Saturated Conductivity Research Articles

Analysis and Upscaling of Unsaturated Flow through Randomly Heterogeneous Soil

The spatial variability of soil hydraulic properties has to be considered to provide realistic predictions of unsaturated flow and transport at field scale. Steady unsaturated flow through randomly heterogeneous soils is analyzed and upscaled in this study. Numerical experiments of unsaturated flow have been performed on single realizations of unsaturated soil parameters generated by using threedimensional turning band random generator. In the first part of the study a linear relation for unsaturated hydraulic conductivity as a function of soil suction (.) given by K = Ksea. is used, with constant beta and saturated hydraulic conductivity (K-s) as perfectly correlated random space functions. In the first part of the study, linear conductivity relation given by Gardner is used, with Gardner's constant (beta) and saturated conductivity (Ks) as perfectly correlated random space functions. The steady flow fields generated are analyzed to explore the effect of variability of the product (a): the pore-size distribution parameter whose reciprocal represents the characteristic capillary length (h(cap)) and the correlation length (lambda Z) of the generated soil properties. A set of one-dimensional simulations are performed, with various values of the product beta lambda(Z) ratio of correlation length to capillary dispersion length (lambda(z)/ hcap = 1, >> 1 and e 1) used to compare the moisture distribution tendency. The resulting steady pressure fields are compared and analyzed. In some cases, the soil behaves as homogeneous, and in other cases as stratified. The second part of the study seeks to identify simple upscaling laws for block-scale nonlinear constitutive relationships under high tension, with the parameters of their measurement scale counterparts represented by the van Genuchten model. Random fields are generated to represent layering of perfect and imperfectly stratified soils, and numerical simulations are performed in flows that are perpendicular and parallel to stratification. Upscaling of hydraulic conductivity curve Kd.and moisture retention curve theta(Psi) is performed for perfectly stratified and imperfectly stratified soils, and anisotropy is also studied for both types of layering considered. It is demonstrated that the upscaled nonlinear curves can be represented by simple exponential relations and/ or by linear relations obtained by piecewise linearization. The linear relations obtained can be expressed in equivalent terms that can be used in analytical solutions to directly obtain effective hydraulic conductivity values. (C) 2016 American Society of Civil Engineers.

Investigation on thermal characteristics and prediction models of soils

This paper presents details of a study that deals with evaluation of thermal characteristics of soils across a range of soil types and saturation levels. Investigations were carried out with respect to the effect of moisture content, dry density, degree of saturation, particle size, and mineralogy composition on thermal resistivity of the soils. In addition, the prediction models developed by previous researchers for estimating the thermal conductivity of various soils at unfrozen state were reviewed and evaluated. The study reveals that the moisture content, dry density, and mineralogy composition have a considerable influence on the thermal resistivity of a soil. The critical moisture content is an important index to characterize the rates of change in thermal resistivity with increasing moisture content. An exponential decrease in thermal resistivity with degree of saturation is observed for fine-grained soils, whereas a linear correlation between thermal resistivity and dry density is shown for soils regardless of the moisture contents. The differences in thermal resistivity of samples with the same dry density are mainly attributed to variations of mineralogy composition. Based on the concept of normalized thermal conductivity, a simple step by step method to calculate the thermal conductivity is proposed and the empirical soil parameters for fine-grained soils in different areas are also presented. It has been demonstrated that the normalized thermal conductivity is able to correlate the actual thermal conductivity with thermophysical parameters of the soils (viz., moisture content, degree of saturation, porosity, and thermal conductivity of solid particles). The accuracy of the prediction method can be improved by employing the empirical parameters to fit the experimental data.

