Mesh Size Research Articles

A damage constitutive model for concrete under uniaxial compression capturing strain localization

This paper presents a damage constitutive equation capturing the feature of strain localization and, on this basis, proposes a novel damage constitutive model for concrete under uniaxial compression. It is found that the proposed model can better simulate the stiffness degradation behavior of concrete under cyclic loading, well reproduce the dependency of the post-peak stress-strain curve on specimen or measuring length under monotonic loading, and provide FE simulation results that are insensitive to mesh size. Influence of the maximum aggregate size on the strain localization zone length is discussed.

An adaptive finite element method for distributed elliptic optimal control problems with variable energy regularization

We analyze the finite element discretization of distributed elliptic optimal control problems with variable energy regularization, where the usual L2(Ω) norm regularization term with a constant regularization parameter ϱ is replaced by a suitable representation of the energy norm in H−1(Ω) involving a variable, mesh-dependent regularization parameter ϱ(x). It turns out that the error between the computed finite element state u˜ϱh and the desired state u‾ (target) is optimal in the L2(Ω) norm provided that ϱ(x) behaves like the local mesh size squared. This is especially important when adaptive meshes are used in order to approximate discontinuous target functions. The adaptive scheme can be driven by the computable and localizable error norm ‖u˜ϱh−u‾‖L2(Ω) between the finite element state u˜ϱh and the target u‾. The numerical results not only illustrate our theoretical findings, but also show that the iterative solvers for the discretized reduced optimality system are very efficient and robust.

No deleterious circumference effects for T90 codends in an Australian fish trawl targeting tiger flathead, Platycephalus richardsoni

In an attempt to improve the selectivity of Australian fish trawls targeting tiger flathead, Platycephalus richardsoni (≥28 cm total length), the utility of four-seam codends with shortened lastridge ropes and comprising 71-mm meshes turned 90° (T90) hung at the narrowest and widest coherent circumferences was compared against a traditional 91-mm diamond-mesh (T0) codend. Significant effects of codend configuration were limited to an increase in the catches of another commercially important species, latchet, Pterygotrigla polyommata, by both T90 codends, and greater escape of some small tiger flathead from the wide 71-mm T90 codend than from the 91-mm T0 codend. Notwithstanding a need to investigate slightly larger T90 mesh sizes for the fishery, the data imply that unlike most codend configurations, circumference does not negatively affect selection in the stated designs and might not require future regulation.

Demonstrating scale-up of a novel water treatment process using super-bridging agents

Fiber-based materials have emerged as a promising option to increase the efficiency of water treatment plants while reducing their environmental impacts, notably by reducing the use of unsustainable chemicals and the size of the settling tank. Cellulose fiber-based super-bridging agents are sustainable, reusable, and versatile materials that considerably improve floc separation in conventional settling tanks or via alternative screening separation methods. In this study, the effectiveness of fiber-based materials for wastewater treatment was evaluated at lab-scale (0.25 L) and at pilot-scale (20 L) for two separation methods, namely settling and screening. For the fiber-based method, the performance of floc separation during settling was slightly affected by an 80x upscaling factor. A small decrease in turbidity removal from 93 and 86 % was observed for the jar and pilot tests, respectively. By contrast, the turbidity removal of the conventional treatment, i.e., no fibers with a settling separation, was largely affected by the upscaling with turbidity removals of 84 and 49 % for jar and pilot tests, respectively. Therefore, results are suggesting that fiber-based super-bridging agents could be implemented in full-scale water treatment plants. Moreover, the tested fibers increase the robustness of treatment by providing better floc removal than conventional treatment under several challenging conditions such as low settling time and screening with coarse screen mesh size. Furthermore, at both lab-scale and pilot-scale, the use of fiber-based materials reduced the demand for coagulant and flocculant, potentially lowering the operational costs of water treatment plants and reducing the accumulation of metal-based coagulants and synthetic polymers in sludge. Acute toxicity tests using the model organism Daphnia magna show that the cellulose fibers introduce insignificant toxicity at the optimized fiber concentration. Although dedicated mechanistic studies are required at various scales to understand in detail the influence of fibers on water treatment (coagulation/flocculation time, floc formation, floc size distribution velocity gradient, etc.), the efficacy and scalability of the fiber-based approach, along with its minimal environmental impact, position it as a viable and sustainable option for existing and future wastewater treatment plants.

