Non-isothermal Field Research Articles

Sulphate influence on strength development of cemented paste backfill with superplasticizer under field-like curing conditions

This study investigates the impact of sulphate on the strength development of cemented paste backfill (CPB) with polycarboxylate ether-based superplasticizers (PES) under curing conditions mimicking real field environments. These conditions include thermal (T, non-isothermal field temperature), hydraulic (H, drainage), mechanical (M, overburden stress), and chemical (C, PES, sulphate ions) factors. CPB samples with varying sulphate and PES contents were examined through mechanical and microstructural tests under these THMC conditions. The findings reveal that traditional methods for assessing sulphate influence on CPB strength, typically under standard lab conditions, do not adequately capture the mechanical response of CPB structures to sulphate in field scenarios. Real field curing conditions such as temperature, drainage, and stress significantly affect CPB’s mechanical response to sulphate. CPB samples incorporating PES and sulphate show notable improvements in early-age strength, emphasizing the beneficial role of elevated temperatures and the complex relationship between drainage, sulphate, and strength development. Elevated curing temperatures counterbalance sulphate's negative effects, boosting initial strength, while drainage conditions play a critical role in strength development by facilitating the removal of sulphate ions and reducing capillary water. Additionally, stress application at the start of curing aids solid particle rearrangement, promoting the release of free water and enhancing mechanical strength. The competitive adsorption between sulphate ions and PES on the cementitious matrix influences the dispersion of particles and strength development. This research offers crucial technical insights for designing durable CPB mixes suited to various on-site curing conditions, particularly enhancing initial strength across diverse field curing scenarios.

Self-desiccation behavior of nano-cemented tailings backfill plug: Insights from thermo-mechanical-chemical column experiments

This paper examines the influence of various factors, including the addition of nano-calcium carbonate particles (chemical processes, C) to CPBs, non-isothermal field curing temperatures (thermal factor, T), and field vertical curing stress (mechanical factor, M), on the self-desiccation capacity of CPB plugs. The assessment of self-desiccation involves the determination of pore water pressure (PWP) and volumetric water content (VWC) in the examined CPBs. Thermo-mechanical-chemical (TMC) column experiments were conducted to investigate the interaction among these factors and their collective impact on the evolution of PWP and VWC within the CPB plug. The findings underscore that each factor, both individually and in combination, significantly affects the magnitude and progression of self-desiccation in CPB plugs. Notably, the factors of elevated field temperature and the introduction of nano-calcium carbonate (NC) to the CPB exert the most substantial influence on the extent and enhancement of self-desiccation, whereas the impact of field curing stress in isolation is comparatively much weaker. The integration of nano-calcium carbonate, especially under non-isothermal conditions and concurrent field stress, emerges as a key contributor to enhanced PWP and VWC dissipation rates. The role of non-isothermal field curing temperature is underscored as a significant contributing factor in the self-desiccation of CPB plugs. The results presented in this paper will contribute to a more cost-effective design of CPB plugs and the improved optimization of CPB mixtures with nano-calcium carbonate particles.

Thermocapillary dynamics of a surfactant-laden droplet with internal thermal singularity

Thermocapillary droplets with internal thermal singularities have potential applications in drug delivery and cell analysis. Inspired by the work of Pak et al. (J. Fluid Mech., vol. 753, 2014, pp. 535–552), which was investigated for a surfactant-laden non-deformable droplet in an isothermal Poiseuille flow, we have explored the droplet dynamics by taking account of additional internal thermal singularities, namely monopole and dipole. A generalized mathematical model is developed, which is solved by using the solenoidal decomposition to describe the flow field in any arbitrary Stokes flow, and results are shown extensively for the case of a non-isothermal Poiseuille flow. Under small Péclet number ( $Pe_s$ ) limit, the droplet with an off-centred monopole or a dipole oriented along the flow direction shows cross-stream migration at $O(Pe_s^2)$ . However, a dipole oriented perpendicular to the flow direction results in an $O(1)$ effect due to thermocapillarity, and from $O(Pe_s)$ onwards, we observe the combined impact of thermocapillary and surfactant-induced Marangoni stresses. As a surprise, we see cross-stream migration of the droplet from the Poiseuille flow centreline in a non-isothermal field, in contrast to existing findings which rule out any cross-stream migration. We show the trade-off between thermal Marangoni number ( $Ma_T$ ) and surfactant Marangoni number ( $Ma_\varGamma$ ). Our findings on droplet dynamics inspire new possibilities for microfluidics-based design.

