WIND ACTIONS, FIRE AND SMOKE SPREAD, HVAC VALIDATION
WIND ACTIONS, FIRE AND SMOKE SPREAD, HVAC VALIDATION
WIND ACTIONS, FIRE AND SMOKE SPREAD, HVAC VALIDATION
WIND ACTIONS, FIRE AND SMOKE SPREAD, HVAC VALIDATION
CFD simulations
Computational Fluid Dynamics (CFD) is an advanced method of fluid flow modelling, allowing for calculating realistic yields of physical parameters within the computational domain. Simulation outcome is not a single value averaged across all volume – but rather a spatial distribution of analyzed properties. CFD modelling is an extremely helpful tool in cases where complex geometry and conjugated physical phenomena exceed typical engineering practice (or applicability of engineering standards). CFD simulations are time-consuming (both in model preparation and computation time), therefore it is critical to properly include their usage in project planning. This type of analysis allows for optimization of the proposed design solution at an early stage, helping eliminate costly mistakes difficult to resolve during further project phases.
CFD SIMULATIONS:
Simulations inside buildings:
- HVAC systems efficiency validation,
- Thermal comfort analysis (PMV, PPD),
- Pollutant spread inside rooms,
- Pollutant spread outside the building.
Fire simulations:
- Fire and smoke spread simulations,
- SHEVS systems efficiency verification,
- Fire impact on structural elements.
Large scale external aerodynamics:
- Wind actions on buildings facades,
- Pedestrian wind comfort analysis.
Software used:
- NIST FDS + PYROSIM,
- ANSYS FLUENT.
EXAMPLES OF CFD SCOPE OF APPLICATION:
EXAMPLE 1
High rise building located within the urban dense built-in environment. Pressure distribution caused by wind is completely different than determined by Eurocode procedures. Aerodynamic velocity build-up on flow over buildings creates increased static pressure yields on the windward upper side and significantly smaller in lower parts shielded by surrounding structures. This means completely different input data for structural design.
EXAMPLE 2
SHEVS system was designed based on Polish standards or NFPA. But will it perform efficiently under the most unfavorable design fire scenario providing safe means of escape? Fire CFD simulations can easily make this verification. It is quite common that after performing CFD analysis resulting net area of smoke vents or smoke exhaust fans must be increased, sometimes by a factor of 2x or 3x compared to standard calculation procedures. Investment in professional CFD service on SHEVS verification can prevent the huge cost of system reworking after unsuccessful commissioning tests or Fire Authority handover – and what is most important: to prevent loss of human life in event of a real fire.
EXAMPLE 3
Sometimes building regulations provide strict rules about roof exhaust and intake placement, but some of these aspects are not covered in legal documents. In Poland, it is allowed to use a combined exhaust-intake as a single device. But can we be sure that exhaust air is efficiently separated from the intake? What would be the recirculation level under prevailing wind? What would be an impact from the proximity of chillers or other exhaust? To what extend building geometry and aerodynamic shadow can negatively impact fresh air intakes? Investing in professional CFD analysis can answer these questions and prevent poor efficiency or extensive used air recirculation back into the intakes.
EXAMPLE 4
A fume stack has been located on the roof. The building is located nearby of other, surrounding buildings, few of them are higher than the stack discharge level. Can we be sure that pollutants will be diluted to acceptable levels during prevailing wind direction and speed? Can we be sure that windows and intakes of surrounding buildings are safe? It is a perfect opportunity to use CFD simulations to answer this question and prevent costly consequences if owners of surrounding buildings will decide to go against the stack discharge employing a legal lawsuit.
EXAMPLE 5
Let’s assume that we have a production building with a high-capacity heat source. The cheapest and commonly used solution to condition such spaces is to use an array of swirl diffusers located high within the zone ceiling. Can we be sure that such a system will prevent excessive temperature build-up in the occupational zone (~2.0m)? Where can we expect to have and aerodynamic dead zones where dust or pollutants can concentrate? Using the same amount of air, we can create much better working conditions within the occupational zone. Using CFD simulation we can test several concepts of air distribution and chose the most optimal solution. Investing in professional CFD services can spot and identify potential issues with HVAC efficiency during the early stages of the design, helping to avoid big costs of system re-design or re-work during further project stages.
WHAT INFLUENCES THE COST AND SIMULATION TIME?
CFD modelling requires big computational power. It is necessary to use a special workstation equipped with high-end processors with at least 12-16 physical cores and 128GB RAM or more. The cost of such a workstation is 10 to 20 times greater compared to the price of a typical office-PC. We have our computational workstation at our disposal. At least 2/3 of the service price is the cost of a fixed-term lease of Ansys Fluent license. This is might seem very high cost, but our philosophy is to use the best and more advanced software available. The typical computational domain consists of several to several-dozen millions grid (mesh) elements. Single case computation time can even take up to full 2 weeks of computation depending on model sophistication level, grid resolution, turbulence model used, and simulation type (steady-state, or transient). Additional time must be spent on the careful pre-processing stage (clean model preparation) and post-processing (generating the visual results).
Each case is different and is a subject of tailored service pricing. Please do not hesitate to contact us, we look forward to providing you any clarification and help decide on the CFD modeling scope for your project.
Due to the FLUENT license lease method, CFD quotations (other than fire simulations) should be ordered as a group/set of several variants or several different simulations (for ie: 8 different wind directions). This is due to the fix-term license costs, which will elevate costs for single or small simulation cases. Temporary license is acquired for a specific project.