Temporal Stability Analysis Research Articles

Magnetic Dipole Effects on Radiative Flow of Hybrid Nanofluid Past a Shrinking Sheet

The boundary layer flows exhibit symmetrical characteristics. In such cases, the flow patterns and variables are symmetrical with respect to a particular axis or plane. This symmetry simplifies the analysis and enables the use of symmetry-based boundary conditions or simplifications in mathematical models. Therefore, by using these concepts, the governing equations of the radiative flow of a hybrid nanofluid past a stretched and shrunken surface with the effect of a magnetic dipole are examined in this paper. Here, we consider copper (Cu) and alumina (Al2O3) as hybrid nanoparticles and use water as a base fluid. The heat transfer rate is enhanced in the presence of hybrid nanoparticles. It is observed that the heat transfer rate is increased by 10.92% for the nanofluid, while it has a 15.13% increment for the hybrid nanofluid compared to the base fluid. Also, the results reveal that the non-uniqueness of the solutions exists for a certain suction and shrinking strength. Additionally, the ferrohydrodynamic interaction has the tendency to reduce the skin friction and the heat transfer coefficients for both solution branches. For the upper branch solutions, the heat transfer rate increased over a stretching sheet but decreased for the shrinking sheet in the presence of the radiation. It is confirmed by the temporal stability analysis that one of the solutions is stable and acceptable as time evolves.

Multiple solutions of Hiemenz flow of CNTs hybrid base [formula omitted] nanofluid and heat transfer over stretching/shrinking surface: Stability analysis

The purpose of the current article is to numerically and theoretically examine the flow of two-dimensional (2D) steady Hiemenz with the transfer of heat of carbon nanotubes (CNTs) hybrid base C2H6O2+H2O (Ethylene glycol + water) nanofluid across a linear shrinking/stretching surface. The equations of Navier–Stokes have been converted into equations of self-similar applying suitable transformations of similarity variables, and then numerically resolved using the three-stage Labatto-three-A formula. In addition, an endeavor is made to extend the behavior of asymptotic of the solution to massive stretching. The comparison between the found asymptotic solutions and previously reported numerical results is rather impressive. Observations indicate that equations of self-similar display double solutions within the restricted shrinking parameter range. There exists one solution for every case of stretching. In the first solution, the impacts of nanoparticle solid volume fraction and shrinking parameters on velocity and thermal fields exhibit an increasing trend. Consequently, the linear analysis of temporal stability has been performed to establish the most fundamentally viable option. The smallest eigenvalue sign determines whether a solution is unstable or stable for the purposes of stability analysis. The analysis of stability demonstrates that the first solution describing the primary flow is stable.

Slip and radiative effect on magnetized CNTs/[formula omitted] hybrid base nanofluid over exponentially shrinking surface

In current research, the physical characteristics of the laminar steady boundary layer flow of CNTs/ C2H6O2+H2O hybrid base nanofluid across a permeable exponentially contracting surface along the influence of magnetic force, heat radiation, and velocity slip of the first order have been examined. The effect of magnetic field stability analysis on the hybrid-based nanofluid flow of CNTs with thermal radiation was not previously explored for the numerous solutions, which is the originality of the current work. The partial differential equations (PDEs) controlling the model were transformed to ordinary differential equations (ODEs), and then the ODEs were solved using the three-stage Lobatto IIIa numerical approach in the MATLAB program. For different nanofluids constituted of SWCNTs and MWCNTs as nanoparticles and C2H6O2+H2O as the hybrid base nanofluid, the impacts of changes in the values of various parameters on temperature, velocity, heat transfer, and skin friction coefficient profiles were explored. Tables and figures illustrate numerically and quantitatively the outcomes. In addition to the effects of outputs, there are two solutions within the range of suction parameter. In addition, the parameter ∅ has a diminishing influence on heat transfer rate and skin friction coefficient in the first solution, resulting in a decrease in the surface drag force and heat transfer rate. Moreover, the selection of nanoparticle kinds has a substantial effect on the cooling/heating processes and stream function. Finally, a linear temporal stability analysis was performed to classify the stable solution among the dual solutions.