Defining biological thresholds associated to plant water status for monitoring water restriction effects: Stomatal conductance and photosynthesis recovery as key indicators in potato

The definition of irrigation schedules depends on the understanding of the response of key plant traits to different water restriction characteristics with the aim to avoid physiological impairment. In this study, different timings (at tuber initiation and bulking) and intensities (four soil moisture levels) of water restriction were tested in the potato crop. The temporal patterns of mid-morning or maximum, light saturated stomatal conductance (gs_max), recovery of net photosynthesis (Arecovery), stem water potential (Ψstem), carbon isotope discrimination in tubers (Δtuber), plant water concentration (PWC), photochemical reflectance index (PRI) and crop water stress index (CWSI) were analyzed. Early-severe water restriction caused a drastic yield reduction, with low recovery of physiological responses (gs_max, Δtuber, Ψstem, CWSI, Arecovery) after 15days of post-restriction irrigation and even a continued reduction of some of them (PWC, PRI). It also caused a prolonged gs_max reduction below 0.05mol H2O m−2s−1 (≈5μmol CO2 m−2s−1 of net photosynthesis) suggesting that this value defines a physiological severity threshold in potato, under which a metabolic impairment occurs. CWSI and PRI showed a close linear (R2=0.76) and no linear (natural logarithm function, R2=0.67) relationship with gs_max respectively. In cloudless dry environments, irrigation schedules in potato should aim to avoiding CWSI values higher than 0.4, especially until before of maximum canopy cover establishment. A close relationship between Arecovery at maximum stress moment and yield reduction was found. The strong relationship between the measured traits (except PWC and Ψstem) and final yield at maximum stress moment found in the present study warrants further research on drought phenotyping immediately before post-restriction irrigation or when the defined severity threshold in potato is reached.

Diesel oil infiltration in soils with selected antecedent water content and bulk density

The effects of soil texture, initial water content and bulk density on diesel oil infiltration in fine sand and silty clay loam materials were evaluated. Three physical and two empirical equations express diesel oil infiltration through soils with time, with coefficients of determination greater than 0.99. Diesel oil infiltrates more quickly in the fine sand than in the silty clay loam material. Diesel oil infiltration rates are found to decrease with increasing initial water content and bulk density for the silty clay loam material. The infiltration rate of diesel oil in the fine sand material increases slightly with increasing initial water content. The diesel oil saturated conductivity (Kdiesel) decreases with increasing bulk density for the silty clay loam column. Diesel oil sorptivity(S) decreases linearly with increased initial water content and bulk density of the silty clay loam material. Changes in empirical parameters relative to initial water content and bulk density are similar to the parameter S.

Estimation of Soil Erosion Rates in Oil Palm Plantation with Different Land Cover

Soil losses from hill slopes in oil palm plantation in Sedenak Estate, Johor were measured using runoff plot and rainfall simulator. The plot was designed to be removable but the size was fixed at 8 x 3.75m. Four types of surface covers were investigated for the plots, i.e. half bare soil and half grass cover (HGC), half bare soil and half dry frond (HDF), fully grass cover (FG), and fully bare soil (BS). The influence of initial soil moisture, saturated hydraulics conductivity, Ks, bulk density and slope on rates of soil loss were also evaluated. The rainfall simulator produced rainfall intensities between 90 and 160 mm/hr with durations from 45 to 60 min per run. BS plot exhibited the highest Ks value among all plots but the percentage of initial soil moisture on this surface was low. BS plot recorded the highest runoff coefficient (C) and soil loss values of 73.6 ± 4 percent and 5.26 ± 3.2 t/ha respectively, while the lowest was from plot FG with 41.7 ± 5.7 percent and soil loss of 2.85 ± 2.1 t/ha. Meanwhile, the results suggested that the ground cover had the ability to reduce soil loss by 67% and 17%, respectively for plots BS-HGC and BS-HDF. Overall, soil erosion control such as surface is effective measures in reducing level of runoff and soil erosion.

