Applications in engineering science最新文献

This study investigates the horizontal injection of a heavy Newtonian fluid into a lighter viscoplastic ambient fluid, in a large reservoir. The flow dynamics is experimentally captured via camera imaging, laser-induced fluorescence, and particle image velocimetry techniques. The flow parameters include various density differences, injection velocities, and ambient fluid viscoplastic properties. Our analysis identifies two key dimensionless numbers, the Froude number ($Fr$) and the effective viscosity ratio ($m$), which includes the rheology of the viscoplastic fluid. Our study also examines the effects of these dimensionless numbers on critical jet characteristics, such as bifurcation length, transition length, deviation length, and jet trajectory, and provides correlations using $Fr$ and $m$, to predict these characteristic lengths. A regime classification based on the bifurcation phenomenon is also presented in the $Fr-m$ plane.

Rheological models capture the behaviour of soil structures and effectively evaluate the response of various transport corridors. These models represent the elastic and plastic behaviour of a structure. This paper reviews several rheological models that incorporate elasticity, viscosity, and plasticity principles. The review encompasses various rheological models developed as viscoelastic, elastoplastic, viscoplastic, elastoviscoplastic and viscoelastoplastic models, specifically for a better understanding of high-speed rail dynamics. Analytical solutions for these models are elaborated, focusing on the behaviour of soil structures and the interaction of layers, particularly in scenarios involving two or more layers. Additionally, detailed discussions cover the results and interpretations of various studies on these rheological models.

Mashrabiya are oriel windows characteristic of Islamic architectural tradition that were historically integrated into buildings located in places with arid climates. The present paper formulates a novel design approach to Mashrabiya systems, by employing origami modules equipped with photovoltaic cells. The examined oriel window is able to complement the main traditional functions of a Mashrabiya with solar energy harvesting. A primary folding motion of the origami modules designed to tessellate its surface permits the sunlight to pass through the system in a controlled way. A secondary tilting folding motion of the photovoltaic cells placed on these modules lets the system harvest solar energy and produce electric power. The paper illustrates the architectural and mechanical design of the examined Mashrabiya window, as well as its energy harvesting properties, using both numerical and experimental methods.

Concrete, essential to global infrastructure, confronts urgent environmental challenges due to its high carbon footprint and resource-intensive production. In response, researchers are exploring nanoparticles, such as nano-silica (nS) and nano-titanium dioxide (nT), to enhance sustainability and performance. This review examines recent advances in their application. Nano-silica, prized for rapid hydration and enhanced strength, emerges as a promising additive. Studies indicate nS accelerates cement hydration, densifies the matrix, and improves durability and impermeability. Silica-based nano-coatings on glass textile-reinforced composites bolster bond strength and resilience. Similarly, nT offers diverse benefits to concrete. Beyond its traditional applications in photocatalysis, nS has been proven to refine pore structure, increase compressive strength, and enhance resistance to elevated temperatures. Additionally, nT adds to the self-cleaning properties of concrete surfaces, making it a promising additive for sustainable construction practices. Despite these advancements, challenges persist in the effective dispersion of nanoparticles within concrete matrices and ensuring their economic feasibility and regulatory compliance. Addressing these challenges will require interdisciplinary collaboration and innovative approaches to optimize dispersion methods, mitigate health risks, and develop robust regulatory frameworks. Future research directions should focus on developing multifunctional nanomaterials capable of imparting multiple desirable properties to concrete simultaneously, such as self-sensing, self-cleaning, and energy harvesting capabilities. Furthermore, efforts to optimize manufacturing processes and scale up production will be essential to realizing the full potential of nano-modified concrete in addressing the sustainability challenges facing the construction industry.

Membrane finite elements with drilling degrees of freedom have sparked interest in many research works since they can be conveniently combined with plates to form shell elements. This study presents two non-conforming strain-based four-node quadrilateral membrane elements, SBQ13 and SBQ13E, for static analysis. SBQ13 partially satisfies the equilibrium equations, while SBQ13E completely fulfils the force balance equations. Both elements carry drilling rotations at each node. One difficulty when formulating quadrilateral elements is the singularity in the transformation matrix, which is addressed in this study by utilising the properties of singular matrices. Both quadrilateral elements were tested in several benchmark problems. It has been found that both elements passed the higher-order patch test but failed the constant stress patch test. Nevertheless, SBQ13 produced accurate responses in most numerical tests, but SBQ13E unreasonably overestimated the solution. Solving the eigenvalue problem revealed that the SBQ13E element has a near-zero energy deformation mode, which might explain the anomaly. Although fulfilling equilibrium does not always enhance solution accuracy, it is essential to overcome volumetric locking. Apart from the newly developed elements, this paper presents several new ideas that may apply to strain-based element formulations.

Boiling flow presents a significant concern, especially when a liquid surpasses its boiling point, potentially leading to catastrophic consequences. This research utilizes a two-phase code in the OpenFOAM software to investigate bubble formation during flow boiling. The well-established empirical models for calculating wall heat components were selected based on the operating conditions. The study incorporates experimental data from high-pressure boiling flow (10–30 bars) with variable properties of refrigerant R-12. The predictions reveal underpredictions in void fraction and liquid temperature compared to experimental observations. Significantly, the impact of the subcooling degree on void fraction behaviour is emphasized, and a potential underprediction of the evaporation portion is highlighted, particularly near the wall. Challenges in modelling bubble size distribution are evident through discrepancies in bubble diameter and velocity data, indicating the necessity for further advancements in the code. In summary, this numerical study provides valuable insights into the intricate dynamics of high-pressure subcooled boiling flow, especially when considering variable working fluid properties. Future efforts will focus on refining models for nucleation site density, bubble departure size, and lift-off frequency to enhance prediction accuracy.

