Downburst Flow Simulation and Evaluation of Downburst Wind Effects on Buildings

Authors

Alvaro Danilo MejiaFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Civil Engineering

First Advisor's Name

Amal Elawady

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Arindam Gan Chowdhury

Second Advisor's Committee Title

Co-Committee Chair

Third Advisor's Name

Peter Irwin

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Ioannis Zisis

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Seung Jae Lee

Fifth Advisor's Committee Title

Committee Member

Sixth Advisor's Name

Pezhman Mardanpour

Sixth Advisor's Committee Title

Committee Member

Keywords

Downburst, Low-rise buildings, Thunderstorm, Nonsynoptic wind, Wall of Wind, Wind tunnel testing, Pressure Coefficient, Gable-roof, Transient loading, Wind Engineering.

Date of Defense

9-30-2022

Abstract

Downbursts are non-stationary, non-Gaussian, transient, localized high wind events that constitute considerable damage to structures. Five different downburst simulator designs were tested and assessed in a 1:15 small-scale replica of the Wall of Wind (WOW) Experimental Facility (EF) from which only one was chosen to be constructed in the large-scale WOW EF. The chosen simulator consists of a two-louver slat system opening from 0° to 90° with respect the vertical plane with a blockage system in the upper region so that it can redirect the flow to a 2-D wall jet. The original WOW flow management box is utilized as the main flow inlet source to produce large outflows in the testing area. The simulations provided three fundamental characteristics of a downburst for large-scale structural testing. These include, the formation of a main rolling vortex, the vertical profile of horizontal wind velocities resembling a ‘nose shape’ and the transient peak zone found in the velocity time history. Also, the simulations provided maximum velocities occurring near the ground with peak wind speed height relatively high. The large size of the formed main rolling vortex indicates high Reynold Number which is suitable for large-scale testing to minimize possible scaling effects. In addition, three different aerodynamic scaled models of a one-story, nearly flat, gabled-roof representing the Texas Tech University Wind Engineering Field Research Laboratory (TTU WERFL) experimental building were tested to assess the downburst-induced aerodynamic loads. The geometrical scales comprised 1:100, 1:50 and 1:20 in an open terrain. The instantaneous and peak pressure coefficients were first compared to those recorded for a full-scale downburst that occurred in Lubbock, Texas on June 19th, 2003. Second, the scaling effect was determined amongst the three scaled models. Third, the observed peak pressure coefficients were compared to Atmospheric Boundary Layer (ABL) tests on the same building models at different angles of incidence in increments of 45°. It was concluded that the pressure distribution in the experiments were similar to those obtained at full-scale but with smaller magnitudes. The scaling effects showed the smaller models obtained higher suction in the roof and downbursts governed the design over ABL.

Identifier

FIDC010857

ORCID

0000-0003-0632-5079

Previously Published In

Mejia, Alvaro Danilo, Amal Elawady, Krishna Sai Vutukuru, Dejiang Chen, and Arindam Gan Chowdhury. "Examination of different Wall Jet and Impinging Jet concepts to produce large-scale downburst outflow." Frontiers in Built Environment: 185.

Recommended Citation

Mejia, Alvaro Danilo, "Downburst Flow Simulation and Evaluation of Downburst Wind Effects on Buildings" (2022). FIU Electronic Theses and Dissertations. 5222.
https://digitalcommons.fiu.edu/etd/5222