Temperature Variance Research Articles

Numerical investigation and experimental verification of topological optimized double-layer mini-channels

Double-layer micro/mini channel heat sinks have great potential in the thermal management for integrated chips. In this work, two bi-objective optimization design of mini-channels is implemented using the variable density topology optimization method to get two topological single-layer mini-channel heat sinks (SL-MHSs). Among them, the SL-MHS obtained with the minimization of average temperature and power dissipation as the optimization objectives is named S1, while the SL-MHS obtained with the minimization of temperature variance and power dissipation as the optimization objectives is named S2. Then, S1 and S2 are used as the upper/lower layer of the double layer mini channel heat sink (DL-MHS), respectively. Therefore, four different topological DL-MHSs including D11, D12, D21 and D22 are achieved by assembling S1 and S2. Subsequently, the flow and thermal characteristics of the four topological DL-MHSs and conventional straight DL-MHS (C1) are studied numerically. The results show that when Re = 315, compared with C1, the maximum temperature of the substrate of the topological DL-MHSs (D11, D12, D21 and D22) can be respectively reduced by 17.0,16.6, 14.0 and 13.6 K, while the Nusselt number can be improved by 27.3%, 26.6%, 27.1% and 26.4%, respectively. Additionally, the total thermal resistance is also reduced at least 20%. However, although topological DL-MHSs produce higher pressure drop penalty, the PEC values of topological DL-MHSs are always greater than 1, which indicates that the new topological DL-MHSs is meaningful. Finally, the flow and thermal characteristics of the best one D11 are investigated experimentally. The simulated results agree well with the experimental results.

Computational Domain Size Effects on Large-Eddy Simulations of Precipitating Shallow Cumulus Convection

Idealized large-eddy simulations of shallow convection often utilize horizontally periodic computational domains. The development of precipitation in shallow cumulus convection changes the spatial structure of convection and creates large-scale organization. However, the limited periodic domain constrains the horizontal variability of the atmospheric boundary layer. Small computational domains cannot capture the mesoscale boundary layer organization and artificially constrain the horizontal convection structure. The effects of the horizontal domain size on large-eddy simulations of shallow precipitating cumulus convection are investigated using four computational domains, ranging from 40×40km2 to 320×320km2 and fine grid resolution (40 m). The horizontal variability of the boundary layer is captured in computational domains of 160×160km2. Small LES domains (≤40 km) cannot reproduce the mesoscale flow features, which are about 100km long, but the boundary layer mean profiles are similar to those of the larger domains. Turbulent fluxes, temperature and moisture variances, and horizontal length scales are converged with respect to domain size for domains equal to or larger than 160×160km2. Vertical velocity flow statistics, such as variance and spectra, are essentially identical in all domains and show minor dependence on domain size. Characteristic horizontal length scales (i.e., those relating to the mesoscale organization) of horizontal wind components, temperature and moisture reach an equilibrium after about hour 30.

Tropical Pacific Influence on Summertime South African High‐Frequency Temperature Variability and Heat Waves

AbstractThe dominant mode of interannual variability in summertime high‐frequency tropospheric temperature fluctuations over Southern Africa is found to be associated with tropical Pacific sea surface temperature variability, in such a manner that El Niño is typically accompanied by enhanced high‐frequency variability. This relationship is established via El Niño's teleconnection that contributes to shifting the midlatitude jetstream and associated baroclinic zone equatorward, into the vicinity of Southern Africa, which enhances the baroclinic conversion of energy from the seasonal‐mean flow to high‐frequency eddies. The enhanced temperature variance, combined with the overall warmer summertime‐mean temperatures induced by El Niño, results in more frequent warm extremes over Southern Africa.

Spatial and temporal patterns of near‐surface ground temperature in the Arctic mountain catchment

