One-dimensional Method Research Articles

Structure Optimization of Natural Gas Engine’s Intake Pipe Based on One-Dimensional and Three-Dimensional Coupled Simulation

A one-dimensional and three-dimensional coupled simulation model of a natural gas engine was established by using GT-POWER and FLUENT software based on the one-dimensional and three-dimensional coupling simulation method, and the structure of the intake pipe pressure-stabilized cavity was optimized by numerical simulation. Firstly, the veracity of the above model was verified according to the engine bench test results. Then, the average intake air flow and non-uniformity of intake air at different engine speeds were simulated and analyzed by using the above model. According to the simulation results, a multi-objective optimization model was established, and a single objective evaluation function was established by using the linear weighted sum method. The results show that when the inclination angle of the stabilized cavity is 15 degrees, the comprehensive intake capacity of the intake pipe will get the best. In which the average intake air flow rate is increased by 4.3%, and the maximum air inlet non-uniformity is reduced by 10.98% compared with the original machine.

Analytical method for estimating leakage of reservoir basins for pumped storage power stations

Pumped storage power stations are increasingly constructed around cities to provide electric power and ensure grid stability. However, the upper reservoirs are typically located on mountaintops, and the reservoir leakage, which directly affects the economic benefits, is typically difficult to estimate. Therefore, to calculate the leakage within a short period, a one-dimensional simplified analytical method for estimating the leakage of pumped storage power station reservoir basins is proposed based on the stable seepage theory and Darcy’s law. Formulae are derived to calculate the seepage flux of the reservoir basin with different groundwater levels, which can be below or above the bottom of the reservoir basin. The reliability of this analytical method was validated using numerical analysis with regard to a pumped storage power station in China, and the relative errors between the analytical results and the numerical results are less than 5%. The proposed method is beneficial for engineering decision-making and design before the construction of pumped storage power stations.

A new method for calculating failure probability of landslide based on ANN and a convex set model

Calculating the failure probability of a landslide is important in engineering related to geological process and geomorphological evolution. Strength parameters of a soil (i.e., cohesion and internal friction angle) are regarded as uncertain-but-bounded parameters. In this study, a new method is proposed for computing the landslide failure probability based on a convex set model and artificial neural network (ANN). In the new method, ANN is used to determine the limit state function of landslide stability, and the failure probability is determined using a simple iterative algorithm. The new method was applied to calculate the failure probability of the Gufenping landslide in Nanjiang, Sichuan, China. The results calculated using a Monte Carlo simulation (MCS) method confirmed that the new method accurately and quickly obtains the failure probability of a landslide. Additionally, compared with the two-dimensional calculation method, the one-dimensional analysis method overestimates the failure probability of the landslide. The results of single factor and global sensitivity analysis indicate that the average of internal friction angle is the main factor affecting the stability of the landslide. It is easy to calculate failure probability of landslides using the novel method than using the conventional methods.

Generalized multiscale approximation of a mixed finite element method with velocity elimination for Darcy flow in fractured porous media

In this paper, we propose a multiscale method for solving the Darcy flow of a single-phase fluid in two-dimensional fractured porous media. We consider a discrete fracture-matrix (DFM) model that treats fractures as one-dimensional objects, and flows in both the matrix and fractures respect the Darcy’s law. A multipoint flux mixed finite element (MFMFE) method with the broken Raviart–Thomas (RT12) element and the trapezoidal quadrature rule is employed to approximate the matrix velocity and pressure, which results in a block diagonal, symmetric and positive definite mass matrix for the matrix velocity on general quadrilateral grids; the one-dimensional RT0 mixed finite element method with the one-dimensional trapezoidal quadrature rule is exploited to approximate the fracture velocity and pressure, which leads to a diagonal and positive definite mass matrix for the fracture velocity in each single fracture. All these features of the obtained mass matrices allow for velocity elimination. Multiscale basis functions are constructed for the two-dimensional matrix pressure following the generalized multiscale finite element method (GMsFEM) framework to capture the fine-scale information of heterogeneous fractured porous media and effectively reduce the degrees of freedom for the matrix pressure, while fine-grid basis functions are utilized for the one-dimensional fracture pressure in fractures. Various numerical tests with the oversampling technique for different fracture distributions are performed to show that the proposed multiscale method is effective and able to provide good approximations for the fine-grid solution.

