Computational Fluid Dynamics (CFD) is a technique best-known to Formula One racing teams, where it has superseded air tunnels in their search to gain maximum aerodynamics by modelling airflows.
It has also been adopted by the aerospace, general automobile and wind turbine industries, and although not new, is still an emerging science.
Greater computational power is adding to its development, enabling designers to accurately predict what will happen under a given set of circumstances. Parameters can be set, and the CFD software provides the outcome and answer to the ‘what if’ question.
Variations to a design can be tested until an optimal result is found, removing the cost of physical prototyping. In F1, it leads to better, faster cars that meet FIA compliance rules and can be demonstrated to conform to stringent motor racing regulations.
So how does F1 technology translate into an airport environment? What have modelling airflows got to do with enhancing the passenger experience, ensuring operational reliability, and saving the airport operator money in the longer-term?
Modelling airflows to help keep an environment cool in the summer and warm in the winter is an essential part of improving the passenger journey. This is especially true when going through central search security halls, where the heat generated by conveyors and X-ray equipment presents a particular challenge, especially when no two individual airport environments are ever the same.
Add to this the heat generated by hundreds of passengers passing through a relatively confined space every minute, and the challenge becomes even more apparent.
And, it is not just in the security halls that this challenge arises. New and ever more sophisticated baggage handling and explosive screening systems, as mandated by the European Civil Aviation Conference (ECAC) Standard 3 regulations, have added a further tier of complexity.
Such systems create operational challenges for airport operators, not least in the energy they consume, and the need for the equipment to manage high volumes of throughput.
Keeping these machines ‘cool’ to prevent the cut-in of built-in air conditioning units requires intelligent design and modelling of airflows. Air conditioning systems generate heat in their own right, as well as consuming more energy.
Whilst they are an essential safeguard, ensuring the reliability and operational efficiency of the equipment installed (to prevent them from overheating, for instance), it is better still if the environment in which they are installed is such that this failsafe is not required. Through this, damage to an airport’s reputation and disruption to passengers’ travel plans in the event of systems failure can be avoided.
Infrastructure varies vastly at each airport, so every environment requires its own bespoke design. In one example, at an international airport in Europe, CFD was used to review the performance of a new displacement ventilation system being used by the airport operator to control the temperature within its refurbished central security search hall.
Displacement ventilation is essentially a method of directing cool air at low velocity into a space through the movement of air from floor to ceiling. A gentle flow of air is distributed into the room at floor level through a series of wall-mounted diffusers around the hall’s perimeter.
The heat created by people, lights, and scanning equipment in the room draws the cooler air up from the floor in a movement known as ‘thermal stratification’. The warmed air then continues to rise towards the ceiling where it is discharged through vents at ceiling level.
In this example, CFD was used to review a number of design factors, and in particular to assess whether the location and number of diffusers were sufficient to condition the room evenly, given that the centre of the hall was up to 20 metres away from the walls.
It was also used to review the likelihood of drafts within the zones adjacent to each diffuser, which may cause discomfort to passengers, as well as the performance of the system under so-called ‘low load’ conditions (when the number of search lanes being used was reduced during the least busy times of the day, for example).
It was important to measure whether the displacement system was capable of conditioning the occupied areas during reduced loads, whilst not over-cooling areas that were temporarily unoccupied.
The ultimate objective of using CFD in this case was to ensure the displacement design was capable of delivering the desired levels of cooling while maintaining a comfortable environment for passengers and staff (21ºC +/-2).
During the construction of the security search hall, the operator decided to introduce further desks into the design which would impact on airflows. With CFD, however, the designers were able to model the impact of additional furniture and easily establish whether any minor amendments to the scheme/design were required.
Using CFD, the designers were able to show that the displacement design was capable of achieving the outcomes the operator desired. More than this, however, it was also able to show that during the summer months, an increase in the supply temperature actually reduced the cooling requirement, thereby reducing energy consumption and, consequently, operational costs.
In another example at a different major international airport, the introduction of a new baggage Explosion Detection System (EDS) presented a further challenge. These machines have to operate within the manufacturer’s specified operational temperatures and were being installed in an existing space that used high-level fan coil units (FCUs) to draw cool air into the hall.
The challenge was to keep the temperature of the space surrounding the machines to less than 32ºC, a temperature beyond which the machine’s own first stage air conditioning units would kick in.
Two FCUs were located on either side of the EDS machines, distributing cooled air from high level to the equipment’s air inlets at lower level. Extract grilles located adjacent to the screening machines allow the heat from the machines to be dissipated.
In this example, designers used CFD to find the optimum location for the supply grilles and confirm the temperatures being generated around each of the machines. By ensuring the temperatures do not exceed the stated thresholds, the built-in air conditioning units are not required, so less energy is being consumed and the reliability and performance of the baggage screening system is enhanced, bringing tangible benefits and peace of mind to the facilities team.
Right first time
Computational Fluid Dynamics is a proven technology for allowing theories to be validated, well before the expense of any building work is started or equipment installed. Achieving a ‘right first time’ approach to building design avoids all of the post-install issues that can add unwanted costs, disruption and delay.
Put another way, it helps operators achieve the levels of customer satisfaction and operational efficiency that are essential for managing a successful airport environment.