AbstractWe consider the case of a mountain catchment representative of southwest Spitsbergen to investigate the spatial and temporal variation in temperature of the near‐surface ground. We set up 20 thermistor strings distributed in different parts of the catchment, combine the measured data with land surface temperature (LST) retrieved from Landsat imagery, and verify the depth of ground thawing using electrical resistivity tomography. Under current climatic conditions, the thickness of the active layer (ALT) is at least 1.5 m, and in the lower parts of the catchment, between 3.5 and 4 m. The maximum ground surface temperature in the study area can be 27°C, and the temperature at a depth of 1.5 m, 5.4°C. We identified unfrozen ground (taliks) to a depth of 10–30 m in zones of water concentration at foot slopes and under river channels. The persistence of year‐round taliks at lake shores is possible. We verify the hypothesis that topographic parameters significantly determine the spatial variation of near‐surface ground temperature. For each level of temperature aggregation (from 6 h to 12 months data) and each examined the depth of the active layer, it is possible to identify environmental variables—related to energy conditions, heights, terrain relief, and ground surface moisture—significantly correlated with ground temperature, and consequently to specify multiple regression models. Topographic exposure and LST (used only in daily models), altitude, and various approximations of relative height are crucial in their construction. The ground temperature variance, unexplained in the regression analysis, prompts recognition of the critical role of factors not included in the modelling (groundwater, soil structure).

Can nesting behaviour allow reptiles to adapt to climate change?

A range of abiotic parameters within a reptile nest influence the viability and attributes (including sex, behaviour and body size) of hatchlings that emerge from that nest. As a result of that sensitivity, a reproducing female can manipulate the phenotypic attributes of her offspring by laying her eggs at times and in places that provide specific conditions. Nesting reptiles shift their behaviour in terms of timing of oviposition, nest location and depth of eggs beneath the soil surface across spatial and temporal gradients. Those maternal manipulations affect mean values and variances of both temperature and soil moisture, and may modify the vulnerability of embryos to threats such as predation and parasitism. By altering thermal and hydric conditions in reptile nests, climate change has the potential to dramatically modify the developmental trajectories and survival rates of embryos, and the phenotypes of hatchlings. Reproducing females buffer such effects by modifying the timing, location and structure of nests in ways that enhance offspring viability. Nonetheless, our understanding of nesting behaviours in response to climate change remains limited in reptiles. Priority topics for future studies include documenting climate-induced changes in the nest environment, the degree to which maternal behavioural shifts can mitigate climate-related deleterious impacts on offspring development, and ecological and evolutionary consequences of maternal nesting responses to climate change. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

Statistical Behaviour and Modelling of Variances of Reaction Progress Variable and Temperature During Flame-Wall Interaction of Premixed Flames Within Turbulent Boundary Layers

The statistical behaviour of the transport of reaction progress variable variance, c″2~,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{{c^{^{\\prime\\prime}2} }},$$\\end{document} and non-dimensional temperature variance, T″2~,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{{T^{^{\\prime\\prime}2} }},$$\\end{document} have been analysed using three-dimensional Direct Numerical Simulation (DNS) data of turbulent premixed flame-wall interaction with isothermal inert walls within turbulent boundary layers for (i) an unsteady head-on quenching of a statistically planar flame propagating across the boundary layer, and (ii) a statistically stationary oblique wall quenching of a V-flame. It has been found that the reaction rate contribution acts as a leading order source term to the transport of both reaction progress variable variance, c″2~,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{{c^{^{\\prime\\prime}2} }},$$\\end{document} and non-dimensional temperature variance, T″2~,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{{T^{^{\\prime\\prime}2} }},$$\\end{document} whereas the molecular dissipation term remains the leading order sink term for both configurations analysed here. With the progress of flame wall interaction, the magnitude of all the source terms for the transport equations of both reaction progress variable and non-dimensional temperature variances vanish in the near-wall region with the onset of flame quenching. However, the molecular dissipation term continues to act as a sink term. The performances of the existing models for turbulent scalar flux, reaction rate and scalar dissipation rate contributions have been assessed for both flame-wall interaction configurations based on a priori DNS analysis. The existing available models for scalar dissipation rate for temperature and the reaction rate contribution in the variance transport equations even with the previously proposed wall corrections do not adequately predict the behaviour in the near-wall region. Modifications have been suggested to the existing closure models for the scalar dissipation rate and the reaction rate contribution to the scalar variance transport equations to improve the predictions in the near-wall region. Furthermore, the recommended closures for the unclosed terms of both reaction progress variable variance, c″2~,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{{c^{^{\\prime\\prime}2} }},$$\\end{document} and non-dimensional temperature variance, T″2~,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\widetilde{{T^{^{\\prime\\prime}2} }},$$\\end{document} are shown to accurately capture the corresponding variations obtained from DNS data for both near to and away from the wall.

