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Publisher: Springer-Verlag   (Total: 2302 journals)

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Diabetologia Notes de lecture     Hybrid Journal  
Diabetology Intl.     Hybrid Journal   (Followers: 1, SJR: 0.273, h-index: 5)
Dialectical Anthropology     Hybrid Journal   (Followers: 8, SJR: 0.314, h-index: 9)
Die Weltwirtschaft     Hybrid Journal   (Followers: 2)
Differential Equations     Hybrid Journal   (Followers: 2, SJR: 0.364, h-index: 15)
Differential Equations and Dynamical Systems     Hybrid Journal   (Followers: 1, SJR: 0.63, h-index: 7)
Digestive Diseases and Sciences     Hybrid Journal   (Followers: 4, SJR: 1.19, h-index: 89)
Directieve therapie     Hybrid Journal  
Discrete & Computational Geometry     Hybrid Journal   (Followers: 2, SJR: 1.269, h-index: 40)
Discrete Event Dynamic Systems     Hybrid Journal   (Followers: 2, SJR: 0.42, h-index: 32)
Distributed and Parallel Databases     Hybrid Journal   (Followers: 4, SJR: 0.766, h-index: 30)
Distributed Computing     Hybrid Journal   (Followers: 2, SJR: 1.41, h-index: 31)
DNP - Der Neurologe und Psychiater     Full-text available via subscription  
Documenta Ophthalmologica     Hybrid Journal   (Followers: 2, SJR: 0.946, h-index: 40)
Doklady Biochemistry and Biophysics     Hybrid Journal   (Followers: 2, SJR: 0.2, h-index: 10)
Doklady Biological Sciences     Hybrid Journal   (SJR: 0.248, h-index: 10)
Doklady Botanical Sciences     Hybrid Journal  
Doklady Chemistry     Hybrid Journal   (SJR: 0.272, h-index: 12)
Doklady Earth Sciences     Hybrid Journal   (SJR: 0.48, h-index: 17)
Doklady Mathematics     Hybrid Journal   (SJR: 0.345, h-index: 13)
Doklady Physical Chemistry     Hybrid Journal   (SJR: 0.299, h-index: 12)
Doklady Physics     Hybrid Journal   (Followers: 1, SJR: 0.293, h-index: 17)
Douleur et Analg├ęsie     Hybrid Journal   (SJR: 0.113, h-index: 6)
Drug Delivery and Translational Research     Hybrid Journal   (Followers: 2, SJR: 0.607, h-index: 8)
Drug Safety - Case Reports     Open Access  
Drugs : Real World Outcomes     Hybrid Journal   (Followers: 1)
Dynamic Games and Applications     Hybrid Journal   (Followers: 2, SJR: 0.481, h-index: 5)
Dysphagia     Hybrid Journal   (Followers: 243, SJR: 0.822, h-index: 52)
e & i Elektrotechnik und Informationstechnik     Hybrid Journal   (Followers: 9, SJR: 0.279, h-index: 9)
e-Neuroforum     Hybrid Journal  
Early Childhood Education J.     Hybrid Journal   (Followers: 14, SJR: 0.466, h-index: 16)
Earth Science Informatics     Hybrid Journal   (Followers: 3, SJR: 0.282, h-index: 7)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 6, SJR: 0.303, h-index: 29)
Earthquake Engineering and Engineering Vibration     Hybrid Journal   (Followers: 7, SJR: 0.482, h-index: 21)
Earthquake Science     Hybrid Journal   (Followers: 8, SJR: 0.418, h-index: 9)
East Asia     Hybrid Journal   (Followers: 7, SJR: 0.18, h-index: 9)
Eating and Weight Disorders - Studies on Anorexia, Bulimia and Obesity     Hybrid Journal   (Followers: 9, SJR: 0.362, h-index: 27)
EcoHealth     Hybrid Journal   (Followers: 2, SJR: 0.88, h-index: 26)
Ecological Research     Hybrid Journal   (Followers: 8, SJR: 0.847, h-index: 43)
Economia e Politica Industriale     Hybrid Journal  
Economia Politica     Hybrid Journal   (SJR: 0.375, h-index: 6)
Economic Botany     Hybrid Journal   (Followers: 9, SJR: 0.527, h-index: 44)
Economic Bulletin     Hybrid Journal   (Followers: 4)
Economic Change and Restructuring     Hybrid Journal   (Followers: 1, SJR: 0.264, h-index: 9)
Economic Theory     Hybrid Journal   (Followers: 9, SJR: 2.557, h-index: 34)
Economic Theory Bulletin     Hybrid Journal   (Followers: 2)
Economics of Governance     Hybrid Journal   (Followers: 2, SJR: 0.408, h-index: 14)
Ecosystems     Hybrid Journal   (Followers: 19, SJR: 1.909, h-index: 93)
Ecotoxicology     Hybrid Journal   (Followers: 10, SJR: 1.333, h-index: 56)
Education and Information Technologies     Hybrid Journal   (Followers: 234, SJR: 0.366, h-index: 16)
Educational Assessment, Evaluation and Accountability     Hybrid Journal   (Followers: 17, SJR: 0.374, h-index: 15)
