Computational Fluid Dynamics (CFD)

Click on the CFD screen tab to start CFD calculations.

The rest of this section covers the processes involved in running CFD calculations in DesignBuilder.

What is CFD?

Computational Fluid Dynamics (CFD) is the term used to describe a family of numerical methods used to calculate the temperature, velocity and various other fluid properties throughout a region of space.  

CFD when applied to buildings can provide the designer with information on probable air velocities, pressures and temperatures that will occur at any point through a predefined air volume in and around building spaces. Boundary conditions are specified which may include the effects of climate, internal heat gains and HVAC systems. DesignBuilder CFD can be used for both external and internal analyses.

See also the Introduction to CFD and External CFD Tutorial

External CFD analysis

External CFD analysis provides the distribution of air velocity and pressure around building structures due to the wind effect and this information can be used to assess pedestrian comfort, determine local pressures for positioning HVAC supply and extract grilles and to calculate more accurate pressure coefficients for EnergyPlus calculated natural ventilation simulations.

Example External CFD Analysis Output - Wind Pressure Study

Internal CFD analysis

Internal CFD analysis provides information on the distribution of air velocity, pressure and temperature (and several other calculated parameters) throughout the inside of building spaces. Also calculated is 'age of air' to indicate the relative 'freshness' of the air through the domain and also a comfort index. This information can be used to assess the effectiveness of various HVAC and natural ventilation system designs and to evaluate consequent interior comfort conditions.

Example Internal CFD Analysis Output - Occupant Comfort

CFD Calculations Topics Contents

• Creating Model Geometry for CFD
• Finite Volume Grid and Geometric Modelling Considerations
• Building Levels and CFD Analyses
• CFD Boundary Conditions
• Boundary Conditions for Internal CFD Analyses
• Component Blocks and Assemblies as CFD Boundaries
• Setting Up a New External CFD Analysis
• Setting Up a New Internal CFD Analysis
• Editing the CFD Grid
• CFD Grid Information
• Setting Up CFD Cell Monitor Points
• CFD Calculation Options
• Residuals and Cell Monitor Graphs
• Convergence Difficulties and Troubleshooting
• Displaying Results
• CFD Comfort Calculations
• Age of Air and Air Change Effectiveness
• CFD Analysis Manager
• Example - CFD External Analysis
• Example - CFD Internal Analysis Basics
• Example - CFD Internal Analysis Including Assemblies
• Appendix - CFD Calculations and Convergence

Tip: You can find details on the calculation method used in the CFD Technical online document.