Quasi One-dimensional Model Research Articles

Numerical investigation of roping in multi-die meltblowing

This work aims at conducting a numerical investigation of the effect of the inter-die distance on the probability of roping during meltblowing. The results are qualitatively compared with the experimental data obtained by the present group in studies of roping in a model situation of solution blowing. The effectiveness of nonwoven products as filter membranes and others depends on the fiber size and geometrical fiber distributions in fiber mats. Jet roping in meltblowing results in a distortion of the laydown structure, which is detrimental to the product's efficiency. A quasi one-dimensional model is utilized here to predict the probability of jet–jet intersection in flight leading to roping, which was observed experimentally in the prior works of this group. The results of the present work are expected to be helpful in optimizing operating parameters to minimize roping in meltblown products.

Electrical environment can be altered at 1 km distances from high voltage power lines.

High voltage powerlines emit electrical charges into the atmosphere which can then attach to aerosols. This space charge above ground can be measured directly using ion spectrometers or indirectly through perturbations of the Earth’s potential gradient using field mills. Several publications are reviewed to find evidence of aerosol charging at a distance from power lines. Field measurements of charge state near to high voltage power lines selected due to their high emissions of ions measured a small positive enhancement of electrical charge on aerosols at distances greater than 300 m, corresponding to a transit time of up to 400 s A quasi one-dimensional model of ion-aerosol interactions from a high voltage powerlines found that the addition of new ions to an aerosol population will result in those ions transferring charge to the aerosol which would then remain the dominant carrier of charge several hundred meters downwind. 10-min PG measurements from a fixed site measuring in 2008 compared measurements when the site was downwind of a 275 kV powerline to times with no wind and found evidence of space charge overhead through greater fields and variability at distances over 800 m These studies combined show evidence that the electrical environment near to power lines can be altered beyond 1 km from AC high voltage power lines, with excess charges likely to be concentrated on aerosol.

Eleven competing phases in the Heisenberg-Gamma ( JΓ ) ladder

The spin-orbit generated Γ interaction is known to induce strong frustration and to be significant in realistic models of materials. To gain an understanding of the possible phases that can arise from this interaction, it is of considerable interest to focus on a limited part of parameter space in a quasi one-dimensional model where high precision numerical results can be obtained. Here we study the Heisenberg–Gamma ( JΓ ) ladder, determining the complete zero temperature phase diagram by analyzing the entanglement spectrum (ES) and energy susceptibility. A total of 11 different phases can be identified, among them the well known rung-singlet (RS) phase and 5 other phases, FM, FM-Z, FM-XY, AF and AF-Z, with conventional long-range magnetic order. The 3 ferromagnetic phases, FM, FM-Z and FM-XY simultaneously have non-zero scalar chirality. Two other phases, the antiferromagnetic Gamma (AΓ) and ferromagnetic Gamma (FΓ) phases, have previously been observed in the Kitaev–Gamma ladder, demonstrating that the AΓ-phase is a symmetry protected topological phase (SPT) protected by TR ×Rb symmetry, the product of time-reversal (TR) and π rotation around the b-axis ( Rb ), while the FΓ-phase is related to the RS phase through a local unitary transformation. The 3 remaining phases, ϒ, Ω and δ show no conventional order, a doubling of the ES and for the ϒ and Ω-phases a gap is clearly present. The δ-phase has a significantly smaller gap and displays incommensurate correlations, with a peak in the static structure factor, S(k) continuously shifting from k/π=2/3 to k=π . In the Ω-phase we find pronounced edge-states consistent with a SPT phase protected by the same TR ×Rb symmetry as the AΓ-phase. The precise nature of the ϒ and δ-phases is less clear.

A nonlinear multi-scale model for blood circulation in a realistic vascular system.