Investigation of the impact of near-wall mesh size on the transition from microscopic wall boiling mechanism to macroscopic multiphase-CFD models

CFD method enables high-fidelity investigation of complex systems. Numerous sensitivity studies on boiling sub-models improve the applicability and reliability of the multiphase-CFD approach. These studies recommend that the mesh size near the wall should typically be large. A multiphase-CFD model for subcooled flow boiling in a tube was developed to investigate the impact of near-wall mesh size on calculation results. Five distinguished scale meshes were employed to evaluate the effect of mesh scale on the transition from microscopic wall boiling mechanism to macroscopic multiphase-CFD models. A more reliable multiphase-CFD thermal phase change model that accounts for superheated liquid layer evaporation was also developed based on the Lee model. The calculation results indicate that the near-wall mesh size is numerically robust in predicting wall temperature but significantly influences the heat flux partitioning. Smaller mesh sizes produce higher evaporation heat flux and a more significant increase in the deviation of liquid temperature from the saturation temperature, which leads to an incorrect reliance on the condensation model to calculate superheated liquid evaporation. This is why a larger mesh size is typically recommended in previous sensitivity studies. Applying the developed model presented in this paper can ensure that the deviation between the liquid temperature and the saturation temperature of the cell adjacent to the wall remains within acceptable limits. The void fraction displays a substantial mesh sensitivity, and as the mesh size decreases, the OSV (Onset of Significant Void) moves forward. However, the maximum mean void fraction remains unaffected by mesh size. The results of this research can provide valuable insights into the development of more accurate and reliable CFD models for subcooled flow boiling.

Stock Evaluation of the Euryhaline Cichlid, Etroplus suratensis (Bloch, 1790), from Significant Brackish and Freshwater Regions of India

The present study evaluates stocks of Etroplus suratensis concerning length-weight relationships (LWRs), condition factor (K), and truss analysis from different habitats, viz., West Bengal (freshwater hatchery), Gujarat (brackish water grow-out pond), and Odisha (Chilika lagoon) in India. All the stocks were collected using gill nets with various mesh sizes of 20–50 mm and cast nets with mesh size of 15 mm from February 2021 to September 2021. The total length (L), weight (W), and digital pictures were taken for LWRs and principle component analysis (PCA). The total length (L) and total weight (W) were measured to the nearest 0.1 cm and 0.01 gm, respectively, followed by regression analysis. The values of parameters “b” in the LWRs equation were estimated within the range of 2.50–3.82 and intercept “a” values (0.235–0.779) and “K” (1.07–3.37), respectively, for all different habitats and ecosystems with significant correlation values (R2 ≥ 0.85). In truss morphometric analysis, principal component 1 (PC1) contributed the highest (93.1%) and principal component 2 (PC2) contributed 4.6% to the size and shape variation amongst the stocks from different habitats and ecosystems. The scatter plot analysis and canonical variate analysis (CVA) have shown that the Gujarat and West Bengal stocks are closely placed and separated from the Chilika-Odisha stock. Similar variations were also observed in the ANOSIM boxplot analysis, where Chilika-Odisha stock scored higher than the other two stocks. Since data available regarding LWRs and truss morphometry studies of E. suratensis from different habitats are limited, the present study will provide a clear insight into the differentiation of E. suratensis stocks from different habitats in India. The overall findings of the present study could be utilized for the conservation and sustainable management of E. suratensis.