Temporal instability of the liquid film formed by a liquid jet impinging on a curved cylindrical wall

The linear temporal instability of the confined curved liquid film formed by a liquid jet impinging on a curved wall has been investigated. The corresponding dispersion relation between the non-dimensional wave growth rate and wave number was derived. The dispersion relation further involves the influences of the local radius of curvature and the azimuthal angle of the liquid film. The dispersion relation could be verified with previous researches, and the optimal wavelength has been verified with experiments. Temporal stability analysis shows that the effects of gas-to-liquid velocity ratio, gas-to-liquid density ratio, the relative thickness of the liquid phase to the gas phase, and azimuthal wave number are similar to previous researches, but the unstable ranges are smaller than that in previous researches. This paper further studied the effects of the local radius of curvature and azimuthal angle of the liquid film. As the local radius of curvature decreases, the instability of confined curved films increases for the given conditions. And both the growth rate and instability range increase with the increase of the azimuthal angle. The solutions would be helpful to understand the atomization process of the liquid film formed by a liquid jet impinging on a curved wall.

The effect of side walls on the stability of falling films

We study the influence of side walls on the stability of falling liquid films. We combine a temporal biglobal stability analysis based on the linearised Navier–Stokes equations with experiments measuring the spatial growth rate of sinusoidal waves flowing downstream an inclined channel. Very good agreement was found when comparing the theoretical and experimental results. Strong lateral confinement of the channel stabilises the flow. In the wavenumber-Reynolds number space, the instability region experiences a fragmentation due to selective damping of moderate wavenumbers. For this range of parameters, the three-dimensional confined problem shows several prominent stability modes which are classified into two categories, the well-known Kapitza hydrodynamic instability mode (H-mode) and a new unstable mode, we refer to it as wall-mode (W-mode). The two mode types are stabilised differently, where the H-modes are stabilised at small wavenumbers, while the W-modes experience stabilisation at high wavenumbers, and at sufficiently small channel widths, only the W-mode is observed. The reason behind the unique H-modes stabilisation is that they become analogous to waveguide modes, which can not propagate below a certain cut-off wavenumber. The spatial structure of the eigenmodes experiences significant restructuring at wavenumbers smaller than the most damped wavenumber. The mode switching preserves the spatial symmetry of the unstable mode.

Immiscible viscous fingering in time-dependent fluids: A linear stability analysis

When a less viscous fluid displaces a more viscous fluid, the interface between the two fluids becomes unstable. The instability exhibits itself as a large number of fingers of the displacing fluid penetrating the displaced fluid. This phenomenon is called viscous fingering or Saffman–Taylor instability, and plays a key role in oil industry, among others. The present study aims at investigating the immiscible viscous fingering of inelastic time-dependent fluids (i.e., fluids for which viscosity varies with time even at a fixed shear rate) in a homogeneous saturated porous medium. To represent such fluids, in the present work, use is made of the Quemada model. As an inelastic structural-kinetic rheological model, it can capture both thixotropy and anti-thixotropy through proper setting of model parameters. The model incorporates a natural time, which, in dimensionless form, is represented by a nominal Deborah number. Using this rheological model, the generalized Darcy’s law is derived, which is used to derive the basic flow. The interfacial instability is investigated by using the linear temporal stability analysis; that is, infinitesimally-small, normal-mode perturbations are introduced to the basic flow and their evolution in time is monitored. Using the Young–Laplace equation, the generalized dispersion relation is derived, which is solved numerically. The results show that the thixotropy and anti-thixotropy stabilize the Newtonian/time-dependent and time-dependent/Newtonian displacements, respectively. On the other hand, the Newtonian/time-dependent and time-dependent/Newtonian displacements are destabilized by the anti-thixotropy and thixotropy, respectively.