Educational Psychology Review     Hybrid Journal   (Followers: 15, SJR: 2.776, h-index: 61)
Educational Research for Policy and Practice     Hybrid Journal   (Followers: 7, SJR: 0.273, h-index: 9)
Educational Studies in Mathematics     Hybrid Journal   (Followers: 11, SJR: 0.825, h-index: 32)
Educational Technology Research and Development     Partially Free   (Followers: 219, SJR: 1.785, h-index: 52)
Electrical Engineering     Hybrid Journal   (Followers: 13, SJR: 0.336, h-index: 18)
Electrocatalysis     Hybrid Journal   (SJR: 0.883, h-index: 10)
Electronic Commerce Research     Hybrid Journal   (Followers: 4, SJR: 0.582, h-index: 16)
Electronic Markets     Hybrid Journal   (Followers: 5, SJR: 0.411, h-index: 8)
Electronic Materials Letters     Hybrid Journal   (Followers: 3, SJR: 1.407, h-index: 15)
Elemente der Mathematik     Hybrid Journal   (Followers: 1)
Emergency Radiology     Hybrid Journal   (Followers: 4, SJR: 0.678, h-index: 25)
Emission Control Science and Technology     Hybrid Journal  
Empirica     Hybrid Journal   (Followers: 3, SJR: 0.319, h-index: 16)
Empirical Economics     Hybrid Journal   (Followers: 8, SJR: 0.489, h-index: 31)
Empirical Software Engineering     Hybrid Journal   (Followers: 5, SJR: 1.285, h-index: 39)
Employee Responsibilities and Rights J.     Hybrid Journal   (Followers: 2, SJR: 0.361, h-index: 15)
Endocrine     Hybrid Journal   (Followers: 5, SJR: 0.878, h-index: 57)
Endocrine Pathology     Hybrid Journal   (Followers: 2, SJR: 0.638, h-index: 31)
Energy Efficiency     Hybrid Journal   (Followers: 11, SJR: 0.732, h-index: 14)
Energy Systems     Hybrid Journal   (Followers: 11, SJR: 1.176, h-index: 7)
Engineering With Computers     Hybrid Journal   (Followers: 5, SJR: 0.433, h-index: 30)
Entomological Review     Hybrid Journal   (Followers: 3, SJR: 0.144, h-index: 5)
Environment Systems & Decisions     Hybrid Journal   (Followers: 2)
Environment, Development and Sustainability     Hybrid Journal   (Followers: 29, SJR: 0.419, h-index: 29)
Environmental and Ecological Statistics     Hybrid Journal   (Followers: 5, SJR: 0.458, h-index: 32)
Environmental and Resource Economics     Hybrid Journal   (Followers: 18, SJR: 1.632, h-index: 54)
Environmental Biology of Fishes     Hybrid Journal   (Followers: 4, SJR: 0.725, h-index: 58)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 2, SJR: 0.741, h-index: 28)
Environmental Earth Sciences     Hybrid Journal   (Followers: 11, SJR: 0.724, h-index: 63)
Environmental Economics and Policy Studies     Hybrid Journal   (Followers: 6, SJR: 0.524, h-index: 4)
Environmental Evidence     Open Access  
Environmental Fluid Mechanics     Hybrid Journal   (Followers: 2, SJR: 0.437, h-index: 24)
Environmental Geochemistry and Health     Hybrid Journal   (Followers: 2, SJR: 1.013, h-index: 36)
Environmental Geology     Hybrid Journal   (Followers: 12)
Environmental Health and Preventive Medicine     Hybrid Journal   (Followers: 3, SJR: 0.522, h-index: 19)
Environmental Management     Hybrid Journal   (Followers: 32, SJR: 0.942, h-index: 66)
Environmental Modeling & Assessment     Hybrid Journal   (Followers: 11, SJR: 0.533, h-index: 31)
Environmental Monitoring and Assessment     Hybrid Journal   (Followers: 8, SJR: 0.685, h-index: 52)
Environmental Science and Pollution Research     Hybrid Journal   (Followers: 14, SJR: 0.885, h-index: 46)
Epidemiologic Perspectives & Innovations     Open Access   (Followers: 3, SJR: 1.4, h-index: 17)
Epileptic Disorders     Hybrid Journal   (Followers: 1, SJR: 0.608, h-index: 38)
EPJ A - Hadrons and Nuclei     Hybrid Journal   (Followers: 1, SJR: 1.287, h-index: 63)
EPJ B - Condensed Matter and Complex Systems     Hybrid Journal   (Followers: 3, SJR: 0.731, h-index: 89)
EPJ direct     Hybrid Journal  
EPJ E - Soft Matter and Biological Physics     Hybrid Journal   (Followers: 1, SJR: 0.641, h-index: 62)
EPMA J.     Open Access   (SJR: 0.284, h-index: 6)
ERA-Forum     Hybrid Journal   (Followers: 2, SJR: 0.128, h-index: 3)
Erkenntnis     Hybrid Journal   (Followers: 13, SJR: 0.621, h-index: 16)
Erwerbs-Obstbau     Hybrid Journal   (SJR: 0.206, h-index: 9)