Cryogenic thermal conductivity of 7050 aluminum alloy subjected to different heat treatments

The cryogenic thermal conductivity of high-strength 7050 aluminum alloy subjected to the processes with different combinations of solution, aging and deep cryogenic treatment, was measured by a one-dimensional steady-state thermal conduction method. The microstructure evolution of this alloy after different treatments was also characterized to investigate the changes in thermal conductivity. The results showed that the thermal conductivity of aluminum alloy was approximately linearly reduced with the decrease of temperature in general. Under the effects of different treatments, it was found that the thermal conductivity at different temperatures was sharply decreased by 30% after solution. Deep cryogenic treatment further decreased the thermal conductivity when it was conducted after solution. However, the conduction of aging increased the thermal conductivity after solution or solution-deep cryogenic treatment. Intensive lattice distortion and abundant of point defects that enhanced the electro scattering were the main reasons for decreasing the thermal conductivity after solution. The relatively large size of Al-Cu precipitates and increased dislocation density contributed to the further decrease of thermal conductivity after deep cryogenic treatment. The precipitation of a large number of ultra-fine secondary phase particles after aging increased the thermal conductivity by sufficiently releasing the lattice distortion. This work also provided an efficient method for investigating the mechanisms of deep cryogenic treatment on aluminum alloy by studying the thermal conductivity at low temperatures.

A Reduced-order Model for Lock-on via Vortex-combustion-acoustic Closed-loop Coupling in A Step Combustor

ABSTRACT The lock-on of the frequency of acoustic oscillations to the frequency of the vortex shedding in a reacting flow in a backward-facing step combustor is demonstrated using a reduced-order model. Individual models for the flow, flame and acoustic models are developed. A two-dimensional flow field with growth and shedding of vortices is modeled using a potential flow model derived via a conformal mapping of the step geometry. Combustion and acoustic models are derived using thermo-diffusive equations and the one-dimensional Galerkin method, respectively. A modulation of heat release rate fluctuations is thus enabled by vortices advecting past the flame, overcoming the time and space-localized assumptions in vortex kicked oscillator models. Comparisons with results from kicked oscillator models show a better prediction of the dominant frequencies during stable and unstable operations. A Reynolds number sweep is performed to reveal the transition from stable to unstable operation and thus the onset of instability. A shift in the dominant frequency of pressure fluctuations from the natural duct acoustic mode to the natural vortex shedding mode is observed, indicative of a lock-on. The results compare well with past experimental and computational data for similar geometry and flow conditions.

Identification methods of nonlinear systems based on the kernel functions

Membership function identification is the basis for solving the fuzzy control problems. In order to complete the fuzzification process and reflect the dynamic quality of the nonlinear systems accurately, this paper constructs a kernel function-based nonlinear system by introducing the multi-model control strategy, and it has a good performance in fitting nonlinear systems. Then we focus on the parameter estimation problem of the nonlinear systems based on the kernel functions. To overcome the difficulty due to the highly nonlinear relations between the parameters and the model output, we transform the original optimization problem into a quadratic and a nonlinear optimization problems by decomposing the complex identification model into two sub-models. Based on the hierarchical identification principle and the multi-innovation theory, two recursive identification algorithms are proposed for the nonlinear systems. Considering the difficulty to determine the step sizes, we derive the optimal step sizes by the one-dimensional search method. The effectiveness of the proposed algorithms are tested by a numerical example. The simulation results show that the proposed parameter identification methods can identify the nonlinear systems effectively.

Time-Frequency Analysis and Target Recognition of HRRP Based on CN-LSGAN, STFT, and CNN

Aiming at the problem of radar target recognition of High-Resolution Range Profile (HRRP) under low signal-to-noise ratio conditions, a recognition method based on the Constrained Naive Least-Squares Generative Adversarial Network (CN-LSGAN), Short-time Fourier Transform (STFT), and Convolutional Neural Network (CNN) is proposed. Combining the Least-Squares Generative Adversarial Network (LSGAN) with the Wasserstein Generative Adversarial Network with Gradient Penalty (WGAN-GP), the CN-LSGAN is presented and applied to the HRRP denoise. The frequency domain and phase features of HRRP are gained by STFT in order to facilitate feature learning and also match the input data format of the CNN. These experimental results show that the CN-LSGAN has better data augmentation performance and can effectively avoid the model collapse compared to the generative adversarial network (GAN) and LSGAN. Also, the method has better recognition performance than the one-dimensional CNN method and the Long Short-Term Memory (LSTM) network method.