Dual Solutions and Stability Analysis of Cu-H2O-Casson Nanofluid Convection past a Heated Stretching/Shrinking Slippery Sheet in a Porous Medium

In this study, we examined the impact of Cu-H2O nanoparticles on two-dimensional Casson nanofluid flows past permeable stretching/shrinking sheet embedded in a Darcy-Forchheimer porous medium in the presence of slipperiness of surface, suction/injection, viscous dissipation, and convective heating. Using some realistic assumptions and appropriate similarity transformations, the governing nonlinear partial differential equations were formulated and transformed into a system of nonlinear ordinary differential equations and then numerically solved by using the shooting technique. Numerical results are displayed for dimensionless fluid velocity and temperature profiles, skin friction, and the local Nusselt number. The impacts of different governing physical parameters on these quantities are presented and discussed using graphs, tables, and a chart. For the specific range of shrinking sheet, the result shows that dual solutions exist, and temporal stability analysis is performed by introducing small disturbances to determine the stable solutions. It is detected that the upper branch solution is hydrodynamically stable and substantially realistic; however, the lower branch solution is unstable and physically unachievable. The fluid flow stability is obtained by enhancing the suction, surface slipperiness, and viscous dissipation parameters. However, augmenting the values of the Casson factor, Cu-H2O nanoparticle volume fraction, porous medium, porous medium inertia, and convective heating parameters increases the blow-up stability of the fluid flow. The rate of heat transfer enhances with the increment in the Casson factor, porous medium, porous medium inertia, suction, velocity ratio, nanoparticle volume fraction, and convective heating parameters, whereas it reduces as the slipperiness of the surface and viscous dissipation parameters rise. Increment of Cu-H2O nanoparticle volume fraction into the Casson fluid boosts the heat transfer enhancement rate higher for the shrinking sheet surface.

Bateria testów abilitest – własności psychometryczne narzędzi: badania wstępne

Cognitive efficiency is crucial for many areas of human activity. It affects the employees' efficiency and safety at the workplace. An important element of the prevention of accidents at work is the appropriate professional selection, which consists in checking the characteristics of candidates needed for a given position, and for this purpose, a psychological diagnosis is carried out. The aim of the study was to develop tools for cognitive diagnosis that are characterized by good psychometric properties. Tools for the diagnosis of simple reaction time (Abili-time), choice reaction time (Abili-select), prolonged attention (Abili-space, Abili-digit), and working memory (Abili-langmem, Abili-mathmem) were developed. Validation studies were conducted with 221 individuals aged 20-60 to assess relevance and reliability (internal consistency and temporal stability), and with the participation of 61 in a retest 3 months after the first measurement. Paper tests (CTT, TUS, Digit Span from WAIS-R(PL)) and tests from the Vienna test system (RT, SIGNAL, CORSI, ALS) were used to assess validity. The analysis showed that the Abili-time and Abili-select tests have satisfactory internal consistency. Analysis of temporal stability showed significant test-retest correlations for Abili-select, Abili-space, Abili-digit and Abili-langmem. Abili-time had slightly lower temporal stability. The temporal stability of Abili-mathmem was not confirmed. Significant correlations were obtained between the results of the developed tools with measures measuring similar constructs. The conducted research confirms the validity and reliability of Abili-time, Abili-select and Abili-space. Further work is needed on working memory tests, which are noteworthy due to the lack of other tools available on the market to test these functions. Further research should involve more people as well as carrying out standardization work. Med Pr. 2023;74(2):103-18.