Strength and microstructure of cemented paste backfill modified with nano-silica particles and cured under non-isothermal conditions

A series of mechanical and microstructural tests and monitoring experiments are performed on different cemented paste backfill (CPB) specimens made with different types of tailings (silica tailings, gold tailings) to investigate the effects of adding nano-silica (SiO2) particles on the strength and microstructure (pore structure, mineralogical composition) of CPB cured under isothermal and non-isothermal conditions that simulate the field thermal curing conditions of CPB structures. The results show that the CPB with nano-SiO2 (NS-CPB) has a higher strength and finer pore structure than the control samples for all curing times and in all test conditions. Nano-SiO2 particles are effective in increasing the UCS of CPB in isothermal room conditions and non-isothermal field curing conditions. The increase in mechanical performance is higher when CPB is cured under non-isothermal conditions. Most of the increase in strength of the NS-CPB occurs at the early ages (3 days) of curing. The reason for the improvement in the mechanical strength is due to increase in binder hydration and the filler effect of the nanomaterial, which are in agreement with the results from microstructural analyses and electrical conductivity (EC) measurements. It is also found that the increase in temperature due to field thermal curing conditions greatly affect the strengthening properties of nano-SiO2. The NS-induced pozzolanic reactions are much more sensitive to higher temperatures compared to Portland cement hydration. The strengthening properties of the nano SiO2 are affected by the sulphate content in the tailings due to sulphate attacks (inhibition of cement hydration by sulphate ions), as less CH is available for pozzolanic reactions and C-S-H production. The findings presented in this manuscript will help to provide a better understanding of the behaviour of CPB and design a more cost-effective CPB modified with nano SiO2 particles.

Nonisothermal cellular automata simulation of two-dimensional snow crystal growth.

Natural snowflakes exhibit remarkable diversity with a fascinating sixfold symmetry and fractal structure. Efforts to discover the snow crystal growth pattern and mechanism behind it have been made in the past 50 years. Among those, cellular automata (CA) have made certain progress. To investigate the influence of latent heat release in snow crystal growth and have a deeper understanding of crystal growth characteristics, an improved CA model combined with vapor diffusion and heat diffusion is proposed to investigate the snowflake growth process in a two-dimensional and nonisothermal field in this paper. Simulation results show that obtained snow crystal growth behavior is consistent with previous experimental observations and satisfies the crystal growth dynamic theory. Latent heat release impacts the small structure of snow crystals, and it could have a more significant influence on snowflake morphology when vapor diffusion is slow and heat diffusion is dominating.

Influence of the Prandtl Number on Wall-to-Fluid Thermal Transfer Rate in a Cubic Cavity

The present paper describes a detailed qualitative and quantitative study of the impacts of the overall Prandtl number on the wall-to-fluid thermal transfer mechanisms in two-phase flows using CFD. The physical model consisted of a bubble inside a cubic cavity subjected to the gravity acceleration and to a non-isothermal field. The variables studied in the present investigation were the size of the bubble radius and the overall Prandtl number of flow. The variations of the overall Prandtl number of the flow and the bubble size were evaluated in order to understand their impact on the spatial mean Nusselt number using a computational fluid dynamics model. The bubble size was controlled modifying the bubbles’ initial radius in the computational simulations and the overall Prandtl number was computed according to the Prandtl number of each phase and its volume fraction. Several computational simulations were performed and the numerical model employed in these simulations were validated with previous numerical results in the literature. The present paper reported the influence of the overall Prandtl number on regulating the thermal transfer rate in the classical problem of a differentially heated cavity. According to the numerical results, the introduction of a dispersed phase in single-phase problems may increase or reduce the thermal transfer rate, depending on the overall Prandtl number. The influence of the bubble size has also played an important role in the variations of the thermal transfer rate, since the bubble movement in the domain was modified according to to the size of this radius, changing the distance between the walls and the dispersed phase. Finally, the generally accepted hypothesis elaborated from the literature regarding the increase of the thermal transfer rate due to the introduction of bubbles in single-phase flows has failed in the cubic cavity configuration from the present research.

