Relevant bibliographies by topics / Higher geometric twists

Academic literature on the topic 'Higher geometric twists'

Author: Grafiati
Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Higher geometric twists"

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Pym, Brent, and Pavel Safronov. "Shifted Symplectic Lie Algebroids." International Mathematics Research Notices 2020, no. 21 (September 7, 2018): 7489–557. http://dx.doi.org/10.1093/imrn/rny215.

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Abstract Shifted symplectic Lie and $L_{\infty }$ algebroids model formal neighborhoods of manifolds in shifted symplectic stacks and serve as target spaces for twisted variants of the classical topological field theory defined by Alexandrov--Kontsevich--Schwarz--Zaboronsky. In this paper, we classify zero-, one-, and two-shifted symplectic algebroids and their higher gauge symmetries, in terms of classical geometric “higher structures”, such as Courant algebroids twisted by $\Omega ^{2}$-gerbes. As applications, we produce new examples of twisted Courant algebroids from codimension-two cycles, and we give symplectic interpretations for several well-known features of higher structures (such as twists, Pontryagin classes, and tensor products). The proofs are valid in the $C^{\infty }$, holomorphic, and algebraic settings and are based on a number of technical results on the homotopy theory of $L_{\infty }$ algebroids and their differential forms, which may be of independent interest.
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Zhu, Wei. "A geometric higher twist effect on nuclear target." Nuclear Physics A 753, no. 1-2 (May 2005): 206–32. http://dx.doi.org/10.1016/j.nuclphysa.2005.02.085.

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Evans, David E., and Ulrich Pennig. "Equivariant higher twisted K$K$‐theory of SU(n)$SU(n)$ for exponential functor twists." Journal of Topology 15, no. 2 (June 2022): 896–949. http://dx.doi.org/10.1112/topo.12219.

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Phila, Arnut, Chinaruk Thianpong, and Smith Eiamsa-ard. "Influence of Geometric Parameters of Alternate Axis Twisted Baffles on the Local Heat Transfer Distribution and Pressure Drop in a Rectangular Channel Using a Transient Liquid Crystal Technique." Energies 12, no. 12 (June 18, 2019): 2341. http://dx.doi.org/10.3390/en12122341.

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This paper reports the effects of alternate axis twisted baffle geometric parameters on the heat transfer and flow characteristics within rectangular channels. In our experiments we used modified shapes of alternate axis twisted baffles according to relative pitch ratios (s/w) equal to 2–12 and twist ratios (y/w) equal to 1–5, under conditions where the angle of attack (α) was 90° and the relative blockage height (e/Dh) was at a constant value of 0.095. The results for the Reynolds numbers based on the duct hydraulic diameter ranged from 9000 to 24,000 at a constant Prandtl number, Pr = 0.707, using air as a working fluid. A 0.05 mm thick stainless-steel foil was used as a heater, and a thermochromic liquid crystal technique was used to obtain the local temperature distribution on the heated surfaces. Images were captured in areas with periodic, fully developed regions in the channel. The results show that rectangular channels equipped with alternate axis twisted baffles demonstrated 80%–185% greater heat transfer than rectangular channels with no baffles. Channels with alternate axis twisted baffles at higher twist ratios (y/w) and smaller relative pitch ratios (s/w) showed increased heat transfer, as well as pressure loss within the system, compared with other types of twisted baffles. The thermal enhancement factor of the rectangular channels equipped with alternate axis twisted baffles was higher than that for transverse baffles and smooth channels under similar operating conditions.
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Ohrt, Chris. "Twisted higher smooth torsion." Topology and its Applications 272 (March 2020): 107060. http://dx.doi.org/10.1016/j.topol.2020.107060.

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Ikeda, Noriaki. "Higher Dimensional Lie Algebroid Sigma Model with WZ Term." Universe 7, no. 10 (October 19, 2021): 391. http://dx.doi.org/10.3390/universe7100391.