In the last decade, numerical models have become an increasingly important tool in biological and medical science. Numerical simulations contribute to a deeper understanding of physiology and are a powerful tool for better diagnostics and treatment. In this paper, a nonlinear multi-scale model framework is developed for blood flow distribution in the full vascular system of an organ. We couple a quasi one-dimensional vascular graph model to represent blood flow in larger vessels and a porous media model to describe flow in smaller vessels and capillary bed. The vascular model is based on Poiseuille’s Law, with pressure correction by elasticity and pressure drop estimation at vessels' junctions. The porous capillary bed is modelled as a two-compartment domain (artery and venous) using Darcy’s Law. The fluid exchange between the artery and venous capillary bed compartments is defined as blood perfusion. The numerical experiments show that the proposed model for blood circulation: (i) is closely dependent on the structure and parameters of both the larger vessels and of the capillary bed, and (ii) provides a realistic blood circulation in the organ. The advantage of the proposed model is that it is complex enough to reliably capture the main underlying physiological function, yet highly flexible as it offers the possibility of incorporating various local effects. Furthermore, the numerical implementation of the model is straightforward and allows for simulations on a regular desktop computer.

Numerical evaluation of an Oil free Screw Compressor’s Suction Port design using Ansys CFX and SCORG

Quasi one-dimensional chamber models and experimental methods are commonly adopted by researchers to predict and validate the performance of the oil free screw compressors. However, to understand the scope for improvement in performance as impacted by compressor ports, one needs to know the details of physical processes happening in compression chamber. This can be done by understanding flow field such as internal temperature and pressure with the help of CFD model.With this CFD setup, comparison of specific power consumption of oil free screw compressor between the axial and radial suction flange is presented in this paper. A hexahedral numerical mesh is used to represent flow field which is generated by SCORGTM. Flow solver ANSYS CFX has been used for study with these single domain deforming rotor grids.This paper presents the methods used for setting up the CFD model and analysis of specific power consumption for two different suction port geometries, an axial and the radial suction flange. At the design operating condition, although axial suction flange seems to be more favourable in terms of lower suction pressure drops at high operating speed, the radial suction flange when simulated using CFD model predicts almost the similar performance. However, radial suction flange gives an added advantage for ready adaptability with the suction elements like the suction filter. The results of the simulation show that the radial suction flange can be adopted for better compatibility with the oil free package and the CFD model used for the analysis can be used for optimization of the air-end at various operating conditions.

Heavy doped organic crystals ordering

The simple model that can describe structure and charge ordering in complex doped organic crystals is proposed. We consider the quasione-dimensional model of a crystal with chains (stacks) of flat BEDT-TTF molecules. In a chain of large molecules, small molecules fill every space between large molecules. The interaction between all molecules is described by the Lennard-Jones potential. It is shown that the small dopant molecules are in the double-well potential. It is shown that in case of the electrically neutral molecules at low temperatures, there is a fluctuating structural ordering: the small molecules group in pairs near a large molecule, and the lattice period in the fluctuation domain doubles. The structure of the boundary between the fluctuation domains is defined. In case of the charged molecules, correction to electric dipole interaction makes the system essentially three-dimensional, and there is ferroelectric ordering in a chain and an antiferroelectric one between the chains. Structure of the charge domains and domain boundaries are described.

Control-oriented quasi-one dimensional modeling method for scramjet

Abstract The scramjet model used in the control system needs to consider both accuracy and real-time requirements. In this paper, a quasi-one dimensional component level model method for scramjet is proposed. Under the premise of meeting the real-time requirement, this modeling method has higher calculation accuracy, and can obtain higher thrust performance without exceeding the limits. In order to improve the calculation accuracy of the scramjet model, the boundary layer correction and the interaction between shock wave and boundary layer are considered in the inlet and isolator modeling process by using reference temperature method. For the scramjet compression components, the inlet and isolator models are simplified based on shock train theory to improve real-time performance. Meanwhile, the combustor model and nozzle model are established and the combustor model is established with the combination of equal area and isothermal based on temperature limitation. Considering the boundary layer correction, the accuracy of the inlet and isolator model is improved by 8.79 and 7.9% respectively. Compared with the equal area combustion mode, the combined combustion mode can get higher thrust. In the C + + simulation environment, the average calculation time of each state point is about 25 ms which meets the real-time requirements.

