SimScale CAE Forum

Pressure Units change to Pa in incompressible flow simulations


#1

Pressure Units Change To Pascal

SimScale will now use real pressure units ‘Pascal’ (Pa) as a standard for all incompressible Flow Analysis Types. Before pressure was displayed in simulation setups and results as density-normalized pressure (m²/s²) which was not intuitive. This means that the following Analysis Types have undergone the changes detailed below.

  • Incompressible
  • Passive Scalar Transport
  • Convective Heat Transfer with Boussinesq approximation activated

This improvement was requested by many customers and will make the setup and interpretation of flow simulations faster, less error prone and more intuitive. Find detailed questions and answers on this change below.

What happens to existing simulation setups and runs?

  • All Simulation setups for the above stated Analysis Types are updated to incorporate the changes listed below.
  • All existing simulation runs and results will remain unchanged and continue to use the previous units for pressure i.e (m²/s²).
  • All new simulation runs and results will use pressure units of Pascals (Pa).

What are the changes ?

There are 5 main changes made to the stated Analysis Types. These are described in detail with illustrations as follows.

1- Materials:

The Materials section will now include a mandatory entry for density of the material in standard units of (kg/m³). This density value (a constant) will be used as a universal value for the simulation and for ‘Result Control’ items like ‘Forces and Moments’.

Fig.1 Materials now contain density value

Please Note:

  • All simulation setups where no density was specified will be updated with a density value of 1.0.
  • All simulation setups where a density value was specified in the ‘Result Control’ items (e.g Forces and Moments) will be updated with the corresponding density value under Materials.
2- Initial Conditions:

The ‘Initial conditions’ will now have the updated units for pressure of ‘Pascals’ (Pa).

Fig.2 Updated pressure units for Initial Conditions

3- Boundary Conditions:

All Boundary Conditions will now use the updated units for pressure of ‘Pascals’ (Pa). The figure below shows a standard ‘Pressure Outlet’ boundary condition as an example.

Fig.3 Updated pressure units for the ‘Pressure Outlet’ condition

4- Result Control Items:

The ‘Result Control’ items will no longer require the density value and will use the density as specified under ‘Materials’.

Please Note:

  • All simulation setups where a density value was previously specified in the ‘Result Control’ items (e.g Forces and Moments) will be updated with the corresponding density value under Materials.
5- Post-Processor-Results:

The results in the ‘Post-Processor’ will now use pressure units of ‘Pascals’ (Pa) for all new runs, while all existing runs will remain unchanged with pressure units as (m²/s²).

Please Note:

  • Downloaded result files for all ‘New’ runs are also updated with pressure units of ‘Pascals’ (Pa) and would show same results as SimScale in local ParaView.

Platform Update 02/2017
Step-by-Step Tutorial: Session 2
#2

#3