A note on premixed flame-turbulence interactions

This note focuses on the three fundamental mechanisms behind premixed flame-turbulence interactions that result in progressive acceleration of a spark-ignited flame in a turbulent environment such as that inside a spark-ignition engine cylinder. In addition, as a small step in further advancing our understanding on flame-turbulence interactions, experiments were conducted to quantify the changing turbulence parameters associated with a near-isotropic turbulent free-stream as it approaches a solid sphere in a wind tunnel. It has been observed in some previous studies that when a premixed combustible mixture is ignited in a turbulent environment, the turbulent flame speed / turbulence intensity ratio increases as the flame grows. Depending on the chemical and physical parameters involved, this accelerating turbulent flame may develop into a detonation wave. Over the years, three fundamental mechanisms have been postulated by different experts to explain this progressive turbulence enhancement in flame speed. 1) During the initial stages after ignition, only eddies that are smaller than the flame ball influence the flame front significantly. As the flame grows, the flame / eddy size ratio increases and consequently, increasingly larger portion of the eddying motion associated with the turbulent energy cascade becomes effective in affecting the flame front. 2) Analogous to the exponential increase of a material surface in homogeneous isotropic turbulence, proposed by Batchelor in 1952, the ongoing flame surface-turbulence interactions can lead to continuous increase in reacting flame front surface. 3) In 1995, Ashurst postulated that for a wrinkled flame, volume expansion of a portion of the reacting surface pushes the adjacent flame surface away from it. This expansion-pushing effect enhances flame front corrugation, and hence, accelerates the flame. The characterization of near-isotropic turbulence as it approaches a sphere was conducted in a 75 cm by 75 cm wind tunnel. The turbulent free-stream was generated by a 43% solid, perforated plate having orifice holes of diameter D of 3.75 cm. The stream-wise root mean square velocity fluctuation, turbulence intensity, integral and Kolmogorov scales were deduced from instantaneous velocity measurements via a normal hot-wire anemometer. These measurements were made at 6.4 cm (2.5a3) and 8.9 cm (3.5a3) upstream of a 10 cm diameter (d) sphere fixed at 20D downstream of the perforated plate, at a Reynolds number based on the mean flow velocity and the diameter of the sphere of 5 x 104. Copyright © 2005 SAE International

Small hydropower for sustainable energy development in India

Adequate amount of energy generation in a sustainable manner is a major challenge in the present energy scenario. Fast depleting fossils fuels and their environmental effects forces to look towards renewable sources for sustainable development. Among all renewable sources, small hydropower (SHP) is one of the promising sources for sustainable water and energy development. The geography of India supports the development of small hydro projects to enhance the energy generation. Small hydropower development is also necessary for proper utilization of available water resources. Present study has been carried out to highlight the water resource and small hydropower potential in India. Utilization of small hydropower sources for sustainable development has also been presented.Small hydropower Renewable Energy Water resources

Synthesis and spectral studies of some lanthanide(III) complexes with 4-[N-(<i>p</i>-dimethylaminobenzalidene)amino] antipyrine semicarbazone

In the present work, we describe the isolation of some lanthanide(III) complexes of 4-[N-(<i>p</i>-dimethylaminobenzalidene)amino]antipyrine semicarbazone (DABAAPS) with general composition [Ln(DABAAPS)2X3] (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy or Ho and X = Cl^- and NCS^-). All the isolated compounds were characterized through various physico-chemical studies. The coordinating ligand DABAAPS behave as tridentate N,N,O-donors. The central metal ion displays the coordination number nine in these complexes. Thermal stabilities of these complexes were also studied through thermogravimetric analysis

Experimental investigation of perforated plate turbulent flow past a solid sphere

As the first stage of a comprehensive investigation of turbulence effect on the aerodynamics of sphere, the effect of freestream turbulence on the wake generated behind a sphere is investigated in this study. A 10 cm (4 in) diameter plastic sphere was placed in a wind tunnel of cross section 75 cm by 75 cm. The freestream turbulence was generated by fixing a perforated plate to the entrance of the test section. The wake was characterized using a normal constant-temperature hot-wire at 30D, 40D and 50D (11.25d, 15d & 18.75d respectively) downstream of the sphere (where D = 3.75 cm is the diameter of the perforated plate hole, and d is the diameter of the sphere). The Reynolds number of the flow, based on the mean velocity and the diameter of the sphere, was 6.6 × 104. Based on the instantaneous velocity measurement, Kolmogorov length scale, integral length scale and relative turbulence intensity in the wake were deduced. Copyright © 2004 by ASME

