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November 2020

,

Luma Bendini

Adding trees to Wind Comfort Simulations

Trees function as a porous obstacle of airflow, therefore affecting wind direction and wind speed. Although modelling trees is a big challenge for numerical simulations, its impact on pedestrian comfort and safety analysis cannot be ignored. So, here’s how you can add porous media to your urban wind analysis with Ingrid Cloud.

Easy access:
Download standard tree model
How to insert trees in my Wind Comfort Simulation?
Frequently Asked Questions

Starting note. Trees and vegetation change density based on season and geolocation. In order to best represent the most common of those variants, we use the internationally established Leaf Area Index (LAI). The index quantifies the foliage of a tree, thus defining its density input for a virtual wind tunnel calculation.

LAI is a dimensionless number that defines plan canopies. Basically, it is defined as the green leaf area per unit ground area. Ingrid Cloud models trees as porous media1, where the average height of a tree in a city is set to 10 m.

1. Mohamed Hefny Salimab K., Heinke Schlünzena, David Grawea. Including trees in the numerical simulations of the wind flow in urban areas: Should we care? Journal of Wind Engineering and Industrial Aerodynamics (2015)

How to insert tree in my Pedestrian Comfort Analysis?

1. Download the standard tree model and insert in your CAD geometry 

Ingrid Cloud solver will identify and resolve the porous media included in the geometry automatically – that’s why users need to insert the standard tree geometry provided by us - click here to download standard tree model. The unit is in meter and it’s possible to rescale the tree size.

2. While setting up the simulation, click Advanced Parameters and choose the Leaf Area Index.

This option is available when Ingrid Cloud detects the standard tree model in your geometry. If you don't see this setup option, trees were not detected, please, make sure you have followed the previous step correctly. 

include-trees-ingrid-cloud

See descriptions below for each value available:

Basic Tree Model

Biome

LAI 

standard-tree-image

Evergreen needleleaf as Pine and Spruce

2.7

Deciduous broadleaf
as Maple, Oak, Silver birch

5.1

If you need to insert a customised value for LAI, please, contact us.

LAI 2.7 - Evergreen needleleaf as Pine and Spruce

LAI-2-7Information and image from Earth Observatory – NASA

This category corresponds to a biome with coniferous forest. Conifers are trees that grow needles and cones instead of leaves and flowers respectively. Their characteristics are to be evergreen and that they can survive in a very cold and dry area. Typical representatives are spruces, pines and firs.

 

LAI 5.1 - Deciduous Broadleaf as Maple, Oak, Silver Birch

LAI-5-1Information and image from Earth Observatory – NASA

A biome with deciduous broadleaf is most notable because they go through four seasons: Winter, Spring, Summer, and Fall. Leaves alter color in autumn, fall off in the winter, and grow back in the spring. Typical representatives are maple, oak and silver birch.

Frequently Asked Questions

When should I include trees in my simulations?
When you have already assessed the pedestrian comfort and safety of the area of interest with a validation wind simulation. Wind mitigation evaluation should always be an additional step of a Wind Study, never a stand-alone analysis. For a comprehensive evaluation, we recommend to always run simulations with and without tree present in the area of interest.

Does the index adjust to seasons?
No, the LAI is kept constant for the pedestrian comfort analysis.

Do I have to use the model provided by Ingrid Cloud?
Yes, when you use our standard tree model, you allow our solver to identify and refine the tree geometry automatically – which is a key factor for accuracy and ease of use.

Can I edit the standard tree model provided by Ingrid Cloud?
It’s possible to resize the standard model. Other options for tree geometries will be added soon.

I need to consider a different tree type or vegetation. Is it possible?
Yes, we can implement a custom solution on demand, please, contact us here.

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References

Mohamed Hefny Salimab K., Heinke Schlünzen, David Grawea. Including trees in the numerical simulations of the wind flow in urban areas: Should we care? Journal of Wind Engineering and Industrial Aerodynamics Vol. 144, 84 – 95 (2015).

Asner, G.P., Scurlock, J.M.O. and A. Hicke, J. Global synthesis of leaf area index observations: implications for ecological and remote sensing studies. Global Ecology and Biogeography, 12: 191-205 (2003).

Lalic B, Mihailovic DT. An empirical relation describing leaf-area density inside the forest for environmental modeling. J. Appl. Meteor. (2004)

Evergreen needleleaf as Pine and Spruce

Deciduous Broadleaf as Maple, Oak, Silver Birch