Volumetric Term Research Articles

CFD Modeling of Film Condensation from a Steam-Air Mixture in Vertical Channels

Steam condensation in the presence of a noncondensable gas is of vital importance for passive cooling containment systems. The noncondensable gas causes a significant reduction in the condensation rate and heat transfer across the containment, which is important for postulated loss-of-coolant accidents in a nuclear reactor. In this work, computational fluid dynamics models of condensation and the adjacent single-phase steam-air mixture flow are developed for laminar and turbulent flow in vertical channels by two distinct wall condensation modeling approaches using the commercial code STAR-CCM+. The first is the fluid film model available in STAR-CCM+, which solves liquid layer governing equations with connections to the adjacent gas mixture flow. The second is a user-defined wall condensation model that neglects the fluid film and instead accounts for mass, momentum, and heat transfer via user-defined volumetric sink terms adjacent to the cold wall. The condensation models are assessed by first comparing the calculated results with the numerical solution of laminar flow, solved using a complete two-phase model that solves parabolic equations based on conservation of mass, momentum, energy, and species for each phase. Next, the results of a two-dimensional analysis are compared with COPAIN experiments and existing numerical solutions from three-dimensional analyses. The comparisons include new, detailed results that have not been reported in previous analyses of a COPAIN case. These new results include local field profiles of velocity, temperature, and air mass fraction, and local mass flux.

Information model for assessing the impact of tactical material procurement risks on order fulfillment in make-to-order manufacturing

Manufacturing businesses are showing increased interest in the issue of supply risks for materials and components. In recent decades, numerous studies and reviews have been published on the subject of supply chain risks. However, most research examines the global impact of risks on business as a whole and proposes a multi-level procedure for identifying, assessing, and developing risk mitigation measures, which should be carried out in advance with the involvement of specialists and experts. Nevertheless in maketo-order manufacturing, it is important to assess the risks of material supply for individual production orders, at the same time taking into account constant changes in production state and supply chains. The problem of assessing the risks of material supply gets even more complicated at enterprises with a high mix of manufactured products. To solve the above-mentioned problems, the authors propose an automated model for risks evaluation. The model is implemented as a component of the enterprise's information system (ERP) and uses data from the technological, production, inventory, and logistics modules to calculate the probability of deviation in order fulfillment time from the planned schedule due to potential disruptions in material supply chains. When executing the model, it analyzes the production's material requirements in both volumetric and calendar terms, inventory levels, and the condition of supply channels. The risks of delayed delivery for each material are expressed as the standard deviation of the delivery date from the planned date and are calculated by composing the risks for segments (elements) of the supply chain, the risks for which are, in turn, calculated based on performance data accumulated in the logistics module, with the possibility of introducing correction coefficients and expert evaluations. The overall risk of order material supply is determined by summing up the delivery risks of individual materials, expressed as the corresponding standard deviations. The model's results can be used for managerial decision-making in production and procurement or for communicating expected order fulfillment times to customers. The model has been tested at an enterprise in the electrical engineering industry.

Validation of an experimentally-based heat source for flash heating modeling of directed energy deposition: Systematic study of process and simulation parameters

Computational prediction of the temperature history during directed energy deposition (DED) is a fundamental input for the subsequent numerical analysis of microstructural characteristics and thermomechanical response. In order to allow for industrial implementation of such simulations, the development of computationally efficient methods taking advantage of multi-scaling techniques is needed. This work provides a new formulation for the flash heating (FH) method to be applied when modeling DED. As with other FH methods, this formulation ensures energy conservation when defining the volumetric heat source term, however, in the present case, the actual deposited cross-sectional area obtained from experiments is used instead of hatch spacing and layer thickness as usually done in FH methods for laser powder bed fusion (LPBF). A new feature of the model is that the high-resolution cross-sectional area of the multi-layer geometry is extracted from optical micrographs, resulting in a curvilinear top surface of every track. The method is validated through comparison with experimental monitoring data and provides valuable information regarding cooling rates, development of the molten area, and heat accumulation when varying process parameters within relevant limits. The influence of varying simulation parameters, such as the partitioning of the geometry and the time used for heating (contact time), on computational cost and accuracy is moreover studied. It is found that a very short contact time is mandatory to ensure the melting of the geometry and, consequently, the proper evaluation of cooling rates and thermal gradients.

