scholarly journals Groundwater flow, heat flux, and permeability inferred from borehole temperature profile in Izu-Oshima volcano, Japan – Implications for subsurface hydrothermal system

2020 ◽  
Author(s):  
Shin'ya Onizawa ◽  
Nobuo Matsushima
Keyword(s):  
Heat Flux ◽  
Groundwater Flow ◽  
Temperature Profile ◽  
Hydrothermal System ◽  
Heat Fluxes ◽  
Total Heat ◽  
Conductive Heat ◽  
Upward Flow ◽  
Total Heat Flux ◽  
Layer Formation

Abstract Groundwater flow velocity as well as conductive and convective heat fluxes were estimated using temperature profile data from a 1000 m–deep borehole in the central part of the Izu-Oshima volcano, Japan. Two depth intervals below groundwater level with upward groundwater flow patterns were examined assuming a one-dimensional vertical steady flow. The groundwater velocity and total heat flux were estimated to be 5.0–5.4×10-10 m/s and 0.54–0.59 W/m2, respectively, for the basement layer (Formation 4). For the shallower layer (Formation 2), both the upward velocity and heat flux were higher, indicating greater contributions of convective mass and heat transfer compared to those in the deeper layer. Furthermore, assuming that the upward flow was buoyancy-driven, vertical permeabilities of 2.8–5.1×10-15 and 1.7–3.1×10-16 m2 , respectively, were estimated for Formations 2 and 4. The temperature patterns of the lava-dominant region (Formation 3), sandwiched between Formations 2 and 4, suggested the occurrence of lateral cooler groundwater inflow in fractures. These results were used for understanding a hydrothermal system beneath the volcano. The total heat flux estimated for Formation 4 (0.54–0.59 W/m2) was nearly three times higher than the conductive heat flux in the northwestern coastal area, suggesting a higher heat supply below the central part of the volcano. A hydrothermal free convection system was inferred in Formations 2 and 3. In Formation 2, buoyancy-driven upward flow was enhanced because of the heat below and the higher permeability. Cooler groundwater was laterally supplied in lava fractures in Formation 3 to compensate for the mass loss by the upward flow at the bottom of Formation 2.

Wave-Coherent Air–Sea Heat Flux

2008 ◽  
Vol 38 (4) ◽  
pp. 788-802 ◽  
Author(s):  
Fabrice Veron ◽  
W. Kendall Melville ◽  
Luc Lenain
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Wave ◽  
Momentum Transfer ◽  
Latent Heat ◽  
Heat Fluxes ◽  
Total Heat ◽  
Research Progress ◽  
Total Heat Flux ◽  
Wave Conditions

Abstract Air–sea fluxes of heat and momentum play a crucial role in weather, climate, and the coupled general circulation of the oceans and atmosphere. Much progress has been made to quantify momentum transfer from the atmosphere to the ocean for a wide range of wind and wave conditions. Yet, despite the fact that global heat budgets are now at the forefront of current research in atmospheric, oceanographic, and climate problems and despite the good research progress in recent years, much remains to be done to better understand and quantify air–sea heat transfer. It is well known that ocean-surface waves may support momentum transfer from the atmosphere to the ocean, but the role of the waves in heat transfer has been ambiguous and poorly understood. Here, evidence is presented that there are surface wave–coherent components of both the sensible and the latent heat fluxes. Presented here are data from three field experiments that show modulations of temperature and humidity at the surface and at 10–14 m above the surface, which are coherent with the surface wave field. The authors show that the phase relationship between temperature and surface displacement is a function of wind speed. At a 10–12-m elevation, a wave-coherent heat transfer of O(1) W m−2 is found, dominated by the latent heat transfer, as well as wave-coherent fractional contributions to the total heat flux (the sum of latent and sensible heat fluxes) of up to 7%. For the wind speeds and wave conditions of these experiments, which encompass the range of global averages, this wave contribution to total heat flux is comparable in magnitude to the atmospheric heat fluxes commonly attributed to the effects of greenhouse gases or aerosols. By analogy with momentum transfer, the authors expect the wave-coherent heat transfer to decay with height over scales on the order of k−1, where k is the characteristic surface wavenumber; therefore, it is also expected that measurements at elevations of O(10) m may underestimate the contribution of the wave-induced heat flux to the atmosphere.