602 Numerical Analysis on Reducing Effect of Knock Intensity in a non-Isothermal Field

602 Numerical Analysis on Reducing Effect of Knock Intensity in a non-Isothermal Field

Heat-conduction error of temperature sensors in a fluid flow with nonuniform and unsteady temperature distribution

In temperature measurement of non-isothermal fluid flows by a contact-type temperature sensor, heat conduction along the sensor body can cause significant measurement error which is called "heat-conduction error." The conventional formula for estimating the heat-conduction error was derived under the condition that the fluid temperature to be measured is uniform. Thus, if we apply the conventional formula to a thermal field with temperature gradient, the heat-conduction error will be underestimated. In the present study, we have newly introduced a universal physical model of a temperature-measurement system to estimate accurately the heat-conduction error even if a temperature gradient exists in non-isothermal fluid flows. Accordingly, we have been able to successfully derive a widely applicable estimation and/or evaluation formula of the heat-conduction error. Then, we have verified experimentally the effectiveness of the proposed formula using the two non-isothermal fields-a wake flow formed behind a heated cylinder and a candle flame-whose fluid-dynamical characteristics should be quite different. As a result, it is confirmed that the proposed formula can represent accurately the experimental behaviors of the heat-conduction error which cannot be explained appropriately by the existing formula. In addition, we have analyzed theoretically the effects of the heat-conduction error on the fluctuating temperature measurement of a non-isothermal unsteady fluid flow to derive the frequency response of the temperature sensor to be used. The analysis result shows that the heat-conduction error in temperature-fluctuation measurement appears only in a low-frequency range. Therefore, if the power-spectrum distribution of temperature fluctuations to be measured is sufficiently away from the low-frequency range, the heat-conduction error has virtually no effect on the temperature-fluctuation measurements even by the temperature sensor accompanying the heat-conduction error in the mean-temperature measurements.

An Efficient Method of Non-Gray Analysis for Studying Raditive Heat Transfer in Furnaces with Comparable Accuracy to Line-by-Line Analysis (Proposal of Method and Examination in Non-Isothermal Field)

An Efficient Method of Non-Gray Analysis for Studying Raditive Heat Transfer in Furnaces with Comparable Accuracy to Line-by-Line Analysis (Proposal of Method and Examination in Non-Isothermal Field)

Development of Fluid Temperature Scanner (Adaptive Response Compensation and Image Motion Measurement of In-Line Fine-Wire-Thermocouple Probe)

A novel measurement technique to visualize the spatial temperature distribution of a non-isothermal flow is developed. Two-dimensional temperature profiles are obtained by quantitatively tracking the path of a rod-type probe with a high-speed CCD camera, and superimposing it on the image of a measured object photographed by the same camera. The rod-type probe consists of 8 two-thermocouple sensors set in line. Each two-thermocouple sensor used in the present experiment is composed of two fine-wire thermocouples (type K) of unequal diameters, i.e., 51 μm and 76 μm, respectively. The key technique is an adaptive response-compensation scheme by which the response lag of the temperature sensors can be adequately compensated; hence the temperature profile can be reconstructed accurately. It is demonstrated that the non-isothermal field can be visualized readily and quantitatively.