Investigation of multi-scale flow structures and combustion characteristics in a cavity-enhanced circular scramjet

This study delves into the investigation of multi-scale flow structures and combustion characteristics in a cavity-enhanced circular scramjet operating under a Mach-4.5 freestream flow condition with a total temperature of 2200 K and a total pressure of 164 kPa. To achieve this, a hybrid large-eddy/Reynolds-averaged Navier-Stokes method, coupled with a pressure-corrected Flamelet/Progress Variable model, is employed and validated. The combustion flow field shows abundant small- and medium-scale flow structures induced by compressibility and combustion heat release. Vorticity alteration is found to be mainly caused by these factors, with the volumetric expansion term and baroclinic term serving as the primary driving terms. The whole combustion process is characterized by zoning and multi-scale features in spatial, temporal, heat release and species distribution, arising from differences in fuel-air mixing state and chemical reaction rates in the flow field. The injection-formed bow shock and the cavity ramp-formed compression wave interact intensively with the fuel plume, enriching the turbulent structures and strongly coupling with the chemical reaction process. The cavity not only promotes fuel-air mixing and combustion, but also facilitate the rapid transition from the laminar-like flame to thickened turbulent combustion. Statistical analysis reveals that the combustion heat release is predominantly governed by the scramjet mode and the diffusion flames, and further demonstrates the multi-scale flow and chemical reaction characteristics. Most of the combustion flow field is observed to be governed by fast chemistry, primarily in the corrugated flamelet regime, while some slow chemistry zones are also identified, lying in the distributed reaction zone regime.

A 0D parallel transport model for varying density regimes for use in 2D drift‐fluid turbulence codes

AbstractIn this paper, a new model of the parallel transport in 2D drift‐fluid turbulence codes is formulated as a 3‐point model and benchmarked against SOLPS‐ITER. The model allows for the existence of parallel temperature gradients and local recycling near the target. To realize this, the volume of the flux tube is split into two zones: (1) a connection zone extending from the outer midplane to the ionization zone entrance and (2) an ionization zone covering the remaining space until the sheath edge. By assuming a linear increase of the parallel particle and conductive heat fluxes in the connection zone, and assuming an ad‐hoc relation for the electron pressure evolution, expressions for the plasma fields at the entrance of the ionization zone are obtained. The evaluation of the integral balances over the ionization zone leads to an implicit system in terms of the parallel fluxes. To benchmark the model, we compare with reference data from density, current and recycling scans for a flux tube with SOLPS‐ITER. From these scans, one observes that the model predicts well the parallel particle flux in the density and recycling scans. Discrepancies that arise at higher densities for both the conductive heat fluxes and the required floating upstream potential are analyzed and partly explained by the superlinear evolution of the heat fluxes in the SOLPS‐ITER simulations. It is concluded that the model can be used to construct the effective volumetric sink terms in 2D drift‐fluid turbulence models.

Natural convection–thermal radiation interaction in a non-Newtonian nanofluid-filled square cavity with a conductive baffle

This research aims to investigate the combination of natural convection and surface and volumetric radiation in water-aluminum oxide nanofluid with non-Newtonian effects in a square cavity with a conductive baffle on its hot wall. The left wall is hot while the right one is cold. Moreover, the horizontal walls are insulated, and the internal walls are radiatively active. The mass, momentum, and energy conservation equations are solved numerically using the control-volume-based finite difference method and the SIMPLE algorithm considering the surface radiation for the interior surfaces of the cavity and volumetric radiation for the non-Newtonian nanofluid. The volumetric radiation term in the energy equation is approximated using the Rosseland method. The effect of the Rayleigh number (Ra), the power-law index, and the volumetric radiation parameter on the flow field and the heat transfer rate are investigated using the numerical analysis results. Based on the results, an increase in Ra and a decrease in the power-law index lead to a rise in the heat transfer rate at a constant radiation parameter. As the Ra rises in the range, the average Nusselt number increases to 10 times at n = 0.8. Moreover, a rise in the volumetric radiation parameter increases the radiative Nusselt number and decreases the convective Nusselt number in both shear thickening and shear thinning fluids, although it increases the overall Nu. Increasing the volumetric radiation parameter from 0 to 2 enhances the average Nusselt number by more than 2.5 times at Ra = 103 and less than 2 times at Ra = 105.

