Zonal Method Research Articles

A zonal grid method for incompressible two-phase flows

We present a zonal grid based numerical method applicable to two-phase flows. The method is aimed at reducing the computational costs for interfacial flows involving local high velocity gradients such as those encountered in atomization systems. The objective is to fully resolve the primary atomization region while at the same time limiting the number of grid points in secondary or dispersed zones where a very fine grid is not required, along with the ability to use a local zone based time step. Calculations of a rising bubble and liquid jet atomization configurations were performed on a coarse grid with a fine zone superimposed on small domains with the strongest gradient. The results show good agreement with simulations carried out with a complete refined mesh with only a fraction of the CPU time. The results indicate that the two-phase zonal grid model approach introduced here has the potential to provide an accurate and cost-effective approach for modeling two-phase flow problems that have multiple temporal and spatial scales.

Thermal performance of vortex-based solar particle receivers for sensible heating

We report a first-order assessment of a novel vortex-based solar particle receiver and the sensitivity of its thermal performance to a number of key operational parameters. This assessment is made with a one-dimensional numerical model developed here to adapt the zonal method to calculate heat and mass transport within the enclosure of the solar vortex receiver (SVR) and to incorporate radiative and convective heat transfer between the particle phase, the air phase and the receiver wall together with re-radiative and conductive loss from the receiver. This simplified one-dimensional model allows for the systematic assessment of first order trends of mass and energy balance within the SVR and is used here to advance understanding of the dominant mechanisms controlling its thermal performance. Sensitivity studies of the thermal performance of the SVR reveal that the receiver can be configured to operate as either an air-heater or a particle-heater, depending primarily on the particle mass loading. For the present SVR configuration, the critical value of mass loading, ṁp/ṁair ≈ 1 was found to define the boundary, above which the device acts as a particle heater, and below which it acts as an air heater. Furthermore, an assessment of the two-phase flow direction found that a counter-flow (relative to the incident concentrated solar radiation) tends to result in a higher efficiency than a co-flow direction. The first order trends of the sensitivity of thermal performance of the SVR to the particle and air mass flow rates, particle size and receiver length were also assessed, finding that the ratio of receiver thermal input to heat capacity of the two-phase flow has a controlling influence on the thermal efficiency of the SVR, particularly with the front entry configuration. Overall receiver thermal efficiencies of up to 88% were predicted for the SVR operating with high mass flow rates of both particles and air, but it is expected that the thermal efficiency of the device for all operating conditions assessed here would increase with an increase in receiver scale from the laboratory-scale device considered here.

Orthogonal function extension to enclosure theory

Enclosure theory is widely used to solve radiative heat transfer problems. This paper proposes a mathematical model to handle radiative heat transfer between spatially inhomogeneous surfaces and volumes by using sets of orthogonal functions to represent the spatial variation of surface and volume radiative intensities and properties. This method facilitates development of finely tuned solvers to exploit the properties of the basis functions while providing an improved pedagogical framework behind Hottel’s zone method. Additionally, this interpretation provides insight into error analysis for these types of computations. A simple case study is performed on a two-dimensional empty box with homogeneous, diffuse-gray emissivity, utilizing indicator functions, Fourier series, and Legendre polynomials as sample function bases. An additional proof-of-concept study with participating media was performed with the orthogonal functions using a ray tracing solver in a Monte Carlo wrapper. The studies show that this orthogonal function method can be practically used to mitigate truncation error without any increase in the amount of run-time calculations compared to standard zonal methods.

Radiation-convective heat transfer from the crystals in methods of pulling from melts

The radiation-convective heat transfer from the crystals in methods of pulling from melts such as Czochralski, Stepanov and floating zone is investigated numerically in the conjugate statement of the problem. The calculations are performed in the ranges of Grashof numbers from 1000 to 25000, with the gas Prandtl number equal to 0.68. Calculations of convective heat transfer are carried out by finite element method, and radiation fluxes are calculated by the zonal method. The relative role of thermal conductivity, convective heat transfer and radiation heat transfer is investigated.