An experimental study of non-isothermal miscible displacements in a Hele-Shaw cell

Non-isothermal miscible displacements in a radial Hele-Shaw cell were experimentally investigated using a scheme in which room temperature liquids of relatively high viscosity were displaced by high-temperature (80 °C), less-viscous liquids. Fundamental characteristics have been presented regarding how the effect of a non-isothermal field on miscible displacement patterns varies in terms of factors such as the viscosity ratio of the more- and less-viscous liquids at 20 °C, M 20, the rate of an increase in the pattern’s area, R, and the gap width of the cell, b. The concept of area density was used to quantitatively evaluate the effect of the non-isothermal fields on the patterns. We have found that the effect of the non-isothermal field on the patterns does not monotonically vary with M 20 and b. In contrast, it increases with R in the present experimental condition. The experimental results can be explained by introducing an assumption in which heat is transferred mainly to the plates of the cell, in other words, the temperature of the more-viscous liquid remains constant, whereas that of the less-viscous liquid spatiotemporally decreases and the viscosity of it increases along with the temperature decrease. Visualization of non-isothermal field in the cell has been done by means of a thermo sheet and the results support the assumption mentioned above.

2-D Simulation of Non-isothermal Fate and Transport of a Drip-applied Fumigant in Plastic-mulched Soil Beds. I. Model Development and Performance Investigation

Pre-plant application of toxic fumigants to soil beds covered by plastic film is commonly used in agriculture to control soil-borne pathogens. Plastic mulch covers tend to physically suppress the emissive loss of gaseous fumigant to the atmosphere. When liquid fumigant metham sodium (MS) is applied in irrigation water to field soil, it is rapidly transformed to the gaseous methyl isothiocyanate (MITC). The gaseous MITC is a potential atmospheric contaminant, and any untransformed MS is a potential contaminant of underlying groundwater due to the high water solubility of MS. A finite element numerical model was developed to investigate two-dimensional MITC fate/transport under non-isothermal soil conditions. Directional solar heating on soil beds, coupled heat and water flow in the soil, and non-isothermal chemical transport were included in the model. Field soil data for MITC distribution, soil water content, meteorological data, and laboratory data were used to verify the model for soil beds covered with plastic mulch. Four possible scenarios were considered: low and high drip-irrigation rates and low and high water contents. The movement of the center of MITC mass in the soil profile was effectively simulated. The lower drip-irrigation rate of MS yielded more extensive coverage of MITC in the plastic-covered soil bed. The lower soil air contents due to higher soil water contents for the higher irrigation rate resulted in high concentrations of soil MITC. NRMSE (normalized root mean square error) calculations further verified that the model predicted fumigant fate/transport well under these non-isothermal field conditions.

F223 界面活性剤添加溶液における抵抗低減現象の温度特性(一般セッション 熱伝達)

This study investigates the influence of temperature-dependent physical properties in drag-reduced flow to clarify at which location temperature should be changed in order to contribute to drag reduction, by effecting wall beating so as to arrange a vertically and longitudinally "non-isothermal field" in channel flow. Temperature profiles have been measured by a fine thermocouple probe. Non-isothermal Field causes fluctuation of pressure gradient. Temperature profiles was changed by Non-isothermal field.

Development of Calculation Method for Radiative Heat Transfer in an Infrared-active Gas with Narrow-Band Nonuniformity and Its Examination Based on an Absorption Line Data Base (In Case of a Nonisothermal Field Including a Single Infrared-Active Gas)

This paper proposes a rational, explicit and practicable approach for incorporating the spectral non-uniformity of absorption coefficient within a narrow band into a nongray analysis of radiative heat transfer in a nonisothermal field including a single infrared-active species. In the development of this new approach, attention is paid to securing rationality and explicitness even when the approach is applied to nonisothermal fields. This aim is achieved based on the fact that the line center of each absorption line does not move even if the gas temperature varies. Validity of the proposed approach is examined in detail trough comparison of the results obtained by the proposed approach with the results of line-by-line analysis base on a high-resolution database of absorption lines. It was confirmed in a typical nonisothermal field that the proposed approach can properly incorporate the influence of narrow band non-uniformity into a nongray analysis of radiative heat transfer in a nonisothermal field including a single infrared-active species.

