scholarly journals Technical note: Fourier approach for estimating the thermal attributes of streams

2016 ◽  
Vol 20 (8) ◽  
pp. 3411-3418 ◽  
Author(s):  
Masahiro Ryo ◽  
Marie Leys ◽  
Christopher T. Robinson
Keyword(s):  
Fourier Analysis ◽  
Thermal Characteristics ◽  
Stream Temperature ◽  
Technical Note ◽  
Swiss Alps ◽  
Diel Periodicity ◽  
Seasonal Periodicity ◽  
Average Temperature ◽  
Poor Site ◽  
Periodic Components

Abstract. Temperature models that directly predict ecologically important thermal attributes across spatiotemporal scales are still poorly developed. This study developed an analytical method based on Fourier analysis to estimate seasonal and diel periodicities, as well as irregularities in stream temperature, at data-poor sites. The method extrapolates thermal attributes from highly resolved temperature data at a reference site to the data-poor sites on the assumption of spatial autocorrelation. We first quantified the thermal attributes of a glacier-fed stream in the Swiss Alps using 2 years of hourly recorded temperature. Our approach decomposed stream temperature into its average temperature of 3.8 °C, a diel periodicity of 4.9 °C, seasonal periodicity spanning 7.5 °C, and the remaining irregularity (variance) with an average of 0.0 °C but spanning 9.7 °C. These attributes were used to estimate thermal characteristics at upstream sites where temperatures were measured monthly, and we found that a diel periodicity and the variance strongly contributed to the variability at the sites. We evaluated the performance of our predictive mechanism and found that our approach can reasonably estimate periodic components and extremes. We could also estimate the variability in irregularity, which cannot be represented by other techniques that assume a linear relationship in temperature variabilities between sites. The results confirm that spatially extrapolating thermal attributes based on Fourier analysis can predict thermal characteristics at a data-poor site. The R scripts used in this study are available in the Supplement.

scholarly journals Technical note: Fourier approach for estimating the thermal attributes of streams

2016 ◽  
Author(s):  
Masahiro Ryo ◽  
Marie Leys ◽  
Christopher T. Robinson
Keyword(s):  
Analytical Method ◽  
Methodological Approach ◽  
Stream Temperature ◽  
Technical Note ◽  
Swiss Alps ◽  
Diel Periodicity ◽  
Seasonal Periodicity ◽  
Relative Contribution ◽  
Spatio Temporal ◽  
Recorded Temperature

Abstract. Temperature models that directly predict ecologically important thermal attributes across spatio-temporal scales are still poorly developed. This study developed an analytical method to estimate seasonal and diel periodicities as well as irregularities in stream temperature at data-poor sites based on Fourier analysis. We first quantified the thermal attributes of a glacier-fed stream in the Swiss Alps using 2-years of hourly-recorded temperature. Stream temperature was accurately decomposed to an average 3.8 °C, diel periodicity spanning 4.9 °C, seasonal periodicity spanning 7.5 °C, and an irregularity having an average of 0.0 °C but spanning 9.7 °C. These thermal attributes then were used to estimate thermal attributes at spot-measured sites along the river, resulting in a different relative contribution (weighting) of attributes among sites. The results confirm that the developed method can infer stochastic behaviors in stream thermal attributes at spot-measured sites. Additional ways to further improve the methodological approach are discussed.

scholarly journals Thermal Characteristics of a Beaver Dam Analogues Equipped Spring-Fed Creek in the Canadian Rockies

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 990
Author(s):  
Tariq M. Munir ◽  
Cherie J. Westbrook
Keyword(s):  
Thermal Characteristics ◽  
Cutthroat Trout ◽  
Rocky Mountain ◽  
Optimal Growth ◽  
Stream Temperature ◽  
Mountain Stream ◽  
Suitable Habitat ◽  
Restoration Technique ◽  
Beaver Dam ◽  
In Series

Beaver dam analogues (BDAs) are becoming an increasingly popular stream restoration technique. One ecological function BDAs might help restore is suitable habitat conditions for fish in streams where loss of beaver dams and channel incision has led to their decline. A critical physical characteristic for fish is stream temperature. We examined the thermal regime of a spring-fed Canadian Rocky Mountain stream in relation to different numbers of BDAs installed in series over three study periods (April–October; 2017–2019). While all BDA configurations significantly influenced stream and pond temperatures, single- and double-configuration BDAs incrementally increased stream temperatures. Single and double configuration BDAs warmed the downstream waters of mean maxima of 9.9, 9.3 °C by respective mean maxima of 0.9 and 1.0 °C. Higher pond and stream temperatures occurred when ponding and discharge decreased, and vice versa. In 2019, variation in stream temperature below double-configuration BDAs was lower than the single-configuration BDA. The triple-configuration BDA, in contrast, cooled the stream, although the mean maximum stream temperature was the highest below these structures. Ponding upstream of BDAs increased discharge and resulted in cooling of the stream. Rainfall events sharply and transiently reduced stream temperatures, leading to a three-way interaction between BDA configuration, rainfall and stream discharge as factors co-influencing the stream temperature regime. Our results have implications for optimal growth of regionally important and threatened bull and cutthroat trout fish species.