Increasing trammel mesh size reduces biomass removal, mitigates discards and increases economic revenue in artisanal fisheries

Small-scale fishing plays a major role in regional economies worldwide and, with a large number of small vessels involved, it provides employment and livelihood to coastal communities. Generally recognized as more selective than other fishing practices, small-scale fishery can nevertheless be subjected to high rates of discards of both non-target species and small-sized individuals, which in turn could lead to both decreased incomes for fishers and increased depletion of fish stocks. However, if the relationship between fish size and price has long been assessed, the effect of enhanced size-selectivity of fishing gears and consequent economic gains has been little investigated. This study, set in the Porto Cesareo Marine Protected Area (Italy, Ionian Sea), aimed at testing effective strategies to improve trammel net selectivity, reducing discards and maximizing the income for fishers. Different mesh sizes (20, 22 and 24 mm) trammel nets were employed. The study consisted in 72 fishing days from July 2012 to September 2013 and each day involved experimental fishing with the three mesh sizes. A total of 16008 specimens (103 species) were collected but the analysis focused on the 18 most common species in the area for a total of 12782 individuals. Mesh size trammel nets of 20 mm and 22 mm yielded most of the biomass, 324.8 and 321.5 kg respectively, while the 24 mm mesh yielded 280.7 kg. The 24 mm mesh, even if accounted for lower income compared to the 22 mm mesh (2383.9 € vs 2590.5 €, respectively), provided significant 50% reduction of discards compared to the 20 and 22 mm mesh. The use of 24 mm mesh size was found to be an effective strategy to reduce the number of discarded organisms and, consequently, the pressure exerted on local fish stocks with associated higher revenue for fishers. The results of this study demonstrated that trammel net selectivity can improve and support conservation measures and concurrently increase profitability of local fishery.

Use of effective multiscale cohesive models in the simulation of spall in metal plates

AbstractDuctile fracture of metals is the net result of void nucleation, growth and coalescence mechanisms that operate at the microscale. Optimal scaling analysis provides the analytical form of the effective material law that models the ductile fracture phenomena at the macroscale. The upscaled model of ductile behavior assumes the form of a cohesive relation—surface traction versus displacement—of the power‐law type with well‐defined exponents. In the present work, we demonstrate how the effective cohesive law derived from optimal scaling can be conveniently inserted into macroscale calculations by recourse to cohesive elements. The plastic deformation outside the cohesive elements is of moderate size and can be modeled by means of conventional plasticity models. In particular, the mesh size is dictated by accuracy considerations at the macroscale structural level and is not in any way constrained by microscale features and mechanisms, which happen at the subgrid level and are accounted for by the effective cohesive law. We illustrate the multiscale paradigm by means of spall calculations.

Ghost Fishing Threatens Biodiversity in an African Great Lake

We conducted an investigation into ghost fishing, a phenomenon in which abandoned fishing equipment remains operational for extended durations, in the southern region of Lake Tanganyika, Republic of Zambia. The perils associated with ghost fishing have achieved international recognition; however, there exists a conspicuous dearth of scholarly investigations in particular regions, notably inland aquatic environments and developing countries. Employing scuba diving for field observations, we discovered that ghost fishing was solely evident in monofilament nylon nets, despite the presence of four different net types in the littoral area of the lake. Notably, endemic crabs Platythelphusa armata and P. maculata from Lake Tanganyika constituted 65.2% of the organisms captured by abandoned nets, with the remainder comprising various fish species. The number of captured organisms exhibited a dependence on the interplay between the length and mesh size of the abandoned nets, indicating that the risk of ghost fishing is heightened when both net and mesh size are substantial. Furthermore, we encountered predatory Spiny Eels Mastacembelus moorii ensnared in nets around their jaws and teeth. Intriguingly, the digestive tract of one of the Spiny Eels contained a partially digested cichlid species entangled in the same nets, strongly suggesting the occurrence of secondary ghost fishing.

