Airport windshear – NASF B

What is windshear?

Windshear is a sudden and drastic change in wind direction and/or speed over a relatively short distance in the atmosphere. Various factors, such as thunderstorms, mountainous terrain and buildings can all generate problematic windshear. Windshear is a significant hazard to aviation, particularly during takeoff and landing.

In recent years, interest in the potential impacts of buildings on airport operations and safety due to windshear and turbulence has been increasing globally.

The Australian National Airports Safeguarding Framework guidelines detail a range of criteria for developments at or near airports. The purpose of these criteria is to minimize the risk of buildings contributing to accidents and near misses. For large buildings the most challenging guideline is Guideline B, “Managing the risk of building generated windshear and turbulence at airports” (NASF B). NASF B details both recommended maximum safe windshear and turbulence criteria, and regions in which this criteria should be assessed. Aviation regulators and airports are also requesting similar assessments in other regions, including Europe and the Middle East.

Figure 1: Synergetics use CFD modelling to test compliance with the NASF B guidelines for building generated windshear over an airport runway.

Analytical methods can quickly confirm minimal wind shear impacts of simple building geometries with a large separation from the runway. However, analysing more complex building designs and those in close proximity to a runway requires sophisticated analysis.

Figure 2: Relatively minor changes to the building façade can have a profound effect on the downstream wind profile.

CFD assessments against NASF B

Synergetics employ computational fluid dynamics (CFD) to perform this analysis. This provides accurate estimates of the wind shear and turbulence during critical wind conditions. These results  provide a clear statement of the impact of the building with regard to NASF B. If a proposed building design is non-compliant, the same results can be analysed in detail to determine the cause of the elevated shear levels, and what modifications can be used to reduce the levels, whilst maintaining maximum building value and appeal. Assessing different design options and wind directions can be done rapidly once the model is constructed. This provides an accurate, cost effective way to achieve compliance while also managing risks.

Using these methodologies, Synergetics have assisted with the design and approval of dozens of buildings on and near airports. Synergetics also have experience using CFD to assess terrain induced wind shear and turbulence effects at airports located near complex terrain.

For further examples of computer modelling related to airports see our sector page.