scholarly journals Technical Note: Quantification of interferences of wet chemical HONO LOPAP measurements under simulated polar conditions

2008 ◽  
Vol 8 (22) ◽  
pp. 6813-6822 ◽  
Author(s):  
J. Kleffmann ◽  
P. Wiesen
Keyword(s):  
Technical Note ◽  
Swiss Alps ◽  
Pollution Level ◽  
Research Station ◽  
Polar Regions ◽  
Alpine Research ◽  
Absorption Photometer ◽  
Present Pilot Study ◽  
Good Agreement

Abstract. In the present pilot study, an optimized LOPAP instrument (LOng Path Absorption Photometer) for the detection of nitrous acid (HONO) in the atmosphere (DL 0.2 pptV) was tested at the high alpine research station Jungfraujoch at 3580 m altitude in the Swiss Alps under conditions comparable to polar regions. HONO concentrations in the range <0.5–50 pptV with an average of 7.5 pptV were observed at the Jungfraujoch. The diurnal profiles obtained exhibited clear maxima at noon and minima with very low concentration during the night supporting the proposed photochemical production of HONO. In good agreement with recent measurements at the South Pole, it was demonstrated, that interferences of chemical HONO instruments can significantly influence the measurements and lead to considerable overestimations, especially for low pollution level. Accordingly, the active correction of interferences is of paramount importance for the determination of reliable HONO data.

scholarly journals Distinguishing ice-rich and ice-poor permafrost to map ground temperatures and ground ice occurrence in the Swiss Alps

2019 ◽  
Vol 13 (7) ◽  
pp. 1925-1941 ◽  
Author(s):  
Robert Kenner ◽  
Jeannette Noetzli ◽  
Martin Hoelzle ◽  
Hugo Raetzo ◽  
Marcia Phillips
Keyword(s):  
Solar Radiation ◽  
Thermal Characteristics ◽  
Mapping Method ◽  
Swiss Alps ◽  
Ground Ice ◽  
Climate Conditions ◽  
Distribution Maps ◽  
Ground Temperatures ◽  
Incoming Solar Radiation ◽  
Gravitational Processes

Abstract. Mountain permafrost is invisible, and mapping it is still a challenge. Available permafrost distribution maps often overestimate the permafrost extent and include large permafrost-free areas in their permafrost zonation. In addition, the representation of the lower belt of permafrost consisting of ice-rich features such as rock glaciers or ice-rich talus slopes can be challenging. These problems are caused by considerable differences in genesis and thermal characteristics between ice-poor permafrost, occurring for example in rock walls, and ice-rich permafrost. While ice-poor permafrost shows a strong correlation of ground temperature with elevation and potential incoming solar radiation, ice-rich ground does not show such a correlation. Instead, the distribution of ice-rich ground is controlled by gravitational processes such as the relocation of ground ice by permafrost creep or by ground ice genesis from avalanche deposits or glacierets covered with talus. We therefore developed a mapping method which distinguishes between ice-poor and ice-rich permafrost and tested it for the entire Swiss Alps. For ice-poor ground we found a linear regression formula based on elevation and potential incoming solar radiation which predicts borehole ground temperatures at multiple depths with an accuracy higher than 0.6 ∘C. The zone of ice-rich permafrost was defined by modelling the deposition zones of alpine mass wasting processes. This dual approach allows the cartographic representation of permafrost-free belts, which are bounded above and below by permafrost. This enables a high quality of permafrost modelling, as is shown by the validation of our map. The dominating influence of the two rather simple connected factors, elevation (as a proxy for mean annual air temperature) and solar radiation, on the distribution of ice-poor permafrost is significant for permafrost modelling in different climate conditions and regions. Indicating temperatures of ice-poor permafrost and distinguishing between ice-poor and ice-rich permafrost on a national permafrost map provides new information for users.