Analytic spherical harmonic coefficients for polygonal area lights

Spherical Harmonic (SH) lighting is widely used for real-time rendering within Precomputed Radiance Transfer (PRT) systems. SH coefficients are precomputed and stored at object vertices, and combined interactively with SH lighting coefficients to enable effects like soft shadows, interreflections, and glossy reflection. However, the most common PRT techniques assume distant, low-frequency environment lighting, for which SH lighting coefficients can easily be computed once per frame. There is currently limited support for near-field illumination and area lights, since it is non-trivial to compute the SH coefficients for an area light, and the incident lighting (SH coefficients) varies over the object geometry. We present an efficient closed-form solution for projection of uniform polygonal area lights to spherical harmonic coefficients of arbitrary order, enabling easy adoption of accurate area lighting in PRT systems, with no modifications required to the core PRT framework. Our method only requires computing zonal harmonic (ZH) coefficients, for which we introduce a novel recurrence relation. In practice, ZH coefficients are built up iteratively, with computation linear in the desired SH order. General SH coefficients can then be obtained by the recently developed sparse zonal harmonic rotation method.

Moment-based wavefront reconstruction via a defocused Shack–Hartmann sensor

An approach for wavefront reconstruction based on a defocused Shark–Hartmann sensor is proposed. In this approach, not only the first-order origin moment (local slope of the input wavefront) but also the second-order central moment (local curvature of the input wavefront) of each spot in the intensity pattern is used to reconstruct the input wavefront. By introducing the second-order moment, an improvement of reconstruction accuracy can be obtained. As the ambiguity of the sense of the local curvature of the input wavefront exists in the scheme of the conventional Shack–Hartmann sensor in focus, a defocusing scheme is adopted to solve this problem. Based on modal and zonal methods, respectively, the corresponding algorithms are invoked to reconstruct the wavefront from the map consisted of both local slopes and curvatures. Numerical experiments show that the reconstructed wavefront by the proposed method is more accurate, in comparison to the result by the conventional method. It should be mentioned that the defocused sensor used in the proposed method sacrifices, to some extent, the dynamic range of measurement.

MODEL OF INDUSTRIAL PROCESS

An analysis of the IT project management was carried out using the Microsoft Project software package. Acquaintance with the essence and tools of project management, which allows to make qualified decisions on coordination of people, equipment, materials, financial resources and schedules for the execution of a certain project at a given time, within the budget and to the customer's satisfaction, taking into account the specifics of the IT field. The optimization of the IT project implementation time by the critical path method is considered. As a result of the calculation, critical, non-critical project operations and reserves or time stocks for non-critical operations are determined. In addition, the method of optimization of the IT project by time and cost is considered. The cross-linking of network graphs and their further ordering by the zonal and matrix method was studied. Prepared recommendations for application of the developed model in the educational process.

Energy and exergy analyses of a mass-fired boiler for a proposed waste-to-energy power plant in Tehran

Thermodynamic analysis of a municipal solid waste-to-energy boiler was thoroughly conducted. For this purpose, mass, energy, and exergy balance equations were formed over the entire boiler and its components. This study aimed to report the first and second law efficiencies to identify the main sources of irreversibility within the boiler. Three districts of Tehran mega city were selected, and the fictive molecule C26.75H3.58O15.79N1.08S0.11 was obtained from the average chemical composition of the aggregated waste. Moreover, the zonal method was applied to design the furnace, following by a simpler approach to design heat recovery steam generator. The energy and exergy analysis was then performed for all components and the entire boiler, followed by a sensitivity analysis on the blow-down water ratio effects. Results indicated that the irreversibility in furnace, with 52,617.3 kJs-1, was the main source of the exergy destruction. In addition, the overall energetic and exergetic efficiency of the studied boiler were reported as 78.7 and 16.0%, respectively.It appears that as a consequence of relatively small lower heating value of the utilized waste and considering the heat loss due to the bottom ash and blow-down water, a considerable reduction in the boiler efficiency occurred.