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We generalize the (n+1)-dimensional twisted R-Poisson topological sigma model with flux on a target Poisson manifold to a Lie algebroid. Analyzing the consistency of constraints in the Hamiltonian formalism and the gauge symmetry in the Lagrangian formalism, geometric conditions of the target space to make the topological sigma model consistent are identified. The geometric condition is an universal compatibility condition of a Lie algebroid with a multisymplectic structure. This condition is a generalization of the momentum map theory of a Lie group and is regarded as a generalization of the momentum section condition of the Lie algebroid.
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Wang, Jun, Yaohui Liu, and Ruoxi Ding. "Analysis of Heat Transfer and Flow Characteristics of a Helically Coiled Tube with Twisted Elliptical in a Low Reynolds Number Flow." Processes 10, no. 11 (October 30, 2022): 2229. http://dx.doi.org/10.3390/pr10112229.

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In this paper, the heat transfer and flow characteristics of a helically coiled tube with twisted elliptical in a low Reynolds number (Re = 500–3000) flow were investigated numerically. The working fluid flowed in a laminar regime. Numerical results were compared with empirical correlations in the existing literature, demonstrating the accuracy of the analysis in this study. Firstly, we investigated the effects of geometric parameters and Reynolds number on the heat transfer and flow characteristics. The results showed that lower twist pitch length and semi-major axis length could induce sufficient fluid mixing and a larger temperature gradient near the tube wall, enhancing the heat exchange and producing larger friction resistance. Overall, the heat transfer performances were improved by about 1.04–1.21 times and 1.02–1.23 times for different semi-major axis lengths and different twist pitch lengths, respectively, compared to the smooth helical coil. Secondly, by changing the working fluid, it was found that the Nu when oil was chosen as the working fluid was all 6–6.8 times higher than that of water. Moreover, the effect of using Al2O3 nanofluids with a concentration of 0.10 wt.%, 0.25 wt.% and 0.50 wt.% was discussed. It can be seen that the heat transfer capacity of nanofluids increased by approximately 2–18% compared to the reference model with water as the working fluid, and the nanofluid solution with higher concentration has better heat transfer performance. Finally, Nu and f correlations are given to predict the heat transfer and pressure drop in practical applications.
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Noohi, Behrang, and Matthew B. Young. "Twisted loop transgression and higher Jandl gerbes over finite groupoids." Algebraic & Geometric Topology 22, no. 4 (October 10, 2022): 1663–712. http://dx.doi.org/10.2140/agt.2022.22.1663.

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Smith, Ivan. "Floer Theory of Higher Rank Quiver 3-folds." Communications in Mathematical Physics 388, no. 3 (November 11, 2021): 1181–203. http://dx.doi.org/10.1007/s00220-021-04252-2.

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AbstractWe study threefolds Y fibred by $$A_m$$ A m -surfaces over a curve S of positive genus. An ideal triangulation of S defines, for each rank m, a quiver $$Q(\Delta _m)$$ Q ( Δ m ) , hence a $$CY_3$$ C Y 3 -category $$\mathcal {C}(W)$$ C ( W ) for any potential W on $$Q(\Delta _m)$$ Q ( Δ m ) . We show that for $$\omega $$ ω in an open subset of the Kähler cone, a subcategory of a sign-twisted Fukaya category of $$(Y,\omega )$$ ( Y , ω ) is quasi-isomorphic to $$(\mathcal {C},W_{[\omega ]})$$ ( C , W [ ω ] ) for a certain generic potential $$W_{[\omega ]}$$ W [ ω ] . This partially establishes a conjecture of Goncharov (in: Algebra, geometry, and physics in the 21st century, Birkhäuser/Springer, Cham, 2017) concerning ‘categorifications’ of cluster varieties of framed $${\mathbb {P}}GL_{m+1}$$ P G L m + 1 -local systems on S, and gives a symplectic geometric viewpoint on results of Gaiotto et al. (Ann Henri Poincaré 15(1):61–141, 2014) on ‘theories of class $${\mathcal {S}}$$ S ’.
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Bochicchio, Marco. "Higher-Spin Currents, Operator Mixing and UV Asymptotics in Large-N QCD-like Theories." Universe 9, no. 2 (January 17, 2023): 57. http://dx.doi.org/10.3390/universe9020057.