Analysis on Thermal Characteristics of Phase Change Roof and Insulation Roof

2011 ◽  
Vol 99-100 ◽  
pp. 1128-1136
Author(s):  
Guo Zhong Wu ◽  
Yan Zhao ◽  
Jing Wang ◽  
Dong Li
Keyword(s):  
Phase Transition ◽  
Heat Flux ◽  
Transition Temperature ◽  
Phase Change ◽  
Thermal Characteristics ◽  
Bottom Surface ◽  
Average Heat ◽  
Average Temperature ◽  
Steady Stage ◽  
Change Material

The two-dimensional unsteady heat transfer models of common roof, insulation roof and phase change roof were established, and the thermal characteristics of common roof, insulation roof and phase change roof with different phase transition temperature were analyzed based on CFD software, the hourly average temperature distribution of their top and bottom surface from initial stage to steady stage and 24-hour hourly average temperature distribution of and average heat flux of bottom surface in steady stage were also attained. The results show that, under air conditioning constant temperature mode, addition of insulation material and phase change material observably improve the heat insulation performance of roof structures, the cooling and energy saving effect of roof more obviously, the attenuation multiple and delay time of roof more obviously, and make the hourly distribution of average temperature and average heat flux of roof bottom surface much gentler. In addition, choosing a phase change material with suitable phase transition temperature according to outside air comprehensive temperature is the key to utilize its latent heat more effectively.

Thermal Management of Electronic Chips in a Channel Using Input Power to Control Flow Velocity

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Esam M. Alawadhi
Keyword(s):  
Steady State ◽  
Pressure Drop ◽  
Thermal Management ◽  
Heat Generation ◽  
Electronic Device ◽  
Thermal Characteristics ◽  
Input Power ◽  
Control Flow ◽  
Steady State Condition ◽  
Average Temperature

In this research, thermal management of an electronic device using the input power is investigated numerically using the finite element method. The considered geometry consists of a horizontal channel with three volumetrically heated chips mounted on the bottom wall of the channel. The magnitude of the channel’s inlet velocity is varied with the variation of heat generation in the chips. The thermal characteristics of the system are presented, and compared with thermal characteristics of a system at a steady state condition. The effect of the Reynolds number and the oscillating period of the heat generation on the chips’ average temperature and Nusselt number is presented. The pressure drop in the channel is also calculated. The results indicated that the transient operating condition causes temperature to be higher than steady state by more than 45%, and difference between the transient and steady operations is reduced if the frequency is high. However, flow frequency has nearly no effect on the pressure drop in the channel.

scholarly journals Thermal Characteristics of the Permafrost within an Active Rock Glacier (Murtèl/Corvatsch, Grisons, Swiss Alps)

1990 ◽  
Vol 36 (123) ◽  
pp. 151-158 ◽  
Author(s):  
Daniel Vonder Mühll ◽  
Wilfried Haeberli
Keyword(s):  
Heat Flow ◽  
Thermal Characteristics ◽  
Thermal Conditions ◽  
Swiss Alps ◽  
Mean Annual Temperature ◽  
Seasonal Temperature ◽  
Rock Glacier ◽  
Vertical Heat ◽  
Glacial Time

AbstractTemperatures from a bore hole through an active rock glacier in the eastern Swiss Alps are presented and thermal conditions within the slowly creeping permafrost are analyzed. Present mean annual temperature in the uppermost part of the permafrost is −3°C. Permafrost is 52 m thick and reaches heavily fissured bedrock. Thermal conductivity as determined in situ from seasonal temperature variations and measured in a cold laboratory using frozen samples is close to 2.5–3.0 W m−1 °C−1. Vertical heat flow is anomalously high (around 150 mW m-2), probably due to heat advection from circulating ground water or air within the fissured bedrock zone. Beneath this zone, which could in fact represent a non-frozen intra-permafrost layer or “talik”, relic permafrost from past centuries may possibly exist as indicated by a corresponding heat-flow inversion. Given the current temperature condition at the surface of the rock glacier and the fact that the twentieth century is among the warmest in post-glacial time, permafrost conditions may be assumed to have existed during the whole of the Holocene and, hence, during the entire time of rock-glacier formation.

A Study on Impact Strength of CFRP Using Infrared Thermography

2012 ◽  
Vol 628 ◽  
pp. 390-395 ◽  
Author(s):  
Hee Jae Shin ◽  
Lee Ku Kwac ◽  
Sun Ho Ko ◽  
Tae Hoon Kim ◽  
Hong Gun Kim
Keyword(s):  
Thermal Characteristics ◽  
High Strength ◽  
Reinforced Plastics ◽  
Advanced Composite ◽  
Average Temperature ◽  
Advanced Composite Materials ◽  
Weight Test ◽  
Strength And Stiffness ◽  
Falling Weight ◽  
The Impact