MAPPING SPATIAL MOISTURE CONTENT OF UNSATURATED AGRICULTURAL SOILS WITH GROUND-PENETRATING RADAR

Soil subsurface moisture content, especially in the root zone, is important for evaluation the influence of soil moisture to agricultural crops. Conservative monitoring by point-measurement methods is time-consuming and expensive. In this paper we represent an active remote-sensing tool for subsurface spatial imaging and analysis of electromagnetic physical properties, mostly water content, by ground-penetrating radar (GPR) reflection. Combined with laboratory methods, this technique enables real-time and highly accurate evaluations of soils' physical qualities in the field. To calculate subsurface moisture content, a model based on the soil texture, porosity, saturation, organic matter and effective electrical conductivity is required. We developed an innovative method that make it possible measures spatial subsurface moisture content up to a depth of 1.5 m in agricultural soils and applied it to two different unsaturated soil types from agricultural fields in Israel: loess soil type (Calcic haploxeralf), common in rural areas of southern Israel with about 30% clay, 30% silt and 40% sand, and hamra soil type (Typic rhodoxeralf), common in rural areas of central Israel with about 10% clay, 5% silt and 85% sand. Combined field and laboratory measurements and model development gave efficient determinations of spatial moisture content in these fields. The environmentally friendly GPR system enabled non-destructive testing. The developed method for measuring moisture content in the laboratory enabled highly accurate interpretation and physical computing. Spatial soil moisture content to 1.5 m depth was determined with 1–5% accuracy, making our method useful for the design of irrigation plans for different interfaces.

MAPPING SPATIAL MOISTURE CONTENT OF UNSATURATED AGRICULTURAL SOILS WITH GROUND-PENETRATING RADAR

Abstract. Soil subsurface moisture content, especially in the root zone, is important for evaluation the influence of soil moisture to agricultural crops. Conservative monitoring by point-measurement methods is time-consuming and expensive. In this paper we represent an active remote-sensing tool for subsurface spatial imaging and analysis of electromagnetic physical properties, mostly water content, by ground-penetrating radar (GPR) reflection. Combined with laboratory methods, this technique enables real-time and highly accurate evaluations of soils' physical qualities in the field. To calculate subsurface moisture content, a model based on the soil texture, porosity, saturation, organic matter and effective electrical conductivity is required. We developed an innovative method that make it possible measures spatial subsurface moisture content up to a depth of 1.5 m in agricultural soils and applied it to two different unsaturated soil types from agricultural fields in Israel: loess soil type (Calcic haploxeralf), common in rural areas of southern Israel with about 30% clay, 30% silt and 40% sand, and hamra soil type (Typic rhodoxeralf), common in rural areas of central Israel with about 10% clay, 5% silt and 85% sand. Combined field and laboratory measurements and model development gave efficient determinations of spatial moisture content in these fields. The environmentally friendly GPR system enabled non-destructive testing. The developed method for measuring moisture content in the laboratory enabled highly accurate interpretation and physical computing. Spatial soil moisture content to 1.5 m depth was determined with 1–5% accuracy, making our method useful for the design of irrigation plans for different interfaces.

Comparing between the performance of mobile drip irrigation and surface irrigation on some soil Physical properties and yield of wheat Triticum aestivum L.