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We extend to operator mixing—specifically, to higher-spin twist-2 operators—the asymptotic theorem on the ultraviolet asymptotics of the spectral representation of 2-point correlators of multiplicatively renormalizable operators in large-N confining QCD-like theories. The extension is based on a recent differential geometric approach to operator mixing that involves the Poincaré-Dulac theorem and allows us to reduce generically the operator mixing to the multiplicatively renormalizable case, provided that γ0β0 is diagonalizable and a certain nonresonant condition for its eigenvalues holds according to the Poincaré-Dulac theorem, with γ0 and β0 the one-loop coefficients of the anomalous dimension matrix and beta function respectively. Relatedly, we solve a conundrum about the generic nonconservation of higher-spin currents versus the conservation—up to contact terms—of the corresponding free propagators in the spectral representation of 2-point correlators of higher-spin operators of pure integer spin to the leading large-N order.
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Dissertations / Theses on the topic "Higher geometric twists"

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Nordblad, Erik. "Opening New Radio Windows and Bending Twisted Beams." Doctoral thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-158797.

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In ground based high frequency (HF) radio pumping experiments, absorption of ordinary (O) mode pump waves energises the ionospheric plasma, producing optical emissions and other effects. Pump-induced or natural kilometre-scale field-aligned density depletions are believed to play a role in self-focussing phenomena such as the magnetic zenith (MZ) effect, i.e., the increased plasma response observed in the direction of Earth's magnetic field. Using ray tracing, we study the propagation of ordinary (O) mode HF radio waves in an ionosphere modified by density depletions, with special attention to transmission through the radio window (RW), where O mode waves convert into the extraordinary (X, or Z) mode. The depletions are shown to shift the position of the RW, or to introduce RWs at new locations. In a simplified model neglecting absorption, we estimate the wave electric field strength perpendicular to the magnetic field at altitudes normally inaccessible. This field could excite upper hybrid waves on small scale density perturbations. We also show how transmission and focussing combine to give stronger fields in some directions, notably at angles close to the MZ, with possible implications for the MZ effect. In a separate study, we consider electromagnetic (e-m) beams with helical wavefronts (i.e., twisted beams), which are associated with orbital angular momentum (OAM). By applying geometrical optics to each plane wave component of a twisted nonparaxial e-m Bessel beam, we calculate analytically the shift of the beam's centre of gravity during propagation perpendicularly and obliquely to a weak refractive index gradient in an isotropic medium. In addition to the so-called Hall shifts expected from paraxial theory, the nonparaxial treatment reveals new shifts in both the transverse and lateral directions. In some situations, the new shifts should be significant also for nearly paraxial beams.
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Brook, David Leonard. "Higher twisted K-theory." Thesis, 2020. http://hdl.handle.net/2440/125740.

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Books on the topic "Higher geometric twists"

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editor, Donagi Ron, Katz Sheldon 1956 editor, Klemm Albrecht 1960 editor, and Morrison, David R., 1955- editor, eds. String-Math 2012: July 16-21, 2012, Universität Bonn, Bonn, Germany. Providence, Rhode Island: American Mathematical Society, 2015.

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Book chapters on the topic "Higher geometric twists"

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Zha, Chao-Zheng. "The Minimal Set of the Generators of Dehn Twists on a High Genus Riemann Surface." In Differential Geometric Methods in Theoretical Physics, 455–63. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4684-9148-7_46.

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"The Geometry of the Structure of Nucleic Acids With Regard to the Higher Dimension of the Components." In Attractors and Higher Dimensions in Population and Molecular Biology, 203–18. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-9651-6.ch008.