Of the advanced composite materials for aerospace structures such as aircrafts and space devices, the carbon fiber reinforced plastics (CFRP) is applied to many sectors that require lightweight materials for its high strength and stiffness. One of the disadvantages of the CFRP, however, is that it is weak against impact. In this study, impact test specimens were manufactured with five fiber stacking angles (0°/0°, 0°/15°, 0°/30°, 0°/45°, 0°/90°) according to ASTM D7136[15], and a falling weight test was performed to analyze the correlation between their mechanical and thermal characteristics. As a result, the impact energy applied to the five test specimens with different fiber stacking angles was almost constant at 30.63 J - 30.78 J. The absorbed energy increased with the increase in the fiber stacking angle, and decreased after 0°/45°. The average temperature on the fractured surface increased with the increase in the fiber stacking angle in all specimens other than the 0°/0° specimen.

scholarly journals Association between the Area of the Highest Flank Temperature and Concentrations of Reproductive Hormones during Pregnancy in Polish Konik Horses—A Preliminary Study

Animals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1517
Author(s):  
Małgorzata Maśko ◽  
Łukasz Zdrojkowski ◽  
Małgorzata Wierzbicka ◽  
Małgorzata Domino
Keyword(s):  
Lateral Surface ◽  
Regional Blood Flow ◽  
Thermal Characteristics ◽  
Reproductive Hormones ◽  
Ambient Temperatures ◽  
Estrone Sulfate ◽  
Average Temperature ◽  
Pregnancy Status ◽  
Thermal Features ◽  
Preliminary Study

Determination of the pregnancy status is one of the most important factors for effective pregnancy management. Knowledge of the stage of pregnancy is important to interpret many of the reproductive hormones’ concentrations, including progesterone (P4), estrone sulfate (E1S), 17-ß estradiol (E2), and relaxin (REL). However, it is limited in wildlife or captive equids that cannot be handled. Reproductive hormones affect regional blood flow, the proliferation of tissues, and local metabolism intensity. Therefore, this preliminary study aimed to assess changes in thermal features of the abdomen lateral surface and concentrations of reproductive hormones in Polish native pregnant mares. The study was carried out on 14 non-pregnant and 26 pregnant Polish Konik mares during eleven months of pregnancy. Infrared thermography was conducted to image the lateral surface of mares' abdomen (Px1) and flank area (Px2); P4, E1S, E2, and REL concentrations in serum were also determined. The evidence of the association between the area with the highest temperatures (Area of Tmax) and serum concentrations of P4 (the slope = 1.373; p = 0.9245) and REL (the slope = 1.342; p = 0.4324) were noted dependent across months of pregnancy. Measures of superficial body temperatures were found to change monthly, similarly to ambient temperatures, with no evidence of coincidence with changes in reproductive hormone concentrations. Individual thermal characteristics of the lateral surface of the abdomen differed between pregnant and non-pregnant mares in other periods. Differences in maximal and average temperature and Area of Tmax were observed from the sixth month of pregnancy, and those in minimal temperature were observed from the eighth month.

Stabilization of Buoyancy-Driven Unstable Vortex Flow in Mixed Convection of Air in a Rectangular Duct by Tapering Its Top Plate

1999 ◽  
Vol 122 (1) ◽  
pp. 58-65 ◽  
Author(s):  
W. S. Tseng ◽  
W. L. Lin ◽  
C. P. Yin ◽  
C. L. Lin ◽  
T. F. Lin
Keyword(s):  
Aspect Ratio ◽  
Vortex Flow ◽  
Temporal Stability ◽  
Thermal Characteristics ◽  
Axial Distance ◽  
Rectangular Duct ◽  
Average Temperature ◽  
Nusselt Numbers ◽  
Transient Thermal ◽  
Substantial Change

Stabilization of the buoyancy-driven unstable mixed convective vortex air flow in a bottom heated rectangular duct by tapering its top plate is investigated experimentally. Specifically, the duct is tapered so that its aspect ratio at the duct inlet is 4 and gradually raised to 12 at the exit of the duct. In the study the secondary flow in the duct is visualized and the steady and transient thermal characteristics of the flow are examined by measuring the spanwise distributions of the time-average temperature. The effects of the Reynolds and Grashof numbers on the vortex flow structure are studied in detail. Moreover, the spanwise-averaged Nusselt numbers for the horizontal rectangular and tapering ducts are also measured and compared. Furthermore, the time records of the air temperature are obtained to further detect the temporal stability of the flow. Over the ranges of the Re and Gr investigated for 5⩽Re⩽102 and 1.0×104⩽Gr⩽1.7×105, the vortex flow induced in the rectangular duct exhibits temporal transition from a steady laminar to time periodic and then to chaotic state at increasing buoyancy-to-inertia ratio. Substantial change in the spatial structure of the vortex flow is also noted to accompany this temporal transition. The results for the tapering duct indicate that more vortex rolls can be induced due to the increase in the aspect ratio of the duct with the axial distance. But the vortex rolls are weaker and are completely stabilized by the tapering of the top plate. [S0022-1481(00)70301-X]

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