Experimental study of vortex shedding from a solid sphere in turbulent freestream

The study of vortex shedding from a sphere assumes an important role because of its relevance to numerous aerodynamic and hydrodynamic applications. Parameters such as coefficient of drag and static pressure distribution are largely influenced by vortex shedding, and it is found by past studies that the freestream turbulence can interact and alter the vortex formation and shedding drastically. Most of these studies, however, were conducted in the low Reynolds number regime and the vortex shedding results had been described only qualitatively. To better understand the aerodynamics of a sphere in turbulent flow, an experimental study was initiated in a low speed wind tunnel to quantify the vortex shedding characteristics. The Reynolds number of the flow, based on the diameter of the sphere (d), was set at 3.3 × 104, 5 × 104 and 6.6 × 104 by varying the mean flow velocity. The sphere was placed at 20D (= 7.5d) downstream from a perforated plate, where D = 37.5 mm is the size of the holes in the perforated plate, uniquely designed for generating near-isotropic turbulence. Hot-wire measurements were taken at 10D (= 3.75d), 20D (= 7.5d) and 30D (= 11.25d) downstream of the sphere in absence and presence of the perforated plate. The vortex shedding frequency was deduced from the instantaneous flow velocity data. Copyright © 2005 by ASME

Experimental study of vortex shedding from A solid sphere in turbulent freestream

The study of vortex shedding from a sphere assumes an important role because of its relevance to numerous aerodynamic and hydrodynamic applications. Parameters such as coefficient of drag and static pressure distribution are largely influenced by vortex shedding, and it is found by past studies that the freestream turbulence can interact and alter the vortex formation and shedding drastically. Most of these studies, however, were conducted in the low Reynolds number regime and the vortex shedding results had been described only qualitatively. To better understand the aerodynamics of a sphere in turbulent flow, an experimental study was initiated in a low speed wind tunnel to quantify the vortex shedding characteristics. The Reynolds number of the flow, based on the diameter of the sphere (d), was set at 3.3 × 104, 5 × 104 and 6.6 × 104 by varying the mean flow velocity. The sphere was placed at 20D (= 7.5d) downstream from a perforated plate, where D = 37.5 mm is the size of the holes in the perforated plate, uniquely designed for generating near-isotropic turbulence. Hot-wire measurements were taken at 10D (= 3.75d), 20D (= 7.5d) and 30D (= 11.25d) downstream of the sphere in absence and presence of the perforated plate. The vortex shedding frequency was deduced from the instantaneous flow velocity data. Copyright © 2005 by ASME

Measurement of wake properties of a sphere in freestream turbulence

Experimental investigations were carried out for flow past a sphere in a closed circuit wind tunnel. The sphere was made of polymer material and had a diameter of 102 mm. Freestream turbulence was generated by placing an orificed perforated plate at the entrance of the test section. The Reynolds number of the flow, based on the diameter of the sphere (d), was set at 3.3 × 104, 5 × 104 and 6.6 × 104 by varying the mean flow velocity. The sphere was placed at 20D (=7.5d) downstream from the entrance of the test section, where D = 37.5 mm is the size of the holes in the perforated plate. Velocity profile of the flow was measured using a hot wire probe at 10D (=3.75d), 20D (=7.5d) and 30D (=11.25d) downstream of the sphere (center). Experiments were carried out without and with the perforated plate in place in order to study the influence of freestream turbulence on parameters such as Kolmogorov length, dissipation rate, integral length, and the skewness and flatness factors. The presence of freestream turbulence was found to reduce the vortex shedding process behind the sphere, that is, large organized motions were suppressed by the freestream turbulence. © 2005 Elsevier Inc. All rights reserved

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Not AvailableArtificial Intelligence (AI) and Internet of Things (IoT) have a huge potential to effectively address the issues of climate change. The aim of this study is to present the role of AI and IoT based technologies in making environment friendly smarter and higher performing systems. These technologies aid in managing the climate change impacts by utilizing limited resources and less human interference. Integrating IoT and AI technologies, data is collected from sensors in the  eld about soil moisture, weather conditions, fertilization levels, irrigation system, soil composition and temperature. This helps in increasing the crop production which eventually lead to higher income for farmers.Not Availabl