Tornado-strength winds interacting with a highway overpass

Analysis of tornado strength winds interacting with a highway overpass structure is presented with emphasis on air flow patterns above and under the bridge. Experiments were performed in a wind tunnel with the scaled geometry of an overpass. Velocity and dynamic pressure measurements were obtained independently at four locations as the overpass was rotated about its vertical axis between air flow angles of approach between 0° and 90°, at 10° increments. Lift and drag forces on the overpass geometry were also measured. To compare various highway overpass locations with the surroundings, the measured dynamic pressure and velocity, drag and lift forces, and drag coefficients at each of the locations and approach angles were examined. It was found that at all locations, the measured velocities never exceeded the freestream velocity of 190.2 ft/s (58 m/s; 130 mph), with the maximum Re occurring above the overpass and between the I-beams. A theoretical maximum pressure drop for the tornado center was calculated to be 0.5 psi for an Enhanced Fujita 2 scale tornado and compared with the highest pressure drop of 0.278 psi, determined from the experiments. Calculated pressure coefficients Cp were mostly \u3c0 and some close to one dynamic head less than ambient. The drag coefficients Cd remain primarily in the laminar region with later transition to turbulence. Using experimental data from the literature, drag forces on an average size man in crouching and laying positions between the overpass I-beams section were determined to be a maximum of 31 lbf

POTs: Protective Optimization Technologies

Algorithmic fairness aims to address the economic, moral, social, and political impact that digital systems have on populations through solutions that can be applied by service providers. Fairness frameworks do so, in part, by mapping these problems to a narrow definition and assuming the service providers can be trusted to deploy countermeasures. Not surprisingly, these decisions limit fairness frameworks' ability to capture a variety of harms caused by systems. We characterize fairness limitations using concepts from requirements engineering and from social sciences. We show that the focus on algorithms' inputs and outputs misses harms that arise from systems interacting with the world; that the focus on bias and discrimination omits broader harms on populations and their environments; and that relying on service providers excludes scenarios where they are not cooperative or intentionally adversarial. We propose Protective Optimization Technologies (POTs). POTs provide means for affected parties to address the negative impacts of systems in the environment, expanding avenues for political contestation. POTs intervene from outside the system, do not require service providers to cooperate, and can serve to correct, shift, or expose harms that systems impose on populations and their environments. We illustrate the potential and limitations of POTs in two case studies: countering road congestion caused by traffic-beating applications, and recalibrating credit scoring for loan applicants.Comment: Appears in Conference on Fairness, Accountability, and Transparency (FAT* 2020). Bogdan Kulynych and Rebekah Overdorf contributed equally to this work. Version v1/v2 by Seda G\"urses, Rebekah Overdorf, and Ero Balsa was presented at HotPETS 2018 and at PiMLAI 201

Tornado-Strength Winds Interacting with a Highway Overpass

Analysis of tornado strength winds interacting with a highway overpass structure is presented with emphasis on air flow patterns above and under the bridge. Experiments were performed in a wind tunnel with the scaled geometry of an overpass. Velocity and dynamic pressure measurements were obtained independently at four locations as the overpass was rotated about its vertical axis between air flow angles of approach between 0 degrees and 90 degrees, at 10 degree increments. Lift and drag forces on the overpass geometry were also measured. To compare various highway overpass locations with the surroundings, the measured dynamic pressure and velocity, drag and lift forces, and drag coefficients at each of the locations and approach angles were examined. It was found that at all locations, the measured velocities never exceeded the freestream velocity of 190.2 ft/s (58 m/s; 130 mph), with the maximum Re occurring above the overpass and between the I-beams. A theoretical maximum pressure drop for the tornado center was calculated to be 0.5 psi for an Enhanced Fujita 2 (EF2) scale tornado and compared with the highest pressure drop of 0.278 psi, determined from the experiments. Calculated pressure coefficients Cp were mostly \u3c 0 and some close to one dynamic head less than ambient. The drag coefficients Cd remain primarily in the laminar region with later transition to turbulence. Using experimental data from the literature, drag forces on an average size man in crouching and laying positions between the overpass I-beams section were determined to be a maximum of 31 lbf