The unified impact of thermal radiation and heat source on unsteady flow of tangent hyperbolic nanofluid through a permeable shrinking sheet

The tangent hyperbolic nanofluid behaviour is observed in multiple practical applications and extensively used in different laboratory experiments. It motivates to focus on the two-dimensional boundary layer flow of tangent hyperbolic nanofluid past a shrinking sheet. The goal of this article is to scrutinize the mass and heat transport of an unsteady flow of non-Newtonian tangent hyperbolic nanofluid past a shrinking surface under the influences of a source of heat, thermal radiation and chemical reaction. The flow model is mathematically framed through a coupled nonlinear partial differential equations. To transform the non-linear PDEs to ODEs, we use the similarity transformations and reduced ODEs are solved by RK-IV (Runge-Kutta method of order four) with shooting technique using the computational software MATHEMATICA. The novelty which emerges from the flow pattern lies in the fact that there exist dual solutions for certain parametric domain and the range of the existing solution may be expanded by increasing the power-law index (n) and shortened by increasing the Weissenberg number (We). Another remarkable conclusion which can be drawn from the temporal stability analysis that among these two solutions, first solution is stable and realistic whereas the second solution is not physically realistic. A diversity of the parameter estimates were used to provide solution for velocity f′(η), temperature θ(η) and concentration profiles ϕ(η) of this fluid model. In addition to the above findings, there are graphs and tables with explanation for the skin friction coefficient, the Nusselt number and the Sherwood number. These characteristics of a tangent hyperbolic nanofluid are not reported yet and may be useful in the development of existing technology.

Scrutinization of Unsteady Magnetohydrodynamics Williamson Nanofluid Flow and Heat Transfer Past a Permeable Shrinking Sheet

This study contributes to the thermal characteristics and flow behaviour of magnetohydrodynamics (MHD) unsteady flow of Williamson nanofluid over a permeable stretching/shrinking sheet in the presence of velocity slip at the boundary. The PDEs with the corresponding constraints are transformed into a set of non-linear ODEs using similarity transformations and are then solved numerically using fourth order Runge-Kutta integration scheme along with shooting technique. The results show that for the flow past a shrinking sheet, dual solutions exist for a certain range of physical parameters. The analysis shows that velocity profile is an increasing function of magnetic parameter M (0.0 ≤ M ≤ 0.3), velocity slip parameter δ (0.0 ≤ δ ≤ 0.25) and suction parameter s (2.0 ≤ s ≤ 2.2) while decreasing function of Williamson parameter β (0.0 ≤ β ≤ 0.8) and unsteadiness parameter A (−3.5 ≤ A ≤ 0.0) for the first solution branch. The temperature profile augments due to the increase of M and δ for the first solution branch. Computational outcomes of the skin friction coefficient, the Nusselt number, the Sherwood number are tabulated with suitable interpretations. The temporal stability analysis reveals that among the two solutions, first solution is stable and physically realizable. Our method of finding dual solutions and analyzing stability analysis is of practical importance to those interested in fluid dynamics as it provides one with a way to determine whether a steady state solution is physically meaningful or not.

Multidomain blockchain-based intelligent routing in UAV-IoT networks

The culmination of Unmanned Aerial Vehicle (UAV) and Internet of Things (IoT) is being utilized considerably in a wide industrial domain due to the development of 5G technologies. In the UAV-IoT domain, Software-defined networking (SDN) presents viable networking architecture as it decouples the application execution from the data repository. For effective deployment, the SDN network must be divided into numerous domains, each of which is handled by a controller. Moreover, the network topology is shared by all controller nodes, allowing for cross-domain path routing to be implemented. Furthermore, since the coordinates of the UAV are known, any change in the location due to UAV mobility can be detected. It will trigger the sharing of the updated routing tables in the UAV network. However, cross-domain routing necessitates a certain confidence level in controllers. Conspicuously, vulnerable controllers may exchange incorrect typologies with other controllers, causing them to inadvertently cross domain boundaries. In the current paper, a blockchain-inspired framework is proposed to provide safe routing across several applicability domains of UAV-IoT. Using the smart contract, all SDN controllers post abstract typologies to the blockchain. As a result, the blockchain provides a viable scenario for the network because of its consensus and immutability. Additionally, it is utilized to ensure routing dependability and managing global reputation in the blockchain. The proposed model achieved enhanced measures of accuracy (96.58%), precision (96.66%), recall (96.69%), and F1-measure (96.61%). The simulation results demonstrate that the proposed technique can successfully develop trust between numerous controllers and enable safe routing across different domains when compared to benchmark systems in terms of temporal efficacy, stability analysis, reliability analysis, and statistical parameters.

