The 12-fan Wall of Wind (WOW) at FIU is the largest and most powerful university research facility of its kind and is capable of simulating a Category 5 hurricane – the highest rating on the Saffir-Simpson Hurricane Wind Scale. For more than a decade, FIU researchers and engineers have planned, designed and redesigned numerous concepts and models that have all contributed to the science and technology behind this state-of-the-art machine.
The first prototype, created by experts from FIU’s wind engineering team, was assembled in 2005. The original 2-fan mobile unit could generate 120 mph winds with a water-injection system to simulate horizontal rain. This paved the way for a larger RenaissanceRe 6-fan WOW with the ability to simulate hurricane wind characteristics and engulf large-scale structures.
Now, due to increased demand for higher wind speed testing, FIU has taken yet another step forward with its 12-fan WOW. The new system is capable of performing controlled and repeatable to-scale testing in flows that replicate the same CAT 5 level winds as both hurricanes Katrina and Andrew. This facility will not only fill the void where most current wind-structure experiments fail, it has the potential to be as influential to wind engineering as crash testing was to the automobile industry.
Technical Aspects of the Wall of Wind
The (WOW) was designed to model the turbulent characteristics of the atmospheric boundary layer (ABL). The ABL is the bottommost layer of the atmosphere in which the airflow is influenced by the roughness of the surface. Matching these characteristics for wind engineering purposes is important due to the fact that most of manmade structures are located within this layer of the atmosphere.
ABL characteristics vary with the conditions of the terrain considered. Design standards (as ASCE7-10 Minimum Design Loads for Buildings and Other Structures) take it into consideration and factor the effect of surrounding structures and terrain in the load conditions of the structure of interest. Three different types of terrain will affect shape and thickness of the boundary layer: open terrain, suburban and urban areas and flat unobstructed areas.
Besides the wind speed profile (varying with height) for each surface roughness condition, each will have a particular turbulence content in the flow. In nature, flow rarely occurs in laminar form. Turbulence will be present at different intensities and directions for each case. Thus the importance of properly modeling the characteristics of the flow before the tests happen.
The WOW is an open return, subsonic wind tunnel facility. The system is a blower type, with 12 fans located at the intake section in a semi-circular arrangement. Each fan is powered by a 700-hp medium voltage electric motor, for a combined 8400-hp. The fans push air into a contraction chamber that increases the wind speed and smooths out the speed variations. The flow then travels through a set of triangular spires and floor roughness elements that generate turbulence and boundary layer characteristics.
The WOW can generate a boundary layer profile of a Category 5 hurricane. The maximum wind speeds that can be achieved are in excess of 150 mph. The following graph shows a comparison between the WOW wind profile and Category 5 hurricane conditions for suburban terrain and 3-sec gust, and you may download the full PDF file by clicking HERE.