Development of Calculation Method for Radiative Heat Transfer in an Infrared-active Gas with Narrow-Band Nonuniformity and Its Examination Based on an Absorption Line Data Base (In Case of a Mixed Gases Field Including H2O and CO2)

It is necessary to consider the interrelation of absorption coefficients of emitting side and absorbing side when we carry out numerical predictions of radiative heat transfer through infrared-active gases. If we utilize the combination of a wide-band model and a narrow-band model for dealing with radiative heat transfer through a infrared-active gas that has remarkable narrow band nonumiformity, we have to consider the interrelation of absorption coefficient not only about the representative value within a narrow band but also about the fine structure in a narrow band. Calculation method for radiative transfer in nonisothermal field is constructed considering narrow band nonuniformity. It is compared with line-by-line calculation based on absorption line database HITEMP, and its validity is confirmed.

C234 界面活性剤水溶液流れの抵抗低減現象と非等温場との関係

This study investigates the influence of temperature-dependent physical properties in drag-reduced flow to clarify at which location temperature should be changed in order to contribute to drag reduction, by effecting wall heating so as to arrange a vertically and longitudinally "non-isothermal field" in channel flow. Flow characteristics and temperature profiles have been measured by an LDV system and a fine thermocouple probe. A difference in velocity profiles between the cases of T_w=44℃ and 48℃ has been observed : the former is distributed along the profile for drag-reducing flow, and the latter is similar to that for water as turbulent flow. Investigation of the effect of non-isothermal heating on drag-reducing flow revealed that the temperature dependent condition of flow and temperature field in the buffer layer (50<y^+<100) is an important factor for controlling heat transfer in the drag-reducing flow.

Approach for incorporating narrow band nonuniformity into nongray analysis of radiative heat transfer in nonisothermal and nonhomogeneous gas fields

This paper presents a rational, explicit and practicable approach for incorporating the spectral nonuniformity within a narrow band into a nongray analysis of radiative heat transfer. First of all, emphasis is placed on describing the necessity of a new approach for treating this kind of spectral nonuniformity. In the development of this new approach, attention is paid to securing rationality and explicitness even when the approach is applied to nonisothermal fields. This aim is achieved based on the fact that the line center of each absorption line does not move even if the gas temperature varies. Validity of the proposed approach is demonstrated in a typical nonisothermal field. Furthermore, the extension of the proposed approach to the mixture of more than one infrared-active species is discussed and its validity is examined.

Effect of Narrow-Band Nonuniformity on the Radiative Heat Transfer and Comprehensive Approach for Incorporating the Narrow-Band Nonuniformity Effect into Radiative Heat Transfer Calculation.

This paper emphasizes the serious error induced in radiative heat transfer calculation by neglecting the narrow-band nonuniformity in absorption coefficient. Based on such recognition, a simple, comprehensive and reasonable calculation method is proposed. This calculation method aims at simulating the radiative heat transfer in nonisothermal participating gases considering narrow-band nonuniformity effect through comprehensive approach. Though the concept of narrow band model is adopted in such approach to incorporating the narrow-band nonuniformity effect, the use of the narrow band emissivity given by the algebraic formula based on narrow band model is avoided. Validity of the proposed calculation method in nonisothermal fields is confirmed. Also the extension of this method is proposed in relation to the mixture of multiple radiative species that have overlapping vibration-rotation bands.