Consistent C-bar radial-basis Galerkin method for finite strain analysis

For finite-strain problems of quasi-incompressible materials, with hyperelastic and hyperelasto-plastic behavior, we develop a mixed polynomial-enriched radial-basis function (RBF) interpolation. It is characterized by decoupling quadrature and polynomials for the deviatoric and volumetric terms of the right Cauchy–Green tensor. With an enriched interpolation, first and second derivatives of the deformation gradient are continuous. A finite-element mesh is employed for quadrature purposes with the corresponding distribution of Gauss points. In terms of discretization, linear, quadratic and cubic polynomials are combined and function support is established from the number of pre-assigned nodes. Due to the adoption of a Lagrangian kernel, finite strain elasto-plastic constitutive developments are based on the Mandel stress. Combined with the C¯ technique, these developments are found to be convenient from an implementation perspective, as RBF formulations for finite strain plasticity have been limited in terms of generality and amplitude of deformations in the quasi-incompressibility case. Three benchmark tests are successfully solved, and it was found that a combination of reduced integration with a deviatoric cubic basis and volumetric quadratic basis provides superior results in the quasi-incompressible case. Numerical testing shows very good convergence behavior of the results. Besides absence of locking with selective interpolation, outstanding Newton convergence was observed regardless of strain levels.

Energetic contributions to deformation twinning in magnesium

Modeling deformation twin nucleation in magnesium has proven to be a challenging task. In particular, the absence of a heterogeneous twin nucleation model which provides accurate energetic descriptions for twin-related structures indicates a need to more deeply understand twin energetics. To address this problem, molecular dynamics simulations are performed to follow the energetic evolution of tension twin embryos nucleating from an asymmetrically-tilted grain boundary. The line, surface and volumetric terms associated with twin nucleation are identified. A micromechanical model is proposed where the stress field around the twin nucleus is estimated using the Eshelby formalism, and the contributions of the various twin-related structures to the total energy of the twin are evaluated. The reduction in the grain boundary energy arising from the change in character of the prior grain boundary is found to be able to offset the energy costs of creating the other interfaces. The defect structures bounding the stacking faults that form inside the twin are also found to possibly have significant energetic contributions. These results suggest that both of these effects could be critical considerations when predicting twin nucleation sites in magnesium.

Current Research on Green Ammonia (NH3) as a Potential Vector Energy for Power Storage and Engine Fuels: A Review

Considering the renewable electricity production using sustainable technologies, such as solar photovoltaics or wind turbines, it is essential to have systems that allow for storing the energy produced during the periods of lower consumption as well as the energy transportation through the distribution network. Despite hydrogen being considered a good candidate, it presents several problems related to its extremely low density, which requires the use of very high pressures to store it. In addition, its energy density in volumetric terms is still clearly lower than that of most liquid fuels. These facts have led to the consideration of ammonia as an alternative compound for energy storage or as a carrier. In this sense, this review deals with the evaluation of using green ammonia for different energetic purposes, such as an energy carrier vector, an electricity generator and E-fuel. In addition, this study has addressed the latest studies that propose the use of nitrogen-derived compounds, i.e., urea, hydrazine, ammonium nitrate, etc., as alternative fuels. In this study, the possibility of using other nitrogen-derived compounds, i.e., an update of the ecosystem surrounding green ammonia, has been assessed, from production to consumption, including storage, transportation, etc. Additionally, the future challenges in achieving a technical and economically viable energy transition have been determined.