High-order splitting finite element methods for the subdiffusion equation with limited smoothing property

In contrast with the diffusion equation which smoothens the initial data to C ∞ C^\infty for t > 0 t>0 (away from the corners/edges of the domain), the subdiffusion equation only exhibits limited spatial regularity. As a result, one generally cannot expect high-order accuracy in space in solving the subdiffusion equation with nonsmooth initial data. In this paper, a new splitting of the solution is constructed for high-order finite element approximations to the subdiffusion equation with nonsmooth initial data. The method is constructed by splitting the solution into two parts, i.e., a time-dependent smooth part and a time-independent nonsmooth part, and then approximating the two parts via different strategies. The time-dependent smooth part is approximated by using high-order finite element method in space and convolution quadrature in time, while the steady nonsmooth part could be approximated by using smaller mesh size or other methods that could yield high-order accuracy. Several examples are presented to show how to accurately approximate the steady nonsmooth part, including piecewise smooth initial data, Dirac–Delta point initial data, and Dirac measure concentrated on an interface. The argument could be directly extended to subdiffusion equations with nonsmooth source data. Extensive numerical experiments are presented to support the theoretical analysis and to illustrate the performance of the proposed high-order splitting finite element methods.

Mucus Structure, Viscoelastic Properties, and Composition in Chronic Respiratory Diseases.

The respiratory mucus, a viscoelastic gel, effectuates a primary line of the airway defense when operated by the mucociliary clearance. In chronic respiratory diseases (CRDs), such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), the mucus is overproduced and its solid content augments, changing its structure and viscoelastic properties and determining a derangement of essential defense mechanisms against opportunistic microbial (virus and bacteria) pathogens. This ensues in damaging of the airways, leading to a vicious cycle of obstruction and infection responsible for the harsh clinical evolution of these CRDs. Here, we review the essential features of normal and pathological mucus (i.e., sputum in CF, COPD, and asthma), i.e., mucin content, structure (mesh size), micro/macro-rheology, pH, and osmotic pressure, ending with the awareness that sputum biomarkers (mucins, inflammatory proteins and peptides, and metabolites) might serve to indicate acute exacerbation and response to therapies. There are some indications that old and novel treatments may change the structure, viscoelastic properties, and biomarker content of sputum; however, a wealth of work is still needed to embrace these measures as correlates of disease severity in association with (or even as substitutes of) pulmonary functional tests.

An Implicit Adaptive FDTD Mesh Generation Techniquebased on Tetrahedrons

A novel implicit adaptive FDTD mesh generation method based on tetrahedrons is proposed in this paper. According to the vertex coordinates of tetrahedrons which make up an object, non-uniform grid lines are generated first. These grid lines are constrained by the structure of the object and follow three rules mentioned in the paper. The first rule is to find demarcation points of the object and drop grid lines on these points. The second rule is to make sure all mesh sizes are less than one-tenth of the wavelength by adding more grid lines. The last rule is to densify mesh at the fine structure of the object. Then by comparing the positional relationship between center points of Yee cells and tetrahedrons, the object can be discretized by Yee cells. Finally, numerical examples are given to verify the validity and accuracy of this novel method.

Physical informed memory networks for solving PDEs: implementation and applications

With the advent of physics informed neural networks (PINNs), deep learning has gained interest for solving nonlinear partial differential equations (PDEs) in recent years. In this paper, physics informed memory networks (PIMNs) are proposed as a new approach to solving PDEs by using physical laws and dynamic behavior of PDEs. Unlike the fully connected structure of the PINNs, the PIMNs construct the long-term dependence of the dynamics behavior with the help of the long short-term memory network. Meanwhile, the PDEs residuals are approximated using difference schemes in the form of convolution filter, which avoids information loss at the neighborhood of the sampling points. Finally, the performance of the PIMNs is assessed by solving the KdV equation and the nonlinear Schrödinger equation, and the effects of difference schemes, boundary conditions, network structure and mesh size on the solutions are discussed. Experiments show that the PIMNs are insensitive to boundary conditions and have excellent solution accuracy even with only the initial conditions.