The Continuous Spilling of Hot Oil on Ice

Abstract The continuous spilling of hot Norman Wells crude oil onto an ice surface was investigated with oil temperature, ice temperature and spilling rate as parameters. An equation for spreading of the oil was developed in whick the oil slick area, A, was proportional to t(1,2), where t is the elapsed time. Experimental data showed that A was prow portional to t0.8. Increases in both oil and ice temperatures were found to cause an increase in A, and temperature effects could be taken into account by relating kinematic viscosity to a function of the geometric mean of the ice and oil temperatures. Introduction ALTHOUGH the spreading of hot oil on ice is of interest from the point of view of oil spills in Arctic regions, no controlled quantitative study taking several variables into account has been published. In previous work, Chen et al.(1) studied the instantaneous release of oil under controlled isothermal conditions, and Glaeser(2) and McMinn(3) carried out non-isothermal field tests under a single experimental condition. The present work concerns the continuous spilling of hot crude oil on ice at ice temperatures down to −40 °C and oil temperatures up to 60 °C. Continuous spilling would occur in the event of a pipeline leak. The oil and ice temperatures chosen cover likely pipeline conditions during the Arctic winter. In common with the previous work(1), crude oil from commercial production at Norman Wells, Northwest Territories, Canada, was used. Mackay, Charles and Phillips'" have discussed other aspects of the physical behaviour of crude oil in Arctic environments, with particular reference to Norman Wells crude oil and the Mackenzie Valley of the Northwest Territories. Theoretical Background It has been recognized(1–3, 5–7) that the spreading of a liquid over a solid surface passes through three distinct regions: gravity-inertia, gravity-viscous and surface tension-viscous. However, in continuous spreading, the gravity-viscous region is of primary importance because surface-tension spreading is not likely to occur due to the continuous flow, and the gravity-inertia spreading, which occurs only in the area around the point of deposition, will not be observed. Using the same argument as that used by Chen et al.(1), the gravitational outward pressure force per unit volume is (Equation Available In Full Paper) In application of this model to the non-isothermal case of spreading of hot oil on ice, it should be noted that µ (or υ) must represent an effective viscosity, as there is a temperature gradient across the spreading oil film; any correlation of data in terms of equation (5) will therefore be in terms of such an effective viscosity. This notion is further reinforced by the observation that the spreading of hot oil on ice must of necessity involve flow of oil over a water film formed from the ice at the interface with the hot oil.

Quantitative Studies of Apparent Rotational Temperatures of OH in Emission and Absorption (Spectral Lines with Doppler Contour)

Even if a Boltzmann distribution exists for the population of molecules in various energy levels, it is not possible to obtain a satisfactory interpretation of experimental data by the use of conventional procedures unless the product of maximum spectral absorption coefficient Pmax and optical density X is sufficiently small. Detailed calculations are presented which show that the experimental results, which suggest an anomalous rotational temperature for the 2Σ state of OH in low pressure combustion flames, can be accounted for by using sufficiently large values for PmaxX (Sec. II). Whether or not experimental data should be interpreted in this manner must be determined by auxiliary studies. Representative absorption studies for the determination of rotational temperatures in isothermal systems have been analyzed for the P1 branch, (0,0) band, 2Π→2Σ transitions of OH at 3000°K. The calculations show that erroneous interpretation of experimental results occurs if the product PmaxX is not small compared to unity. Sample calculations for a blackbody light source show that the customary procedure for treating experimental results will permit adequate correlation of the data by straight lines up to relatively large values for PmaxX. It is remarkable that the preceding statement remains true even under conditions in which emission data clearly indicate that PmaxX is no longer small compared to unity (Sec. III). Representative calculations to determine observable peak and total intensity ratios in emission for spectral lines with Doppler contour have been carried out for 2Σ→2Π transitions, (0,0) band, P1 branch of OH at 3000°K. The calculations show that the ratios of peak and total intensities are functions of the products of maximum absorption coefficients (Pmax) and optical density (X) for the lines under study (Sec. IV). Quantitative calculations have been carried out of apparent rotational temperatures in systems containing nonequilibrium distributions of OH at 3000°K and at 6000°K. The calculations on the P1 branch, 2Σ→2Π transitions, indicate that, in the absence of self-absorption, conventional plots showing discontinuities necessarily overestimate one and underestimate the other of the known temperatures of 3000°K and 6000°K (Sec. V). Quantitative calculations on the nature of distortions produced when an isothermal region at 3000°K is viewed through an isothermal region at 1500°K show that the presence of a non-isothermal field of view magnifies the distortion produced by self-absorption alone (Sec. VI). On the basis of the noncontroversial quantitative calculations described in Secs. II to VI for idealized systems, some speculations regarding the significance of reported flame temperature anomalies for OH are presented in Sec. VII.