In PWC analysis, the main goal is to generate pedestrian wind comfort results. To be able to see the flow results for other regions within the domain, the user has to set “Additional results”. This article explains how to set a PWC analysis to be able to generate particle traces (streamlines) and slices.
Please visit the documentation page to learn more about the Pedestrian Wind Comfort Analysis type.
1. Region of Interest and Flow Domain
Region of interest defines the area around the main building on which the pedestrian comfort should be evaluated.
Once it’s defined, the Flow domain (Wind tunnel) around it is automatically created. You can see the flow domain by clicking the eye icon.
In PWC analysis, the LBM solver calculates the aerodynamics effects inside the flow domain and generates a comfort map. Even though the velocity, pressure, and turbulence values are calculated, these data are not saved as default. The user needs to define a region and set additional results for export.
2. Geometry Primitives
2.1 Local Cartesian Box
The aim of particle traces is to track the flow path in three dimensions. Therefore, we need a 3D domain to generate them.
Create a Local cartesian box where you would like to visualize the particle traces. Change the Orientation reference to the External flow domain. This will ensure the box to align itself automatically, with respect to different wind directions.
Saving the additional data in 3D creates a larger results file. You may run out of disk space. Therefore, we strongly recommend keeping the box as small as possible to prevent an increase in simulation time and costs.
2.2 Local Slice
Particle traces is not the only way to observe the flow effects. Similarly, you can create 2D planes and visualize the data on them. Create a Local slice, where you would like to place the contours. Similarly, change the Orientation reference to the External flow domain.
3. Additional Result Export
As a default, flow parameters are not saved. You need to save them additionally. You can either save transient results (Transient output) or steady-state results (Statistical averaging). Statistical averaging uses the results from last time steps, takes the average, and saves them for one time. Due to the storage, computation time, and cost concerns, we strongly recommend saving the results only in statistical averaging.
Activate the local cartesian box and/or the local slice you created before. Saving these results will allow you to create particle traces and slices in PWC analysis.
You can see the results once the simulation is finished. Additional results are always saved per wind direction. Therefore, you need to choose a wind direction and navigate to Additional results.
4.1 Generate Particle Traces
Once you are in solution fields, you will see a green box. This is the Local cartesian box you defined under Geometry primitives. Velocity and pressure values are saved in this region.
- Click the ‘+’ button to create a particle trace. The flow domain will disappear automatically.
- Click on Surface Outline Mesh to visualize flow domain surfaces again.
- Adjust the number of seeds and space in between them.
- Click the Pick button.
- Place the seeds on a flat surface. This surface should be on or inside the flow domain.
Particle traces are generated inside the fluid domain. Next, hide the fluid volume or make it transparent to see the particle traces.
After capturing a nice view, you can animate the particle traces. First, click on Animations, and then the APPLY button.
4.2 Generate Contours on a Slice
- Firstly, ensure that your Local slice is visible.
- Secondly, select Results.
- Finally, select a scalar of interest. For instance, All velocity_e means element values of velocity magnitude.
4.3 Generate Vectors on a Slice
In addition to the above steps, ensure the following steps are performed:
- Under Results Config, select the VEC tab.
- Make Velocity_e visible.
- Under the Results tab, select VEC: Velocity_e.
- Adjust the visibility options of the vectors.
Visit this knowledge base article to learn how to adjust vector visualization settings.
- Firstly, make sure the Orientation Reference for the geometry primitives selected is selected as the External flow domain.
- Secondly, avoid large boxes due to the storage and simulation costs concerns.
- Finally, statistical averaging is useful enough for additional results. Above all, the transient output might cause storage issues or an increase in simulation costs.