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Journal Cover   Environmental Fluid Mechanics
  [SJR: 0.437]   [H-I: 24]   [4 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1573-1510 - ISSN (Online) 1567-7419
   Published by Springer-Verlag Homepage  [2302 journals]
  • RANS simulation of neutral atmospheric boundary layer flows over complex
           terrain by proper imposition of boundary conditions and modification on
           the k - ε model
    • Abstract: Abstract In this study, a modelling methodology is proposed for RANS simulations of neutral Atmospheric Boundary Layer (ABL) flows on the basis of the standard k-ε model, which allows the adoption of an arbitrary shear stress model. This modelling methodology is first examined in the context of an open flat terrain in an empty domain to ascertain there are no substantial changes in the prescribed profiles. The results show that relatively good homogeneity can be achieved with this modelling methodology for various sets of inflow boundary profiles. In addition, to extend the solutions derived from the standard k-ε model to RNG k-ε model, the RNG k-ε model is in detail assembly and tuned. Finally, the topographic effects on surface wind speeds over a complex terrain are assessed with the combined use of the proposed methodology and the modified RNG model. The numerical results are in good agreement with wind tunnel testing results and long-term field observations. A discussion of the effects of horizontal homogeneity and turbulence models on the simulated wind flows over a complex terrain is also given.
      PubDate: 2015-04-18
       
  • Amplification of long-period waves in shallow coastal embayments of the
           Great Lakes
    • Abstract: Abstract Lake water level fluctuations provide an important role in flushing shallow coastal embayments in the Great Lakes, especially if the embayment has a resonant response. Specifically, long-period waves (of periods 4–30 min) can excite resonance in coastal embayments, which greatly increases the flushing rates. We describe how resonance can explain the difference in responses of three shallow \(({\text{depth}} \,{\approx }2\, \hbox {m})\) coastal embayments of Lake Ontario and Lake Huron to similar long-period waves. Higher frequency water level fluctuations were analyzed to determine the most influential frequencies within the embayments. Observations in two adjacent embayments in Lake Huron show dramatic differences between their amplified responses to identical forcing, while in Frenchman’s Bay the oscillations are damped for the whole forcing spectrum. We model the water level response of the shallow coastal embayments to lake long-period wave forcing using a driven Helmholtz harmonic resonator. We compare and find favourable agreement \((R^{2}=78\,\%)\) between the amplification of water level fluctuations predicted by our model and field values for nearly enclosed embayments, where the Helmholtz mode dominates the energy of the oscillations. Additionally, strong peaks corresponding to the first three natural modes are observed in the water level oscillations of one of the Lake Huron embayments. This embayment has a wider entrance and its stronger amplified response can be explained using an analytical model based on an asymptotic theory of nonlinear resonance of free long-period oscillations induced by wind waves.
      PubDate: 2015-04-05
       