This study extends the analysis of natural convection in a viscoplastic fluid to flow within a triangular enclosure. The finite-element approach provided a numerical solution to the continuity, momentum, and energy equations. The governing parameters for this problem are the Rayleigh number, $\left(Ra={10}^4-{10}^6\right)$, yield number, $\left(Y=0-Y_{max}\right)$, aspect ratio, $\left(\frac{H}{L}=0.5-2.5\right)$, and slope angle, $\left(\varnothing =0-\frac{\pi }{2}\right)$. The influence of these parameters on the heat and mass transfer, morphology of yielded/unyielded regions, and fluid flow were thoroughly examined. The results show that two opposing factors influence the flow behavior and heat transmission within the triangular enclosure. The proximity of the walls restricts the convective movement, leading to reduced heat transfer. However, the proximity of hot and cold sources increases the temperature gradient and heat transfer. The unique influence of the viscoplastic material properties, particularly the yield stress, further distinguishes the heat transfer in this triangular enclosure from other geometries. The results indicate that an increase in the Rayleigh number mitigates the effects of yield stress to some extent. However, the accumulation of unyielded material at the triangular apex hinders convection flow. Furthermore, the viscoplastic fluid flow and heat transfer changed significantly with changes in triangle height. In particular, the maximum yield stress increased by more than 100 % as the aspect ratio increased from 0.5 to 2.5. A change in the slope angle causes a continuous transition from subcritical to supercritical bifurcation, significantly affecting the morphology of the yielded and unyielded areas, and the maximum (critical) yield number. Finally, correlations were developed to predict the Nusselt number and maximum yield stress in all cases.

Analytical investigation of the impact of Nano fluids on the melting process of phase change materials (PCM) inside a semi-cylindrical container. In order to analyse the study in a quantitative manner, the combination of enthalpy and porosity was used using the ANSYS/FLUENT 22 programme. This experiment used phase transition materials, namely paraffin wax (RT58). Based on the findings of this research, it is seen that the inclusion of Nano fluid in the PCMs accelerates the dissolving process compared to the PCMs without these materials. The use of nanomaterials results in a reduction in the time needed to complete the melting process by 3 %, 4 %, and 5 % when used at concentrations of 10 %, 20 %, and 30 %, respectively. This study is important for the use of phase-change materials in the cooling of large electronic devices.

This paper emphasizes the significant usage of natural fiber as a reinforced composite in the potential engineering field. Mechanical, civil, textile, agricultural, and other engineering sectors have already initiated the utilization of natural fiber in their multiple fields. After going through some processes like treating chemically and synthesizing them accordingly, natural fiber composites are prepared for respective implementation. Unlike other types of composite materials, natural fiber composites have some unique properties like recyclability, adaptability, environmental safety, and easy persuasion. On the other hand, different types of naturally oriented fiber like jute, cotton, silk, linen, hemp, etc. have almost the same kind of mechanical, thermal, and chemical features as traditional composite materials. Additionally; automobile, marine, aerospace, medical, and recreation industries claim a significant realm in this type of material kingdom. Though moisture problems, fiber swelling, and safe reusability are threatening for natural fiber-reinforced composites, more research will certainly reduce these problems. Researchers play a significant role in the permanent solution of different applications of natural fiber composites in every engineering sector.

Polycarbonate (PC) is a thermoplastic polymer used in many engineering applications such as safety devices and aerospace components. However, the unique behavior of PC under tensile load and its effects on the estimation of its constitutive curve are often overlooked in the literature, neglecting to consider crucial aspects of the characterization process. This work carries out a comprehensive analysis of the mechanical behavior of PC to understand the key points for accurate constitutive modeling and simulation of its static tensile performance, including its unconventional deformation mechanisms. The work starts from the accurate analysis of a representative experimental static tensile test on a rectangular section PC specimen and the evaluation of its true stress-strain curve. This analysis, carried out considering the classic length-based approach and the more accurate area-based approach, makes it possible to evaluate in detail the peculiar tensile behavior of this material. The mathematical form of the PC true stress-strain curve is then justified and the coincidence of the obtained length-based and area-based estimates of the same is demonstrated. Then, based on the in-depth understanding of the dynamics underlying the mechanical behavior of PC and making use of FEM simulations, the key points for obtaining its constitutive curve are defined. It is demonstrated that the constitutive curve is able to completely determine the behavior of PC, including its peculiar deformation mechanism. It is also highlighted which specific characteristics of the constitutive curve are critical in affecting various aspects of the material's behavior. The final constitutive curve of PC at hand is then obtained with an inverse approach, capable of accurately simulating all aspects of its tensile behavior. The validity of the proposed modelling key points is then confirmed, effectively explaining the underlying phenomena controlling the tensile behavior of PC and massively reducing uncertainty in the estimation of its constitutive curve starting from its area-based true curve.