Two-grid parallel stabilized finite element method based on overlapping domain decomposition for the Stokes problem

In this paper, one non-iterative two-grid parallel stabilized finite element method based on overlapping domain decomposition is developed and investigated for the Stokes problem. The lowest-order finite element pairs P1−P1 are utilized to approximate the velocity and pressure, respectively. The difference between a consistent and an under-integrated mass matrices is chosen as the stabilized term to circumvent the so-called inf-sup condition. Algorithm distributes legitimately residuals into local domains with a partition of unity. Error estimates are rigorously established. Theoretical results indicate that patches of diameter H|lnH|(|lnH|−ln|lnH|) or H|lnH| are sufficient to preserve optimal convergence rates with a proper configuration between the coarse mesh size H and the fine mesh size h in 2-D or 3-D case, respectively. Finally, some numerical experiments are reported to support our theoretical results.

Effect of mass and size husk ash adsorbent on acid number and free fatty acid of virgin coconut oil (vco) produced by enzymatic process

Virgin Coconut Oil (VCO) is an oil produced using low temperatures. Efforts to maintain and improve the quality of VCO with papain enzymatic manufacturing method followed by the provision of husk ash adsorbent. The use of papain enzyme as much as 1.5% w/v with an incubation temperature of 40°C 24 hours was effective in reducing acid numbers. The husk ash adsorbent which was treated in an oven at 120°C 2 hours was effective in improving the color quality of the VCO. Variations of husk ash were adsorbent size (60, 80, and 100) mesh and mass (15, 20, and 25) grams. The sample that has been mixed with adsorbent is stirred with a magnetic stirrer at 300 rpm 1 hour then separated by centrifuge at 1000 rpm 1 hour and ends with VCO filtering with filter paper to separate the remaining adsorbent from the oil. Samples were tested for acid number and free fatty acid content. The results show that the smaller the size of the adsorbent and the more the amount added gives a positive effect on decreasing the acid number and free fatty acid content. Production of VCO has low environmental impact because it uses low energy.

Effect of gillnet mesh size on the capture probability and capture patterns in the Asian paddle crab (Charybdis japonica) fishery

In the Asian paddle crab (Charybdis japonica) gillnet fishery in the Yellow Sea, China, the minimum mesh size (MMS) regulation has been of a major importance due to high bycatch rates of undersized crabs. In this study, we evaluated how gillnet mesh size can affect the capture probability of C. japonica and capture patterns in this fishery by comparing the performance of gillnets with four different mesh sizes (60, 70, 80, and 90 mm). Our results showed that changes in gillnet mesh size significantly affect the capture probability of different sizes of crabs. Specifically, increased mesh size decreased the capture probability of undersized crabs and their fraction in the catches decreased from 64 % to 24 % when mesh size was increased from 60 mm to 90 mm. In contrast, gillnets with larger mesh sizes significantly improved the capture probability of legal-sized crabs. Moreover, no significant differences were observed for the species catch composition between gillnets of different mesh sizes. Based on these results, we recommend 90 mm as the MMS in gillnets to improve sustainability in C. japonica fishery.

Improving the Near-Surface Wind and Turbulence at the Edge of the Orographic Drag Gray Zone by Tuning the Roughness Length

