Reproducing tornadoes in laboratory using proper scaling

Refan, Maryam; Hangan, Horia; Wurman, Joshua

doi:10.1016/j.jweia.2014.10.008

Cited by 69 publications

(26 citation statements)

References 24 publications

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“…Both in situ observations (Lee and Samaras, 2004;Samaras and Lee, 2004;Karstens et al, 2010) and laboratory studies (Haan et al, 2008;Mishra et al, 2008;Sabareesh, 2012;Refan et al, 2014) have confirmed the presence of the APD. Simiu and Scanlan (1996) showed that the APD can be theoretically estimated as twice the velocity pressure of the rotating winds.…”

Section: Introductionmentioning

confidence: 85%

“…The reference velocity depends on the assumed length and velocity scales. Length scales are problematic in vortex-driven fluid-structure interaction studies (Refan et al, 2014;Baker and Sterling, 2019;Gairola and Bitsuamlak, 2019), but some reasonable estimate must be made in order to obtain the model scale gust averaging time for the reference velocity. Here we use a length scale of 1/100 and a velocity scale of 1/5.6 and 1/4.74 for the low swirl and high swirl ratio vortices respectively (assuming full-scale wind speed of 60 m/s) to evaluate the maximum 3 s gust (in full scale) wind speed of the translating vortex at or below the roof height (in nominally open terrain since no roughness elements were present and a smooth floor was used), which is used as the reference velocity.…”

Section: Reference Velocitymentioning

confidence: 99%

See 1 more Smart Citation

Tornado-Induced and Straight-Line Wind Loads on a Low-Rise Building With Consideration of Internal Pressure

Roueche

Prevatt

Haan

2020

Front. Built Environ.

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Tornado and straight-line wind events are often discussed and compared in terms of their intensity, e.g., maximum wind speed, however, it is unclear to what extent tornadoinduced and straight-line wind-induced wind loads are equivalent even for the same nominal intensity. This lack of understanding inhibits both tornado design philosophies and policies, and communication of tornado risk to the public. This study directly compares existing wind tunnel databases of tornado-induced and straight-line windinduced pressures, for a similar building model, to evaluate to what extent the induced surface pressures on a typical building differ. The existing datasets used in the study are enhanced with a numerical internal pressure model to facilitate the comparison across a range of opening configurations that would be common in typical buildings. The analysis finds that differences are most pronounced in the overall distribution of pressures across the building surface, and in the magnitudes of pressures in regions of strong flow separation. However, overall the magnitudes of the peak tornado-induced pressures are reasonably similar to straight-line wind-induced pressures, with tornadoinduced pressures on average 13% higher than equivalent straight-line wind-induced pressures. Ultimately, this study demonstrates a framework for such comparisons, while recognizing key sources of uncertainty and further research needs.

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Section: Introductionmentioning

confidence: 85%

Section: Reference Velocitymentioning

confidence: 99%

Tornado-Induced and Straight-Line Wind Loads on a Low-Rise Building With Consideration of Internal Pressure

Roueche

Prevatt

Haan

2020

Front. Built Environ.

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“…Given the sampling rate of 15HZ, the averaging time of the PIV measurements is 132 sec. Refan et al, (2014) reported a length scale of λ l =1/1500 for simulating mid-range EF1 to low-end EF3 rated tornadoes in MWD. The typical velocity scale of F2 tornado simulations is equal to λ v =1/7.7 (Haan et al, 2008).…”

Section: Comparison Considerationsmentioning

confidence: 99%

“…Saying that, the velocity scale of tornado simulation needs to be identified independent of the radial Reynolds number condition. As suggested by Refan et al (2014), the ratio between the overall maximum tangential velocity of a real tornado and that of a simulated one (V tan,max,D /V tan,max,S ) is selected to calculate the velocity length scales for each simulated tornado.…”

Section: Similarity Analysismentioning

confidence: 99%

Physical Simulation of Real Tornadoes

Refan

Hangan

2015

Structures Congress 2015

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Laboratory simulations of tornado-like vortices have the advantage of controlled conditions and repeatability. Previously these experiments have been conducted in Tornado Vortex Chambers (TVC). These TVC's had the advantage of independently controlling the radial/axial flow rate and the tangential components using a fan at the top and a swirling device at the bottom. Because of the swirling device, the flow region of interest is optically inaccessible. The Wind Engineering, Energy and Environment (WindEEE) Dome at Western is a unique large, 3D wind testing chamber, of 25 meters inner diameter and 40 meters outer diameter (including the return circuit). By using a system of 100 dynamic fans on the peripheral walls coupled with 6 larger fans at the ceiling level, WindEEE can produce any type of wind systems including 4 meters in diameter translating tornadoes and downbursts as well as a variety of dynamically shear flows. Flow visualizations and surface pressure measurements demonstrate the variation of the tornado flow field with Swirl ratio which compares very well with the former TVC well controlled experiments. Full scale Doppler radar data and WindEEE PIV measurements are shown to match for a range of Fujita Scales (Fig. 1). Based on this matching, scaling relations between the laboratory (WindEEE Dome) tornadoes and real tornadoes are for the first time drawn.

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“…Haan et al (2008) improved the technique of creating swirling flow by placing the guide vanes at a high position to allow vertical circulation of flow in the process of generating a tornado. Recently, Refan et al (2014) developed a new type of tornado vortex simulator (WindEEE) that can produce swirl winds of variable directionality by manipulating the outflow and direction of the fans provided in the facility.…”

Section: Introductionmentioning

confidence: 99%