76,411 research outputs found
An innovative low-cost aerogel blanket for thermal bridge correction
No full textAerogel-enhanced products are often indicated as promising materials for increasing the thermal resistance of the building envelope. However, their high cost, typically related to the critical conditions needed for the synthesis of the aerogels, is often limiting their diffusion. This paper aims to present a new low-cost aerogel-enhanced blanket manufactured at Ryerson University in Toronto (ON) using ambient pressure drying conditions in an effort to lower the cost, and then to investigate the possible applications of these products for the correction of thermal bridges. In aerogel-enhanced blankets, fiber-matrix bonds together the aerogel structure, compensating the low mechanical properties of the aerogels without reducing their exceptionally low thermal conductivity. Thermal characterization tests confirm the superior performance of aerogel-enhanced blankets, which show thermal conductivity values below 0.016 W/mK. Then, the utility of aerogel-enhanced blankets for correcting typical thermal bridges is assessed through simulations in twelve typical construction nodes: six concrete and six steel constructions. For the scope of thermal bridge correction, the inclusion of 10 mm and 20 mm thick aerogel-enhanced blankets was modeled in both 2D and 3D. Among the investigated nodes, results show that the wall to balcony connection in concrete structures could have the greatest improvement in linear thermal transmittance (88% lower) if the thermal bridge is corrected with thin aerogel-enhanced blankets
U. Sharma, Women's Work, Class and the Urban Household. A Study of Shimla, North India
No full textToffin Gérard. U. Sharma, Women's Work, Class and the Urban Household. A Study of Shimla, North India. In: L'Homme, 1988, tome 28 n°105. La fabrication mythique des enfants. pp. 140-141
U. Sharma, Women's Work, Class and the Urban Household. A Study of Shimla, North India
No full textToffin Gérard. U. Sharma, Women's Work, Class and the Urban Household. A Study of Shimla, North India. In: L'Homme, 1988, tome 28 n°105. La fabrication mythique des enfants. pp. 140-141
The first X-ray structure of a hexaamminecobalt(III) salt with two different complex chlorocadmium anions: synthesis, characterization and crystal structure of [Co(NH3)(6)](4)-[CdCl6][CdCl4(SCN)(H2O)](2)Cl-2 center dot 2H(2)O
No full textIn the title complex salt, tetrakis[ hexaamminecobalt(III)] hexachlorocadmate(II) bis[aquatetrachlorothiocyanatocadmate(II)] dichloride dihydrate, the discrete ions, i.e. [Co(NH3)(6)](3+), Cl-, [CdCl6](4-) (located on an inversion centre) and [CdCl4(SCN)(H2O)](3-), together with cocrystallized water molecules, are assembled by means of a network of hydrogen-bonding interactions. This is the first X-ray structure determination of a hexaamminecobalt(III) salt with two different complex chlorocadmium anion
A Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
Near Wall PIV-Measurements on the Windward Slope of a Hill
No full textThe turbulent flow over periodic hills was measured near to the wall, using planar Particle-Image-Velocimetry (PIV) at high spatial resolution. Our focus is on the near wall turbulence structure on the windward slope of the hill. For large-eddy simulation (LES) we suspect that, if this was not predicted accurately, it affects the prediction of the velocity profiles over the hill crest which in turn will affect the recirculation length downstream of the hill. Regarding the time averaged velocities, we were able to resolve the linear viscous region of the boundary layer. The velocity distribution and also the Reynolds stress does not comply with the law of the wall as it is valid for a turbulent boundary layer at equilibrium
Energy dissipation and flux laws for unsteady turbulence
No full textDirect Numerical Simulations of spatially periodic unsteady turbulence show that the high Reynolds number scalings of the instantaneous energy dissipation rate and interscale energy flux at intermediate wavenumbers are qualitatively different from the well-known cornerstone scalings of equilibrium turbulence where and are time-dependent rms velocity and integral length-scales. Instead, they both scale as where and are length and velocity scales characterizing initial/overall unsteady turbulence conditions
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Real-space Manifestations of Bottlenecks in Turbulence Spectra
No full textAn energy-spectrum bottleneck, a bump in the turbulence spectrum between the inertial and dissipation ranges, is shown to occur in the non-turbulent, one-dimensional, hyperviscous Burgers equation and found to be the Fourier-space signature of oscillations in the real-space velocity, which are explained by boundary-layer-expansion techniques. Pseudospectral simulations are used to show that such oscillations occur in velocity correlation functions in one- and three-dimensional hyperviscous hydrodynamical equations that display genuine turbulence
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