What the study found
Canopy density was not fully captured by frontal density, a common measure of canopy density, for some canopy topologies. The authors found that turbulence penetration into canopies can be used to distinguish sparse, intermediate, and dense regimes.
Why the authors say this matters
The study suggests that measuring turbulence penetration directly may better represent the underlying physics for some canopies than frontal density alone. The authors conclude that an effective spanwise gap and its relation to typical eddy size can be used to characterize penetration.
What the researchers tested
The researchers used direct simulations of turbulent flow over canopies of rigid elements with different geometries, spacings, and Reynolds numbers. They examined isotropic- and anisotropic-layout canopies with frontal densities from about 0.01 to 2.04, heights from about 44 to 266 in wall units, width-to-pitch ratios from about 0.06 to 0.7, and Reynolds numbers from about 180 to 2000.
What worked and what didn't
For the same frontal density, canopies with elements closely packed in the streamwise direction but with large spanwise gaps allowed deeper turbulence penetration and appeared sparser than isotropic or spanwise-packed canopies. For the same spanwise gap, turbulence penetration was similar across canopies regardless of streamwise pitch and gap, while larger spanwise gaps led to deeper and more vigorous penetration.
What to keep in mind
The abstract does not describe experimental limitations beyond the range of canopies and Reynolds numbers studied. The proposed penetration measure is based on the position and extent of individual turbulent eddies, especially those associated with intense Reynolds shear stress, within the simulated cases described.
Key points
- Frontal density did not fully characterize canopy density for some canopy topologies.
- Turbulence penetration differed across canopies with the same frontal density.
- Large spanwise gaps allowed deeper turbulence penetration.
- Turbulence penetration was similar across canopies with the same spanwise gap, regardless of streamwise pitch and gap.
- The same canopy could appear denser at low Reynolds number and sparser at higher Reynolds number.
Disclosure
- Research title:
- Turbulence penetration helps distinguish canopy density regimes
- Authors:
- Chen Zishen, Ricardo García-Mayoral
- Institutions:
- University of Cambridge
- Publication date:
- 2026-04-20
- OpenAlex record:
- View
Get the weekly research newsletter
Stay current with peer-reviewed research without reading academic papers — one filtered digest, every Friday.