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Using three-dimensional visualization of nucleic acid molecules, obtained in the previous chapter, an analysis of the geometry of nucleic acid molecules in the space of higher dimension is carried out. It is shown that phosphoric acid residues and five-carbon sugar molecules in a double-stranded nucleic acid form polytopes of higher dimension with anti-parallel edges. These polytopes are of type n-cross-polytope (n = 5 for phosphoric acid residues, n = 13 for sugar molecules). It was found that these n-cross-polytopes located in right- and left-twisted spirals are enantiomorphic. It has been found that in cross-polytopes constructed of two sugar molecules there are 12 coordinate planes, each of which may contain a bond of nitrogenous bases (one of the 12 known ones). The formation of codons (triplets) corresponds to the separation in space of the highest dimension of nucleic acids of three-dimensional regions. This also occurs in the ribosomes upon contact with transport and adapter RNA during protein synthesis.
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Abdoullaev, Azamat. "The World Code." In Reality, Universal Ontology and Knowledge Systems, 58–75. IGI Global, 2008. http://dx.doi.org/10.4018/978-1-59904-966-3.ch003.

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Formalizing the world in rigorous mathematical terms is no less significant than its fundamental understanding and modeling in terms of ontological constructs. Like black and white, opposite sexes or polarity signs, ontology and mathematics stand complementary to each other, making up the unique and unequaled knowledge domain or knowledge base, which involves two parts: • Ontological (real) mathematics, which defines the real significance for the mathematical entities, so studying the real status of mathematical objects, functions, and relationships in terms of ontological categories and rules. • Mathematical (formal) ontology, which defines the mathematical structures of the real world features, so concerned with a meaningful representation of the universe in terms of mathematical language. The combination of ontology and mathematics and substantial knowledge of sciences is likely the only one true road to reality understanding, modeling and representation. Ontology on its own can’t specify the fabric, design, architecture, and the laws of the universe. Nor theoretical physics with its conceptual tools and models: general relativity, quantum physics, Lagrangians, Hamiltonians, conservation laws, symmetry groups, quantum field theory, string and M theory, twistor theory, loop quantum gravity, the big bang, the standard model, or theory of everything material. Nor mathematics alone with its abstract tools, complex number calculus, differential calculus, differential geometry, analytical continuation, higher algebras, Fourier series and hyperfunctions is the real path to reality (Penrose, 2005).
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Conference papers on the topic "Higher geometric twists"

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Bishara, Fady, Milind A. Jog, and Raj M. Manglik. "Heat Transfer and Pressure Drop of Periodically Fully Developed Swirling Laminar Flows in Twisted Tubes With Elliptical Cross Sections." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-11285.

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Periodically fully-developed swirling laminar flows in twisted tubes with elliptical cross sections are computationally simulated. The tubes are helically twisted and their geometry is described by the 180° twist ratios y of 3.0, 4.5 and 6.0, and ellipse cross-section aspect ratio of 0.7. Constant-property flow of water (nominal Pr = 3.0) with a Reynolds number range of 10 to 1200 is considered. The analysis quantifies the improvement in the Nusselt number as well as the increase in friction factor in order to map the effective heat transfer enhancement due to the twisted-tube-geometry-induced swirl flows. To this effect, the numerical results are compared with the baseline cases having a twist ratio of y = infinity, or straight elliptical cross-section tubes for which well established correlations are available. Numerical results show that the friction factor and the Nusselt number are a strong function of the twist ratio and the Reynolds number. The increase in fRe and Nu is higher as the twist becomes tighter (lower values of y). For Reynolds numbers below about 100, the heat transfer results do not deviate significantly from the straight-tube values, but at higher values of Re, significant enhancement in heat transfer is evident for all twist ratios considered here. The friction factor and Nusselt number results provided in this paper will help practicing engineers in integrating twisted elliptical tubes in various heat transfer applications.
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Samuel, Robello, Stuart Wood, and Greg Olin. "Casing Twist Insight Through Fiber Cable." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206201-ms.