An analytical study of coupled convective heat and mass transfer with volumetric heating describing sublimation of a porous body under most sensitive temperature inputs: Application of freeze-drying

Sublimation heat-mass transfer has great applications in the pharmaceutical and food industries, such as the preservation of biological products, accelerated freeze-drying (AFD), energy storage systems, microwave freeze-drying, and enabling long-time active covid like vaccines. The current technological demand encourages investigators to provide new knowledge for freeze-drying so that it reduces the high economic cost, prevents materials from being denatured, and remains stable for a long time. In connection with this, it is of key interest to analyze the impact of convective heat and mass transfer, the rate of water vaporization, and the volumetric heating source under the most realistic temperature inputs. Despite the available works on sublimation, there is still a lack of mathematical modeling that accounts for these informations together and is presently being considered. This paper presents a heat and mass transfer problem describing sublimation in a half-porous space. The mathematical model accounts for convective heat/mass transfer and a volumetric heat source within dried and frozen regions. In addition, convection driven by the mass transfer of ice crystals within the dried region is also considered. Three different types of temperature input are placed at the surface x=0 to obtain the rapid sublimation process without harming the material properties. The exact solution to the problem is obtained successfully by using similarity transformation. The impact of various problem parameters on sublimation is comprehensively studied. In this study, it is found that with a volumetric heating source term G0, material sublimates faster than without one. Furthermore, convective heat transfer in terms of Pe1 and Pe2, enhances the temperature within the porous medium, and as a result, material sublimates faster than usual. As the value of the convective term β goes up, a reduction in the temperature field is observed. The temperature of the medium rises as the value of the Kirpichev-like number Ki increases. Similar observation is found in the case of Biot like number Bi. The concentration profile decreases as the value of the Luikov number Lu increases. It is also found that Newton-type temperature input offers a faster sublimation rate in comparison to constant and flux-type temperature input. The analytical results obtained in this study show excellent agreement with previous available results. These results provide a comprehensive theoretical and mathematical understanding of sublimation heat/mass transfer and are expected to be useful in energy storage systems, food technology, and accelerated freeze drying.

Quantitative self-verification, a breakthrough in ultrasonic metering technology

The accuracy of ultrasonic metering technology has advanced to a level that it is now the technology of choice in many custody transfer and fiscal applications. With meters capable of meeting the accuracy requirements of these applications when initially calibrated, end-user attention has moved to the diagnostic capability of these meters. Diagnostics are now commonly used to increase the confidence of the user that the meter is functioning accurately between calibrations, which could be a year apart or even longer. Although current ultrasonic meter diagnostics are very powerful, they are qualitative in nature, i.e. they provide an indication if something is wrong or has changed, but they have not yet been able to quantify the possible range of error, correctly termed the ‘measurement uncertainty’. This paper presents new technology that has been developed to equip ultrasonic flowmeters with additional measurement data that is used to quantify the uncertainty in the meter’s output. This capability reduces the complexity of diagnostic monitoring, as the result can be monitored as an uncertainty in volumetric or percentage terms, and hence, it allows for quick and simplified decision making. The paper presents the fundamentals of the new self-verifying technology and the testing that has been conducted to validate the uncertainty output provided by the meter. This includes an independent technology qualification evaluation conducted by DNV where the meter was subjected to a variety of real-world upset conditions and the meter performance and uncertainty output were compared with reference data from traceable test facilities.

Continuous-Energy Time-Dependent Coarse Mesh Transport (COMET) Method for Kinetics Calculations

In this paper, the novel continuous-energy coarse mesh transport (COMET) method is extended to perform time-dependent neutronics calculations in highly heterogeneous reactor core problems. In this method, the time-dependent transport equation is converted into a series of steady-state transport equations by estimating the time derivative term using implicit finite differencing. The resulting steady-state transport equations, having additional terms that are imbedded in the total collision term and in the volumetric source terms, are then solved by the steady-state COMET method, in which all the phase-space variables, including energy, are treated continuously. Finally, the fission density distribution constructed by the steady-state COMET is used to solve a set of ordinary differential equations to obtain the delayed neutron precursor concentrations. The time-dependent COMET method is benchmarked against a direct continuous-energy Monte Carlo method (i.e., MCNP) in a set of infinite homogeneous problems and a set of single-assembly benchmark problems consisting of identical pin cells. It is found that the COMET results agree very well with the Monte Carlo reference solutions while maintaining its formidable computational speed (orders of magnitude faster than the Monte Carlo method).

