Experimental analysis of the vorticity and turbulent flow dynamics of a pitching airfoil at realistic flight (helicopter) conditions

Improved basic understanding, predictability, and controllability of vortex-dominated and unsteady aerodynamic flows are important in enhancement of the performance of next generation helicopters. The primary objective of this research project was improved understanding of the fundamental vorticity and turbulent flow physics for a dynamically stalling airfoil at realistic helicopter flight conditions. An experimental program was performed on a large-scale (C = 0.45 m) dynamically pitching NACA 0012 wing operating in the Texas A&M University large-scale wind tunnel. High-resolution particle image velocimetry data were acquired on the first 10-15% of the wing. Six test cases were examined including the unsteady (k>0) and steady (k=0) conditions. The relevant mechanical, shear and turbulent time-scales were all of comparable magnitude, which indicated that the flow was in a state of mechanical non-equilibrium, and the expected flow separation and reattachment hystersis was observed. Analyses of the databases provided new insights into the leading-edge Reynolds stress structure and the turbulent transport processes. Both of which were previously uncharacterized. During the upstroke motion of the wing, a bubble structure formed in the leading-edge Reynolds shear stress. The size of the bubble increased with increasing angle-of-attack before being diffused into a shear layer at full separation. The turbulent transport analyses indicated that the axial stress production was positive, where the transverse production was negative. This implied that axial turbulent stresses were being produced from the axial component of the mean flow. A significant portion of the energy was transferred to the transverse stress through the pressure-strain redistribution, and then back to the transverse mean flow through the negative transverse production. An opposite trend was observed further downstream of this region

Physical properties of soybean cultivated in NEH region of India

This study was conducted to investigate physical properties of soybean cultivated in NEH region of India.  Major, minor and intermediate mean diameters of soybean seeds were 8.88±0.55 mm, 4.68±0.32 mm and 6.46±0.36 mm, respectively.  Geometric mean diameter was 6.45±0.35 mm. Mean roundness of the seeds was 0.66±0.02, while mean sphericity of the seeds in their natural rest position was 0.73±0.02.  Bulk density, true density, porosity, thousand seeds weight and angle of repose were 749.50±1.59 kg/m3, 1171.80±115.02 kg/m3, 34.62±9.00 %, and 177.55±3.04 g and 25.82±1.88 º, respectively.  The coefficient of static friction over aluminum, mild steel, and plywood surfaces were 0.46±0.03, 0.45±0.03 and 0.47±0.02, respectively. Statistical analysis indicated that the indigenous cultivar commonly found in NEH region was significantly difference from the cultivars found in the plains.   Keywords: soybean, physical properties, NEH region, Indi

Conceptual Design of a Manufacturing Process for an Automotive Microchannel Heat Exchanger

Calls for higher fuel efficiency in the United States and Europe are driving the need for waste heat recovery in automotive markets. While conventional heat exchangers can be designed to meet the heat duty requirement, the resulting volume, weight, and thermal mass are too large for rapid transient response and packaging of the device. The lightweight, compact form factor of microchannel heat exchangers with submillimeter flow passages is attractive for automotive applications. However, the industrial use of microchannel heat exchangers continues to be inhibited by high manufacturing costs. The objective of this paper is to develop a microchannel heat exchanger concept capable of meeting the cost and performance goals for an automotive application. So-called printed-circuit microchannel heat exchangers are produced using a stacked-lamina approach in which individual metal laminae are photochemically machined and diffusion bonded. Here, the conceptual design of a microchannel heat exchanger produced using more conventional stamping and joining technologies is discussed for an automotive application. The device is sized to provide waste heat recovery from an exhaust stream to engine coolant for a representative passenger vehicle with acceptable pressure loss. Using the specified design, a process-based cost model is presented showing cost modeling efforts to date including the capital investment and cost-of-goods-sold as a function of annual production volume. The initial results show a pathway for the cost effective integration of compact microchannel heat exchangers into advanced vehicle thermal management systems

Direct CO2 Addition to a Ni(0)-CO Species Allows the Selective Generation of a Nickel(II) Carboxylate with Expulsion of CO

Addition of CO, to a low-valent nickel species has been explored with a newly designed (PNP)-P-acri pincer ligand ((PNP-)-P-acri = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide). This is a crucial step in understanding biological CO2 conversion to CO found in carbon monoxide dehydrogenase (CODH). A four-coordinate nickel(0) state was reliably accessed in the presence of a CO ligand, which can be prepared from a stepwise reduction of a cationic {((PNP)-P-acri)Ni(II)-CO}(+) species. All three Ni(II), Ni(I), and Ni(0) monocarbonyl species were cleanly isolated and spectroscopically characterized. Addition of electrons to the nickel(II) species significantly alters its geometry from square planar toward tetrahedral because of the filling of the d(x)(-y)(2)(2) orbital. Accordingly, the CO ligand position changes from equatorial to axial, angle N-Ni-C of 176.2(2)degrees to 129.1(4)degrees, allowing opening of a CO, binding site. Upon addition of CO2 to a nickel(0) CO species, a nickel(II) carboxylate species with a Ni(eta(1)-CO2-KC) moiety was formed and isolated (75%). This reaction occurs with the concomitant expulsion of CO(g). This is a unique result markedly different from our previous report involving the flexible analogous PNP ligand, which revealed the formation of multiple products including a tetrameric cluster from the reaction with CO2. Finally, the carbon dioxide conversion to CO at a single nickel center is modeled by the successful isolation of all relevant intermediates, such as Ni-CO2, Ni-COOH, and Ni-CO