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ABSTRACT During perforating operations, identifying the orientation of fiber cable accurately is critical for maintaining the integrity of permanently installed fiber.Beyond completions,it alsoprovides insights into how the casings get twisted and how the mechanical stability of the casing is altered as the string is run in the hole. The drilling and completion system is as unique as the aspect ratio and length/diameter is very high. This puzzles the researchers in modeling forces, stresses, stretch, and twists. To aid the accurate prediction in the position of the casing, radial orientation of downhole fiber optic cables canbe used. The clear images obtained by mapping the equipmentoutside thecasing provides not only how the casings get twisted after running in but also provide improved risk mitigation for perforating operations.The orientation angle of the casing versus depthis then analyzed to get the finaltwist and pitch of the twist of the casing. Several wells datawere analyzed to get a comprehensive view of the casingtwist as the casings were run and versus the model prediction. The raw data obtained using the pulsed-eddy current time-domain decay at each station are used for the analysis. Each installed cable detection clamp (CDC) is placed above a casing centralizer located 2' above each joint of casing that had a clamp installed.This simplifies the process of locating the depth of each CDC. A casing collar locator easily identifies the casingjoints.Further, the data are used to find the casing rotation. Several wells showed normal casing rotation of 2–3 wraps along the lateral and onewell showed more than 12 wraps. Several reasons were considered and analyzed including the wellbore spiraling, borehole torsion,and additional mechanical forces applied duringrunning the casing. The coupling of the geometrical and mechanical twist and mechanical stability of the string are discussed in the paper withmathematical underpinnings. In thecase of abnormal prediction, additional mechanical forcesandgeometrical considerations were overlapped and comparedagainst the torque and drag model prediction.It has also beenfound that in some wells where the wellbore torsion washigh,it resulted in a complete twist of 360° atthe heel and in some cases negative trend.
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Abdullah, Muhammad Azmain, M. Ruhul Amin, and Mohammad Ali. "A Numerical Analysis of Heat Transfer Enhancement by Turbulence Generated From Swirl Flow by Twisted Tape." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86616.

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Heat exchangers are widely used in heating and cooling devices. The primary challenge is to improve the efficiency of the heat transfer equipment. Researchers have utilized various techniques to achieve this goal. Using twisted tapes could significantly increase the heat transfer rate from a circular surface due to turbulence generated from swirl flow. To enhance the heat transfer rate by twisted tape, two types of arrangements namely: (i) plain twisted tape and (ii) altered twisted tape geometries are used. These arrangements result in swirl flows. For improving heat transfer through swirl flow, some important parameters such as Reynolds number, external surface temperature, friction factor, inlet pressure, and surface heat flux are also considered. To identify the aftereffect of the velocity of inlet water, several parameters namely: (i) external surface temperature, (ii) inlet pressure, (iii) external surface heat flux and (iv) twist ratio are varied. A numerical modelling using k-ε method is performed to evaluate the effects of turbulence from the twisted tape on the heat transfer rate. The objective is to analyze the improvement of heat transfer effectiveness due to the swirl flow. The change in the values of the resulting Reynolds number by changing the inlet fluid velocity from 0.1 ms−1 to 0.7 ms−1 and rotational speed from 200 rpm to 600 rpm is studied. It is observed that for such changes heat transfer increases by 17 percent. It is also observed that heat transfer is directly proportional to inlet pressure and inversely proportional to the increment of twist ratio. The rate of heat transfer increased from 17 percent to 19 percent when the angular velocity of the twisted tape is changed from the 0 rpm to 600 rpm while the velocity of the water inside the pipe is held constant at 0.7 ms−1. Higher heat transfer rate is observed with high inlet pressure. Likewise, higher value of the Nusselt number is observed with higher rotational speed of the twisted tape and higher velocity at the pipe inlet. In addition, it is also observed that when the twist ratio is changed from 4 to 6, the rate of heat transfer is diminished by 6 percent.
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Mrabah, Nairouz, Mohamed Bouguessa, and Riadh Ksantini. "Escaping Feature Twist: A Variational Graph Auto-Encoder for Node Clustering." In Thirty-First International Joint Conference on Artificial Intelligence {IJCAI-22}. California: International Joint Conferences on Artificial Intelligence Organization, 2022. http://dx.doi.org/10.24963/ijcai.2022/465.