Nonintrusive Uncertainty Quantification in the Simulation of Steel Reheating Using Polynomial Chaos Expansion

Uncertainty quantification (UQ) is deemed critical in steel reheating simulations due to the significant input uncertainties arising when defining steel surface properties and atmospheric furnace conditions. In order to conduct UQ, the study utilizes polynomial chaos expansion, which has been found to significantly curtail the computational effort needed to obtain reliable convergent statistics for the model of interest. Results from a comprehensive UQ analysis of a walking‐beam reheat furnace simulated using Tata Steel's reheat furnace control model, online slab temperature calculation, are presented. Slab temperature evolution and oxide scale growth are chosen as the study's QoIs. The analysis reveals that at the earlier stages of reheating, the majority of the output variance in slab temperature can be traced back exclusively to the emissivity of the slab surface, and the majority of the output variance in oxide scale growth is traced back to the combination of slab's surface emissivity and the initial scale thickness found on steel products prior to reheating. However, as the steel product advances toward the furnace's discharge end, inputs related to oxide scale growth become increasingly important, ultimately becoming the most influential input parameters, although the dynamics of this transition differ between the QoIs.

A comparison of pre-millennium eruption (946 CE) and modern temperatures from tree rings in Changbai Mountain, Northeast Asia

Abstract. High-resolution temperature reconstructions in the previous millennium are limited in Northeast Asia, but they are important for assessing regional climate dynamics. Here, we present, for the first time, a 202-year reliable reconstruction of April temperature changes before the millennium volcanic eruption in 946 CE using tree rings of carbonized logs buried in the tephra in Changbai Mountain, Northeast Asia. The reconstructed temperature changes were consistent with previous reconstructions in China and the Northern Hemisphere. The influences of large-scale oscillations (e.g. El Niño–Southern Oscillation, ENSO) on temperature variability were not significantly different between the periods of 745–946 CE preceding the eruption and 1883–2012. However, compared to the palaeotemperature of the previous millennium, the temperature changes were more complex with stronger temperature fluctuations, more frequent temperature abruption, and a weaker periodicity of temperature variance during the last 130 years. These recent changes correspond to long-term anthropogenic influences on regional climate.

The impacts of temperature averages, variabilities and extremes on China’s winter wheat yield and its changing rate

China is the world’s largest producer and consumer of wheat. The impact of temperature averages, variabilities, and extremes on winter wheat yield changes is still not very clear. The annual production data for winter wheat in China’s provinces and municipalities and NCEP-NCAR Reanalysis-1 data were used from November to April in the period 1949–2018, to investigate the impact of temperature-related variables, such as the winter average temperature (), winter variance of temperature (), extreme hot days (EHD), and extreme cold days (ECD), on China’s winter wheat yield. Ensemble Empirical Mode Decomposition (EEMD) analysis showed that winter wheat yield has an in-phase relationship with average temperature but an out-of-phase relationship with variance of temperature, extreme hot days, and extreme cold days on timescales greater than 20 years. The changing rates of winter wheat yield and temperature-related variables were well measured by their sliding trends. At the overwintering growth stage, the increasing rate of average temperature and extreme hot days (temperature variance and extreme cold days) exhibit negative (positive) correlations with the rate of winter wheat yield change, with the strongest correlation observed in southeast China. During the tillering growth stage, the changing rates of average temperature exhibited a positive correlation with the rate of winter wheat yield change, whereas negative associations were observed with temperature variance, extreme hot days, and extreme cold days. Among the regions, Central China showed the weakest correlations. At the reviving growth stage, however, the relationship of changing rates of temperature-related variables with that of winter wheat yield was much weaker. These observational results are important and can be used as a reference in climate models for improving the climatic impacts on the winter wheat yield.

Experimental study of phase change microcapsule-based liquid cooling for battery thermal management

Thermal management of power battery is important to ensure the safety of electric vehicle. Coupling phase change materials (PCMs) with liquid cooling technology is an efficient temperature uniformity strategy. In this paper, a self-made microencapsulated PCM (MPCM) was used to prepare MPCM slurry (MPCMS), and three base liquids (water, ethanol, and silicone oil) were evaluated, which confirmed that the silicone oil could maintain slurry without sedimentation for 7 days, providing the best stability. Also, graphene (GE) was introduced to increase the heat transfer rate of slurry. Then the prepared slurries were applied to the prismatic lithium-ion battery module to verify their thermal management performance. The results indicated that the prepared slurries' latent heat, thermal conductivity, and specific heat capacity were all rose with the increase of MPCM concentration. In addition, the slurries' viscosity changed little when the concentration was below 40 wt%. Compared with the blank module, GE-MPCMS-Si could reduce the battery module temperature and the temperature variance by 14.49 °C and 3.8 °C2, respectively. Besides, the influence of flow rate was further investigated, which showed 6 mL/s is the most economical and efficient flow rate option.