PPG buys Dexmet, Whitford & Hemmelrath

The data presented in this data article were on the basis of the study reported in the research articles entitled “A novel quasi-one-dimensional model for performance estimation of a Vaporizing Liquid Microthruster” (De Giorgi and Fontanarosa, 2018). The reference study presented a numerical analysis of the performance of the Vaporizing Liquid Microthruster (VLM) experimentally investigated in the data article entitled “Performance evaluation and flow visualization of a MEMS based Vaporizing Liquid Microthruster” (Cen and Xu, 2010). For the purpose, a novel quasi one-dimensional model was proposed, and results were compared with the numerical predictions provided by 2D and 3D CFD computations.Due to the scarcity of experimental data concerning the flow characterization inside a Vaporizing Liquid Microthruster, the present Data in Brief aims to provide the entire dataset coming from the numerical predictions for benchmark purposes and comparisons with different numerical approach.

Model for a Ferromagnetic Quantum Critical Point in a 1D Kondo Lattice.

Motivated by recent experiments, we study a quasi-one-dimensional model of a Kondo lattice with ferromagnetic coupling between the spins. Using bosonization and dynamical large-N techniques, we establish the presence of a Fermi liquid and a magnetic phase separated by a local quantum critical point, governed by the Kondo breakdown picture. Thermodynamic properties are studied and a gapless charged mode at the quantum critical point is highlighted.

Aluminized composite propellant combustion modeling with Heterogeneous Quasi-One dimensional (HeQu1-D) approach

The Heterogeneous Quasi One-dimensional (HeQu1-D) model for AP/HTPB composite propellant combustion is extended to aluminized propellants. Following the serial burning approach of HeQu1-D, a statistical particle path through an aluminized propellant is taken to consist of aluminized binder-matrix coated AP particles of various sizes. Extending the idea of homogenization of fine-AP particles, aluminum particles are assumed to be homogenized with the binder-matrix. Large Al particles (nominal size ≥ 15 µm) in the binder-matrix are assumed to get ejected into the gas phase and hence do not contribute to heat feedback to the burning surface. With these modifications, the model is shown to accurately predict the burn rate variation with pressure and initial temperature of propellants using Al of nominal sizes in the range of 15–50 µm (termed conventional aluminum, CAl). The experimentally observed reduction in propellant burn rate with substitution of AP by CAl is shown to be due to the increase in fuel richness and energy sink effect of melting of Al. Catalytic effects due to addition of burn rate modifiers (Fe2O3 in space shuttle booster propellant, for instance) are also accounted for by modifications to gas phase rate parameters. Increase in burn rate up to 25% with Al particles of a few µm (3–6 µm) in comparison with non-aluminized propellant is explained by recognizing that there will be non-negligible fraction of sub-micron Al due to the associated particle size distribution. This leads to heat release by sub-micron Al combustion close to the surface and an enhancement in the heat feedback, by a combination of convective and radiative mechanisms. Dramatic increase in burn rate with sub-micron Al (a factor of 4–5 as compared to CAl) is captured by invoking radiation from fine-Al/Al2O3 particles to propellant surface. Agglomeration of sub-micron Al particles is invoked to explain the saturation of burn rate enhancement with reduction in Al particle size and the effectiveness of sub-micron Al substitution in smaller fractions (bi-modal Al). Predictions for over fifteen different propellants with varying fractions of fine and coarse aluminum from earlier literature have been presented. Comparisons of the predictions from the model with experimental results from different sources is shown to be excellent-to-good for most cases. The hitherto unknown radiation dominated ablation (r˙>50mm/s) of coarse AP particles and the effect of Al particle size on propellant temperature sensitivity are brought out. The MATLAB® code based on the model offers opportunity for design of AP-HTPB composite propellants with combination of fine and coarse aluminum with confidence.

