Abstract
A photovoltaic generation has been widely applied due to the maturity of the correlation technique and the falling cost of materials. However, the characteristics of strong volatility and ...uncertainty have limited the consumption of photovoltaic power energy, which is caused by a combination of random factors from the natural environment and photovoltaic device conditions. Compared to the unpredictability of random natural factors, photovoltaic device anomalies can be detected from the spatial correlation. This paper proposed the photovoltaic generation anomalies warning method based on the neighbor profile method. To testify to the efficiency of the proposed method, experiments based on the four real photovoltaic plants are conducted in this paper. The results show the neighbor profile value of abnormal devices is different from the normal ones and verify the feasibility of the proposed method.
•A 3D total enthalpy-based lattice Boltzmann model is proposed.•Smoothed profile method is introduced to treat the no-slip boundary condition at the interface.•3D convection melting in cubical cavity ...are simulated by the lattice Boltzmann model.•2D and 3D results of convection melting problem are compared.
A three-dimensional (3D) lattice Boltzmann model is proposed to solve 3D natural convection with solid-liquid phase change. The total enthalpy-based thermal lattice Boltzmann model are incorporated in the D3Q19 particle velocity model to handle the temperature field. For the velocity field, the smoothed profile method is applied to implement the no-slip boundary condition at the solid-fluid phase interface. The present method is used to simulate several 3D natural convection problems with solid-liquid phase change, including 3D simulation of melting in a cubical cavity, 3D convection melting in an enclosure with inner rectangle cylinders and solid sphere melting in an cubical enclosure. The 3D effects on the temperature field and phase interface are discussed.
•An AHFO-based instantaneous profile method for great depths was introduced.•The proposed method was applied in the field test with a 77 m deep borehole.•Effect of hysteresis and soil heterogeneity ...on field measurement was investigated.
Unsaturated hydraulic conductivity (k(ψ)) is an important soil property that governs transient seepage. Instantaneous profile (IP) method has been routinely applied to determine k(ψ) of unsaturated soils, but its field application is limited to shallow depth because of the difficulty of deep instrumentation. In this study, an actively heated fiber-optic (AHFO) technology-based IP method was introduced for in-situ estimation of k(ψ) at great depths. The proposed method was then applied in a 77-m deep borehole involving two kinds of loess: compacted loess and natural loess. Results show that the permeability of shallow compacted loess, deep compacted loess, and natural loess decreases in sequence. As expected, the measured k(ψ) decreases with suction increase, aligning well with the derived hydraulic conductivity curve using van Genuchten-Mualem model. The value of k(ψ) at zero suction determined by extrapolation at different depths is in good agreement with k(ψ) determined by the variable head method. Further analysis shows that the use of drying soil water retention curve (SWRC) in the wetting process can lead to slight overestimation of k(ψ) at high suction. Besides, the spatial variability of soil dry density contributes to the scattering of k(ψ) data.
A numerical method for describing droplet-driven particle motion at low Weber numbers in fluids is proposed. A coupling strategy combining the Shan-Chen (SC) model and the smoothed profile method ...(SPM) is employed. The proposed scheme correctly resolves the momentum transfer between solid particles and fluid phases, while effectively controlling the wetting condition. An interaction zone where three phases coexist is introduced to solve the contradiction between the SC model and SPM (i.e. whether fluid particles are allowed at the solid nodes). In the interaction zone, partial solid particles are entrapped in the fluids owing to the coexistence of solid and fluid particles, causing solid particles to exchange momentum with fluid particles. Furthermore, the interaction forces between fluid and solid particles near the solid surface are considered at nodes near pure solid particles within this region. Based on the proposed scheme, the interactions between freely moving particles and freely moving droplets were investigated, along with the effects of wettability (Gads) and volume forces (Fp*) on particle-droplet interactions. When a liquid droplet comes into contact with a solid particle, the adhesion force between the droplet and the solid surface promotes the movement of solid particles toward the droplet. When a double emulsion comes into contact with solid particles, the adhesion force between the emulsion film and solid surface causes the double emulsion to break at the connecting point, and the volume force of the emulsion film Fd* causes the solid particles to penetrate the emulsion.