  • A study of flow fields in step-down street canyons
    • Abstract: Abstract A step-down street canyon is a street canyon in which the upwind building height ( \(H_{u}\) ) is greater than the downwind building height ( \(H_{d}\) ) ( \(H_{u}>H_{d}\) ). Here, the effect of downwind building height and canyon width on the flow structure in isolated step-down canyons is investigated through wind-tunnel measurements. The measurements were acquired along the vertical symmetry plane of the model buildings using two-dimensional particle image velocimetry for normal approach flow. For the present study, \(H_{u}\) was kept constant at \(120\) mm, and \(H_{d}\) was increased in increments of \(\approx \) 0.08 \(H_{u}\) , to span the range: \(0.08\le H_{d}/H_{u}\le 1\) . The configuration \(H_{d}/H_{u} \approx 1\) corresponds to a deep canyon. The footprints of the buildings were square, with the widths ( \(W\) ) and lengths ( \(L\) ) being, \(W (= L) \approx 32\)  mm. Four different street-canyon widths ( \(S\) ) were considered, with \(S/W \approx 2.5, 2, 1.5, 1\) . This resulted in a total of 48 test cases, with 12 cases for every street-canyon width. The flow topology in the near-wake of an isolated tall building ( \(H_{d}=0\) ) is characterised by a bow-shaped structure comprising the vortex core, saddle point, and ground originating shear layer. For \(S/W \approx 2.5, 2\) , and \(1.5\) , increasing the downwind building height from \(H_{d}/H_{u} \approx 0.08\) to \(1\) resulted in the in-canyon flow structure transitioning from wake dominated to deep canyon wake interference regimes. Similar increase of the downwind building height for \(S/W \approx 1\) resulted in the flow structure transitioning from wake dominated to deep canyon skimming flow regime. The results indicate that in step-down canyons formed by tall and slender buildings, momentum transport into and out of the canyon around the building sidewalls plays a crucial role in the determining the overall flow patterns in the canyon.
      PubDate: 2015-04-01
       
  • Observations of urban boundary layer structure during a strong urban heat
           island event
    • Abstract: Abstract It has long been known that the urban surface energy balance is different to that of a rural surface, and that heating of the urban surface after sunset gives rise to the Urban Heat Island (UHI). Less well known is how flow and turbulence structure above the urban surface are changed during different phases of the urban boundary layer (UBL). This paper presents new observations above both an urban and rural surface and investigates how much UBL structure deviates from classical behaviour. A 5-day, low wind, cloudless, high pressure period over London, UK, was chosen for analysis, during which there was a strong UHI. Boundary layer evolution for both sites was determined by the diurnal cycle in sensible heat flux, with an extended decay period of approximately 4 h for the convective UBL. This is referred to as the “Urban Convective Island” as the surrounding rural area was already stable at this time. Mixing height magnitude depended on the combination of regional temperature profiles and surface temperature. Given the daytime UHI intensity of \(1.5\,^\circ \mathrm{C}\) , combined with multiple inversions in the temperature profile, urban and rural mixing heights underwent opposite trends over the period, resulting in a factor of three height difference by the fifth day. Nocturnal jets undergoing inertial oscillations were observed aloft in the urban wind profile as soon as the rural boundary layer became stable: clear jet maxima over the urban surface only emerged once the UBL had become stable. This was due to mixing during the Urban Convective Island reducing shear. Analysis of turbulent moments (variance, skewness and kurtosis) showed “upside-down” boundary layer characteristics on some mornings during initial rapid growth of the convective UBL. During the “Urban Convective Island” phase, turbulence structure still resembled a classical convective boundary layer but with some influence from shear aloft, depending on jet strength. These results demonstrate that appropriate choice of Doppler lidar scan patterns can give detailed profiles of UBL flow. Insights drawn from the observations have implications for accuracy of boundary conditions when simulating urban flow and dispersion, as the UBL is clearly the result of processes driven not only by local surface conditions but also regional atmospheric structure.
      PubDate: 2015-04-01
       