Estimation of Local Recreational Value of Seethawaka Wet Zone Botanical Garden

The Seethawaka wet zone Botanic garden is a new botanical garden in the wet zone of Sri Lanka. The garden is entrusted with the dual mandate of providing quality recreation opportunity to visitors while conserving the highly threatened wet lowland forest flora of Sri Lanka. The study intends to estimate local recreational value of the garden which could provide guidance on further investments and improvements of the garden. The economic approach used to estimate the recreational value was the zonal travel cost method. The method involves dividing the surrounding area into concentric zones of increasing distance, which represented increasing levels of travel cost. A questionnaire survey was conducted at the garden to determine zone of origin, visitation rates, travel cost and various socio economic characteristics. Information was gathered from 200 local visitors to garden through direct interviews using a structured questionnaire. The data generated were used to regress visitation rates against the total travel cost and urban population fraction of each zone. The estimated local recreational value of the garden per annum was LKR 283 million and the consumer surplus at the current entrance fee of LKR 60 is LKR 275 million per annum. This figure can be used to demonstrate the contribution of a botanic garden to the economy and to attract more funds to develop infrastructural facilities inside the garden from the government allocations. Key words: Travel cost method, Seethawaka wet zone, Recreational value

Zonal Hybrid Reynolds-Averaged Navier–Stokes/Large-Eddy Simulation of a Hydrogen-Fueled Scramjet Combustor

A zonal hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation framework is implemented to investigate the diffusion combustion of hydrogen–air in a model scramjet combustor. The computational domain is segregated into Reynolds-averaged Navier–Stokes and large-eddy simulation regions. An upwind convective flux discretization method and shear-stress transport turbulence models are applied to the Reynolds-averaged Navier–Stokes region, and the low-dissipative convective flux discretization method and improved delayed detached-eddy simulation are applied to the large-eddy simulation region. To generate turbulence at the Reynolds-averaged Navier–Stokes/large-eddy simulation interface, a synthetic-eddy method is employed. The geometries and boundary conditions of the model scramjet combustor are based on an experiment conducted at German Aerospace Center. The turbulent hydrogen diffusion flame is modeled using the steady flamelet approach. A total of nine computation cases are examined to analyze the influence of the numerical methods. As a result, the zonal hybrid method using the low-dissipative convective flux discretization method and synthetic-eddy method shows the best agreement with the experimental data in terms of quantitative temperature and rms velocity fluctuation profiles.

Improving energy efficiency in a complex natural gas refinery using combined pinch and advanced exergy analyses

A real-life case study of a Heat Exchanger Network (HEN) in a complex natural gas refinery was considered, using the pinch technology concept combined with advanced exergy analysis (so-called CPEA). This could be done by supertargeting, a tradeoff between capital and operational costs, applied to the five divided zones in the plant, based on the concept of zonal targeting method. It was shown that the potential of improvement on both the utility consumption and the heat recovery were about 36.09% and 42.65% respectively, so there was a huge potential of the energy saving relative to the existing network. Meanwhile, a new approach to the advanced exergy analysis of HENs has been proposed by considering ΔTmin = 0 °C in the well-developed Carnot factor-Enthalpy diagram of balanced exergy composite curves. Considering unavoidable exergy loss in the retrofitted network, it was shown that the CPEA method led to the exergetic efficiency of 88.27%, which shows more than 78% improvement compared with 49.45% of the existing network. So from practical points, the CPEA method represents a new attempt to develop a systematic framework to optimize complex HENs in energy systems, by using an integrated set of pinch and advanced exergy analyses, in order to reduce the energy consumption most efficiently, while strongly promoting cleaner production alternatives.

Two dimensional wavefront retrieval using lateral shearing interferometry

A new zonal two-dimensional method for wavefront retrieval from a surface under test using lateral shearing interferometry is presented. A modified Saunders method and phase shifting techniques are combined to generate a method for wavefront reconstruction. The result is a wavefront with an error below 0.7λ and without any global high frequency filtering. A zonal analysis over square cells along the surfaces is made, obtaining a polynomial expression for the wavefront deformations over each cell. The main advantage of this method over previously published methods is that a global filtering of high spatial frequencies is not present. Thus, a global smoothing of the wavefront deformations is avoided, allowing the detection of deformations with relatively small extensions, that is, with high spatial frequencies. Additionally, local curvature and low order aberration coefficients are obtained in each cell.

