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Facilitated by the emergence of cloud computing, computer-aided engineering (CAE) or engineering simulation has become more accessible, and is being adopted by AEC companies worldwide. In building design, simulation—and in particular computational fluid dynamics (CFD)—is used in multiple applications, from pedestrian wind comfort studies to ventilation strategies. Here are three simulation projects that are publicly available and can be used as templates.

Pedestrian Wind Comfort Study of La Défense District in Paris, France

This wind simulation study uses CFD to analyze the district of La Défense, in Paris, to assess the pedestrian wind comfort in the area. La Défense is characterized by tall buildings that are very close to each other. The simulation’s goals were to identify uncomfortable spots and find solutions to tackle these wind effects.

Figure 1: Lawson pedestrian wind comfort criteria in La Défense, Paris, France (Source: SimScale)

Looking at the simulation results, the areas in yellow represent areas that could become uncomfortable for pedestrians and are caused by the wind being channeled through the narrow streets. This happens especially where these passages are aligned with the dominant wind directions. As the wind enters the area, it accelerates its way through the buildings, creating strong winds towards the center. 

For this case, multiple phenomena caused by wind were identified, including downwash, Venturi effect, and corner acceleration

Measures to tackle these effects include installing canopies to shield the wind and keep it from entering the building or positioning entrances away from the corners. In addition, trees could be planted to disrupt the wind; also, panels and fences can be installed. The earlier these wind comfort and pedestrian safety issues are identified in the design process, the higher the chance that engineers and architects can work to prevent them.

Thermal Comfort and Indoor Air Quality Study Inspired by Cité du Design 

With the goal of investigating the thermal comfort and indoor air quality for a building, this HVAC simulation project is an example of how useful CFD simulation can be for early-stage HVAC design. The CAD model analyzed is an exhibition hall, inspired by the Cité du Design building located in Saint-Étienne, France. 

The building poses several challenges that HVAC engineers had to overcome in order to ensure good indoor air quality. Its walls and the main area’s ceiling are made of glass and steel tiles, which rendered the classic strategy of placing diffusers impossible. A custom solution was required in order to ensure indoor air quality and thermal comfort for visitors. In addition, such a space receives a larger amount of solar radiation than regular spaces, which is an element that is hard to quantify without simulation.

The right amount of cooling power necessary to maintain an acceptable thermal comfort value is predicted to be -40000W; for this case, the predicted mean vote (PMV) contour maps are shown below. 

Figure 2: Predicted mean vote contour plot across the exhibition hall at 1.5m height (Source: SimScale)

Overall, these values are within the recommended range specified by ASHRAE 55 thermal comfort standard. The temperature contour map at a height of 1.5m indicates, however, hot spots in the center of the hall, with regions of 1°C above the average temperature of 21.65°C. Cold spots are identified mainly in the corners of the exhibition hall, close to the air intake chimneys.

Figure 3: Heat map at 1.5m height across the exhibition hall (Source: SimScale)



Figure 4: Temperature streamlines at the four corners with air intake “chimneys” (Source: SimScale)
The mechanical power required to maintain the previously defined air change rate can be quantified through the pressure drop across the blower zone shown below and the velocity assigned to this same zone.



Figure 5: Cut-plane showing pressure contours across the exhibition hall and through the underfloor ducting (Source: SimScale)

The simulation results show a pressure drop of 130 Pa at a flow rate of 2.64 m3/s, which gives a mechanical power for the blower of about 343 watts. Simulating the thermal environment and assessing an HVAC system’s performance with CFD, especially in the case of unique space configurations, gives valuable insights for iterative optimization. For this project, the complexity brought by furniture and other elements in the room determined an uneven temperature distribution, even if the PMV values for thermal comfort were within range.

Natural Ventilation in an English Cottage for Summer and Winter Conditions

In natural ventilation, stack effect is an element that needs to be considered. This effect is often present in chimneys and is caused by different air pressure, temperature levels (and associated density changes) between corresponding internal and external environments. 

This natural ventilation simulation demonstrates this effect within a country cottage, along with the seasonal differences in air pressure. Its goal is to understand how the buoyancy forces causing the stack effect can be manipulated as well as understand how a ventilation system can be introduced to utilize this effect.

A convective heat transfer analysis using compressible, turbulent flow was run for the external conditions, considering different average temperatures for summer and winter. In addition, different cooling and heating sources were tested.



Figure 6: Temperature plot of airflow in the cottage during winter (Source: SimScale)

The simulation results above show the resulting velocity plots for winter. As cold air enters the room through the ventilation ducts, there is a smooth transition into room temperature.



Figure 7: Airflow velocity through a chimney (Source: SimScale)

The simulation results show high acceleration through the chimney due to a large temperature gradient (peaks at 10 m/s).



Figure 8: Velocity plot of airflow in the cottage during summer (Source: SimScale)

For the summer scenario, air exists through ventilation ducts as the temperature difference has flipped between the external and internal environments. Warm air is entering from the gaps located above the windows’ frontal artificial ventilation source, which creates an area of recirculation and a heat source. 
These CFD simulation results show flaws of the design, requiring a new strategy for the ventilation system.

From virtually testing external aerodynamics of a building or urban area to analyzing thermal comfort, indoor air quality or contaminant extraction, engineering simulation provides significant value in building design. Depending on the complexity of an architectural project, computer-aided engineering is increasingly required in complying with industry standards. And with the emergence of cloud-based solutions, it is becoming more cost-effective and easier to access for engineers and architects across the globe, from a standard web browser.

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