4. Recap

In this workshop we added a geometry to an atmospheric boundary layer simulation, set up its refinements and mesh, exported the pressure data needed to compute the \(c_p\) of the geometry, and finally processed that data in ParaView.

What we did

Block

What was done

1

Uploaded the building STL, checked its triangulation and attached it to a duplicate of the ABL case with the TBL wall model.

2

Added the buffer and body refinements, updated the simulation time from the building’s convective time scale and set up the two pressure exports.

3

Downloaded the exports, computed \(c_p\) from the body and reference pressures and visualized it in ParaView.

The settings we ended with

Item

Value

Body

ar1_gable, \(20 \times 20\,\text{m}\) base, \(25.75\,\text{m}\) at the ridge, TBL wall model

Buffer refinement

target \(0.8\,\text{m}\), maximum \(1.2\,\text{m}\), resolving to \(0.63\,\text{m}\) (level 4)

Body refinement

target \(0.3\,\text{m}\), maximum \(0.5\,\text{m}\), resolving to \(0.31\,\text{m}\) (level 5)

Mesh

~41.55M nodes

Time window

\(-600\,\text{s}\) to \(1300\,\text{s}\) (500 CTS of acquisition at \(2.66\,\text{s}\))

Exports

body pressure with \(0.62\,\text{m}\) normal offset and a reference point at \(z = 150\,\text{m}\), both at \(0.1\,\text{s}\)

Runtime

~3h13 at the default 500 MLUPS

Things worth carrying to the next case

  • The body’s triangulation is part of the setup. It generates the IBM points and it carries the exported data, so its shape, size and normals decide both how the wall model behaves and the resolution of the results.

  • Refine in steps. The buffer box between the ABL refinement and the body refinement is what keeps the transition smooth instead of jumping several levels at once.

  • The body sets the acquisition time. Once there is a body of interest, the convective time scale is built on its smallest side, not on the fetch.

  • Both pressure exports must share the sampling period. The \(c_p\) is a per-instant subtraction, so a mismatch in timesteps makes the two files impossible to combine.

  • The probes have to sit outside the diffusive layer. A normal offset of 2 cells is what separates a surface pressure from an IBM artefact.

Where to go from here

The pressure time series we ended with is the input for the rest of the work: surface force integration, structural loads and the comparison against code values.

See also