Spatial–temporal transformation for primary and secondary instabilities in weakly non-parallel shear flows

When studying instability of weakly non-parallel flows, it is often desirable to convert temporal growth rates of unstable modes, which can readily be computed, to physically more relevant spatial growth rates. This has been performed using the well-known Gaster's transformation for primary instability and Herbert's transformation for the secondary instability of a saturated primary mode. The issue of temporal–spatial transformation is revisited in the present paper to clarify/rectify the ambiguity/misunderstanding that appears to exist in the literature. A temporal mode and its spatial counterpart may be related by sharing either the real frequency or wavenumber, and the respective transformations between their growth rates are obtained by a simpler consistent derivation than the original one. These transformations, which consist of first- and second-order versions, are valid under conditions less restrictive than those for Gaster's and Herbert's transformations, and reduce to the latter under additional conditions, which are not always satisfied in practice. The transformations are applied to inviscid Rayleigh instability of a mixing layer and a jet, secondary instability of a streaky flow as well as general detuned secondary instability (including subharmonic and fundamental resonances) of primary Mack modes in a supersonic boundary layer. Comparison of the transformed growth rates with the directly calculated spatial growth rates shows that the transformations derived in this paper outperform Gaster's and Herbert's transformations consistently. The first-order transformation is accurate when the growth rates are small or moderate, while the second-order transformations are sufficiently accurate across the entire instability bands, and thus stand as a useful tool for obtaining spatial instability characteristics via temporal stability analysis.

Dual solutions and linear temporal stability analysis of mixed convection flow of non-Newtonian special third grade fluid with thermal radiation

The present study aims to investigate the steady mixed convection stagnation-point flow of a special third grade fluid over a vertical stretching/shrinking sheet with the inclusion of suction and thermal radiation effects. The governing momentum and energy equations are transformed into a system of ordinary differential equations (ODEs) using the Lie scaling group of transformations. The resulting system of highly nonlinear boundary value problems (BVPs) is solved numerically with the help of Matlab solver ‘bvp4c’. Dual similarity solutions are found for the opposing flow case within the range λc≤λ<0, where λ is the buoyancy parameter. Emphasis has been given to conducting a temporal stability analysis to determine the practically reliable solution. The analysis reveals that the primary (upper) solution branch is stable while the other solution branch is unstable. It has been observed that the range of dual solutions and the magnitude of the critical point increase with the increasing value of the suction parameter. The increment of the thermal radiation parameter enhances fluid temperature in the upper solution branch, whereas temperature diminishes far away from the sheet in the lower solution branch.

Dual solutions on three-dimensional nanofluid flow and heat transfer over a permeable non-linearly shrinking surface with second-order velocity slips

PurposeThis paper aims to present the steady dual solutions on three-dimensional flow and heat transfer of nanofluid over a permeable non-linearly shrinking surface with two-order velocity slips conditions. Boundary layer assumption is considered in the mathematical modelling. Authors comprehend from previous studies and papers that the shrinking surfaces are extremely important in current engineering and environmental systems.Design/methodology/approachUsing appropriate similarity variables, the full partial differential equations (PDF) are modified into a specific set of ordinary (similar) differential equations (ODE). The resulting non-linear ordinary differential system is then solved both analytically for some particular cases and numerically for the general case using the function bvp4c from MATLAB for characteristic values of the parameters which govern the equations. The transformed mathematical model is analysed using the bvp4c procedure. Based on the given assumptions, this study is able to produce multiple solutions of the problem.FindingsThe ordinary (similarity) differential equations have two branches solutions, upper and lower branch solutions, given some interval of shrinking and velocity slip parameters. The authors consider here a temporal stability analysis, as they want to establish which of the solutions are stable and which are not. In a distinct paragraph, the authors discuss in detail and present in a graphical manner the effects of shrinking and second-order slip flow model on the skin friction coefficient, surface wall heat flux and dimensionless velocity and temperature profiles. The analysis reveals that the second order slip has a big influence on the flow and heat transfer characteristics.Originality/valueThe present discoveries are unique and truly new for the research of the three-dimensional stretching/shrinking forced convection flow and heat transfer nanofluids. The nanofluid is a water-based nanofluid (H2O), which contains one type of nanoparticles, namely, copper (Cu). Of course, the analysis can be further extended considering other types of nanoparticles such as alumina (Al2O3). The authors assume that the thermal equilibrium is reached for the base fluid together with the suspended nanoparticles and that the nanoparticles are uniform in dimension and form.