Bridging organic, molecular, macromolecular, supramolecular and biological sciences to create functions via fluorine chemistry and fluorinated reagents

After a brief introduction highlighting the challenges of fluorine chemistry and the latest developments in the field, this Perspective will discuss how a combination of fluorine and fluorous chemistry together with fluorinated reagents helped to bridge between organic, molecular, macromolecular, supramolecular and biological sciences to create functions in the laboratory of the corresponding author. The reactivity of fluoride as a leaving group is best illustrated by SNAr reactions when it helped to demonstrate single electron transfer-mediated side reactions and through molecular design replaced activated aryl fluorides with aryl chlorides in the synthesis of poly(etherketone)s. Subsequently it was demonstrated how Ni(II) sigma complexes provided an orthogonal approach to the Suzuki-type cross-coupling of arylfluorides, other halides and all aryl C–O based electrophiles. Fluorinated reagents facilitated cylotrimetrization vs cyclotetramerization of bis(methoxy)benzyl chloride and alcohol and the synthesis of the simplest molecular liquid crystals. Triflic acid, methyl triflate facilitated the most tolerant living polymerizations including of cyclic siloxanes, functional vinyl ethers and oxazolines to generate self-organizable dendronized polymers while fluorine, trifluoromethyl and trifluoromethoxy groups facilitated disassembly and reassembly of liquid crystal polyethers and poly(p-phenylenes). Fluorinated stereocenters accessed the first heterochiral recognition in side-chain liquid crystal poly(vinyl ether)s and their model compounds. Alkali metal triflates mediated self-organization of supramolecular nonfluorinated and fluorinated self-assembling minidendrons, dendrons, dendrimers and self-organizable dendronized polymers. The role of fluorinated alkyl groups and of alkali metal triflates in the self-assembly, disassembly and isomorphic replacement analysis, of supramolecular helical columns, of the assembly of helical cogwheel coat and of spherical supramolecular dendrimers forming Frank-Kasper periodic and quasiperiodic arrays was highlighted. A brief discussion of fluorinated amino acids, peptides and peptoids and their potential role in the self-assembly and functions resulted from dendritic dipeptides followed by a discussion of semifluorinated amphiphilic Janus dendrimers as models of biological membranes, including for cell fusion and fission, concludes this Perspective

Molecular design principles of helical pyramidal chirality self-organized from achiral hexakis(alkyloxy)triphenylene

2,3,6,7,10,11-Hexakis(alkyloxy)triphenylene (HATn) containing n = 4 to 12 carbons in its alkyl groups, are a classic group of discotic molecules self-organizing columnar liquid crystals. The structure of the crystalline assemblies of these discotic molecules were neglected since they were invented 45 years ago. Recently, we discovered that the crystal state of HAT4 consists of a highly ordered 8/1 helical chiral pyramidal 3D self-organization. In this publication we report the structural analysis of all 3D self-organizations of HATn containing n = 4 to 12 carbons in their achiral alkyls. Unexpectedly, the highly ordered 8/1 helical chiral pyramidal crystalline columns assembled from the crown-conformation of HAT4 is encountered also in the crystalline periodic array of HAT5. HAT6 self-organizes a 5/1 helical chiral pyramidal 3D column. HAT7 to HAT10 maintain their crown conformation in their 3D supramolecular pyramidal columns. However, their 3D pyramidal assemblies exhibit a nonhelical criss-cross arrangement. HAT11 and HAT12 self-organize 3D nonhelical columns from criss-cross arrangements of disc-like conformers. The structures of all these 3D helical and nonhelical pyramidal as well as of nonhelical discotic columns were resolved for the first time at the molecular level by reconstruction of their oriented fiber X-ray diffractograms with the help of molecular models. These results demonstrate that a single self-assembling building block can self-organize either helical chiral pyramidal or nonhelical pyramidal or even nonhelical discotic assemblies via two of its constitutional isomers. This outcome prompts essential questions related to the current standing of helical self-organizations. The most important question is, why over the past many years the scientific community explored helical self-organizations derived from long alkyl groups when the ideal alkyls for this process seem to be short? A hypothetic explanation of the findings reported here and of their impact on the field of helical self-organizations is presented