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Most recent graph clustering methods rely on pretraining graph auto-encoders using self-supervision techniques (pretext task) and finetuning based on pseudo-supervision (main task). However, the transition from self-supervision to pseudo-supervision has never been studied from a geometric perspective. Herein, we establish the first systematic exploration of the latent manifolds' geometry under the deep clustering paradigm; we study the evolution of their intrinsic dimension and linear intrinsic dimension. We find that the embedded manifolds undergo coarse geometric transformations under the transition regime: from curved low-dimensional to flattened higher-dimensional. Moreover, we find that this inappropriate flattening leads to clustering deterioration by twisting the curved structures. To address this problem, which we call Feature Twist, we propose a variational graph auto-encoder that can smooth the local curves before gradually flattening the global structures. Our results show a notable improvement over multiple state-of-the-art approaches by escaping Feature Twist.
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Albanese, Leonardo C., Farhan Gandhi, and Susan W. Stewart. "Adaptive Geometry Wind Turbine Blades for Increasing Performance." In ASME 2010 4th International Conference on Energy Sustainability. ASMEDC, 2010. http://dx.doi.org/10.1115/es2010-90236.

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With wind turbines working to capture energy at different wind speeds rotor morphing could potentially increase energy capture over wind speeds up to the rated speed. This study examines what the optimal geometry might look like at different wind speeds, how it might differ from one speed to another, and how much increase in power and annual energy production could be realized with the optimal geometry at each wind speed. Using a blade-element theory based analysis and conducting simulations on the 1.5 MW WindPACT turbine and the 5MW NREL concept turbine, variations in blade twist and collective pitch, chord, radius, and airfoil characteristics were considered. The results indicate that there are negligible benefits to changing blade collective pitch, twist, chord, and airfoil characteristics. Only radius increase has a dominant effect, with 20% increase in radius resulting in power increase of over 45% at 8 and 10 m/s and much higher percentage increases at lower speeds, for both turbines. The increase in annual energy production is in the range of 20%. However, a larger radius increases rotor thrust.
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Zitoune, Redouane, Sofiane Alma Bouacif, Krishnaraj Vijayan, and Collombet Francis. "Design of Double Cone Twist Drill Geometry to Improve the Holes Quality While Drilling in Multi-Stack Made of CFRP/Al." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-36526.

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In this paper, experimental and numerical studies on drilling of multi-material made of CFRP laminate sandwiched with aluminum part have been carried out. These tests have been conducted using carbide drills (K20) to study the influence of spindle speed, feed rate and lip length of the double cone drill on cutting forces and holes quality. From the experimental study it was found that the double cone drills used for the experimental analysis encountered less thrust force compared to the standard twist drill. In addition the quality of the holes after drilling was evaluated, and found that no delamination (entry and exit of the hole of the composite part) even at higher feed rate (> to 0.1 mm/rev). By numerical modeling, it was noticed that, after machining with standard twist drill at higher feed rates, the thrust force generated induces a small opening at the CFRP/Al interface.
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Zafar, Sayem, and Mohamed Gadalla. "Design and Evaluation of a Rooftop Wind Turbine Rotor With Untwisted Blades." In ASME 2013 Power Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/power2013-98217.

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A small horizontal axis wind turbine rotor was designed and tested with aerodynamically efficient, economical and easy to manufacture blades. Basic blade aerodynamic analysis was conducted using commercially available software. The blade span was constrained such that the complete wind turbine can be rooftop mountable with the envisioned wind turbine height of around 8 m. The blade was designed without any taper or twist to comply with the low cost and ease of manufacturing requirements. The aerodynamic analysis suggested laminar flow airfoils to be the most efficient airfoils for such use. Using NACA 63-418 airfoil, a rectangular blade geometry was selected with chord length of 0.27[m] and span of 1.52[m]. Glass reinforced plastic was used as the blade material for low cost and favorable strength to weight ratio with a skin thickness of 1[mm]. Because of the resultant velocity changes with respect to the blade span, while the blade is rotating, an optimal installed angle of attack was to be determined. The installed angle of attack was required to produce the highest possible rotation under usual wind speeds while start at relatively low speed. Tests were conducted at multiple wind speeds with blades mounted on free rotating shaft. The turbine was tested for three different installed angles and rotational speeds were recorded. The result showed increase in rotational speed with the increase in blade angle away from the free-stream velocity direction while the start-up speeds were found to be within close range of each other. At the optimal angle was found to be 22° from the plane of rotation. The results seem very promising for a low cost small wind turbine with no twist and taper in the blade. The tests established that non-twisted wind turbine blades, when used for rooftop small wind turbines, can generate useable electrical power for domestic consumption. It also established that, for small wind turbines, non-twisted, non-tapered blades provide an economical yet productive alternative to the existing complex wind turbine blades.
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Janke, Christian, Markus Goller, Ivo Martin, Lilia Gaun, and Dieter Bestle. "3D CFD Compressor Map Computation of a Multi-Stage Axial Compressor With Off-Design Adjusted Rotor Geometries." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56745.

