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Volume Averaging for Urban Canopies.
Manuel F Schmid1, Gregory A Lawrence1, Marc B Parlange2
11Department of Civil Engineering, University of British Columbia, Vancouver, BC Canada.
Boundary-Layer Meteorology
|November 12, 2019
Summary
Understanding canopy flow requires careful consideration of averaging methods. Intrinsic and superficial averages yield different results when solid canopy elements are present, impacting flow profile interpretations.
Area of Science:
- Fluid dynamics
- Environmental science
- Urban meteorology
Background:
- Spatial averaging of canopy flows is crucial for understanding mean profiles.
- Previous studies often assumed negligible solid volume fraction, limiting applicability.
- Non-negligible solid volume fractions introduce complexities in averaging methods.
Purpose of the Study:
- To review and discuss volume averaging methods for canopy flows.
- To highlight the impact of non-negligible solid volume fractions on mean profiles.
- To apply averaging concepts to urban canopy flow scenarios.
Main Methods:
- Exploration of intrinsic and superficial averaging definitions.
- Analysis of spatial averaging properties in porous media flow.
- Simulation of flow over constant-height cubes for illustration.
Main Results:
- Intrinsic averages are relevant for non-linear terms; superficial averages for gradients.
- Inconsistencies arise when solid volume fraction is ignored.
- Mean profiles are significantly affected by the choice of averaging method.
Conclusions:
- Careful consideration of averaging methods is essential for accurate urban canopy flow modeling.
- The impact of solid volume fraction must be accounted for in derived mathematical relations.
- Volume averaging provides a robust framework for analyzing complex canopy flows.
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