scholarly journals Heat Fluxes Localization and Abnormal Size Effect Induced by Multi-Body Vibration in Complex Networks

2021 ◽  
Author(s):  
Kezhao Xiong ◽  
Zhengxin Yan ◽  
You Xie ◽  
Yixian Wang ◽  
Chunhua Zeng ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Size Effect ◽  
Complex Networks ◽  
Heat Fluxes ◽  
Total Heat ◽  
Total Heat Flux ◽  
Theoretical Understanding ◽  
Body Vibration ◽  
Multi Body

Abstract Heat conduction in real physical networks such as nanotube/nanowire networks has been attracting more and more attention, but its theoretical understanding is far behind. To open a way to this problem, we present a multi-body vibration model of heat conduction to study how heat is conducted in complex networks, where nodes’degrees satisfy a random distribution and links consist of 1D atom chains with nonlinear springs. Based on this model, we find two interesting phenomenons: (1) The main heat fluxes of network are always localized in a skeleton subnetwork, which may have potential applications in thermal management and thermal concentrators, etc; (2) There exists an abnormal size effect of heat conduction in complex networks, i.e. the total heat flux of network will be enlarged with the increase of atoms on links, which is in contrast to the previous result on a 1D chain. Furthermore, we introduce a transmission diagram to characterize the skeleton of localized heat fluxes and then discover a phase transition of total heat flux in the process of removing links, implying that the control of heat flux can be effective only when the change of network topology is focused on the links within the skeleton. A brief theory is introduced to explain the abnormal size effect.

Aero-Thermal Investigation of Tip Leakage Flow in a Film Cooled Industrial Turbine Rotor

2008 ◽  
Author(s):  
S. K. Krishnababu ◽  
H. P. Hodson ◽  
G. D. Booth ◽  
G. D. Lock ◽  
W. N. Dawes
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flow ◽  
Turbine Rotor ◽  
Total Heat ◽  
Leakage Flow ◽  
Total Heat Flux ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow And Heat Transfer

A numerical investigation of the flow and heat transfer characteristics of tip leakage in a typical film cooled industrial gas turbine rotor is presented in this paper. The computations were performed on a rotating domain of a single blade with a clearance gap of 1.28% chord in an engine environment. This standard blade featured two coolant and two dust holes, in a cavity-type tip with a central rib. The computations were performed using CFX 5.6, which was validated for similar flow situations by Krishnababu et al., [18]. These predictions were further verified by comparing the flow and heat transfer characteristics computed in the absence of coolant ejection with computations previously performed in the company (SIEMENS) using standard in-house codes. Turbulence was modelled using the SST k-ω turbulence model. The comparison of calculations performed with and without coolant ejection has shown that the coolant flow partially blocks the tip gap, resulting in a reduction of the amount of mainstream leakage flow. The calculations identified that the main detrimental heat transfer issues were caused by impingement of the hot leakage flow onto the tip. Hence three different modifications (referred as Cases 1 to 3) were made to the standard blade tip in an attempt to reduce the tip gap exit mass flow and the associated impingement heat transfer. The improvements and limitations of the modified geometries, in terms of tip gap exit mass flow, total area of the tip affected by the hot flow and the total heat flux to the tip, are discussed. The main feature of the Case 1 geometry is the removal of the rib and this modification was found to effectively reduce both the total area affected by the hot leakage flow and total heat flux to the tip while maintaining the same leakage mass flow as the standard blade. Case 2 featured a rearrangement of the dust holes in the tip which, in terms of aero-thermal-dynamics, proved to be marginally inferior to Case 1. Case 3, which essentially created a suction-side squealer geometry, was found to be inferior even to the standard cavity tip blade. It was also found that the hot spots which occur in the leading edge region of the standard tip and all modifications contributed significantly to the area affected by the hot tip leakage flow and the total heat flux.

scholarly journals Round robin study of total heat flux gauge calibration at fire laboratories

2004 ◽  
Author(s):  
William M Pitts ◽  
Annageri V Murthy ◽  
John L deRis ◽  
Jean-Remy R Filtz ◽  
Kjell Nygard ◽  
...  
Keyword(s):  
Heat Flux ◽  
Round Robin ◽  
Total Heat ◽  
Total Heat Flux

scholarly journals Numerical Simulation of Thawing Process in Frozen Soil

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Zhaoyu Yan ◽  
Wei Pan ◽  
Junjie Fang ◽  
Zihui Liu
Keyword(s):  
Numerical Simulation ◽  
Heat Flux ◽  
Liquid Water ◽  
Minimum Temperature ◽  
Frozen Soil ◽  
Total Heat ◽  
Water Volume ◽  
Total Heat Flux ◽  
Volume Curve ◽  
Thawing Process