A hydro-mechanical phase field model for hydraulically induced fractures in poroelastic media

This paper presents a hydro-mechanical phase field model that integrates the unified phase field fracture theory and Biot's theory, emphasizing the correction of the volumetric strain term in the fluid mass conservation equation. After numerically implementing the multi-field finite element method, the proposed model is validated using examples with analytical solutions. The model accurately predicts fluid pressure, crack width, and crack length while capturing complex fracture behaviors, such as crack merging and non-planar propagation. The study reveals that the physical meaning of the volumetric strain in the fractured domain is the volume change of the space for fluid storage, and confirms the importance of considering the volumetric strain term in the fractured domain, as ignoring it can severely underestimate the injection volume required for fracturing. The proposed hydro-mechanical coupling method is also shown to be superior to previous methods, as it accurately simulates the relationship between crack width variation and pressure, and avoids the incorrect effective stress resulting from the assumption that the Biot coefficient equals the porosity. Overall, this study provides an effective tool for predicting the fracture process and essential insights into hydro-mechanical phase field modeling.

Transient heat transfer and electro-osmotic flow of Carreau–Yasuda non-Newtonian fluid through a rectangular microchannel

PurposeThe purpose of this study is to investigate heat transfer and electrokinetic non-Newtonian flow in a rectangular microchannel in the developed and transient states.Design/methodology/approachThe Carreau–Yasuda model was considered to capture the non-Newtonian behavior of the fluid. The dimensionless forms of governing equations, including the continuity equation for the Carreau–Yasuda fluid, are numerically solved by considering the volumetric force term of electric current (DC).FindingsThe impact of pertinent parameters such as electrokinetic diameter (R), Brinkman number and Peclet number is examined graphically. It is observed that for increasing R, the bulk velocity decreases. The velocity of the bulk fluid reaches from the minimum to the maximum state across the microchannel over time. At the electrokinetic diameter of 400, the maximum velocity was obtained. Temperature graphs are plotted with changes in the various Brinkman number (0.1 < r < 0.7) at different times, and local Nusselt are compared against changes in the Peclet number (0.1 < ℘e < 0.5). The results of this study show that by increasing the Brinkman number from 0.25 to 0.7, the temperature along the microchannel doubles. It was observed that increasing the Peclet number from 0.3 to 0.5 leads to 200% increment of the Nusselt number along the microchannel in some areas along the microchannel. The maximum temperature occurs at Brinkman number of 0.7 and the maximum value of the local Nusselt number is related to Peclet number 0.5. Over time in the transient mode, the Nusselt number also decreases along the microchannel. By the increasing of time, the temperature increases at given value of Brinkman, which is insignificant at Brinkman number of 0.1. The simulation results have been verified by Newtonian and non-Newtonian flows with adequate accuracy.Originality/valueThis study contributes to discovering the effects of transient flow of electroosmotic flow for non-Newtonian Carreau–Yasuda fluid and transient heat transfer through rectangular microchannel. To the authors’ knowledge, the said investigation is yet not available in existing literature.

Impacts of trees-grass area ratio on thermal environment, energy saving, and carbon benefits

