Applications in engineering science最新文献

This paper investigates the influence of the use of the cubic equation of state (EOS) in the isothermal cavitation of compressible fluids. To do so, a thermodynamic consistent cavitation model that was recently proposed has been used. This model is derived under the Thermodynamics of Irreversible Processes and considers the irreversible dissipative character of the phase change transformation. Numerical simulations carried out using linear and cubic EOS are presented and compared. Neglecting surface tension effects, the results obtained demonstrate that there is no significant difference between the responses of these two types of EOS for water up to saturation pressures up to about 200 kPa. Hysteresis loops observed in the simulations with both types of EOS are virtually the same. It suggests that linear EOSs can provide good approximations for metastable behaviors (intrinsically present in cubic EOS) as well as for the Gibbs free energy difference (the thermodynamic force associated with irreversible phase change transformation), rendering a great simplification in the analysis.

This paper presents a comprehensive study on Herschel–Bulkley flow, where the flow parameters are dependent on the density. The Herschel–Bulkley model is a generalized power-law model used to simulate viscoplastic fluids defined by a plasticity threshold. We consider the case where the plasticity threshold and the viscosity depend on the shear rate and fluid density. To analyze this model, we use a Huber regularization of the stress and propose an H(div)-conforming and discontinuous Galerkin (DG) numerical approximation for the coupled equations governing the flow. We discuss the stability and existence of discrete solutions and propose a semismooth Newton linearization for the numerical solution of the discretized system. Our numerical scheme is validated through several experiments that explore the behavior of Herschel–Bulkley flow under different conditions. The results demonstrate the robustness of our numerical method.

The stability of steady, fully developed flow in a long cylindrical pipe for a shear-thinning fluid (which approximates a class of viscoplastic materials) is studied using linear stability analysis. The eigenvalues of the frequency of the perturbation of the steady-state solution are obtained using the shooting method. The eigenvalues are negative in the Reynolds number range studied and asymptotically tend to zero as the Reynolds number increases. This shows the pipe flow is stable in the Reynolds number range studied. A qualitatively similar trend is shown by the eigenvalues of a Navier–Stokes fluid of equivalent viscosity. However, the eigenvalues are much lesser than those of the shear-thinning fluid, and this shows that the flow of the Navier–Stokes fluid can be expected to be stable over a much larger Reynolds number range than the shear-thinning fluid.

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.