OpenFOAM

May 08, 2017

The wall shear stress, , is given by: Where is the dynamic viscosity, is the flow velocity parallel to the wall and is the distance to the wall. The SI unit of wall shear stress is pascal ( ), which is identical to . The skin friction coefficient, , is defined by: Where is the local wall shear stress , is the fluid density and is the free-stream velocity (usually taken ouside of the boundary layer or at the inlet). Incompressible Flow Laminar In OpenFOAM, wallShearStress usually is in "kinematic pressure", namely in "m2/s2". It doesn't take into account the density of the fluid. So, you should multiply by rho to reach tau. tau = (wallShearStress) * rho or with wallGradU utility tau = (wallGradU) * mu You can use the Calculator filter in ParaView to multiply the "wallShearStress" field by the density value. Turbulence Compressible Flo...

Parallel run with Fluent on a HPC cluster

January 31, 2018

Fluent Fluent is used for computational fluid dynamics (CFD). Fluent Journal Script A Fluent journal script (e.g. " journalfile.jou ") might look like this: file/read-case-data aircraft.cas it 1000 wd "aircraft.dat" Submitting a Batch Fluent Job to Slurm With the correct journal file set up, the final step is to submit this to the Slurm queuing system. #!/bin/sh #SBATCH -n 1 # 1 core #SBATCH -t 1-03:00:00 # 1 day and 3 hours #SBATCH -p compute # parition name #SBATCH -J fluent_batch # sensible name for the job # load the relevant module files. NB: if unsure about # what you need, please contact ops source /etc/profile.d/modules.sh module load apps fluent # run slurm in batch on the allocated node(s) # the '-t4' specifies 4 cores (academic licensing) fluent 2d -g -t4 -i journalfile.jou > outputfile.out The fluent options in the above Slurm script are: 2d the fluent version used -g no graphical environment -i journ...

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