Field experiment was conducted in a silty loam soil at Al-anbar University, College of Agriculture, in Ramadi during fall season 2013-2014 to study the Compared to the performance of mobile drip irrigation and continuous surface irrigation in some physical properties of the soil (moisture distribution curves and hydro saturated conductivity and infiltration average). The study included two main factors: mobile drip irrigation and Continuous surface irrigation. The lay out of the study was according to RCBD with three replicates. The moisture distribution was studied for the treatments during three stages from plant growth stages between 0 - 0.40 m in horizon and vertical directions from the drippers and depth 0 - 0.40 m in Beginning, middle and end of the board bar Continuous surface irrigation .The moisture curves were blotted by surfer software; some of the physical properties for the treatments, As well as some of growth and productivity of the crop wheat. The moisture content was increased at source of dripping and decreased away from the dripper horizontally and vertically after ending irrigation process, The treatment of drip irrigation reduced the vertical & horizontal distribution of water in soil as compared with the surface irrigation. mobile drip irrigation caused density values rate reduction as it reached to 1.38 in comparison with 1.44 Mgm.m-3 for continuous surface irrigation, and increase soil porosity to 0.45 in comparison with 0.4treatmentsrespectivel. The irrigation system had a vital role in hydro saturated conductivity, however the mobile drip irrigation had led to significant increase in this average, the highest average was 9.18 cm.hr-1 at the mobile drip irrigation comparing to 8.15 cm.hr-1 for Continuous surface irrigation The mobile drip irrigation had a role in average increase of infiltration which gave 9.4 and 8.6 cm.hr-1 for continuous surface irrigation treatments. It was significantly increased productivity in the treatment of mobile drip irrigation if reached 5.360 ton. ha-¹ compared with 4.230 ton. ha-¹ in continuous surface irrigation.

Anomalous Hall effect in the prospective spintronic material Eu1−xGdxO integrated with Si

Remarkable properties of EuO make it a versatile spintronic material. Despite numerous experimental and theoretical studies of EuO, little is known about the anomalous Hall effect in this ferromagnet. So far, the effect has not been observed in bulk EuO, though has been detected in EuO films with uncontrolled distribution of defects. In the present work doping is taken under control: epitaxial films of Gd-doped EuO are synthesized integrated with Si using molecular beam epitaxy and characterized with x-ray diffraction and magnetization measurements. Nanoscale transport studies reveal the anomalous Hall effect in the ferromagnetic region for samples with different Gd concentration. The saturated anomalous Hall effect conductivity value of 5.0 S·cm−1 in Gd-doped EuO is more than an order of magnitude larger than those reported so far for Eu chalcogenides doped with anion vacancies.

Effects of Ant (Formica subsericea) Nest Development on Physical and Hydrological Properties in a Coarse-Textured Soil

Ants may compose a large portion of the total biomass in an ecosystem and can play a significant role in soil turnover and nutrient cycling. Monitoring ant nest architecture and growth in the field can be difficult because of the destructive nature of casting ant nests. To examine nest effects on soil hydrology during different stages of development, 828 Formica subsericea workers were placed in each of two large (1.0 × 1.0 × 0.1 m) formicaria and allowed to excavate for 82 days in a coarse-textured soil collected from the field. Photographs and transparencies were used to record nest structure for five different time steps during development. After the fifth time step on Day 82, the nest was cast with dental plaster and the formicarium media were sampled. The development of the nest was associated with an increase in saturated conductivity of the soil. Backfilled entrances and vertical galleries contributed to decreasing saturated conductivity as worker numbers declined toward the end of the experiment. The presence of nests was associated with an increase in water flux through the soil material, although the effect was not as dramatic as in soils with a naturally lower saturated hydraulic conductivity.

Tension‐saturated and unsaturated flows from line sources in subsurface irrigation: Riesenkampf's and Philip's solutions revisited

AbstractRiesenkampf's (1938), R‐38 (referred to here as R‐38), analytical solution for steady 2‐D flow from a buried line source in a homogeneous Green‐Ampt soil, with a wetting plume bounded by a free surface (capillary fringe), is compared with Philip's (1969), (P‐69), one for genuinely unsaturated wetting of Gardner's infinite‐extension soil. Conformal mappings are used in R‐38, from which we derived the flow net, pore‐water isobars, isochrones, fields of Darcian velocity and resultant force acting on saturated porous skeleton, fine geometry (shape and size) of the constant‐head contour encompassing a mole‐emitter or leaky‐pipe, as well as the dependence of the total discharge per unit pipe length on uniform pressure in the pipe, capillarity of the soil, radius of the pipe, and saturated hydraulic conductivity. An ovalic “water table” isobar, encompassing P‐69 source, is compared with one of R‐38 for a fixed discharge and saturated conductivity but adjusted sorptive numbers. The Whisler and Bouwer (1970) relation between the static height of capillary rise and sorptive number is shown to give a good match between R‐38 and P‐69 isobars. This allows to use R‐38 in the source vicinity and P‐69 in the far‐field zone. Computer algebra (Mathematica) routines are used for visualization of the known and extended R‐38 and P‐69 solutions.