Razvoj i ocena rada mernog mehanizma za širokorednu sejalicu na brdskim terenima

Inclined plate seed metering device was designed and evaluated in laboratory for singulation and uniform placement of maize and soybean seeds at three different cell shapes and sizes. The performance parameters like average spacing, multiple index, quality of feed index and precision were measured. Among the combinations of design variables, the seed metering plate with semi-circular cell shape having cell size 7 mm diameter was found to be the optimum for metering maize seed. Average spacing, quality of feed index, multiple index, miss index and precision were 17.48 cm, 79.33 %, 18.67 %, 2 % and 10.5 %, respectively. Likewise, the seed metering plate with semi- circular cell shape having cell size of 12 mm diameter was found to be optimum for metering soybean seed. Average spacing, quality of feed index, multiple index, miss index and precision were 9.65 cm, 77.33 %, 14.33 %, 8.34 % and 18.73 %, respectively. Therefore, considering all the performance parameters, inclined plate metering device with semi-circular shape of cell diameters 7 mm and 12 mm were selected for maize and soybean seeds, respectively.Merni uređaj sa kosom pločom za merenje izbacivanja zrna konstruisan je i ispitivan u laboratoriji. Ispitivani su pojedinačno polaganje i ujednačenost polaganja semena kukuruza i soje sa tri različita oblika i veličine ćelija. Mereni su parametri kao što su: srednje rastojanje, index umnožavanja, indeks kvaliteta punjenja i preciznost. Među kombinacijama promenljivih veličina u konstrukcijama, merna ploča sa polukružnim ćelijama i prečnikom ćelije od 7 mm bila je optimalna za merenje izbacivanja semena kukuruza. Srednje rastojanje, indeks kvaliteta punjenja, index umnožavanja, indeks greške i preciznost iznosili su 17.48 cm, 79.33 %, 18.67 %, 2 % i 10.5 %, redom. Merna ploča sa polukružnim ćelijama i prečnikom ćelije od 12 mm bila je optimalna za merenje izbacivanja semena soje. Srednje rastojanje, indeks kvaliteta punjenja, index umnožavanja, indeks greške i preciznost iznosili su 9.65 cm, 77.33 %, 14.33 %, 8.34 % i 18.73 %, redom. Imajući u vidu sve parametre, merni uređaji sa kosim pločama sa polukružnim ćelijama prečnika 7 mm i 12 mm bili su izabrani za setvu semena kukuruza i soje, redom

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Not AvailableWeeding is one of most important operation in crop cultivation. Although, there are several methods are available of mechanical weeding, but weeding operation poses a special problem in ridge planted crop. Therefore, to address this problem a ridge profile power weeder was developed with 2.20 kW petrol-start kerosene-run engine and evaluated for its performance in terms of weeding efficiency, plant damage percentage and field capacity. Weeder comprised of main frame, handle, cutting blades, rotor shaft, belt and pulley, engine and ground wheel. Experiments were conducted at three different levels of each parameter viz, soil moisture content (15.26 ±0.96, 12.42 ±0.52 and 9.44 ±0.68%), blade types (Ltype, C-type and Flat-type) and gang speed (160, 180 and 200 rpm). Results revealed that, C-type blades were most suitable at gang speed of 200 rpm and 15.26 ±0.96% (d.b) soil moisture content with average weeding efficiency, plant damage, actual field capacity of 83.93%, 1.77%, and 0.066 ha h-1, respectively. The total estimated cost of machine was Rs.27,600 ($460) and its cost of operation was Rs. 640/- per ha. The saving in cost of operation was 88.3% as compared to manual weeding (Rs. 5,470). Time saving with ridge profile power weeder as compared to manual weeding was 93.93%. The ridge profile power weeder had a breakeven point at 179.38 h yr-1 with a payback period of 2.74 yearsNot Availabl

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Not AvailableA two-row self-propelled multicrop planter for hilly areas was developed, and its performance evaluated for planting of maize and soybean seeds. Power was transmitted from a 1.57 kW engine to the drive wheels and metering mechanism through chain and sprockets. Inclined plate type seed metering mechanism was used in the planter. Seeds were placed in the furrows at desired depths through adjustable system. The average depths of seed placement were 22.50 mm and 21.50 mm for maize and soybean, respectively. The average draft requirement for the planter was 1.57 kN, which was within the capacity of the power source. Average field capacity of 0.11 ha.h-1 was obtained for continuous operation of the planter at an average forward speed of 1.36 km.h-1 for planting both maize and soybean. The average field efficiency and field machine index of the planter were observed to be 80.98 and 71.78 %, respectively. The man-hour requirement for planting of one hectare land with the planter was 9.09. The cost of sowing with the planter was Rs.1100/- per hectare, which saved 64.80 % operational costs as compared to manual planting. The savings in man-hours and cost of planting were substantial.Not Availabl