Rapid urbanization potentially increases the diversity of building morphological characteristics (e.g., heights), causing urban ecological environment problems, such as urban heat islands, energy loss, and carbon emissions. Greenery (e.g., trees and grasses) can alleviate urban environmental problems, further improving the benefits of cooling effect, energy saving, and carbon emission reduction. With limited land resources, it is significant to effectively combine multiple greeneries and quantitatively optimize the greenery design. This paper designed the trees-grass area ratio (TAR) and explored its effect on the benefits at the community scale. The ranges of 0–90% TARs were considered in the communities as well as three building heights. A low-cost computational fluid dynamics (CFD) method of volumetric source term (VST) was proposed to simulate the thermal environment. Energy performance simulation of buildings was performed. Results indicated that the VST method can reduce computing costs by up to 81% compared with the traditional simulation. Air temperature (T), energy consumption (E), and carbon emission (Ce) decreased with increasing TAR in three types of communities. Carbon sequestration (Cs) linearly increased with increasing TAR. When the TAR was 90%, the maximum reduction of T, E, and Ce were 6 °C, 17.3%, and 20%, respectively. Furthermore, the quantified relationships between TAR, building height, and benefits were proposed. This work can serve as a guideline for the optimal design of urban ecological environment.

A Novel Decomposition Approach Preventing Spurious Entropy Generation in Hybrid Thermoacoustic Stability Computations

Abstract Prominent approaches for the computation of thermoacoustic stability are hybrid methods like the linearized Navier–Stokes equations (LNSE) or the linearized Euler equations (LEE). The transient fluctuations around a precomputed steady-state mean flow field solved with these sets of equations naturally include the energy transition between acoustic, vertical, and entropic modes. It is common practice to account for flame-acoustic interactions by applying measured or computed flame transfer functions (FTF) as a volumetric source term proportional to the mean heat release rate in the energy equation. However, the underlying assumption of a static flame is the root cause of spurious entropy production, which may ultimately falsify the thermoacoustic stability predictions. In the present paper, a methodology to include arbitrary flame movement in the governing set of equations is presented. The procedure makes use of an arbitrary Lagrangian-Eulerian (ALE) description of conservation equations and is demonstrated for the Euler equations. The resulting set of linear perturbation equations is then applied to two test cases. First, the frequency response of a one-dimensional premixed air-methane flame is evaluated. Secondly, the frequency response of the first longitudinal eigenmode of an experimental premixed, swirl-stabilized combustor is computed. To demonstrate the reduction of spurious entropy waves, the results are compared to those of the classic LEE.

Properties of aerosol and surface derived from OLCI/Sentinel-3A using GRASP approach: Retrieval development and preliminary validation

The Ocean and Land Color Instrument (OLCI) onboard the Copernicus Sentinel-3A satellite is a medium-resolution and multi-spectral push-broom imager acquiring radiance in 21 spectral bands covering from the visible to the far near-infrared. These measurements are primary dedicated to land & ocean color applications, but actually include also reliable information for atmospheric aerosol and surface brightness characterization. In the framework of the EUMETSAT funded study to support the Copernicus Program, we describe the retrieval of aerosol and surface properties from OLCI single-viewing multi-spectral Top-Of-Atmosphere (TOA) radiances based on the Generalized Retrieval of Atmosphere and Surface Properties (GRASP) algorithm. The high potential of the OLCI/GRASP configuration stems from the attempt to retrieve both aerosol load and surface reflectance simultaneously using a globally consistent high-level approach. For example, both over land and ocean surfaces OLCI/GRASP uses 9 spectral channels (albeit with different weights), strictly the same prescribed aerosol models and globally the same a priori constraints (though with some differences for observations over land and ocean). Due to the lack of angular multi-viewing information, the directional properties of underlying surface are strongly constrained in the retrieval: over ocean the Fresnel reflection together with foam/whitecap albedo are exclusively computed using a priori wind speed; over land, the Bidirectional Reflectance Distribution Function (BRDF) is slightly adjusted from a priori values of climatological Ross-Li volumetric and geometric terms. Meanwhile, the isotropic reflectance is retrieved globally under mild spectral smoothness constraints. It should be noticed that OLCI/GRASP configuration employs innovative multi-pixel concept (Dubovik et al., 2011) that enhance retrieval by simultaneously inverting large group of pixels. The concept allows for benefiting from knowledge about natural variability of the retrieved parameters.The obtained OLCI/GRASP products were validated with the Aerosol Robotic Network (AERONET) and Maritime Aerosol Network (MAN) and intercompared with the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and surface products. The overall performance is quite comparable to the community-referenced MODIS. Over ocean the OLCI/GRASP results are encouraging with 67% of the AOD (550 nm) satisfying the Global Climate Observing System (GCOS) requirement using AERONET coastal sites and 74% using MAN deep ocean measurements, and an AOD (550 nm) bias 0.01 with AERONET and nearly zero bias with MAN. Over land, 48% of OLCI/GRASP AOD (550 nm) satisfy the GCOS requirement and a bias within ±0.01 for total and AOD < 0.2. Key challenges are identified and discussed: adequate screening of cloud contaminations, retrieval of aerosol over bright surfaces and in the regions containing complex mixtures of aerosol.