  • Transport processes in and above two-dimensional urban street canyons
           under different stratification conditions: results from numerical
           simulation
    • Abstract: Abstract Thermal stratification (neutral, unstable and stable) plays an important role in determining the transport processes in and above urban street canyons. This paper summarizes the recent findings of the effect of thermal stratification on the transport of momentum, heat, and pollutants in the two-dimensional (2D) urban street canyons in the skimming flow regime. Special attention is paid to the results from large-eddy simulations (LESs), while other experimental and numerical results are referred to when necessary. With increasing Richardson number, \(Ri\) , the drag coefficient of the 2D street canyon as felt by the overlying atmosphere decreases in a linear manner. Under neutral and stable stratification, a nearly constant drag coefficient of 0.02 is predicted by the LESs. Under unstable stratification, the turbulent pollutant transport is dominated by organized turbulent motions (ejections and sweeps), while under stable stratification, the unorganized turbulent motion (inward interactions) plays a more important role and the sweeps are inhibited. The unstable stratification condition also enhances the ejections of turbulent pollutant flux, especially at the leeward roof-level corner, where the ejections dominate the turbulent pollutant flux, outweighing the sweeps. With increasing \(Ri\) , both the heat (area active scalar source) and pollutant (line passive scalar source) transfer coefficients decrease towards a state where the transfer coefficients become zero at \(Ri \approx 0.5\) . It should be noted that, due to the limit of the 2D street canyon configuration discussed in this paper, great caution should be taken when generalising the conclusions drawn here.
      PubDate: 2015-04-01
       
  • On the representation of urban heterogeneities in mesoscale models
    • Abstract: Abstract The size and arrangement of the obstacles and the presence of a source of heat (anthropogenic heat flux) are distinctive characteristics of an urban area. These two elements, together with the specific applications oriented to improve citizen’s comfort, determine the way urban heterogeneities are represented in mesoscale models. In this contribution two examples are presented. In the first a microscale fluid dynamics model is used to investigate the role of organized motions (dispersive fluxes) of a passive tracer emitted at the surface in a staggered and in an aligned array of cubes. The impact of the dispersive flux, that can reach 90 % of the total flux in the staggered array, is then assessed in a column model. The second example deals with the representation of anthropogenic heat fluxes and the estimation of thermal comfort by means of an urban canopy parameterization with a simple building energy model, implemented in a mesoscale model. The simulation of a typical summer day over the city of Madrid (Spain) shows that the anthropogenic heat fluxes have the largest impact on the air temperature in the evening-night, and that the presence of the city prolongs to the late evening the period of thermal discomfort, compared with the rural areas surrounding the city. The paper is concluded by pointing out that future work must be devoted to deep on the relationship between the real morphology of a city and the simplified morphology adopted in the urban canopy parameterizations.
      PubDate: 2015-04-01
       
  • On flows in simulated urban canopies
    • Abstract: Abstract Flow and turbulence within building canopies continue to be a topic of profound interest in the context of pedestrian comfort, wind loading, contaminant dispersion and energy usage in populated urban areas. Many experimental studies have been reported on this topic, but they either deal with wind/water tunnel measurements (at low Reynolds numbers) or complex urban building clusters (where the results are site dependent and difficult to interpret). To avert such problems, an instrumented mock building cluster made of a regular array of man-sized objects (shipping containers) placed in the atmospheric boundary layer was used to investigate spatial flow adjustment, flow patterns (as a function of approach angle) and turbulence within the building canopy. A new scaling is proposed for the characteristic canopy velocity based on the approach flow and canopy morphology, which was found to perform well when evaluated against experimental data. The flow adjustment at the leading and trailing edges of the canopy was found to be in good agreement with the formulation of Belcher et al. (J Fluid Mech 488:369–398, 2003). The results have applications to developing simple and fast contaminant transport and dispersion models that can be used in conjunction with emergency response.
      PubDate: 2015-04-01
       