Primary total hip arthroplasty using a grit-blasted, press-fit femoral prosthesis.Long-term results with survivorship analysis.

This report presents the initial experience with the use of a grit-blasted, press-fit femoral prosthesis. The first 300 consecutive primary total hip arthroplasty procedures using a collarless, three-dimensional tapered, straight, titanium alloy stem with a grit-blasted surface (performed in 299 patients) were evaluated with independent clinical and radiographic follow-up examinations up to sixteen years. Eight different types of acetabular components, including a cementless all-polyethylene socket in 80 percent of the cases, were used. Radiographic evaluation, performed by an independent observer using a zonal analysis method, included assessment of component migration, Enghs implant-bone femoral fixation score, implant-bone demarcations, and periprosthetic osteolysis. The average duration of long-term radiographic follow-up was 12.6 years (range; 10 to 16 years). At last examination only five hips were lost to follow-up and 69 patients were deceased. The overall mechanical failure rate (i.e. unstable with or without revision) of the femoral component was 2 percent. The femoral revision rate was 7 percent (two hips for aseptic loosening, five hips for septic loosening, and twelve hips with osseointegrated stems for severe progressive femoral osteolysis) and the acetabular revision rate was 27 percent (revised for either socket migration or progressive peri-acetabular osteolysis or both). Survivorship, based on any revision (femoral or acetabular) was 89 percent at ten years and 62 percent at fourteen years; survivorship of the femoral component was 95 percent at ten years and 90 percent at fourteen years. The incidence of femoral periprosthetic osteolysis, by radiographic examination at ten years or more was 47 percent, including 12 hips (5 percent) with distal endosteal osteolysis. Femoral implant-bone fixation was stable, bone-ongrowth in 97 percent; stable, fibrous-fixation in 1 percent, and unstable, fibrous-fixation in 2 percent of the cases. The grit-blasted, press-fit, collarless, tapered femoral component continued to per-form well clinically and radiographically up to sixteen years of follow-up despite the challenging environment of periprosthetic osteolysis associated with the acetabular component design. The high incidence of failure among the cementless all-polyethylene sockets was not unexpected and the use of this acetabular implant was discontinued in 1985. While considered a "first-generation" cementless stem, this implant is still in use virtually without design modifications. This study demonstrates the durability of the results of the grit-blasted femoral component and indicates that such an implant offers a viable alternative for fixation without bone cement. (Hip International 2002; 2: 55-72).

Error inhomogeneity in the computation of spherical mean displacement

The traditional method for computing the mean displacement in latitude–longitude coordinates is a spherical meridional–zonal resultant displacement method (MRDM), which regards the displacement as the resultant vector of the meridional and zonal displacement components. However, there are inhomogeneity and singularity in the computation error of the MRDM, especially at high latitudes. Using the NCEP/NCAR long-term monthly mean wind and idealized wind fields, the inhomogeneity in the MRDM was accessed by using a great circle displacement computing method (GCDM) for non-iterative cases. The MRDM and GCDM were also compared for iteration cases by taking the trajectories from a three-time level reference method as the real trajectories. In the horizontal direction, the GCDM assumes that an air particle moves along its locating great circle and that the magnitude of the displacement equals the arc length of the great circle. The inhomogeneity of the MRDM is evaluated in terms of the horizontal distance error from the products of wind speed, lapse time, and angle difference from the GCDM displacement orient. The non-iterative results show that the mean horizontal displacement computed through the MRDM has both computational and analytical errors. The displacement error of the MRDM depends on the wind speed, wind direction, and the departure latitude of the air particle. It increases with the wind speed and the departure latitude. The displacement magnitude error has a four-wave pattern and the displacement direction error has a two-wave feature in the definition range of the wind direction. The iterative result shows that the displacement magnitude error and angle error of the MRDM and GCDM with respect to the reference method increase with the lapse time and have similar distribution patterns. The mean magnitude error and the angle error of the MRDM are nearly twice as large as those of the GCDM.