Topology Optimization Design for Heat Dissipation Performance of Semiconductor Ignition Device

Abstract The trend of miniaturization and intgration of the electronic device has put forward higher requirements on efficiency of heat radiating, which can hardly be satisfied by the traditional forced convection heat dissipation method. In this paper, the strategy of topology optimization technique is adopted to greatly improve the heat dissipation efficiency of a semiconductor ignition device. The penalization method is used to implement the topology optimization process. Three kinds of objective functions of thermal compliance, temperature variance and geometric average temperature were separately applied in the topological optimization of two typical uniform heat generation cases, and the resulted topologically optimization results were analyzed and compared. Based on the two benchmark cases, the appropriate objective function was selected to conduct structural optimization of semiconductor bridge ignition devices with the aim of making the highest temperature in the design domain the lowest possible. Additionally, a parametric study on the effect of thermal conductivity on topology optimization results was conducted, which leads to a design suggestion beneficial for heat dissipation and material selection.

Insight into heat dissipation in fractured rock influenced by groundwater influx and heat source configurations using numerical analysis

The characterization and evaluation of heat dissipation effects in fractured rock is becoming a priority topic with respect to the potential application of low-temperature thermal remediation in these settings. A three-dimensional numerical model was utilized to investigate heat dissipation-related thermo-hydrological processes in an upper fractured rock layer and a lower impermeable bedrock layer. To identify the factors controlling spatial temperature variances in the fractured rock layer accounting for a scaled heat source and variable groundwater flow, global sensitivity analyses were conducted on the variables using three categories: heat source, groundwater flow, and rock properties. A discrete Latin-hypercube-one-at-a-time method was used to conduct the analyses. A heat dissipation coefficient was proposed to evaluate the correlation between heat dissipation effects and transmissivity based on a case study using the hydrogeological setting of a well-characterized Canadian field site. The results show a significance ranking of three sets of variables controlling heat dissipation processes in both the central and the bottom areas of the heating zone: specifically, heat source > groundwater > rock. The groundwater influx and heat conduction in the rock matrix are key factors determining heat dissipation at the upstream and bottom areas of the heating zone, respectively. The heat dissipation coefficient is closely associated with the transmissivity of the fractured rock in a monotonic relationship. A significant growth rate of the heat dissipation coefficient appears when the transmissivity is between 1 × 10−6 and 2 × 10−5m2/s. The results suggest that the low-temperature thermal remediation can be a promising technique to adapt the significant heat dissipation in highly weathered fractured rock.

Influence of Temperature Variance on the Mechanical Properties of a Welded Bearing Support Flange Under Transient Conditions Using Finite Element Approach

During a welding process, the influence of temperature distribution plays an important role affecting the vulnerable regions of the welded component. This research aims at presenting data on similar cases where a detailed comparative evaluation provides necessary data for designing a component based on its structural behaviour due to induced temperature variance during the groove welding process using finite element approach.
 The finite element simulations render a real-world scenario of the groove welding process by integrating the concept of ‘Moving heat source’ under transient conditions in ANSYS. The numerical comparative study is achieved by simulating a thermal study of the welded components of different bearing support flange plate thickness and evaluating its structural behaviour under induced thermal loads.
 The numerical solutions obtained from these simulations provide necessary data which helps in identifying the feasible design approach to increase the life of a welded component under such temperature-dependent conditions.

Paper‐Based Printed Antenna: Investigation of Process‐Induced and Climatic‐Induced Performance Variability

Printing technologies have emerged as a viable method for the fabrication of various electronic components, including sensors, actuators, energy harvesters, thin‐film transistors and circuits, as well as antennas. However, printing processes have limitations in terms of surface roughness and thickness. Printing conductive structures on novel substrates, such as cellulose‐based sustainable paper, also leads to further challenges linked to the high surface porosity and ink carrier absorption. Herein, the variability of paper‐based printed antenna performance due to different printing processes, ink carrier absorption, and temperature is investigated. The resonance frequency and gain of different printed antennas (e.g., screen, inkjet, and dispense‐printed) are compared in terms of surface roughness, thickness, and resonance frequency. Screen‐printed antennas show better performance compared to other printed antennas. The results show that the resonance frequency of antenna shifts 20, 30, and 50 MHz for screen printed, dispense printed, and inkjet printed respectively, from the nominal 2.6 GHz. In the case of the inkjet‐printed antenna, a clear effect of skin depth is observed, due to the 0.91 thickness. Furthermore, it is demonstrated that the permittivity/dielectric constant of the paper substrate is significantly influenced by ink carrier absorption and temperature variance.