Применение параллельных алгоритмов при численном моделировании кровотока в квазиодномерном приближении

The main goal of modern hemodynamic simulation is the prediction of blood pressure in the arteries, as well as the study of the various factors complex effect on the cardiovascular system characteristics. Quasi-one dimensional models of blood flow through blood vessels are the most popular. They allow to model the blood flow in the entire vascular system. Since full-scale simulation of the cardiovascular system requires large computational costs, the problem of parallelizing computation is actual. In this paper, the efficiency study was carried out for parallel algorithms in the numerical simulation of blood flow in the quasi-one-dimensional approximation. For simplicity, we consider the problem of the blood flow simulation in a separate blood vessel. When constructing a parallel algorithm, the domain decomposition method was applied. In each subdomain, the problem at each time step splits into a hyperbolic and parabolic subproblems. To solve the hyperbolic subtask, an integro-interpolation method based on the MUSCL scheme is used. To integrate over time, the second order Runge-Kutta and Adams-Bashfort methods are applied. The Crank-Nicholson method is used to solve the parabolic subproblem. At the subdomains conjunctions, the interface conditions are non-linear systems with three unknowns. These systems are solved using the Newton method. The time-cost structure was obtained for solving the test problem in a serial mode using the AMD CodeAnalyst profiler. Computations were carried out at the cluster of the BMSTU "Applied Mathematics" FN-2 department. The computational results showed that the time gain achieved by using the MPI library does not exceed a few percent in comparison with the OpenMP technology usage. Taking into account the simplicity of parallelizing algorithms through OpenMP, we can choose this technology, but MPI usage allows to make the software package universal (it can work both on shared memory systems and on distributed memory systems).

Comparison of two-dimensional and quasi-one-dimensional scramjet models by the example of VAG experiment

In the paper two-dimensional and quasi-one dimensional models for scramjet combustion chamber are described. Comparison of the results of calculations for the two-dimensional and quasi-one dimensional code by the example of VAG experiment are presented.

Enhancement of thermal performance of micro heat pipes using wettability gradients

We present a methodology for enhancing thermal performance of micro heat pipes (MHPs) by creating wettability gradients on the inner surface of MHPs. We analyse the effect of wettability gradients on MHP performance using a quasi one-dimensional mathematical model that accounts for axially-varying solid–liquid contact angle. For our analysis, we consider MHPs with various wettability schemes, such as uniform, step-variation, and linear variation in the contact angle. Our model predictions show that increasing the wettability of the evaporator surface and reducing the wettability of the condenser surface of MHP can lead to an increase in the heat transfer capacity of MHP by over 35%. We demonstrate the favourable effect of wettability gradients on MHP performance for different working fluids over a wide range of operating temperature and fluid charge. We also discuss the underlying physical mechanism that leads to enhanced thermal performance of MHP with mixed wetting surfaces. We show that the optimal choice of wettability gradient in MHP is governed by the competing effects of high liquid flow resistance in the lower wetting condenser and high liquid mass in the higher wetting evaporator.

Revisiting argon cluster formation in a planar gas jet for high-intensity laser matter interaction

We determine the size of argon clusters generated with a planar nozzle, based on the optical measurements in conjunction with theoretical modelling. Using a quasi-one dimensional model for the moments of the cluster size distribution, we determine the influence of critical physical assumptions. These refer to the surface tension depending on the presence of thermal equilibrium, the mass density of clusters, and different methods to model the growth rate of the cluster radius. We show that, despite strong variation in the predicted cluster size, 〈N〉, the liquid mass ratio, g, can be determined with high trustworthiness, because g is predicted as being almost independent of the specific model assumptions. Exploiting this observation, we use the calculated value for g to retrieve the cluster size from optical measurements, i.e., calibrated Rayleigh scattering and interferometry. Based on the measurements of the cluster size vs. the nozzle stagnation pressure, we provide a new power law for the prediction of the cluster size in experiments with higher values of the Hagena parameter (Γ*>104). This range is of relevance for experiments on high-intensity laser matter interactions.

Electron-correlation driven capture and release in double quantum dots

We recently predicted that the interatomic Coulombic electron capture (ICEC) process, a long-range electron correlation driven capture process, is achievable in gated double quantum dots (DQDs). In ICEC an incoming electron is captured by one quantum dot (QD) and the excess energy is used to remove an electron from the neighboring QD. In this work we present systematic full three-dimensional electron dynamics calculations in quasi-one dimensional model potentials that allow for a detailed understanding of the connection between the DQD geometry and the reaction probability for the ICEC process. We derive an effective one-dimensional approach and show that its results compare very well with those obtained using the full three-dimensional calculations. This approach substantially reduces the computation times. The investigation of the electronic structure for various DQD geometries for which the ICEC process can take place clarify the origin of its remarkably high probability in the presence of two-electron resonances.