Frequency filtering and vibrational spectrum of multiple-valley one-dimensional phononic crystals

In the present study, we have fixed the number of atoms in a one-dimensional phononic chain and changed the number of the valleys (or numbers of wells NOW) in it (by adding new terms to the system Hamiltonian) and studied the transmission properties of his system. Then, we have obtained the phononic transmission coefficient by using a one-dimensional transfer matrix method. We have also investigated the vibrational modes of the assumed system by using a direct diagonalization technique. We show that in our assumed system, there is an Omni-k bandgap within which bandgap exists for all values of the studied spring constant k. In our assumed system, we have also obtained some bi-convex lens-shaped phononic bandgaps as a function of the parameter $$V_{{{\text{conf}}}}$$ which their surface areas can be tuned by changing the number of valleys NOW. An interesting fact is that the transmission coefficient is found to be quantized versus variation of the number of wells NOW which may help experimentalists to use lower values of the material to fabricate their desired system (see the text). We observe that the transmission coefficients as a function of the NOW are some Cantor-like ones that obey self-similar bandgap structure patterns. Besides, we show that NOW and $$V_{conf}$$ are good tuning parameters that can localize the eigenmodes of the system in any part of the chain. We have provided some animation to more clearly illustrate the effect of different parameters on the transmission and vibrational properties of the system. Finally, by using a few parameters, which we have presented in this paper, we can do bandgap engineering and determine the bandgap widths, as well as their places on the frequency axis.

Non-contact and direct electrocaloric effect measurement for high-throughput material screening.

A non-contact and direct electrocaloric effect (ECE) measurement system was developed for rapid ECE measurement. The ECE of ferroelectric materials was measured directly using two measurement methods, namely, the constant heating rate method (CH method) and one-dimensional temperature gradient method (1D method), with the measurement system. The CH method continuously measures the ECE while gently heating the sample, and it can evaluate the performance of the sample more quickly than conventional methods that measure the ECE at steady state. The 1D method directly measures the ECE using a 1D temperature distribution applied to the sample. This method can measure the temperature dependence of the ECE faster than the CH method. The measurement system achieved a high signal-to-noise ratio, and the temperature dependence of the ECE measured by the two methods was consistent. The proposed measurement system and methods enable promising candidate materials for electrocaloric cooling systems to be screened more rapidly than when using conventional approaches.

High-order compact LOD methods for solving high-dimensional advection equations

In this paper, by using the local one-dimensional (LOD) method, Taylor series expansion and correction for the third derivatives in the truncation error remainder, two high-order compact LOD schemes are established for solving the two- and three- dimensional advection equations, respectively. They have the fourth-order accuracy in both time and space. By the von Neumann analysis method, it shows that the two schemes are unconditionally stable. Besides, the consistency and convergence of them are also proved. Finally, numerical experiments are given to confirm the accuracy and efficiency of the present schemes.

Quantum spin Hall effect in Ta2M3Te5 (M=Pd,Ni)

Quantum spin Hall (QSH) effect with great promise for the potential application in spintronics and quantum computing has attracted extensive research interest from both theoretical and experimental researchers. Here, we predict monolayer Ta$_2$Pd$_3$Te$_5$ can be a QSH insulator based on first-principles calculations. The interlayer binding energy in the layered van der Waals compound Ta$_2$Pd$_3$Te$_5$ is 19.6 meV/A$^2$; thus, its monolayer/thin-film structures could be readily obtained by exfoliation. The band inversion near the Fermi level ($E_F$) is an intrinsic characteristic, which happens between Ta-$5d$ and Pd-$4d$ orbitals without spin-orbit coupling (SOC). The SOC effect opens a global gap and makes the system a QSH insulator. With the $d$-$d$ band-inverted feature, the nontrivial topology in monolayer Ta$_2$Pd$_3$Te$_5$ is characterized by the time-reversal topological invariant $\mathbb Z_2=1$, which is computed by the one-dimensional (1D) Wilson loop method as implemented in our first-principles calculations. The helical edge modes are also obtained using surface Green's function method. Our calculations show that the QSH state in Ta$_2M_3$Te$_5$ ($M=$ Pd, Ni) can be tuned by external strain. These monolayers and thin films provide feasible platforms for realizing QSH effect as well as related devices.

