Portfolio
Atmospheric Boundary Layer¶
1. Project Description¶
The objective of this project is to reproduce the properties of atmospheric boundary layer (ABL) through CFD-LES simulations. The wind profiles must reproduce the logaritmic equation from [1].
The reference heights used for velocity normalization was measured at \(H\) = 150 m. One convective time scale is defined as \(CTS = H / U_{H}\).
To achieve different velocity profiles for each terrain category, fins with height \(h\) are distributed across the floor. The fins width was fixed in \(6\) m and the spacing \(x\times y\) in \(16\times32\) m.
After calibration steps, the required height for each category was:
Roughness Category |
CAT 0 |
CAT I |
CAT II |
CAT III |
CAT IV |
\(\boldsymbol{z_0}\) [m] (roughness height) |
0.003 |
0.01 |
0.05 |
0.3 |
1 |
\(\boldsymbol{h / z_{0}}\) (fin height to \(\boldsymbol{z_{0}}\) ratio) |
0 |
100 |
40 |
13 |
8 |
2. Simulation Setup¶
The Synthetic Eddy Method (SEM) boundary condition is applied at the inlet of the computational domain. A Neumann boundary condition is applied at the remaining boundaries.
The reference position is at \(1200\) m from the inlet, and 3 grid refinement levels were assessed:
The simulation parameters were:
\(\boldsymbol{\Delta x / H}\) (spatial res.) |
0.0267 |
0.0133 |
0.00667 |
\(\boldsymbol{\Delta t / CTS}\) (temporal res.) |
0.0016 |
0.0008 |
0.0004 |
\(\boldsymbol{T / CTS}\) (statistical sample size) |
128 |
128 |
128 |
\(\boldsymbol{Re_H = U_{H} H / \nu}\) (temporal res.) |
337500 |
337500 |
337500 |
The equivalent parameters in full scale are:
\(\boldsymbol{\Delta x}\) [m] |
4 |
2 |
1 |
\(\boldsymbol{\Delta t}\) [ms] |
8 |
4 |
2 |
\(\boldsymbol{T}\) [s] |
640 |
640 |
640 |
The computational resources required were:
Device |
NVIDIA RTX A5500 |
NVIDIA RTX A5500 |
NVIDIA RTX A5500 |
Refinement |
Ref 4 m |
Ref 2 m |
Ref 1 m |
Node count (million) |
16.26 |
28.55 |
51.85 |
Allocated memory (Gb) |
2.38 |
4.17 |
7.62 |
Ellapsed time (h) |
2.13 |
3.50 |
7.70 |
3. Results: Reference Position¶
Average Velocity¶
Category 0:
Category 1:
Category 2:
Category 3:
Category 4:
Turbulence Intensity¶
Category 0:
Category 1:
Category 2:
Category 3:
Category 4:
Integral Lenght Scale¶
Category 0:
Category 1:
Category 2:
Category 3:
Category 4:
Energy Spectra¶
Category 0:
Category 1:
Category 2:
Category 3:
Category 4:
Execution Notes¶
Execution Date (YYYY-MM-DD) |
2025-3-11 |
Solver Version |
1.6.20 |
Changelog¶
Execution Notes
18 April 2024
Uploaded point comparisons, simulations executed with Nassu release v1.5.4.