Reduced genetic diversity and restricted gene flow of broadcast-spawning coral Galaxea fascicularis in the South China Sea reveals potential degradation under environmental change

Under the dual effects of climate change and anthropogenic activities, coral reefs in the South China Sea (SCS) are at serious risk of degradation. Galaxea fascicularis is a widely distributed species in the SCS, and the study of its genetics, survival, and adaptability is conducive to further understanding the future characteristics of coral reefs in the SCS. In this study, 146 G. fascicularis samples were selected from 9 survey stations across 12 latitudes in the SCS, and 8 pairs of microsatellite markers were used to characterize their genetic diversity and structure. The results showed moderate genetic diversity index values (Ar = 3.444–4.147, He = 0.634–0.782, Ho = 0.367–0.586). The AMOVA results and pairwise FST values showed a moderate level of genetic differentiation (ΦST = 0.119, P < 0.05) among G. fascicularis populations in the SCS, whereas its genetic structure showed high genetic differentiation (FST = 0.062–0.225) among relatively high-latitude populations (n = 3) and low genetic differentiation (FST = 0.012–0.064) in low-latitude populations (n = 6). The living environment of relatively high-latitude populations is disturbed by high-intensity human activities, leading to the specialization of local populations. Mantel test results showed a significant positive correlation between genetic differentiation among G. fascicularis populations and sea surface temperature (SST) variance (R2 = 0.4885; Mantel test, p = 0.010 < 0.05) in addition to geographical distance (R2 = 0.1134; Mantel, test p = 0.040 < 0.05), indicating that SST and geographical isolation were primary factors affecting the genetic structure of this species in the SCS. The lower genetic diversity and limited gene flow of G. fascicularis indicate limited genetic adaptation, and corresponding vulnerability may be more pronounced under future environmental changes. These findings provide a theoretical basis for the conservation and restoration of coral reefs in the SCS.

Experimental Efficiency of Single Pass Solar Air Heater

The solar heat collector with the impingement of jet lower plate (SAHJF) experimentally designed and operated with typical parameters obtained from theoretical analysis to contained the maximum efficiency of the performance of thermal transfer. Then it was developed by replacing the flat absorber by the corrugated absorber (SAHJC) to enhance the efficiency. The flow rate of mass was selected equal and more than the typical value and the intensities of the solar radiation were chosen equal and less than the typical value to investigate the effect of both on the thermal transfer efficiency for SAHJF and SAHJC. Since the system works with a short range of temperature, the temperatures recorded were sensitive and needed a large accuracy. Therefore, an analysis method was proposed and applied to the data to be sure that it reflects the variance of temperature with different operating parameters. The correlation of temperature difference between the outlet and the inlet air with different flow rate and different intensities of irradiation for SAHJF and SAHJC was presented and compared.

Effect of tubular heater structures on the thermal behaviors of waxy crude oil

In this paper, we research the temperature field, flow field and melting law of gelled crude oil with different diameters, locations and inclination angles of heating tube by numerical simulation method. Using the synergy angle, temperature variance and effective heating ratio as evaluation indices, the effect of the heating tube and distribution homogeneity of the temperature field were examined. The simulation results show that the temperature field and velocity field of waxy crude oil and the melting law of gelled crude oil are basically the same under different conditions. The most important factor affecting average temperature and temperature variance is the location of heating tube, which can increase the average temperature by 1.252 °C and decrease the temperature variance by 9.019°C2. The most important factor affecting the synergy angle is the inclination angle of heating tube, which can be reduced by 4.104°. In the 8 cases, when the inclination angle of the heating tube is 45°, the temperature maintaining effect of tubular heating is the best, and the synergy angle is the smallest. The least temperature variance is the uniform arrangement of heating tube. The results of this study will provide theoretical guidance for the optimization design of tubular heater structure.

