Characterization of the morning transition from downslope to upslope winds and its connection with the nocturnal inversion breakup at the foot of a gentle slope

2021 ◽  
Author(s):  
Sofia Farina ◽  
Dino Zardi ◽  
Silvana Di Sabatino ◽  
Mattia Marchio ◽  
Francesco Barbano
Keyword(s):  
Salt Lake ◽  
Vertical Direction ◽  
Blow Down ◽  
Physical Mechanisms ◽  
Morning Transition ◽  
Thermally Driven ◽  
Slope Wind ◽  
Slope Flow ◽  
Nocturnal Inversion

<p>Thermally driven winds observed in complex terrain are characterized by a daily cycle dominated by two main phases: a diurnal phase in which winds blow upslope (anabatic), and a nocturnal one in which they revert their direction and blow down slope (katabatic). This alternating pattern also implies two transition phases, following sunrise and sunset respectively. </p><p>Here we study the up-slope component of the slope wind with a focus on the morning transition based on from the MATERHORN experiment, performed in Salt Lake Desert (Utah) between Fall 2012 and Spring 2013. </p><p>The analysis develops along three main paths of investigation. The first one is the selection of the suitable conditions for the study of the diurnal component and the characterization of the morning transition. The second one focuses on the deep analysis of the erosion of the nocturnal inversion at the foot of the slope in order to investigate the physical mechanisms driving it. And the third one consists in the comparison between the experimental data and the results of an analytical model (Zardi and Serafin, 2015). The study of the morning transition in the selected case studies allowed its characterization in terms of the relation with the solar radiation cycle, in terms of its seasonality and in terms of its propagation along the slope and along the vertical direction. Most of the results of this investigation are related to the identification of the main mechanisms of erosion of the nocturnal inversion at the foot of the slope and to its role to the beginning of the transition itself. Finally, it is shown how the above model can fairly reproduce the cycle between anabatic and katabatic flow and their intensity.</p><p>Zardi, D. and S. Serafin, 2015: An analytic solution for daily-periodic thermally-driven slope flow. Quart. J. Roy. Meteor. Soc., 141, 1968–1974.</p>

scholarly journals Characterization of the morning transition from downslope to upslope winds and its connection with the nocturnal inversion breakup at the foot of a gentle slope.

2021 ◽  
Author(s):  
Sofia Farina ◽  
Francesco Barbano ◽  
Silvana Di Sabatino ◽  
Mattia Marchio ◽  
Dino Zardi
Keyword(s):  
Salt Lake ◽  
Convective Boundary ◽  
Morning Transition ◽  
Driving Mechanisms ◽  
American Meteorological Society ◽  
Thermally Driven ◽  
Slope Wind ◽  
Upward Growth ◽  
Slope Flow ◽  
Nocturnal Inversion

<p>Thermally driven winds observed in complex terrain are characterized by a daily cycle dominated by two main phases: a diurnal phase in which winds blow upslope (anabatic), and a nocturnal one in which they revert their direction and blow downslope (katabatic). This alternating pattern also implies two transition phases, following sunrise and sunset respectively. </p><p>Here we study the upslope component of the slope wind with a focus on the morning transition from the katabatic to the anabatic flow based on data from the MATERHORN experiment, performed in Salt Lake Desert (Utah) between Fall 2012 and Spring 2013 (Fernando et al, 2015). </p><p>First of all, a criterion for the selection of purely thermally driven slope wind days is proposed and adopted to select five case studies, taken from both the spring and the autumn periods. Then, the analysis allowed the investigation of the driving mechanisms through the connection with the patterns of erosion of the nocturnal inversion in the valley bed at the foot of the slope under analysis. Three main patterns of erosion of the inversion in the particular topography of a gentle and isolated slope are identified: a) erosion due to upward growth of a convective boundary layer, b) erosion due to descent of the inversion top, and c) erosion due to a mix of the two previous mechanisms. The three patterns are then linked to the initiation of the transition by two different and competing mechanisms: mixing from above (top-down dilution) and surface heating from below. Finally, an analytical model for the description of slope circulation (Zardi and Serafin, 2015) has been used to diagnose the time of the transition.</p><p>Zardi, D. and S. Serafin, 2015: An analytic solution for daily-periodic thermally-driven slope flow. Quart. J. Roy. Meteor. Soc., 141, 1968–1974. </p><p>Fernando, H. J. S., Pardyjak, E. R., Di Sabatino, S., Chow, F. K., De Wekker, S. F. J., Hoch, S. W, Zsedrovits, T., 2015, The MATERHORN: Unraveling the intricacies of mountain weather. <em>Bulletin Of The American Meteorological Society</em>, 96, 1945-1967. </p>

Process and Manufacturing Challenges for High-K Gate Stack Systems

1999 ◽  
Vol 567 ◽  
Author(s):  
M.C. Gilmer ◽  
T-Y Luo ◽  
H.R. Huff ◽  
M.D. Jackson ◽  
S. Kim ◽  
...  
Keyword(s):  
Silicon Surface ◽  
Gate Dielectrics ◽  
Electrical Characterization ◽  
Metal Electrode ◽  
Significant Variable ◽  
Tem Analysis ◽  
Physical Mechanisms ◽  
High K ◽  
Commercial Equipment