Unsteady flow with heat transfer over a shrinking surface and linear temporal stability analysis

The present study accentuates an unsteady flow and heat transfer over a shrinking surface in the presence of magnetic field and suction effects. Similarity solutions of the self-similar equations are generated via Matlab solver ‘bvp4c’. The solutions corresponding to different values of the velocity ratio parameter (c) reveal some interesting results, which are discussed in detail. It has been observed that adequate suction is required to obtain the similarity solutions. The shear stresses and heat transfer rate are prominently affected by the intensity of suction, velocity ratio parameter, and magnetic field. Unlike an unsteady stretching sheet problem, dual solutions of the self-similar equations are found in a certain range of unsteadiness parameter. An emphasis has been given to performing a temporal stability analysis which reveals that the upper branch is a stable solution branch.

Non-Unique Solutions of Magnetohydrodynamic Stagnation Flow of a Nanofluid towards a Shrinking Sheet Using the Solar Radiation Effect

This study aims to investigate the magnetohydrodynamic flow induced by a moving surface in a nanofluid and the occurrence of suction and solar radiation effects using the Buongiorno model. The numerical findings are obtained using MATLAB software. The effects of various governing parameters on the rates of heat and mass transfer along with the nanoparticles concentration and temperature profiles are elucidated graphically. Non-unique solutions are discovered for a specific variation of the shrinking strength. The temporal stability analysis shows that only one of them is stable as time passes. Furthermore, raising the Brownian motion parameter reduces both the local Sherwood number and the local Nusselt number for both solutions. It is also observed that increasing the thermophoresis parameter reduces the rate of heat transfer, whereas the opposite trend is observed for the rate of mass transfer.

Construct Validity of Triarchic Model Traits in the Dunedin Multidisciplinary Health and Development Study Using the Multidimensional Personality Questionnaire.

The triarchic model of psychopathy emphasizes the role of three phenotypic personality domains (boldness, meanness, and disinhibition) that have been operationalized using the well-established Multidimensional Personality Questionnaire. The present study sought to further validate the MPQ-Tri scales and examine their temporal stability and predictive validity across two time points (ages 18 and 26) from the Dunedin Multidisciplinary Health and Development Study, a population-representative and longitudinal sample (N = 1,037). This investigation necessitated modification of the MPQ-Tri scales to enable their use in a broader range of samples, including the Dunedin Study. The revised MPQ-Tri scales demonstrated good temporal stability, and correlation and multiple linear regression analyses predominantly revealed associations consistent with theoretical expectations. Overall, the findings provide support for the MPQ-Tri scales as reliable, stable, and valid measures of the triarchic constructs, which provide a unique opportunity to examine highly novel research questions concerning psychopathy in a wide variety of samples.