  • Numerical study of the urban geometrical representation impact in a
           surface energy budget model
    • Abstract: Abstract The aim of this work is to investigate how both the orientation of the urban canyon and the modeling of the edge effects (i.e. urban canyons of finite length) are important in the numerical simulation of the surface energy budget in urban areas. Starting from the town energy balance scheme, two models of increasing complexity of the canyon geometry are developed. A sensitivity analysis of the role played by the chosen hypothesis and parameterizations is performed by coupling the canyon schemes with the numerical weather prediction model RAMS. The results suggest that a detailed description of the urban geometry could produce non-negligible differences of the energy balances and of the temperature fields with respect to what occurs using simpler schematizations, in particular during the summer.
      PubDate: 2015-04-01
       
  • Flow and turbulence characteristics in a suburban street canyon
    • Abstract: Abstract Flow and turbulence data collected during a yearlong experiment in a street-canyon configuration located in suburban terrain are analyzed. The instrumentation included 13 sonic anemometers deployed on two masts within the street canyon and on three masts on the building roofs. Flow patterns were classified as being in the wake-interference regime. The in-canyon flow and turbulence structure showed a strong dependence on the above-roof wind direction. While channeling along the street dominates for most wind directions, recirculation patterns develop for narrow sectors with above-roof wind directions perpendicular to the street. For these cross-flow scenarios, different scaling velocities were tested and the influence of upwind fetch and stability was investigated in more detail. Similar to previous studies, our findings confirmed that it is difficult to identify a single velocity scale that unifies both mean flow and turbulence properties inside the canyon. Turbulence properties scaled best with the friction velocity at the upwind roof but scaling with mean wind speeds measured at the upwind roof or at an operational meteorological station 5-km away from the study area, resulted in comparable or even better statistics for the mean flow parameters. Turbulence kinetic energy in the shear-layer region at roof layer varied depending on upwind fetch and stability. As turbulence is transported from the shear layer into the canyon region, the in-canyon turbulence characteristics also varied as a function of these two parameters.
      PubDate: 2015-04-01
       
  • Flow structure and mean residence times of lateral cavities in open
           channel flows: influence of bed roughness and shape
    • Abstract: Abstract Natural lateral cavities in open channels are important because their lower water velocities promote water quality and provide refugia for organisms. Little is known about the influence of natural cavity shapes and roughness on flow structure and exchange dynamics. We investigated the effects of cavity shape (semi-circular, backward conic, and forward conic) and bed roughness on the flow structure and mean residence time (MRT) of a lateral cavity in a flume. All cavity shapes have a flow field dominated by a one-gyre recirculation pattern, contrasting results of rectangular cavities at similar Reynolds number and aspect ratios. Transverse velocity energy spectra indicate the flow is dominated by large-scale quasi-2D coherent structures. Fundamental frequencies of mixing layer vortex shedding are fastest for forward conic cavities and slowest for backward conic cavities. Fluid enters cavities at shallower mixing layer depths, and fluid exits cavities at deeper mixing layer depths. MRTs are smaller for hydraulically smooth cases and forward conic cavities due to higher recirculation velocities. MRTs are larger for rough bed cases and backward conic cavities. Rough flow cases have a strong correlation to a predictive MRT relationship derived by Jackson et al. (Water Resour Res: 10.1002/wrcr.20272, 2013) (R 2 = 0.77); however, this predictive model does not work well for smooth cavities. Two MRT relationships were derived for smooth lateral cavities and both have strong power-law correlations to normalized MRT. Understanding cavity shape and bed roughness effects will provide a guideline for designing lateral embayments in stream restoration projects.
      PubDate: 2015-04-01
       