ABSTRACTA design-of-experiments methodology was implemented to assess the commercial equipment viability to fabricate the high-K dielectrics Ta2O5, TiO2 and BST (70/30 and 50/50 compositions) for use as gate dielectrics. The high-K dielectrics were annealed in 100% or 10% O2 for different times and temperatures in conjunction with a previously prepared NH3 nitrided or 14N implanted silicon surface. Five metal electrode configurations—Ta, TaN, W, WN and TiN—were concurrently examined. Three additional silicon surface configurations were explored in conjunction with a more in-depth set of time and temperature anneals for Ta2O5. Electrical characterization of capacitors fabricated with the above high-K gate dielectrics, as well as SIMS and TEM analysis, indicate that the post high-K deposition annealing temperature was the most significant variable impacting the leakage current density, although there was minimal influence on the capacitance. Further studies are required, however, to clarify the physical mechanisms underlying the electrical data presented.

scholarly journals Evolution of Late Wintertime Thermally Driven Local Flows and Temperature Fields over Far-Western Nepal

2016 ◽  
Vol 21 (1) ◽  
pp. 35-47
Author(s):  
Ram P. Regmi ◽  
Sangeeta Maharjan
Keyword(s):  
Thermal Environment ◽  
Flow Characteristics ◽  
Temperature Fields ◽  
Valley Wind ◽  
Plain Area ◽  
Slope Winds ◽  
Thermally Driven ◽  
Slope Wind ◽  
Wrf Modeling ◽  
Southern Plain

Atmospheric processes over the Himalayan complex terrain are yet to be studied extensively. Only a few significant researches are reported from this region and the Far-Western Region (FWR) of Nepal still remains untouched. Thus, the present study was conceived to understand the meteorological flow characteristics and thermal environment over the region and associated areas during the late wintertime with the application of the state-of-the-art-of Weather Research and Forecasting (WRF) Modeling System. The study revealed that the northern mountainous region developed strong down slope wind during the night and morning times, which sweeps out the southern plain area of Nepal and may reach just beyond the border. The wind over the plain was very shallow whose depth was just about 100 m. The down slope winds over the southern slope of the Daijee and Nandhaur mountain ranges were significantly enhanced by the subsidence of the southerly wind that prevails above 1 km height above the mean sea level. Close to the noon time a very gentle southerly valley wind from the southern plain replaced the nighttime down slope. Very shallow but strong surface inversion builds up over the plain that breaks up in the late morning. The depth of the mixed layer and the valley wind may reach up to 1km in the afternoon. The thermal environment over the FWR of Nepal was fairly hot that may remain around 35°C in the afternoon around the Mahendranagar area whereas the temperature during the nighttime may go as low as 23°C. The study revealed that, contrary to the general perception, temperature over plain areas of Nepal was significantly higher than further southern areas belonging to India. The meteorological flow fields over the FWR of Nepal executed diurnal periodicity with little day-to-day variation during the late wintertime.Journal of Institute of Science and TechnologyVolume 21, Issue 1, August 2016, page: 35-47

Analysis Tools for Thermally Driven Microfluidics

2010 ◽  
Author(s):  
M. Sigurdson ◽  
C. D. Meinhart
Keyword(s):  
Heat Pipe ◽  
Electronics Cooling ◽  
Velocity Fields ◽  
Microfluidic Systems ◽  
Infrared Thermometry ◽  
Analysis Tools ◽  
Thermally Driven ◽  
Temperature And Velocity Fields ◽  
Fluorescence Thermometry

Thermally driven microfluidics, that is, flow that is driven by a temperature gradient, has applications from lab-on-a-chip to electronics cooling. Development of such devices requires tools to predict and probe temperature and velocity fields. We have developed analytical, numerical, and experimental analysis tools for design and characterization of thermally driven microfluidic systems. We demonstrate these tools through the analysis of two different systems: an electrothermal microstirring biochip, and a high aspect heat pipe for cooling. First, a numerical model is developed for temperature and velocity fields, in a hybrid electrothermal-buoyancy microstirring device. An analytical tool, the electrothermal Rayleigh number, is used to further explore the relative importance of electrothermal and buoyancy driven flow. Finally, two experimental thermometry techniques are described: fluorescence thermometry and infrared thermometry. These analytical, numerical, and experimental tools are useful in the design of thermally driven microfluidic systems, as demonstrated here through the development and analysis of microstirring and heat pipe systems.