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The hydraulic conductivity of unsaturated soils can span several orders of magnitude. The measurement of hydraulic conductivity over a wide suction range is a challenging task for ...decades. In this study, numerical tests are carried out to check the assumption, error sources, and applicable conditions of the wetting front advancing method and instantaneous profile method. Based on the numerical test results, a digital wetting front advancing method is proposed to measure hydraulic conductivity of unsaturated soils in the relative high suction range and the traditional instantaneous profile method is found to be robust in measuring hydraulic conductivity in the low suction range, e.g. for soil with a degree of saturation above 0.9. Further, a combination of the digital wetting front advancing method and the traditional instantaneous profile method is implemented in the same soil column test and leads to an accurate soil hydraulic conductivity function over a wide suction range. The proposed method is applicable to various soil types and the test duration is only 1 ~ 5 days, thus makes the measurement of hydraulic conductivity a routine experiment for unsaturated soil mechanics.
To investigate the Brownian motion of individual particles suspended in viscoelastic fluids, the stochastic smoothed profile method (SPm) for direct numerical simulation is developed by extending ...deterministic SPm for suspensions in viscoelastic media. To simulate viscoelastic flow driven by thermal fluctuations in the suspending medium, the random stress in the fluid momentum equation as well as the random driving force for the conformation tensor in the Oldroyd-B model are incorporated according to the fluctuating hydrodynamics and fluctuating viscoelasticity formalisms. The thermal equilibrium and dynamical properties calculated by using numerical simulations successfully reproduce the analytic predictions, validating the direct simulation for the coupled fluctuating Navier–Stokes and Oldroyd-B equations and for the coupling between the stochastic viscoelastic medium and individual particles. As an application of the stochastic SPm, we investigate finite system-size effects under periodic boundary conditions (PBCs) on the passive microrheological relationship between the mean-square displacement (MSD) of a Brownian particle and the medium's dynamic modulus. Comparing the modulus that was microrheologically calculated from the MSD with the input modulus reveals that the effect of periodic image cell interaction appears not only in the long-time diffusive regime but also in the short-time region. A frequency-dependent finite system-size correction is implemented by phenomenologically extending the long-time diffusive regime correction, allowing passive microrheology analysis under PBCs. This result can be directly applied to other mesoscale numerical simulations including coarse-grained molecular dynamics and dissipative particle dynamics simulations.
•A direct simulation for particle dynamics in thermally driven viscoelastic flow is developed.•Fluctuating viscoelasticity is combined with Smoothed profile method.•Simulated thermally driven viscoelasitc flow and Brownian motion are validated.•Passive microrheology under periodic boundary conditions is analyzed.•Direct simulation reveals a frequency-dependent finite system-size correction.
Numerical comparison serves as a major tool in evaluating the performance of optimization algorithms, especially nondeterministic algorithms, but existing methods may suffer from a "cycle ranking" ...paradox and/or a "survival of the nonfittest" paradox. This article searches for paradox-free data analysis methods for numerical comparison. It is discovered that a class of sufficient conditions exist for designing paradox-free analysis. Rigorous modeling and deduction are applied to a class of profile methods employing a filter. It is thus further discovered and proven that algorithm-independent filter conditions can prevent cycle ranking and survival of nonfittest paradoxes from occurring. By adopting an algorithm-independent filter, popular profile methods such as the "modified data profile method," "the accuracy profile method," and "the operational characteristics zones method" can be paradox free in comparing or benchmarking the performance of optimization algorithms.
•This work is the first ever attempt to use the Smooth Profile method for the rod-like particles.•The scaling of velocity fluctuations and their relaxation times and the orientation preference of the ...particles with respect to volume fraction is explored.•Normalized drag and lift coefficients of a single rod of aspect ratio 3, followed the well known sin2θ and sinθcosθ curves, against the incident angle θ, respectively.•We found that the inhomogeneity in the microstructure of the settling rods cause the formation of clusters, even at low volume fractions. These clusters move as a large lump, inducing pronounced hydrodynamic interactions.•The average settling velocity normalized by the terminal velocity of an isolated rod, shows a non-monotonic behavior; increasing at low concentration because of these pronounced hydrodynamic interactions.•Histogram of particles’ orientation angle shows that the majority of the particles are vertically aligned.