  • Near-surface flow in complex terrain with coastal and urban influence
    • Abstract: Abstract A simple conceptual model is presented to describe the near-surface flow of a long, partially urbanized valley of slope \(\beta \) located normal to a coastline, considering forcing due to differential surface temperatures between the sea, undeveloped (rural) land and urban area. Accordingly, under weak synoptic conditions and when the coastal and urban (thermally induced pressure-gradient) forcing are in phase with that of the valley thermal circulation, the mean flow velocity \(U\) is parameterized by the cumulative effects of multiple forcing: \(U = \varGamma w_*\beta ^{1/3} +C(g\alpha \varDelta TL)^{1/2}\) . This accounts for the coastal/urban forcing due to surface-air buoyancy difference \(g\alpha \Delta T\) over a distance \(L\) . Here \(\varGamma \) and \(C\) are constants and \(w_*\) the convective velocity. Comparisons with data of the Meteo-diffusion field experiment conducted in a coastal semi-urbanized valley of Italy (Biferno Valley) reveal that the inferences of the model are consistent with observed valley flow velocities as well as sharp morning and prolonged evening transitions. While the experimental dataset is limited, the agreement with observations suggests that the model captures essential dynamics of valley circulation subjected to multiple forcing. Further observations are necessary to investigate the general efficacy of the model.
      PubDate: 2015-04-01
       
  • Small-scale spatial variability of turbulence statistics, (co)spectra and
           turbulent kinetic energy measured over a regular array of cube roughness
    • Abstract: Abstract The spatial variability of flow and turbulence properties above an outdoor scale model of regular cube roughness under neutral stability is investigated using eight simultaneously employed sonic anemometers which are characterized by an extra short transducer span (0.05 m) and high sampling rate (50 Hz). Measurements are conducted in a layer between the top of the cubes with a plan area density of 0.25 and two times the height of the roughness, \(H\) . Large spatial variability (horizontal and vertical) is observed at the two lowest measurement levels ( \(z=H\) and \(1.25H\) ) for all variables considered which include mean wind, Reynolds stress, integral statistics, (co)spectra, budget of turbulent kinetic energy and a spatial quadrant analysis of the momentum transfer. The spatial inhomogeneity almost disappears at \(z = 1.5H\) where normalized variables attain homogeneous surface layer values for neutral stratification. The present results support a new conceptual framework to explain the turbulence behavior just above the canopy consisting of two sublayers which develop in response to the strongly varying surface. Although an individual measurement location below \(z = 1.5H\) is unable to produce representative turbulence statistics above the present bluff body roughness, averaging across a sufficient number of measurement locations to achieve complete spatial sampling of all surface characteristics (canyon spaces, rooftops, etc.), produces representative statistics even at heights which are probably still within the roughness sublayer with values close to the respective inertial subrange predictions.
      PubDate: 2015-04-01
       
  • Urban fluid mechanics: current issues and trends—summary of the
           special symposium on urban fluid mechanics at the ASME 2014 4th joint
           US-European fluid engineering division summer meeting
    • Abstract: Abstract As part of ASME 4th joint US-European Fluid Engineering Division Summer Meeting, which took place in Chicago in August 2014, a symposium was held on Urban Fluid Mechanics, spanning from urban issues such as climate and heat island effect, to small city-scale effects, such as the flow around isolated buildings. The aim of the present note is to make a synthesis of the presentations, in order to highlight current trends of research and issues.
      PubDate: 2015-04-01
       
  • Large-eddy simulation of turbulent flow in a densely built-up urban area
    • Abstract: Abstract Turbulent flow in a densely built-up area of Seoul, South Korea, is numerically investigated using the parallelized large-eddy simulation model. Based on the analysis of streamwise velocity and column-averaged vertical turbulent momentum flux, three areas of interest are selected: a downstream area of an apartment complex, an area behind high-rise buildings, and a park area. In the downstream area of the apartment complex, a large wake develops and a region of strong vertical turbulent momentum flux appears above the wake. At the height of maximum vertical turbulent momentum flux magnitude, all the four quadrant events occur in larger magnitude and contribute more to the vertical turbulent momentum transport than the averages in the main domain. In the area behind the high-rise buildings, fluctuating wakes and vortices are distinct flow structures around the top of the tallest building and updrafts induced by the flow structures appear as strong ejections just behind the high-rise buildings or farther downstream. While strong ejections are dominant at building-top heights, downdrafts along the windward walls of high-rise buildings are distinct below building-top heights and they induce high turbulent kinetic energy and winding flow around the high-rise buildings near the ground surface, transporting momentum downward and intermittently into nearby streets. In the park area located downstream in the main domain, turbulent eddies exist well above the ground surface, and the thickness of the interfacial region between low-speed air and high-speed air increases and complex turbulent flow appears in the interfacial region.
      PubDate: 2015-04-01
       