Experimental study of the anisotropic thermal conductivity of 2D carbon-fiber/epoxy woven composites

The anisotropic micro-structure of fiber will lead to the macroscopic anisotropic properties of fiber reinforced composites in both heat transfer and mechanical strength. However, few experimental studies have be made on the anisotropic heat transfer properties of fiber reinforced composites. In this study, the anisotropic thermal conductivities of two-dimensional (2D) plain woven and twill woven carbon-fiber/epoxy composites are measured at different temperature with the one-dimensional (1D) steady-state method, transient plane source (TPS) method and transient hot wire method, respectively. The out-of-plane thermal conductivity and in-plane thermal conductivity at the temperature ranging from −45 °C to 160 °C are obtained and comparisons are made among the three methods. The results show that all the three methods can be used to measure the anisotropic thermal conductivity of fiber/epoxy woven composites. Both the out-of-plane thermal conductivity and in-plane thermal conductivity of carbon-fiber/epoxy woven composites increase with temperature, and the in-plane thermal conductivity is approximately four times as high as the out-of-plane thermal conductivity for the plain woven composites. Compared with the results of 1D steady-state method, the max deviations of TPS method and hot wire method are 18.1% and 17.1%, respectively. The sources of error that leading to the deviations are also discussed.

Field Measurements and Numerical Modeling of Hydraulic Transients in HDPE Pipeline with PRV Interaction

Pressure reducing valves (PRVs) and high-density polyethylene (HDPE) pipes are commonly used in urban water supply systems (UWSS). To study the joint effect of PRV and viscoelasticity on transient wave propagation, extensive experiments have been conducted in a field-scale reservoir-PRV-viscoelastic pipeline system covering a wide range of internal pressure heads (∼10 to 60 m) and air temperatures (12°C–33°C). In addition, a one-dimensional method of characteristics (MOC) based model that incorporates a PRV model and the generalized Kelvin-Voigt (K-V) model for pipe viscoelasticity is developed and validated against field data for the first time. The simulated transient pressures are in good agreement with field measurements. The K-V parameters exhibit a clustered distribution and the mean value for each element can provide a satisfactory simulation. The PRV in hydraulic transients can be interpreted as a quasi-dead-end with a self-adjusting opening, and causes additional positive pressure wave reflections that are gradually damped due to viscoelasticity. The dynamic changes in PRV opening, head loss, pressure wave reflection, and transmission induced by an incident pressure surge are predicted. Due to the joint action of PRV and pipeline viscoelasticity, the pressure oscillations in an intact pipe settle to a value that is considerably higher than the initial PRV set pressure. In a leaking pipe, the downstream pressure reverts to the original set pressure within a few wave cycles. Leaks can be detected by wave reflections in the time domain signals. The existence of leaks is also found to be associated with the the amplification and damping of the frequency response function (FRF) of the system at certain resonance peaks. This study provides new insights into wave propagation in HDPE pipeline with PRV interaction and an original data set for validation of leakage detection methods.

Truly multi-dimensional all-speed schemes for the Euler equations on Cartesian grids

Finite volume schemes often have difficulties to resolve the low Mach number (incompressible) limit of the Euler equations. Incompressibility is only non-trivial in multiple spatial dimensions. Low Mach fixes, however generally are applied to the one-dimensional method and the method is then used in a dimensionally split way. This often reduces its stability. Here, it is suggested to keep the one-dimensional method as it is, and only to extend it to multiple dimensions in a particular, all-speed way. This strategy is found to lead to much more stable numerical methods. Apart from the conceptually pleasing property of modifying the scheme only when it becomes necessary, the multi-dimensional all-speed extension also does not include any free parameters or arbitrary functions, which generally are difficult to choose, or might be problem dependent. The strategy is exemplified on a Lagrange Projection method and on a relaxation solver.