Magnetohydrodynamics streamwise and cross flow of hybrid nanofluid along the viscous dissipation effect: Duality and stability

One of the most pressing issues in contemporary applied mathematics is the regulation of energy transfer via the application of external forces. The processes of heat transfer are affected by magnetic force, which has many practical uses in industry, engineering, and medicine. This research explores the magnetohydrodynamics (MHD) three-dimensional stable axisymmetric boundary layer over a permeable moving plate, which consists of water as a base liquid and binary distinct nanoparticles to generate a hybrid nanofluid. In all of these, flow beyond the boundary layer area might be calculated by a small crosswise velocity. As a result of its high thermal conductivity, a pair of distinct kinds of nanoparticles have been considered, namely alumina and copper, which are integrated into the base water. The mathematical model is built within a boundary of specified geometry and then converted into a set of ordinary differential equations (ODEs). Resultant ODEs are solved numerically using the technique of three-stage Lobatto IIIa in bvp4c solver in 2017, MATLAB software. Results revealed that two branches exist in certain ranges of moving parameter. The impacts of an increasing physical parameter on profiles of velocities and temperature with skin friction as well as with heat transfer rate are represented in graphs. Furthermore, as the volume fraction of copper increases, so does the skin friction coefficient in the positive direction of λ. The effect of viscous dissipation on the temperature profile in the z-direction has the same rising results as observed in the x-direction. According to the results of the temporal stability analysis, the upper branch is realizable and stable.

Brownian and thermophoresis diffusion effects on magnetohydrodynamic Reiner–Philippoff nanofluid flow past a shrinking sheet

The aim of this paper is to highlight the output of the investigation on the MHD and radiative flow and thermal characteristics of a non-Newtonian Reiner–Philippoff nanofluid with Brownian and thermophoresis diffusion effects. The model studied is embedded in the Buongiorno theory. This unique model is designed to observe both shear thickening and shear thinning properties on that particular fluid with embedded Brownian and thermophoresis diffusion implications. The proposed model consists of continuity, momentum, energy, and concentration equations constructed using the theoretical assumptions and are reduced to a set of ordinary differential equations (ODEs) before solving it using the bvp4c function in MATLAB software. Two solutions are observed, and their physical significance is justified using the temporal stability analysis. From the standpoint of the Reiner–Philippoff fluid parameter, the skin friction coefficient as well as the heat and mass transfer rates are at maximum for the shear-thickening fluid followed by the Newtonian and shear-thinning fluids. The thermophoresis parameter is noticed to decline the heat and mass transfer rate whereas the Brownian motion parameter boosts the mass transfer rate but decreases the heat transfer rate.

Hillslope-scale variability of soil water potential over humid alpine forests: Unexpected high contribution of time-invariant component

Soil water potential (SWP) gradients control water and energy fluxes in the Soil – Plant – Atmosphere Continuum. Exploring the spatial – temporal variability of SWP at the hillslope scale is an essential step towards developing ecohydrological models. In this study, SWP monitoring was carried out on two contrasting, alpine, humid forested hillslopes (i.e., coniferous and broadleaf forests) at three depths (10, 50, and 100 cm). The effects of static (soil properties and topography) and dynamic (precipitation dynamics and soil wetness conditions) factors on SWP dynamics and variability were investigated based on statistical methods, temporal stability, and variance decomposition analysis. The results showed that the SWP in the soil – root zone (10 and 50 cm depths) in the broadleaf forest exhibited higher variability and lower temporal stability than in the coniferous forest, likely because of the stronger evapotranspiration and more variable soil hydraulic conductivity. The relatively high SWP variability in the deeper soil layer (100 cm depth) of both forested hillslopes was due to the frequent lateral/preferential flow. Furthermore, topographic factors (i.e., distance of hillslope to stream and slope) and soil properties (clay and rock fragment contents) regulated the spatial patterns in SWP and influenced representative site selection in the coniferous and broadleaf forests, respectively. Decomposition of the spatial variance showed that the time-invariant component was the dominant contributor to the total spatial variance. An exponentially increasing relationship between the time-invariant component and mean SWP and a concave-up parabolic shape between the contribution of the temporal anomalies and mean SWP were observed. Our results provide an improved understanding of the temporal and spatial variability in terms of SWP in forested hillslopes.