M205 局所振動子を有するメタマテリアルに基づいた準一次元非線形格子モデルの動力学特性(GS1,3 材料力学・計算力学(3),修士研究発表セッション)

M205 局所振動子を有するメタマテリアルに基づいた準一次元非線形格子モデルの動力学特性(GS1,3 材料力学・計算力学(3),修士研究発表セッション)

Crossover between ferroelectric order and dipolar glass disorder in betaine phosphate0.06betaine phosphite0.94mixed crystals

The dielectric properties of mixed betaine phosphate0.06betaine phosphite0.94(BP0.06BPI0.94) ferroelectric crystals were investigated in a wide frequency range from 20 Hz to 3 GHz. Although the dielectric anomaly is clearly observed close to the ferroelectric phase transition temperatureTc= 121 K, the dielectric dispersion is very broad around and below this temperature. Temperature dependences of the dielectric strength, the mean relaxation frequency and the spontaneous polarization cannot be described together according to the Landau theory for ferroelectric phase transition with a single order parameter or according to the quasione-dimensional Ising model. The polarization shows a pronounced distribution in the ferroelectric phase and only a partial ordering of hydrogen atoms occurs down to the lowest temperatures. The unordered hydrogen atoms form a glassy phase and its formation is observed in dielectric spectra at very low temperatures. The proton freezing temperature was estimated.

Quasi One-Dimensional Model of Natural Draft Wet-Cooling Tower Flow, Heat and Mass Transfer

The article deals with the development of CFD (Computational Fluid Dynamics) model of natural draft wet-cooling tower flow, heat and mass transfer. The moist air flow is described by the system of conservation laws along with additional equations. Moist air is assumed to be homogeneous mixture of dry air and water vapour. Liquid phase in the fill zone is described by the system of ordinary differential equations. Boundary value problem for the system of conservation laws is discretized in space using Kurganov-Tadmor central scheme and in time using strong stability preserving Runge-Kutta scheme. Initial value problems in the fill zone is solved by using standard fourth order Runge-Kutta scheme. The interaction between liquid water and moist air is done by source terms in governing equations.

A quasi one-dimensional bleed flow rate model for terminal normal shock stability in mixed compression supersonic inlet

Ninety-degree (normal) bleed slots have been used to stabilize the terminal normal shock in the throat of a mixed compression supersonic inlet. In this study, a quasi-one-dimensional bleed flow rate model, consisting of a constant-area channel with a pair of normal slots symmetrically located along the upper and lower endwalls, is developed. The bleed flow rate is shown to be a function of the terminal normal shock position within the slot. Some key factors, such as the bleed discharge coefficient, taken from the Bragg model, were derived from the basic laws of conservation for a one-dimensional simplification. Furthermore, numerical simulations based on Reynolds-averaged Navier–Stokes equations were performed to analyze the flow characteristics around the bleed slots. The predictions of the bleed flow rate model agree well with computational fluid dynamics results. This method may be helpful to predict the stability of the terminal normal shock in mixed compression supersonic inlets.

PAni-SnO<sub>2 </sub>Nanocomposite: Irradiation Induced Charge Transport Processes

The films of polyaniline–tin oxide (PAni–SnO2) nanocomposites were synthesized by chemical oxidative polymerization technique. These films were irradiated with 90 MeV O7+ ions at the fluences of 5×1010, 1×1011, 5×1011, and 1×1012 ions/cm2. X-ray diffraction studies show that microstrain and domain crystallite size of SnO2 nanoparticles in PAni matrix increase with the increase of ion fluence, resulting in highly ordered PAni–SnO2 nanocomposites. DC electrical conductivity is found to increase with the increase of fluence and conduction mechanism follows a quasi one-dimensional variable-range hopping model. AC electrical conductivity also increases with the increase of ion fluence and obeys correlated barrier-hopping model.