Hydrodynamics of rod-like particles, found extensively in the chemical and process industry, is investigated here, using direct numerical simulations. A recently developed formulation of the smoothed profile method for rigid bodies is first validated for rod-like particles (rods) and then used to characterize the concentration effects on the static and dynamic properties of rods in the Stokes regime. Normalized drag and lift coefficients of a single rod of aspect ratio 3 and 4, followed the well known sin2θ and sinθcosθ curves against the incident angle (θ), respectively. We found significant inhomogeneity in the microstructure of the settling rods. These inhomogeneties, cause the formation of clusters, even at low volume fractions. These clusters move as a large lump, inducing pronounced hydrodynamic interactions, which have significant effects on the settling system. The average settling velocity normalized by the terminal velocity of an isolated rod, shows a non-monotonic behavior; increasing at low concentration because of the cluster formation in which rod packets settle faster than an isolated rod, and decreasing at high concentration because of many particle interactions. Furthermore, velocity fluctuations are larger than those of spherical particles because of the cluster formation. Histogram of particles’ orientation angle shows that the majority of the particles are vertically aligned.
Recently updated Smooth Profile Method ( SPM ) is validated for rigid particles by performing Direct Numerical Simulations for isolated regular ( prolate , disk, fiber and scalene prolate ) and ...irregular-shaped particles, settling in a Newtonian fluid. These non-spherical particles are generated by joining the spherical beads, which gives the added benefit to use SPM for any arbitrary rigid particle. Drag and lift coefficients are calculated for regular-shaped particles, as a function of orientation angle (θ), aspect ratio (ω), and Reynolds number (Re). Drag coefficients, as a function of Re and θ, are in good agreement with literature and normalized drag coefficients followed the well-known sin2θ curve for all shapes. Normalized lift coefficients also showed good agreement with the literature. New correlations for fiber, disk, and scalene prolate are also suggested based on the regression of our data to calculate the drag and lift coefficients, which incorporates parametric effects of Re, θ, and ω.
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•SPM is validated for rigid particles by calculating the drag and lift coefficients.•Correlations are proposed for drag and lift coefficients of non-spherical particles.•The correlations are valid for multiple aspect ratios of non-spherical particles.•The normalized drag coefficient follows the well-known sin2θ curve.•SPM can be used to simulate any arbitrarily shaped particle.
Bentonite pellet mixtures are considered as one of the candidate sealing materials for deep geological disposals of radioactive waste. One of the particularities of this material is the initial ...heterogeneous distribution of pellets and porosity within the mixture, leading to complex hydro-mechanical behaviour. In this paper, the hydro-mechanical properties of GMZ bentonite pellet mixtures were investigated in the laboratory by carrying out water retention tests on pellet mixtures under constant-volume condition and single pellets under free swelling condition, as well as a infiltration test on a column specimen of pellet mixture. In the infiltration test, the relative humidity and radial swelling pressure were monitored at five heights, the axial swelling pressure was also recorded. The instantaneous profile method was applied to determine the unsaturated hydraulic conductivities. Results show that, in high suction range (> 10 MPa) the water retention curve of pellet mixture under constant-volume condition was comparable to that of a single pellet under free swelling condition, while in low suction range (< 10 MPa) the latter exhibits a much higher water retention capacity. Due to clogging of large pores, the unsaturated hydraulic conductivity decreases as suction decreases to around 25 MPa. However, with further suction decrease, the hydraulic conductivity increases continuously until the value at saturated state, as in the case of most unsaturated soils. The radial swelling pressure at different heights develops with local sudden increase and decrease, which was attributed to local rearrangement of pellets upon wetting. By contrast, as the axial swelling pressure was measured on the global surface of the specimen, it develops in a more regular fashion.