Detection of edible insect derived phospholipids with polyunsaturated fatty acids by thin-layer chromatography, gas chromatography, and enzymatic methods

Dietary phospholipid (PL) intake from various animals and plants accounts for about 10 % of total lipids; however, the presence of PLs and their species in edible insects have yet to be fully reported. We therefore investigated the quantity and quality of PLs in edible insects (crickets, migratory locusts, and silkworms) using thin-layer chromatography (TLC), gas chromatography (GC), and enzymatic methods. Separation of PLs from total lipids extracted by a Folch method (chloroform and methanol mixture) was achieved using a two-dimensional TLC method. Based on retention factor values, this method successfully separated phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine, lysophosphatidylcholine, and cardiolipin (CL). Crickets contained higher levels of choline-binding PLs than either migratory locusts or silkworms. Fatty acid profiles of triglyceride (TG) and PL fractions from a one-dimensional TLC method reflected those of total lipids from GC analysis. Crickets were rich in TGs and PLs (PC and PE/CL), which bound n-6 polyunsaturated fatty acids (PUFAs), whereas migratory locusts and silkworms were rich in TGs and PE/CL, which bound n-3 PUFAs. A modified enzymatic quantitative PC-specific analysis showed that PC was the dominant PL in edible insects. In conclusion, edible insects, particularly migratory locusts and silkworms, may be novel sources of n-3 PUFAs containing functional PLs.

A simple finite element procedure for free vibration of rectangular thin and thick plates

A simple finite element procedure is introduced and developed to solve the free vibration problem of rectangular plates. The proposed method first reduces the original plate problem to two simple beam problems. Each beam problem is then discretized separately with the help of one-dimensional finite element method (FEM). Since only the one-dimensional FEMs are dealt with in the proposed approach, the implementation of the proposed approach is much easier than the case where the two-dimensional FEM is applied to the problem. The reliability and applicability of the proposed method are demonstrated herein through the solution of some illustrative problems, including the vibration problems of thin and thick rectangular plates. The simulations have been done for plates with different boundary conditions including the simply supported, clamped, and free boundary conditions. The results generated by the proposed method are compared with analytical and numerical results available in the literature and excellent agreement is achieved.

Performance prediction of transonic axial multistage compressor based on one-dimensional meanline method

This study proposes a 1D meanline program for the modeling of modern transonic axial multistage compressors. In this method, an improved blockage factor model is proposed. Work-done factor that varies with the compressor performance conditions is added in this program, and at the same time a notional blockage factor is kept. The coefficient of deviation angle model is tuned according to experimental data. In addition, two surge methods that originated from different sources are chosen to add in and compare with the new method called mass flow separation method. The salient issues presented here deal first with the construction of the compressor program. Three well-documented National Aerodynamics and Space Administration (NASA) axial transonic compressors are calculated, and the speedlines and aerodynamic parameters are compared with the experimental data to verify the reliability and robustness of the proposed method. Results show that consistent agreement can be obtained with such a performance prediction program. It was also apparent that the two common methods of surge prediction, which rely upon either stage or overall characteristic gradients, gave less agreement than the method called mass flow separation method.

Research of an SHPB Device in Two-by-Two Form for Impact Experiments of Concrete-Like Heterogeneous Materials

A split Hopkinson pressure bar (SHPB) device in two-by-two form, including the bar bundle form and the single cylindrical bar form, was designed in response to the demand for the dynamic mechanical experiments for brittle materials such as concrete, rock, etc. The stress waveforms generated through a projectile impacting two different types of incident bars have been studied based on the one-dimensional stress wave theory and numerical simulation method. At last, based on the established two types of mesoscale concrete models with random convex polyhedral aggregates, we performed comparison analysis of SHPB numerical simulations for concrete materials with bar bundle and single cylindrical bar separately, so as to provide technical support for the manufacture and development of this experimental device. The results showed that the introduced two-by-two form SHPB device expanded the scope of practical application, and the wave dispersion effect existing in a large-diameter bar can be evidently reduced when we employed the bar bundle form, indicating its applicability to the dynamic mechanical experiments of concrete-like heterogeneous materials.

Experimental and Numerical Study of Air Vessel in Quasi-Two-Dimensional Transient Flow Analysis

Abstract An air vessel is a simple and effective device for protecting a pipeline system from abnormal pressure events. In order to design and select a suitable air vessel, analysis of the pipeline system is necessary. A quasi-2D approach can overcome some of the limitations of the conventional one-dimensional transient flow analysis method. However, only a few hydraulic components can be implemented in the quasi-2D approach. In this study, we propose a methodology for applying an air vessel in the quasi-2D model. An experimental study is performed for validating the proposed model. Although an identical approach involving an accumulator model is used to model the air vessel as in the 1D model, the quasi-2D model shows improved performance for the experimental system.