This study forms one component of my Master’s thesis at Politecnico di Torino, MSc Architecture for Sustainability, which investigates a Performance-Based Design (PBD) approach for evaluating and optimizing passive design strategies in multi-story office buildings in hot-humid tropical climates. The analysis uses SimScale as the CFD platform, with an OpenFOAM-based incompressible flow solver. The airflow field is obtained through the numerical solution of the governing fluid-flow equations, based on the conservation of mass and momentum represented by the Navier–Stokes equations.

Within this framework, the urban wind study focuses on one central question:

How much of the regional wind resource is actually available to a high-rise office building after being modified by the atmospheric boundary layer and dense urban morphology?

01. From Regional Climate to a Representative Wind Condition 

The annual wind regime is divided into three seasonal periods: the transitional period, the Southwest Monsoon, and the Northeast Monsoon. The Southwest Monsoon, from May to October, is identified as the dominant regime, with the highest occurrence frequency and relatively strong wind speeds of approximately 2–7 m/s. This CFD study focuses on the Southwest Monsoon as a representative case, and is is based on the TMYx 2011–2025 Ho Chi Minh City – Tan Son Nhat International Airport weather file, WMO station 489000.

Selected representative condition 

20 September — 14:00, Southwest Monsoon, reference wind speed at 10 m: 4.10 m/s

02. Atmospheric Boundary Layer 

The EPW wind speed represents a meteorological reference condition, whereas wind velocity changes significantly with height because of the Atmospheric Boundary Layer (ABL). Therefore, the regional wind condition is transformed into a vertical velocity profile before entering the urban CFD model.A logarithmic ABL wind profile is applied at the inlet, where the friction velocity is derived from the reference wind speed, the von Kármán constant, and the aerodynamic roughness length:

03. Three Vertical Scales of Wind Availability 

To understand the vertical variation, the CFD results are examined at three representative elevations: 

2 m | Pedestrian Level

At approximately 2 m above ground, the airflow is heavily influenced by the surrounding urban fabric. Despite an inlet velocity of 1.59 m/s, the local flow is strongly redistributed by surrounding buildings. This illustrates how the lower urban layer can become relatively sheltered even when regional wind is available.

13 m | Intermediate Office Level

At approximately 13 m, corresponding to an intermediate office floor, the flow becomes significantly more available. The reduced influence of the lower urban obstruction allows a greater proportion of the incoming Southwest flow to reach the building.

36.8 m | Upper Office Level

At approximately 36.8 m, corresponding approximately to the upper office levels, the airflow is less constrained by the lower urban fabric. The simulation shows a much stronger wind potential around the building, illustrating the vertical gradient between pedestrian-level stagnation and upper-level wind availability.

References

1. Lawrie, L. K., & Crawley, D. B. (2026). Development of Global Typical Meteorological Years (TMYx). Climate.OneBuilding.org. The 2026 release includes TMYx files covering 2011–2025 and is based on hourly meteorological data from the ISD/NOAA dataset, with updated solar data from ERA5.

2. Building and Construction Authority (BCA), Singapore. (2021). Green Mark 2021 — CFD Guideline. The guideline specifies atmospheric boundary conditions for CFD modelling, including the use of local climatic wind conditions and a logarithmic atmospheric-boundary-layer wind profile.

3. SimScale GmbH. Incompressible Fluid Flow Analysis. SimScale documentation describing incompressible CFD analysis, including the underlying continuity formulation and application to aerodynamic flow.

4. SimScale GmbH. Simulation Control for Fluid Analysis. Documentation describing SimScale fluid-analysis types based on the OpenFOAM solver and the treatment of steady-state fluid simulations.

5. SimScale GmbH. Outputs by Analysis Type. Documentation describing available OpenFOAM CFD outputs, including velocity, pressure, turbulent kinetic energy and dissipation rate, and the export of OpenFOAM results for post-processing in applications such as ParaView.