Enhanced zonal search algorithm for motion estimation in depth-map coding

This paper presents a novel motion estimation scheme for depth-map coding. Depth map has a couple of different characteristics compared with the common color scene, and therefore, careful investigation of the conventional fast motion search schemes is required. In this paper, I first provide the necessity of the depth-oriented motion search scheme based on experiments and then analyze the problems of the conventional methods. On the basis of the analysis, I propose to use the initial position refinement step during a motion search. In detail, the modification of the one-at-a-time search scheme is proposed for improvement of the prediction accuracy, and an initial direction selection and a 1-bit transform scheme follow for complexity reduction. The experimental results show that the proposed scheme can achieve coding gains of more than 3% on average over the state-of-the-art zonal search methods while keeping the overall complexity increase low.

STUDY OF MASS CONDUCTIVITY PROPERTIES OF SEEDS LAYER

Data on the mass conductivity coefficient have been obtained during drying the onion seeds in a thick layer of 5 mm thick ventilated on the surface, which were calculated by the zonal method on the basis of experimental curves of drying and heating. These data are described by the dependence of the mass conductivity coefficient on temperature and moisture content of the material. The comparison of the mass conductivity coefficient values for a layer and for single seeds is given, which shows that: 1) the mass conductivity coefficient in the layer changes significantly during drying, therefore, this change must be taken into account; 2) the change in the mass conductivity coefficient is due to its dependence on both moisture content and temperature, but the influence of temperature prevails over the influence of moisture content, therefore, themass conductivity coefficient increases during drying, 3) the mass conductivity coefficient in the layer is two orders of magnitude higher than for single seeds. The curve of seeds drying in a layer of 5 mm thick have been calculated using the obtained data on the mass conductivity coefficient for the process of oscillating infrared seeds drying carried out at a material temperature fluctuation in the range from tmin = 34 °C to tmax = 40 °C, which showed satisfactory agreement of the results of calculation and experiment. Experimental and calculated curves of oscillating infrared seeds drying in a layer of 5 mm thick are compared with analogous curves of drying the seeds in a monolayer, which showed that, despite the fact that the mass conductivity coefficient of seeds in a layer of 5 mm thick is two orders of magnitude greater than in a monolayer, the drying of seeds in the first case is slower because of the greater thickness of the layer. To calculate the kinetics of the process of oscillating infrared seeds drying in a dense layer, when its surface temperature oscillates in the range from tmin = 34 °C to tmax = 40 °C, the zonal method is recommended using the obtained data on the mass conductivity coefficient, taking into account the change in the mass conductivity during the process.Forcitation:Rudobashta S.P., Zueva G.A., Dmitriev V.M. Study of mass conductivity properties of seedslayer. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 72-77.

Exact multi-shear reconstruction method with different tilts in spatial domain

An improved zonal algorithm based on the multi-shear interferometry with different tilts is proposed to reconstruct two-dimensional wavefront exactly. The method allows large shear and high lateral resolution be achieved simultaneously. Due to environment vibration and mechanical misalignment, different tilt errors added in the measured wavefront will result in unknown and mismatch bias in the difference wavefronts. The effect of tilt errors in multi-shear method is analyzed and an improved zonal method is proposed to deal with tilt errors, which is easy to implement. Numerical simulations are executed and the results indicate that the improved algorithm is immune to tilt errors and has good noise suppression capabilities. In the experiment, we combine multi-shear method but using a Fizeau interferometer. The result demonstrates the effectiveness of the proposed algorithm.

Zonal wavefront reconstruction in quadrilateral geometry for phase measuring deflectometry.