Permafrost has been thawing faster due to climate change which would release greenhouse gases, change the hydrological regimes, affect buildings above, and so on. It is necessary to study the thawing process of frozen soil. A water-heat coupling model for frozen soil thawing is established on Darcy’s law and Heat Transfer in Porous Media interfaces in Comsol Multiphysics 5.5. Three curves of total liquid water volume, minimum temperature, and total heat flux in the thawing process are obtained from a numerical simulation. The distributions of liquid water, temperature, and pressure based on time are simulated too. The liquid water distribution is consistent with the total liquid water volume curve. The temperature distribution is confirmed by the minimum temperature and total heat flux curve. The pressure distribution represents ice in the frozen soil that generates negative pressure during the melting process. The numerical simulation research in this article deepens the understanding of the internal evolution in the process of frozen soil thawing and has a certain reference value for subsequent experimental research and related applications.

scholarly journals A Way to Visualise Heat Transfer in 3D Unsteady Flows

2009 ◽  
Author(s):  
M. F. M. Speetjens
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Motion ◽  
Unsteady Flows ◽  
Unsteady Motion ◽  
Heat Fluxes ◽  
Flow Visualisation ◽  
Conductive Heat ◽  
Steady Flows ◽  
Transfer Coefficients

Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective-conductive heat flux in a way analogous to the transport of fluid by the flow field. The paths followed by the total heat flux are the thermal counterpart to fluid trajectories and facilitate heat-transfer visualisation in a similar manner as flow visualisation. This has great potential for applications in which insight into the heat fluxes throughout the entire configuration is essential (e.g. cooling systems, heat exchangers). To date this concept has been restricted to 2D steady flows. The present study proposes its generalisation to 3D unsteady flows by representing heat transfer as the 3D unsteady motion of a virtual fluid subject to continuity. The heat-transfer visualisation is provided with a physical framework and demonstrated by way of representative examples. Furthermore, a fundamental analogy between fluid motion and heat transfer is addressed that may pave the way to future heat-transfer studies by well-established geometrical methods from laminar-mixing studies.

scholarly journals A Combination of Spatial Domain Filters to Detect Surface Ocean Current from Multi-Sensor Remote Sensing Data

2022 ◽  
Vol 14 (2) ◽  
pp. 332
Author(s):  
Mohammed Abdul Athick AS ◽  
Shih-Yu Lee
Keyword(s):  
Heat Flux ◽  
Remote Sensing Data ◽  
Total Heat ◽  
Sea Surface ◽  
Ocean Current ◽  
Surface Currents ◽  
Total Heat Flux ◽  
Data Set ◽  
Surface Ocean ◽  
Natural Break

This research investigates the applicability of combining spatial filter’s algorithm to extract surface ocean current. Accordingly, the raster filters were tested on 80–13,505 daily images to detect Kuroshio Current (KC) on weekly, seasonal, and climatological scales. The selected raster filters are convolution, Laplacian, north gradient, sharpening, min/max, histogram equalization, standard deviation, and natural break. In addition, conventional data set of sea surface currents, sea surface temperature (SST), sea surface height (SSH), and non-conventional data such as total heat flux, surface density (SSD), and salinity (SSS) were employed. Moreover, controversial data on ocean color are included because very few studies revealed that chlorophyll-α is a proxy to SST in the summer to extract KC. Interestingly, the performance of filters is uniform and thriving for seasonal and on a climatological scale only by combining the algorithms. In contrast, the typical scenario of identifying Kuroshio signatures using an individual filter and by designating a value spectrum is inapplicable for specific seasons and data set. Furthermore, the KC’s centerlines computed from SST, SSH, total heat flux, SSS, SSD, and chlorophyll-α correlate with sea surface currents. Deviations are observed in the various segments of Kuroshio’s centerline extracted from heat flux, chlorophyll-α, and SSS flowing across Tokara Strait from northeast Taiwan to the south of Japan.

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