Kishor C. Mehta

Texas Tech field experiments for wind loads part 1: building and pressure measuring system

Abstract An important research facility has been constructed at Texas Tech University to study wind effects on low buildings in the field. This laboratory features many capabilities not found in past field experiments, and presents tremendous new learning opportunities. The facility is being used to pursue research in wind loads on building surfaces, internal pressures, performance of roofing in wind environment, and ventilation and exhaust studies around the building. The paper includes sufficient detail on the test building and pressure measuring system to permit researchers in physical and analytical modeling to make appropriate comparisons with the field measured data.

Texas tech field experiments for wind loads part II: meteorological instrumentation and terrain parameters

Abstract This paper presents information on the wind and terrain parameters at the Texas Tech Wind Engineering Research Field Laboratory. Details of the meteorological tower and instrumentation are given, as well as a description of the meteorological data which has been collected so far. The data and terra parameters will assist researchers in performing wind tunnel simulations.

Full/model-scale comparison of surface pressures on the Texas Tech experimental building

Abstract Wind characteristics for the Texas Tech University field site and four different flow simulations are discussed in order to evaluate the full/model-scale comparison of the surface pressures on the roof of the experimental building at this site. A total of 700 data records, each of 15 min duration, are used to describe the wind characteristics at the field site. These results are compared with those from the wind tunnel flow simulations at a geometric scale ratio of 1/50. The four simulations were achieved with the standard spire-roughness method and with three modifications of this technique. The final evaluation of each simulation is based on full/modelscale comparison of the extreme suction pressures observed on the roof near the leading edge for normal and oblique angles of attack.

Roof corner pressures measured in the field on a low building

Abstract This paper presents roof corner pressure data collected at the Wind Engineering Research Field Laboratory at Texas Tech University. Roof corner pressure data collected at several taps is analyzed for a large ensemble of records roughly covering all angles of attack. Data on area-averaged pressures and plots of instantaneous pressures over the surface area are also given.

Field measurements of pressures on the Texas tech building

Abstract Early results from the field experiment at Texas Tech University to determine wind pressures on a low-rise building are reported. The capability to rotate the building has provided useful, consistent ensembles of 15-min records for two angles-of-attack: 90° (wind normal to the long walls) and 60°. Mean, rms and peak pressure coefficients are presented for 11 points on the walls and roof along the centerline of the building. Mean wind speed, turbulence intensity, power-law exponent and roughness length data are given for use in wind tunnel testing. The design of the reference pressure system and the effects of moving average filters on the peak pressures are also discussed.

Internal pressures in a low-rise full-scale building

Theoretical analysis, numerical simulation and full-scale measurements were carried out to investigate internal pressures at the WERFL low-rise full-scale test building at Texas Tech. The mean and fluctuating internal pressure coefficients are small in the nominally sealed building; and increase with increasing windward/leeward open-area ratio. The effects of building flexibility on the internal pressure fluctuations are accounted for, in this study. Internal pressure fluctuations above a characteristic frequency are attenuated in the nominally sealed building. The internal pressure energy is increased close to the Helmholtz frequency, in the building with a single-dominant opening.

The distribution and correlation of fluctuating pressures on the Texas Tech Building

Full scale pressure measurements at the Texas Tech Field Research Laboratory have been used to investigate the distribution and correlation of fluctuating pressures on a low rise building. Eigenvector analysis of the covariances indicate that longitudinal and lateral turbulence are responsible for the majority of pressure fluctuations. However, a significant second eigenvector for flow normal to the roof edges corresponds with the rollup and discrete shedding of the separation bubble as a whole. Conditional sampling of peak pressures shows that they are better correlated spatially than the time averaged fluctuations.

Influence of incident wind turbulence on pressure fluctuations near flat-roof corners

Abstract Full-scale experiments were conducted on the low-rise experimental building at the Wind Engineering Research Field Laboratory of Texas Tech University with the aim to understand the mechanism for generation of the conical-vortex flow and its associated high roof-surface suctions. The clear cause-and-effect relationship between the incident wind, the conical vortices, and the induced roof-corner high-suction pressures has been confirmed through analyzing the simultaneously collected wind and pressure data and the synchronized conical-vortex images. Both horizontal and vertical wind angles of attack were found to affect the formation of conical vortices and the generation of high roof-corner suctions significantly. The critical role of the vertical wind angle in inducing extremely high suction peaks is discussed in detail as an effort to understand the basic mechanism for peak pressure generation in the roof-corner region. Thus, for a complete understanding of the turbulence effect of the incident wind on the fluctuations of the roof-corner surface pressures, the incident wind needs to be considered as a three-dimensional velocity vector, as it is in reality.

Climatology of tornadoes of India and Bangladesh

SummaryOn the basis of 51 tomadic events reported since 1835, the climatology of tornadoes across the Indian Subcontinent is elucidated. Tornadoes are most likely to occur during the late afternoon of the pre-monsoon months in northeast India or Bangladesh. A secondary maximum exists for the post-monsoon transitional period in the Northeast; moreover, tornadoes have been reported in a corridor extending to the northwest toward Pakistan. The characteristic weather patterns favoring the pre-monsoon severe storms are described. It is speculated that cycles of tornado years may be correlated to periods of reduced tropical cyclone activity.ZusammenfassungAuf Grund von Berichten über 51 Tornados seit 1835 wird eine klimatologische Beschreibung dieser Wirbelstdrme über dem indischen Subkontinent erstellt. Diese Stürme treten am häufigsten am Spätnachmittag wahrend der Vormonsunmonate in Nordostindien und Bangladesch auf. Ein sekundäres Häufigkeitsmaximum existiert wahrend der postmonsunalen Übergangsjahreszeit im Nordosten Indiens. Überdies wurden Tornados aus einem Korridor berichtet, der sich nordwestwärts gegen Pakistan hin erstreckt. Die charakteristischen Wetterlagen der Vormonsunmonate, welche das Auftreten von Tornados fördern, werden beschrieben. Tornadozyklen scheinen mit Perioden reduzierter tropischer Zyklonenaktivität korreliert zu sein.

Field experiments for building aerodynamics

Abstract A field research facility has been constructed at Texas Tech University to study bluff body aerodynamics for a low-rise building. This facility features new capabilities not found in past field experiments. A variety of research is being pursued at the facility including wind loads on building surfaces, internal pressures, performance of roofing materials, and wind flow around the building. This paper contains a description of the field facility, and provides an introduction to some of the current experiments. The results of an internal pressure study are also presented.