Energy-Based Aerodynamic Analysis on the Blended-Wing-Body Aircraft with Boundary Layer Ingestion

This study is aimed at evaluating the energy saving benefit and its limitation of the boundary layer ingestion (BLI) applied to a transonic blended-wing-body (BWB) aircraft. The power balance method is adopted in the aerodynamic performance analysis of the aircraft. We further improve the one-dimensional analysis framework by adding the pressure volumetric work term in the power balance equation for the application in compressible flow with shock wave regions. A determining expression for the power-saving coefficient (PSC) of the BLI effect is also deduced, which is related to a BLI fraction, the airframe dissipation component ratios, and the specific thrust of the propulsor. This expression provides a way for the preliminary evaluation and comparison of BLI benefits applied in different aircraft configurations. The flow quantities of three different configurations are obtained by 3D Reynolds-averaged Navier–Stokes (RANS) numerical simulations for the calculation of aerodynamic dissipation components. The grid refinement and domain size study shows that the calculated force coefficients and total dissipation coefficient have a good convergence characteristic with the mesh refinement and are insensitive to the variation in domain size. The evaluated PSC of the BWB aircraft with a BLI propulsor is 5% using the previously developed determining expression. The maximum of PSC is 18.8%. The following comparison of dissipation components for the power-on and power-off cases shows that the benefit of BLI is slightly underestimated by the determining expression of PSC. The reason is that the variation in the boundary layer velocity profile at the trailing edge of the center body part is neglected, which is due to the installation of the propulsor. Furthermore, when the BLI propulsor is applied to a BWB aircraft, the variation in trailing edge vortex dissipation and volumetric pressure work term should be studied in detail.

A thermal finite element model with efficient computation of surface heat fluxes for directed-energy deposition process and application to laser metal deposition of IN718

In this study, a numerically efficient thermal finite element process model is developed to predict the melt-pool characteristics of directed-energy deposition (DED) process. The model uses a new technique to compute the effective surface heat loss terms in the form of a volumetric heat sink term in order to avoid the redefinition of surface heat fluxes from the free-surfaces after addition of every layer. In addition, thermal model incorporated the heat losses due to evaporation and Marangoni effect by changing the conductivity at the liquid state. The melt pool dimensions of IN718 were experimentally measured by in-situ thermal monitoring and by ex-situ optical microscopy of the cross-sections of the deposited tracks. The proposed model accurately predicts the experimental melt-pool dimensions of single-track and multi-layer depositions over the range of process parameters.

A Comparative Study on the Behavior of Ride Quality Due to Deflated State of Air Spring Using Different Properties of Hyperelastic Material

Elastomers are widely used in various engineering applications due to their huge elasticity and good dynamic behavior. One of the elastomeric elements is rubber blocks, which are used in many applications, such as vibration isolators, bumpers, shock absorbers, dampers, etc. In this research, the impact on the ride index due to the deflated state of the air spring with various kinds of hyperelastic materials is analyzed by the finite element method. The stress–energy function of rubber materials is first diagnosed, and Poisson’s ratio defined the volumetric terms. The rubber isolator’s stress is studied based on the finite element model, and the structure is improved. It is observed that for the deflated state of the air spring, laminated rubber isolation diminishes the muscular amount of structural responses compared to the conventional rubber base structures, and improves the ride comfort. This study would assist in doing finite element analysis of the secondary suspension system and other vibration-damping components.