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Compressor maps of aero engines show the relation between corrected mass flow, corrected shaft speed, pressure ratio, and efficiency, where different operating conditions of the compressor are represented by different speed lines. These speed lines are an important information for the compressor design process, since they show important operation bounds like surge and choke. Typically, 3D CFD compressor maps are computed with the so called hot geometry given by the aerodynamic design point. But in reality aerofoil shapes change depending on engine speeds and gas loads resulting in twist of the blades and changes of tip clearance. In order to obtain a higher quality compressor map, all these effects must be taken into account. Therefore, a process is utilized which uses coupled CFD and FE analyses to account for load adjusted geometries aside the design point. For transformation of FE results into the CFD model a cold-to-hot blade morphing technique is used. The studies are performed for a 4.5 stage high speed axial compressor, where effects of varying tip clearance and geometry deformation are considered separately from each other. Finally, their combined effects are studied.
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Lennie, Matthew, Alireza Selahi-Moghaddam, David Holst, Georgios Pechlivanoglou, Christian Navid Nayeri, and Christian Oliver Paschereit. "Vortex Shedding and Frequency Lock in on Stand Still Wind Turbines: A Baseline Experiment." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63653.

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During the commissioning and stand-still cycles of wind turbines, the rotor is often stopped or even locked leaving the rotor blades at a standstill. When the blades are at a stand still, angles of attack on the blades can be very high and it is therefore possible that they experience vortex induced vibrations. This experiment and analysis helps to explain the different regimes of flow at very high angles of attack, particularly on moderately twisted and tapered blades. A single blade was tested at two different flow velocities at a range of angles of attack with flow tuft visualisation and hotwire measurements of the wake. Hotwire wake measurements were able to show the gradual inception and ending of certain flow regimes. The power spectral densities of these measurements were normalized in terms of Strouhal number based on the projected chord to show that certain wake features have a relatively constant Strouhal number. The shedding frequency appears then to be relatively independent of chord taper and twist. Vortex generators were tested but were found to have little influence in this case. Gurney flaps were found to modify the wake geometry, stall onset angles and in some cases the shedding frequency.
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Saha, Krishnendu, and Sumanta Acharya. "Effect of Entrance Geometry on Heat Transfer in a Narrow (AR=1:4) Rectangular Two Pass Channel With Smooth and Ribbed Walls." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46076.

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This paper studies the effect of entrance geometries on the heat transfer in a narrow aspect ratio (AR=1:4) rectangular internal cooling channel, representative of a leading edge of a gas turbine blade. Detailed heat transfer coefficient distributions are measured for three different entrance geometries: S-shape entrance, 90 degree bend entrance and a twisted entrance with changing AR. Both smooth and ribbed channels are used in a two pass channel configuration. A baseline straight-entry channel is used as a reference for comparison. The tests are done for Reynolds number ranging from 15000 to 55000. The ribs are placed at an angle of 45° to the mainstream flow. The results show that the effects of entrance geometry persist throughout the first pass (up to a distance of 9 times the hydraulic diameter) for the smooth channel. All the entrance geometries provided enhancement in heat transfer compared to the straight fully developed entrance, with the 90 degree bend entrance providing the highest enhancement. The effect of entrance is less pronounced for the ribbed test section case with the effects confined more in the early developing regions. The 90 degree bend entrance and the twisted-entry cases enhance heat transfer for the ribbed test section, while the S-shape entrance reduces the heat transfer for the ribbed test section relative to the straight entry channel.
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