There are wide applications for zonal reconstruction methods in slope-based metrology due to its good capability of reconstructing the local details on surface profile. It was noticed in the literature that large reconstruction errors occur when using zonal reconstruction methods designed for rectangular geometry to process slopes in a quadrilateral geometry, which is a more general geometry with phase measuring deflectometry. In this work, we present a new idea for the zonal methods for quadrilateral geometry. Instead of employing the intermediate slopes to set up height-slope equations, we consider the height increment as a more general connector to establish the height-slope relations for least-squares regression. The classical zonal methods and interpolation-assisted zonal methods are compared with our proposal. Results of both simulation and experiment demonstrate the effectiveness of the proposed idea. In implementation, the modification on the classical zonal methods is addressed. The new methods preserve many good aspects of the classical ones, such as the ability to handle a large incomplete slope dataset in an arbitrary aperture, and the low computational complexity comparable with the classical zonal method. Of course, the accuracy of the new methods is much higher when integrating the slopes in quadrilateral geometry.

A national assessment of underground natural gas storage: identifying wells with designs likely vulnerable to a single-point-of-failure

The leak of processed natural gas (PNG) from October 2015 to February 2016 from the Aliso Canyon storage facility, near Los Angeles, California, was the largest single accidental release of greenhouse gases in US history. The Interagency Task Force on Natural Gas Storage Safety and California regulators recently recommended operators phase out single-point-of-failure (SPF) well designs. Here, we develop a national dataset of UGS well activity in the continental US to assess regulatory data availability and uncertainty, and to assess the prevalence of certain well design deficiencies including single-point-of-failure designs. We identified 14 138 active UGS wells associated with 317 active UGS facilities in 29 states using regulatory and company data. State-level wellbore datasets contained numerous reporting inconsistencies that limited data concatenation. We identified 2715 active UGS wells across 160 facilities that, like the failed well at Aliso Canyon, predated the storage facility, and therefore were not originally designed for gas storage. The majority (88%) of these repurposed wells are located in OH, MI, PA, NY, and WV. Repurposed wells have a median age of 74 years, and the 2694 repurposed wells constructed prior to 1979 are particularly likely to exhibit design-related deficiencies. An estimated 210 active repurposed wells were constructed before 1917—before cement zonal isolation methods were utilized. These wells are located in OH, PA, NY, and WV and represent the highest priority related to potential design deficiencies that could lead to containment loss. This national baseline assessment identifies regulatory data uncertainties, highlights a potentially widespread vulnerability of the natural gas supply chain, and can aid in prioritization and oversight for high-risk wells and facilities.

Hybrid LES/RANS with wall treatment in tangential and impinging flow configurations

Scale-resolving simulation of high Reynolds number flows is a considerable numerical challenge. One approach to alleviate the matter is to relax near-wall resolution requirements of large eddy simulation (LES) with wall models or hybrid LES/Reynolds-averaged (RANS) methods. In-cylinder engine flows present a particular complexity as the process is inherently governed by wall tangential, wall normal and free shear flows with substantial temporal variation in Reynolds number and boundary layer gradients. In such conditions, robustness regarding wall-normal spacing would also be beneficial. Motivated by these factors, this study investigates the functionality of seamless and zonal hybrid LES/RANS methods in incompressible channel (Reτ=590) and impinging jet (ReD=23,000) flows using relatively coarse grids. Standard (Smagorinsky) and more recent (σ) subgrid-scale (SGS) models are utilized. As a novel contribution, we incorporate a recently developed RANS-based wall model in the zonal hybrid LES/RANS context with considerably coarser near-wall grids in the wall-normal direction. Results show (i) isotropy differences between the SGS models in both LES and hybrid LES/RANS cases and that (ii) the hybrid models mostly improve on corresponding LES results in terms of low-order statistics and wall friction. In addition, (iii) different hybrid implementations enhance different aspects of the solution, especially in the impinging jet flow. Results with the zonal method indicate only marginal interference with the core LES. Finally, (iv) combining zonal hybrid LES/RANS with the presented wall treatment provides favourable indications particularly in tangentially-dominated flow regions, while the complex jet stagnation region benefits from a moderately refined grid. This approach appears promising for decreased near-wall grid sensitivity in scale-resolving simulations.