Testing the hybrid‐3‐D hillslope hydrological model in a controlled environment

AbstractHillslopes are important for converting rainfall into runoff, influencing the terrestrial dynamics of the Earth's climate system. Recently, we developed a hybrid‐3‐D (h3D) hillslope hydrological model that gives similar results as a full 3‐D hydrological model but is up to 2–3 orders of magnitude faster computationally. Here h3D is assessed using a number of recharge‐drainage experiments within the Landscape Evolution Observatory (LEO) with accurate and high‐resolution (both temporally and spatially) observations of the inputs, outputs, and storage dynamics of several hillslopes. Such detailed measurements are generally not available for real‐world hillslopes. Results show that the h3D model captures the observed storage, base flow, and overland flow dynamics of both the larger LEO and the smaller miniLEO hillslopes very well. Sensitivity tests are also performed to understand h3Ds difficulty in representing the height of the saturated zone close to the seepage face of the miniLEO hillslope. Results reveal that a temporally constant parameters set is able to simulate the response of the miniLEO for each individual event. However, when one focuses on the saturated zone dynamics at 0.15 m from the seepage face, a stepwise evolution of the optimal model parameter for the saturated lateral conductivity parameter of the gravel layer occurs. This evolution might be related to the migration of soil particles within the hillslope. However, it is currently unclear whether and where this takes place (in the seepage face or within the parts of the loamy sand soil).

SOIL QUALITY INDEX IN THE UPSTREAM OF BENGAWAN SOLO RIVER BASIN ACCORDING TO THE SOIL FUNCTION IN NUTRIENT CYCLING BASED ON SOYBEAN PRODUCTION IN AGROFORESTRY

Over the function of the upstream region watersheds causes the soil susceptible to degradation of soil fertility. Agroforestry systems that have been implemented should be reviewed to determine their effectiveness in improving soil fertility using a soil quality index. The varieties of soybean that cultivated in the study site were Grobogan, Kaba, and Argomulyo. The variables of this study consists of organic-C, pH, cation exchange capacity (CEC), total-N, available-P, available-K, Na, Ca, Mg, base saturation, and electrical conductivity (EC). Soil quality index calculation performed on selected outcome variables principal component analysis (PCA) which is then multiplied by the weights index on each PC. Selected variables from PCA consist of available-P, available-K, base saturation, and pH. Soil quality index values for all types of Agroforestry in the upstream of Bengawan Solo river basin ( Wonogiri ) is under secondary forest (<4.1) so that it can be concluded that the adoption of Agroforestry in the upstream of Bengawan Solo river basin has not effect on soil quality based on soil functions in the recycling of nutrients. Mean of soybean grain yield in agroforestry system are higher than the mean of national soybean production, but there are an obstacle such as light conditions.

