www.airshaper.com

Solvers - incrompressible

Advanced course

Legal notes:- This offering is not approved or endorsed by OpenCFD Limited, the producer of the OpenFOAM software and owner of the OpenFOAM® and OpenCFD® trade marks. OpenFOAM® is a registered trade mark of

OpenCFD Limited, a wholly owned subsidiary of the ESI Group.- This content was made in 2014 and may contain incorrect or outdated information. The reader is solely responsible for his or her use of this information and AirShaper cannot be held liable for any damages.

www.airshaper.com

Content

• Solver types

• Model properties– Transport properties

– Turbulence properties

– RAS properties

• Boundary conditions

• Solver properties– fvSchemes

– fvSolution

– controlDict

www.airshaper.com

Solver types

Laminar Turbulent

Steady statesimpleFoam

(simulationType: laminar)

simpleFoam (simulationType:

RASModel)

Unsteady state (time dependent)

icoFoampisoFoam

pimpleFoam

web: http://www.openfoam.org/archive/1.7.0/docs/user/standard-solvers.php

www.airshaper.com

Solver types

• IcoFoam– Ico: incompressible

• simpleFoam– Semi-Implicit Method for Pressure Linked Equations– Web: http://en.wikipedia.org/wiki/SIMPLE_algorithm

• pisoFoam:– Pressure Implicit with Splitting of Operator– Web: http://en.wikipedia.org/wiki/PISO_algorithm

• pimpleFoam– merged piso-simple

www.airshaper.com

Solver types

• Next slides: example files based on simpleFoam solver

• Files can be reused for new geometries of the propeller case, without modification

www.airshaper.com

Model properties

• Transport properties

– Location: \constant\transportProperties

– simpleFoam:

• For incompressible flow: 𝜌 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡

• Therefore, only the kinematic viscosity is required

– Dynamic viscosity µ: 𝜏 = µ ∙𝜕𝑢

𝜕𝑦

– Kinematic viscosity ν: ν =µ

𝜌

• Consequence: pressure, force, torque, ... results need to be multiplied by the density to obtain the real value

www.airshaper.com

Model properties

• Turbulence properties

– Location: \constant\turbulenceProperties

– simpleFoam:

• works with the RASModel – Reynolds-Averaged Simulation

• Type of RASModel is defined under “RASProperties”

www.airshaper.com

Model properties

• RASProperties– Location: \constant\RASProperties

– Overview: http://www.openfoam.org/features/RAS.php

– Some examples:• laminar: dummy model for laminar flow• k-epsilon: most commonly used turbulence model• K-omega

– Chosen model has impact on required boundary parameters

www.airshaper.com

Boundary conditions

• Location: \0

• K: turbulent kinetic energy

• Epsilon: rate of dissipation of the turbulent energy

• Nut: turbulent viscosity

www.airshaper.com

Solver properties

• fvSchemes: schemes for the finite volume approach Time

derivative

gradient

interpolation

Flux calculation

Laplacian operator

Divergence (including

turbulence parameters)

Surface normal

gradient

www.airshaper.com

Solver properties

• fvSolution: settings for the iterative solver

Pressure

Velocity

Turbulence intensityDissipation

of turbulent energy

www.airshaper.com

Solver properties

• fvSolution: settings for the iterative solver

Reference pressure for the

domainRelaxation

factors

Required when domain is closed

www.airshaper.com

Boundary conditions

• controlDict(pseudo)

Time control

Solver type

Write control

Include extra output functions

Allow changes in control files

during execution