Comparison of Human Surrogate Responses in Underbody Blast Loading Conditions

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
K. Ott ◽  
D. Drewry ◽  
M. Luongo ◽  
J. Andrist ◽  
R. Armiger ◽  
...  
Keyword(s):  
Vertical Direction ◽  
Whole Body ◽  
Matched Pair ◽  
Loading Conditions ◽  
Occupant Safety ◽  
Vertical Loading ◽  
Impact Biomechanics ◽  
Biomechanical Response ◽  
Hybrid Iii

Abstract Impact biomechanics research in occupant safety predominantly focuses on the effects of loads applied to human subjects during automotive collisions. Characterization of the biomechanical response under such loading conditions is an active and important area of investigation. However, critical knowledge gaps remain in our understanding of human biomechanical response and injury tolerance under vertically accelerated loading conditions experienced due to underbody blast (UBB) events. This knowledge gap is reflected in anthropomorphic test devices (ATDs) used to assess occupant safety. Experiments are needed to characterize biomechanical response under UBB relevant loading conditions. Matched pair experiments in which an existing ATD is evaluated in the same conditions as a post mortem human subject (PMHS) may be utilized to evaluate biofidelity and injury prediction capabilities, as well as ATD durability, under vertical loading. To characterize whole body response in the vertical direction, six whole body PMHS tests were completed under two vertical loading conditions. A series of 50th percentile hybrid III ATD tests were completed under the same conditions. Ability of the hybrid III to represent the PMHS response was evaluated using a standard evaluation metric. Tibial accelerations were comparable in both response shape and magnitude, while other sensor locations had large variations in response. Posttest inspection of the hybrid III revealed damage to the pelvis foam and skin, which resulted in large variations in pelvis response. This work provides an initial characterization of the response of the seated hybrid III ATD and PMHS under high rate vertical accelerative loading.

Evaluating the Effects of Transient Purge Flow on Stator-Rotor Seal Performance

2020 ◽  
pp. 1-55
Author(s):  
Reid A. Berdanier ◽  
Eric DeShong ◽  
Karen A. Thole ◽  
Christopher Robak
Keyword(s):  
Measurement Techniques ◽  
Operating Conditions ◽  
Pressure Measurements ◽  
Physical Mechanisms ◽  
Melting Temperatures ◽  
Thermally Driven ◽  
Purge Flow ◽  
Transient Events ◽  
Critical Components ◽  
The Relationship

Abstract As engine designs target higher efficiencies through increased turbine inlet temperatures, critical components are at risk of damage from conditions exceeding material melting temperatures. In particular, improperly designed underplatform hardware are susceptible to damage when hot gas is ingested into the stator-rotor cavity. While all turbines inherently experience transients during operation, a majority of publicly available turbine studies have been executed using steady operating conditions or transient “blowdown” rigs. For this reason, routine transient events are not well understood. To address this need, this study utilized a combined experimental and computational approach. The test article is a continuous-duration, one-stage turbine operating with true-scale engine hardware and seal geometries at engine-representative flow conditions. The nature of the continuous-duration facility supports assessment of transient events through its ability to transition between steady-state operating conditions. The effects of transient purge flow were investigated to identify general trends for transient events in a full-scale engine. Results from multiple measurement techniques in the wheelspace region show an interdependence of transient purge flow with thermal lag of the underplatform hardware. Through experiments conducted at different coolant-to-main gas path temperature ratios, the use of pressure measurements as an indicator of fully-purged behavior was introduced, and a thermally-driven influence on rim seal performance was quantified. The computational results show good agreement with experimental pressure measurements and provide insight into the physical mechanisms that drive the relationship between pressure and sealing effectiveness observed in the experiments.

Characterization of LDHs prepared with different activity MgO and resisting Cl− attack of concrete in salt lake brine

2019 ◽  
Vol 229 ◽  
pp. 116921 ◽  
Author(s):  
Yaru Hu ◽  
Haihong Li ◽  
Qian Wang ◽  
Jun Zhang ◽  
Qiang Song
Keyword(s):  
Salt Lake ◽  
Salt Lake Brine

scholarly journals Mechanisms of Up-Valley Winds

2004 ◽  
Vol 61 (24) ◽  
pp. 3097-3111 ◽  
Author(s):  
Gabriele Rampanelli ◽  
Dino Zardi ◽  
Richard Rotunno
Keyword(s):  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Free Atmosphere ◽  
Valley Wind ◽  
Main Contributor ◽  
Physical Mechanisms ◽  
Thermally Driven ◽  
Hydrostatic Approximation ◽  
Temperature Contrast

Abstract The basic physical mechanisms governing the daytime evolution of up-valley winds in mountain valleys are investigated using a series of numerical simulations of thermally driven flow over idealized three-dimensional topography. The three-dimensional topography used in this study is composed of two, two-dimensional topographies: one a slope connecting a plain with a plateau and the other a valley with a horizontal floor. The present two-dimensional simulations of the valley flow agree with results of previous investigations in that the heated sidewalls produce upslope flows that require a compensating subsidence in the valley core bringing down potentially warmer air from the stable free atmosphere. In the context of the three-dimensional valley–plain simulations, the authors find that this subsidence heating in the valley core is the main contributor to the valley– plain temperature contrast, which, under the hydrostatic approximation, is the main contributor to the valley– plain pressure difference that drives the up-valley wind.

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