Relating Quantitative Soil Structure Metrics to Saturated Hydraulic Conductivity

Core Ideas Soil structure quantified in the field using a 3D laser scanning technique (MLT). MLT data and coefficient of linear extensibility combined into a structure metric. Soil water contents recorded at four depths in a field lysimeter and used in HYDRUS‐1D. Saturated conductivity (Ks) estimated with a Markov chain Monte Carlo approach. New metric better correlated to Ks in horizons with strong soil structure. Soil structure affects saturated hydraulic conductivity (Ks) by creating highly conductive macropores that preferentially transmit soil water. In this study, we explored the relationship between Ks and macropores in an Oxyaquic Vertic Argiudoll in northeastern Kansas. Macropores were quantified from an excavation wall using multistripe laser triangulation (MLT) scanning. Soil water contents were measured at four depths within a soil lysimeter installed within 2 m of the MLT‐scanned soil profile and adjacent to an Ameriflux tower monitoring precipitation, air temperature, and solar radiation. Selected hydraulic properties of soil horizons within the lysimeter were optimized to water content data using a Markov chain Monte Carlo technique in combination with the mobile–immobile water (MIM) model in HYDRUS‐1D. Estimates of Ks varied between 4198 cm d−1 in the A horizon and 0.6 cm d−1 in a 2Btss2 horizon with strongly expressed wedge structure. Approximately 87% of the variation in Ks was explained by the geometric mean of the widths of pores quantified with the MLT technique and modified by the coefficient of linear extensibility (COLE). The use of the COLE allows the widths of the macropores obtained under dry conditions to be approximated at saturation. Two models that predict Ks from either texture or water retention data resulted in Ks estimates that were similar to each other but significantly lower than Ks values predicted with MIM in horizons where structural pores dominate water flow. This technique shows a great deal of promise in better understanding and predicting the relationship of soil structure to water flow.

Can pore-clogging by ash explain post-fire runoff?

Ash plays an important role in controlling runoff and erosion processes after wildfire and has frequently been hypothesised to clog soil pores and reduce infiltration. Yet evidence for clogging is incomplete, as research has focussed on identifying the presence of ash in soil; the actual flow processes remain unknown. We conducted laboratory infiltration experiments coupled with microscope observations in pure sands, saturated hydraulic conductivity analysis, and interaction energy calculations, to test whether ash can clog pores (i.e. block pores such that infiltration is hampered and ponding occurs). Although results confirmed previous observations of ash washing into pores, clogging was not observed in the pure sands tested, nor were conditions found for which this does occur. Clogging by means of strong attachment of ash to sand was deemed unlikely given the negative surface charge of the two materials. Ponding due to washing in of ash was also considered improbable given the high saturated conductivity of pure ash and ash–sand mixtures. This first mechanistic step towards analysing ash transport and attachment processes in field soils therefore suggests that pore clogging by ash is unlikely to occur in sands. Discussion is provided on other mechanisms by which ash can affect post-fire hydrology.

Seasonal thermal energy storage in shallow geothermal systems: thermal equilibrium stage

This paper is dedicated to the study of seasonal heat storage in shallow geothermal installations in unsaturated soils for which hydrothermal properties such as degree of saturation and thermal conductivity vary with time throughout the profile. In the model, a semi-analytical model which estimates time-spatial thermal conductivity is coupled with a 2D cylindrical heat transfer modeling using finite difference method. The variation of temperature was obtained after 3 heating and cooling cycles for the different types of loads with maximum thermal load of qmax = 15 W.m−1 with variable angular frequency (8 months of heating and 4 months of cooling).and constant angular frequency (6 months of heating and 6 months of cooling) to estimate the necessary number of cycles to reach the thermal equilibrium stage. The results show that we approach a thermal equilibrium stage where the same variation of temperature can be observed in soils after several heating and cooling cycles. Based on these simulations, the necessary number of cycles can be related to the total applied energy on the system and the minimum number of cycles is for a system with the total applied energy of 1.9qmax .

Growth, yield and fruit quality of cherry tomato irrigated with saline water at different developmental stages