  • Entropic approach to estimate the mean flow velocity: experimental
           investigation in laboratory flumes
    • Abstract: Abstract The paper deals with the linear entropic relationship between the maximum velocity, u max , and the mean flow velocity, u m , through a dimensionless parameter Φ(M), in open-channel flow. The analysis is conducted with the aid of experimental data collected in straight laboratory flumes under different bed and side-walls roughness conditions. In particular, rough/vegetated beds and smooth/rough side-walls conditions have been investigated. The results show that, in the investigated conditions (with exception of low-submergence vegetated bed—h/k v  < 2), Φ(M) can be assumed equal to a value that is very close to that found in natural channels. This demonstrates that Φ(M) is able to implicitly reflect the different hydraulic behavior which is determined in rough and submerged vegetated beds. Thus, the entropy-based Manning’s roughness formula has been validated and the sensitivity analysis of Manning’s coefficient with the values of y o (location of the zero-velocity plane) has been also performed. It is found that this formula is quite robust to represent the observed flow resistance also in the presence of vegetation.
      PubDate: 2015-03-17
       
  • Preface
    • PubDate: 2015-03-12
       
  • On the modelling of steady turbulent fountains
    • Abstract: Abstract The paper deals with steady-state turbulent fountains in a homogeneous surrounding. A set of mono-dimensional conservation equations is first derived from the Navier–Stokes equations. In contrast with equations used for plumes or rising fountains, these equations reveal additional terms in order to account for the effect of the (annular) down-flow on the fountain up-flow. Large-eddy simulations are then performed and used to determine, from radial profiles, the values of the constants (associated with these additional terms) to be fitted in the model. With these constants, analytical solutions of the model for steady-state fountain are proposed and compared with previous experiments.
      PubDate: 2015-02-27
       
  • Incipient deposition of sediment in rigid boundary open channels
    • Abstract: Abstract Experimental data available in the literature are used in this study for the investigation of threshold condition and sediment transport in incipient deposition condition. Using data from three different rigid boundary channel cross-sections, namely, rectangular, circular and U-shape, a unique equation is obtained for calculating flow velocity at the moment of sediment incipient deposition. The sediment transport models for incipient deposition condition are proposed in general and for different cross-section of channels. The derived equations are compared with other models in the literature. It is concluded that threshold condition of sediment motion has a range its higher and lower boundaries are related to the incipient deposition and incipient motion of particles, respectively. Results seem to be efficient to hydraulic engineers for designing drainage systems.
      PubDate: 2015-02-25
       
  • Effect of solitary wave on viscous-fluid flow in bottom cavity
    • Abstract: Abstract This study mainly focuses on the interaction between a solitary wave and a bottom cavity. Vortex formation in cavities with different aspect ratios and different Reynolds numbers is considered, revealing the effects on flow patterns, primary vortex trajectories, and transport of imagined particles by the fluid in the cavity. Both numerical and experimental approaches are employed to analyze the vortex motions in cavity flow. The numerical model is based on stream function–vorticity formulations, and the transient body-fit grid combined with an overset grid is adopted for grid systems. To increase computing efficiency, the finite difference method for stream function and the finite analytic method for vorticity are combined to calculate the flow field equations. Part of the experiment uses particle tracing to visualize cavity flow. The numerical results are consistent with the experimental observations and measurements. In the computational case, the Reynolds number is defined from the undisturbed water depth and the linear-long-wave celerity. Three values of Re (Re = 80,000, 8000, and 800) are mainly studied to distinguish their behavior. For lower Re (e.g., Re = 800), a smaller fraction of particles are removed from a wide cavity (e.g., width larger or equal to twice the water depth) For this type of cavity, independent of Re, more particles are removed from the upper right of the cavity than from the upper left area.
      PubDate: 2015-02-25
       
  • Erratum to: Shallow-water solutions for gravity currents in
           non-rectangular cross-area channels with stratified ambient
    • PubDate: 2015-02-24
       
 
 
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