Internal and net roof pressures for a dynamically flexible building with a dominant wall opening

Rajnish N Sharma 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.16 No.1

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

Scaling methods for wind tunnel modelling of building internal pressures induced through openings

Sharma, Rajnish N.,Mason, Simon,Driver, Philip Techno-Press 2010 Wind and Structures, An International Journal (WAS Vol.13 No.4

Appropriate scaling methods for wind tunnel modelling of building internal pressures induced through a dominant opening were investigated. In particular, model cavity volume distortion and geometric scaling of the opening details were studied. It was found that while model volume distortion may be used to scale down buildings for wind tunnel studies on internal pressure, the implementation of the added volume must be done with care so as not to create two cavity resonance systems. Incorrect scaling of opening details was also found to generate incorrect internal pressure characteristics. Furthermore, the effective air slug or jet was found to be longer when the opening was near a floor or sidewall as evidenced by somewhat lower Helmholtz frequencies. It is also shown that tangential flow excitation of Helmholtz resonance for off-centre openings in normal flow is also possible.

Aerodynamics of an intercity bus

Sharma, Rajnish,Chadwick, Daniel,Haines, Jonathan Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.4

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package $CFX^{TM}$ was used. It has been found that dramatic reductions in coefficient of drag ($C_D$) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended.

Aerodynamics of an intercity bus

Rajnish Sharma,Daniel Chadwick,Jonathan Haines 한국풍공학회 2008 Wind and Structures, An International Journal (WAS Vol.11 No.4

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package CFX™ was used. It has been found that dramatic reductions in coefficient of drag (CD) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended

Scaling methods for wind tunnel modelling of building internal pressures induced through openings

Rajnish N Sharma,Simon Mason,Philip Driver 한국풍공학회 2010 Wind and Structures, An International Journal (WAS Vol.13 No.4

Appropriate scaling methods for wind tunnel modelling of building internal pressures induced through a dominant opening were investigated. In particular, model cavity volume distortion and geometric scaling of the opening details were studied. It was found that while model volume distortion may be used to scale down buildings for wind tunnel studies on internal pressure, the implementation of the added volume must be done with care so as not to create two cavity resonance systems. Incorrect scaling of opening details was also found to generate incorrect internal pressure characteristics. Furthermore, the effective air slug or jet was found to be longer when the opening was near a floor or sidewall as evidenced by somewhat lower Helmholtz frequencies. It is also shown that tangential flow excitation of Helmholtz resonance for off-centre openings in normal flow is also possible.

Internal and net roof pressures for a dynamically flexible building with a dominant wall opening

Sharma, Rajnish N. Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.16 No.1

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

A novel CdTe/Eu-MOF photoanode for application in quantum dot-sensitized solar cell to improve power conversion efficiency

Rajnish Kaur,Amit L. Sharma,김기현,Akash Deep 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-

The quantum dots (QDs) and metal-organic frameworks (MOFs) have emerged as the efficient nanomaterials for light harvesting, photocatalysis, and photovoltaic applications. Here, the application of a composite of CdTe QDs with a europium-MOF was demonstrated as a novel photoanode to achieve the improvement in the short circuit current density from 19.8 (CdTe QD) to 28.45 mA/cm2 (CdTe QD/Eu- MOF). So does power conversion efficiency (PCE) between the former (1.67%) and the latter (3.02%). This 1.35% of difference (or absolute enhancement) in the PCE can be attributed to an enhanced surface area and increased photon absorption capacity.

Evolving Constructs & Measurements of Aviation Fuel Consumption: An Analytical View

Jagroop Singh,Somesh Kumar Sharma,Rajnish Srivastava,Deepjyoti Das 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.7

Aviation fuel is a major stakeholder in total operating cost of air transportation. Increasing competition & challenge to keep thetravel expenses low to survive have created interest in fuel consumption reduction. Although interest of researchers for Reduction inAviation Fuel Consumption (RAFC) is growing, yet no study has undertaken initiative towards a development of RAFC frameworkand instruments. Therefore, this article is an effort to present measurement models with different variables for estimating the RAFCthrough non-financial and financial measures. The study, through extensive literature review identifies and integrates various fuelconsumption reduction initiatives and measures to develop key RAFC constructs conducive for further improvement in aviation fuelefficiency. The RAFC is sub classified as driving forces measurement model, implementation measurement model and performancemeasurement model. Factor Analysis (FA) and measurement models were used to investigate various constructs of RAFC. Aftersequence of tests and analysis, study provide refined measurements with acceptable psychometric properties. These measurementscan also be applied to varying contexts to extend conceptualization or to test different conceptual models, advancing RAFC theorybuilding.

Hypercalcemia, multiple osteolytic lesions, and acute renal failure: a rare presentation of B-cell acute lymphoblastic leukemia

Vandana Puri,Pooja Sharma,Sundaram Gopalakrishnan,Meera Sikka,Rajnish Avasthi 대한혈액학회 2017 Blood Research Vol.52 No.1

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Hypercalcemia, multiple osteolytic lesions, and acute renal failure: a rare presentation of B-cell acute lymphoblastic leukemia

Vandana Puri,Pooja Sharma,Sundaram Gopalakrishnan,Meera Sikka,Rajnish Avasthi 대한혈액학회 2017 Blood Research Vol.52 No.1

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