ABSTRACTWater shortage is a serious environmental and agricultural problem and saline underground water has been widely used to make up the fresh water shortage in northwestern China. An open-field experiment was conducted to establish a proper irrigation scheme with saline water for cherry tomato in the Minqin oasis, where very severe salinization occurs. The experiment had four treatments including fresh or saline irrigation over the crop season (control, C, T3), fresh/saline-water irrigation change on days after thinning 50 (DAT 50, T1) and saline/fresh irrigation change on DAT 50 (T2). Leaf area index (LAI), photosynthesis rate (Pn), transpiration rate (Tr), leaf dry matter (LDM), stem dry matter (StDM), yield, marketable fruit and total soluble solids (TSS) of tomato were measured. Saline irrigation, irrespective of the timing, significantly decreased maximum LAI, LDM and StDM, Pn, Tr and stomatal conductance but significantly stimulated water use efficiency. The reduction in maximum LAI, LDM and StDM was lower in T2 than in T1 and T3. Harvest index (HI) and TSS were higher in T2 and T3 than in T1 and C. Marketable fruit had no significant change in T2 but significantly declined in T1 and T3. Maximum saturated soil conductivity without yield reduction (the salt tolerance threshold) was 3.69 dS m−1. Total yield of tomato would decrease by 9.85% with one unit increase of soil salinityhigher than the threshold. Final yield significantly reduced by 24.6% and 23.1% in T1 and T3 treatments, respectively. Our results suggest that irrigation with saline water before DAT 50 and fresh water after DAT 50 should be advocated for cherry tomato plantation in water-scarce areas like the Minqin oasis.

Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

Conjugate heat transfer and entropy generation in a cavity filled with a nanofluid-saturated porous media and heated by a triangular solid

Entropy generation due to conjugate natural convection–conduction heat transfer in a square domain is numerically investigated under steady-state condition. The domain composed of porous cavity heated by a triangular solid wall and saturated with a CuO–water nanofluid. Equations governing the heat transfer in the triangular solid together with the heat and nanofluid flow in the nanofluid-saturated porous medium are solved numerically using the over-successive relaxation finite-difference method. A temperature dependent thermal conductivity and modified expression for the thermal expansion of nanofluid are adopted. A new criterion for assessment of the thermal performance is proposed. The investigated parameters are the nanoparticles volume fraction φ (0–0.05), modified Rayleigh number Ra (10–1000), solid wall to base-fluid saturated porous medium thermal conductivity ratio Kro (0.44, 1, 23.8), and the triangular solid thickness D (0.1–1). The results show that both the average Nusselt number and the entropy generation are increasing functions of Kro, while they are maxima at some critical values of D. It is also found that the addition of nanoparticles increases the entropy generation. According to the new proposed criterion, the results show that the largest solid thickness (D = 1.0) and the lower wall thermal conductivity ratio manifest better thermal performance.

Assessing and improving Noah‐MP land model simulations for the central Tibetan Plateau

AbstractThe Tibetan Plateau (TP) region experiences strong land‐atmosphere interactions, and as an elevated heating source, significantly influences the formation of the Asian monsoon. Those interactions are not well represented in current land‐surface models (LSMs), partly due to difficulties in representing heterogeneities in soil structures in LSM. Simulations using the Noah with multiparameterization options (Noah‐MP) LSM are employed to assess the relative importance of parameterizing vertical soil heterogeneity, organic matter, and soil rhizosphere and their impacts on seasonal evolution of soil temperature, soil moisture, and surface energy and water budgets at the sparsely vegetated Amdo site located in central TP. The LSM spin‐up time at the central TP depends on the complexity of the model physics, ranging from 4 years with simplest soil physics to 30 years with the addition of organic matter and spare to dense rhizosphere parameterization in Noah‐MP. Representing layered soil texture and organic matter does not improve low biases in topsoil moisture. Reducing the saturated conductivity from the mucilage in the rhizosphere produces better results. Surface sensible and latent heat fluxes are better simulated in the monsoon season as well. Adding layered soil texture and organic matter in Noah‐MP retard the thawing in deep soil layers, and the rhizosphere effect delays thawing even more in the transient season. Uncertainties in soil initialization significantly affect deep‐soil temperature and moisture, but uncertainties in atmospheric forcing conditions mainly affect topsoil variables and consequently the surface energy fluxes. Differing land‐surface physics cause 36% uncertainty in the accumulated evapotranspiration and subsurface runoff.