Local hydrothermal characteristics and temperature uniformity improvement of microchannel heat sink with non-uniformly distributed grooves

In order to improve the temperature uniformity of bottom walls, a novel design of microchannel heat sink with From-Sparse-To-Dense embowed grooves (MC-FSTD) was proposed as well as a comparative one with From-Dense-To-Sparse embowed grooves (MC-FDTS). The local hydrothermal characteristics and temperature distribution variance of bottom wall of microchannel heat sinks were numerically investigated for Reynolds number (Re) ranging from 100 to 800. The results showed that the denser grooves led to lower flow velocity, lower local friction factor and higher local pressure as well as the lower bottom wall temperature (Tw) and higher local Nusselt number (Nuz). The local Nusselt number and the bottom wall temperature of MC-FSTD were 2.17 times higher and 9.1K lower than that of MC-SC at z = 10 mm, respectively. MC-FSTD also had the most uniform temperature of the bottom wall and the corresponding temperature variance was 6.42 times lower than that of MC-SC at Re = 795.38. The heat transfer entropy generation rate and the total entropy generation rate of MC-FSTD were also the lowest with an acceptable friction entropy generation rate. Finally, the effects of the decreasing magnitude (Li) of the distance between two adjacent grooves on the local hydrothermal characteristics and temperature uniformity of MC-FSTD were explored and the total entropy generation rate was further reduced to 5.22 × 10−4 W/K at Li = 0.015 mm and Re = 795.38.

Elevated temperatures reduce population-specific transcriptional plasticity in developing lake sturgeon (Acipenser fulvescens).

Rising mean and variance in temperatures elevates threats to endangered freshwater species such as lake sturgeon, Acipenser fulvescens. Previous research demonstrated that higher temperatures during development result in physiological consequences for lake sturgeon populations throughout Manitoba, Canada, with alteration of metabolic rate, thermal tolerance, transcriptional responses, growth and mortality. We acclimated lake sturgeon (30-60 days post fertilization, a period of high mortality) from northern and southern populations (56°02'46.5″N, 96°54'18.6″W and 50°17'52″N, 95°32'51″W, respectively, separated by approximately 650 km) within Manitoba to current (summer highs of 20-23°C) and future projected (+2-3°C) environmental temperatures of 16, 20 and 24°C for 30 days, and we measured gill transcriptional responses using RNAseq. Transcripts revealed SNPs consistent with genetically distinct populations and transcriptional responses altered by acclimation temperature. There were a higher number of differentially expressed transcripts observed in the southern, compared to the northern, population as temperatures increased, indicating enhanced transcriptional plasticity. Both lake sturgeon populations responded to elevated acclimation temperatures by downregulating the transcription of genes involved in protein synthesis and energy production. Furthermore, there were population-specific thresholds for the downregulation of processes promoting transcriptional plasticity as well as mitochondrial function as the northern population showed decreases at 20°C, while this capacity was not diminished until 24°C in the southern population. These transcriptional responses highlight the molecular impacts of increasing temperatures for divergent lake sturgeon populations during vulnerable developmental periods and the critical influence of transcriptome plasticity on acclimation capacity.

A versatile immersed boundary method for high-fidelity simulation of Conjugate Heat Transfer

A numerical strategy based on an immersed boundary method (IBM) is presented for performing high-fidelity simulation of thermal hydraulics while including Conjugate Heat Transfer (CHT). The well documented pipe flow is considered which, despite its academic nature, can be seen as a prototype of complex geometry in the sense that the computational mesh, only regular and Cartesian, is not in any way designed to fit the wall. An original strategy is proposed to impose Neumann boundary conditions in this generic situation where the wall geometry is disconnected from the mesh organization. As a first validation step, the technique is used in the context of heat transfer in pipe flow with isoflux conditions (IF). The actual order of accuracy is assessed in laminar regime and then direct numerical simulation (DNS) results are compared to turbulent data of reference, including first- and second-order one-point statistics, as well as budgets of temperature variance for a Reynolds number Re=5300 and two Prandtl numbers Pr=0.025,0.71. The technique is then used to develop a versatile methodology for CHT simulations, where the coupling between fluid and solid thermal solution is performed by an immersed boundary technique that translates the information from the normal and tangential surface directions into the Cartesian grid directions. Consistent results are presented in laminar and turbulent regimes, through the check of the accuracy order for the former and the analysis of turbulent statistics for the latter, including the assessment of the discontinuity of the temperature variance dissipation across the fluid-solid interface.