Abstract In this paper, we present the implementation and evaluate the impact of the new roughness length configuration in the ALARO canonical model configuration of the ALADIN system at the edge of the orographic gravity wave drag gray zone. As an essential input for turbulence parameterization, the roughness length affects the near-surface turbulent fluxes and the screen-level interpolation of meteorological parameters. We utilize GMTED2010 and ECOCLIMAP-II databases to derive orographic and vegetation components of the effective roughness length and introduce tuning parameters enabling us to optimize predicted near-surface turbulent momentum fluxes and 10-m wind speed. Based on sensitivity tests, we (i) prove the necessity of tuning the roughness length fields, (ii) considerably reduce the RMSE of near-surface turbulent momentum fluxes (6%–7%) and 10-m wind speed for different groups of stations (3%–10%), and (iii) identify the tree height as the most influential input parameter in our computational domain. The RMSE decomposition indicates that the improvement of 10-m wind speed mostly comes from a decrease in the random error and bias of the mean. The variability is slightly underestimated, thus reducing the model accuracy for wind speeds above the 95th percentile but at an acceptable level. We explain that roughness length tuning also compensates for the missing roughness sublayer correction in our system. Finally, we show that, although the impact of the orographic gravity wave drag scheme at a horizontal mesh size of 1.8 km is generally small, it is still beneficial for capturing some finer features observed in atmospheric soundings. Significance Statement Aiming to improve the 10-m wind speed forecast without sacrificing the accuracy of turbulent momentum fluxes in the kilometric resolution numerical weather prediction model, we derived new roughness length fields from high-resolution physiography databases. Therein, we proved the importance of tuning the input orography and vegetation fields and, depending on the time of day and year, reduced the root-mean-square error of 10-m wind speed by 3%–10%. Further, we demonstrated that orographic gravity wave drag parameterization is still needed to predict finer details seen in wind profiles from atmospheric soundings. Finally, we discussed the related simplifications in our model and their implications and proposed steps toward a more consistent and complete treatment of the near-surface turbulence.

Study on impact mechanical characteristics and screening performance of fine coal during flip-flow screening process

ABSTRACT Screening is a key link in the coal preparation, and flip-flow screening is the important method for achieving efficient classification of fine coal. During screening, the mechanical response of the screen plate caused by materials collisions not only changes its impact mechanical behavior, but also affects the final screening effect. It is urgent to clarify the mechanism of interaction between particle swarm and flip-flow screen plate. Therefore, in this study, based on the coupling of Discrete Element Method and Finite Element Method (DEM-FEM), the impact mechanical characteristics of the screen plate was explored during the collision process between the coal particle swarm and the screen plate. Conduct specific research on collision process, the relationship between the motion position of the screen plate and the distribution of impact stress was clarified. The trend of impact stress changes near the collision point was studied, and the optimized design of the flip-flow plate was carried out. On this basis, the influences of the processing capacity on the distribution of the screening products and screening efficiency were clarified. With an increase in the processing capacity of the flip-flow screen, the distribution coefficients of particles with approximate screen mesh size in the oversize gradually increased, resulting in an increase in distribution size and equal error size. Furthermore, the screening efficiency decreased from 84.91% to 81.36%. The study results provided a theoretical basis for the development of efficient screening technology for fine coal.

Chromatin Remodeling Due to Transient-Link-and-Pass Activity Enhances Subnuclear Dynamics.

Spatiotemporal coordination of chromatin and subnuclear compartments is crucial for cells. Numerous enzymes act inside nucleus-some of those transiently link and pass two chromatin segments. Here, we study how such an active perturbation affects fluctuating dynamics of an inclusion in the chromatic medium. Using numerical simulations and a versatile effective model, we categorize inclusion dynamics into three distinct modes. The transient-link-and-pass activity speeds up inclusion dynamics by affecting a slow mode related to chromatin remodeling, viz., size and shape of the chromatin meshes.

A numerical simulation of natural convection in a porous enclosure with nanofluid

In day-to-day life, heat transfer has several applications and hence we have many research areas of interest to learn new things. Nanoparticles improve the characteristics of heat transfer due to the random motion of particles. In this study, a computational approach is used to study natural convection in a porous enclosure with nanofluid. The convective term is solved by the QUICK scheme, and the finite difference method is used to solve the stream function with a 60 × 60 mesh size. CuO-water nanofluid is used in this work since nanoparticles are widely used in almost all engineering fields. In this study, we considered a two-dimensional complex cavity which is solved mathematically by using the Boussinesq approximation method. For validation of the software code, the obtained results are compared with the existing results in the literature and are found to be in good agreement. We see distortion of isotherms increases with an increase in the Rayleigh number and the nanoparticle content. That is, heat transfer takes place by natural convection very fast. Nusselt number increases with increasing nanofluid particles and the Rayleigh number. Also, it can be concluded that the heat transfer is a strong function of the Darcy number and The Rayleigh number.