CFD assessments within strongly transient domains

Assessments based on CFD snapshots of stable conditions within strongly transient domains do not address many aspects of performance associated with occupant interventions, control actions or changing climate. Such domains (e.g. double skin façades) are characterised by transient flow patterns due to changing weather patterns, actuation of dampers intermittent opening of façade windows and operation of building environmental systems. Importing boundary conditions from whole building simulation is an improvement but it discounts the impact of the flow predictions on the building domain. A transient approach is suggested which is fully coupled to flow and thermal solvers for the building fabric, environmental control systems and air flow regime. The paper reviews a number of patterns of flow evolution in strongly transient domains in response to changes in ambient conditions, damper actuation, façade openings and intermittent flow from mechanical ventilation systems.