This paper presents an analysis of magnetohydrodynamic (MHD) electrically conducting Casson fluid flow in a porous medium, incorporating the effects of viscous dissipation over an exponentially stretching sheet. The governing equation of motion is solved analytically, while the temperature profile is computed numerically using MATLAB's built-in function bvp4c. An asymptotic analysis on dimensionless stream function is also discussed for very large magnetic field and Casson parameters. The study shows that as the Casson parameter, magnetic field, suction, and permeability parameters increase, the horizontal velocity drops. In contrast, transverse velocity decreases with these factors, with the exception of suction, which has the inverse effect. The temperature rises as the Casson parameter and Eckert number grow, but the Prandtl number drops. Furthermore, the skin friction coefficient drops as the Casson parameter, magnetic field, and suction rise, but the Nusselt number decreases with the Casson parameter and Eckert number but increases with the Prandtl number. Finally, tabular data are supplied to compare the presented results with current literature. This research may be useful in optimizing heat and mass transport in engineering systems such as cooling technologies, polymer manufacturing, and chemical reactors.
This study investigates the global stability of thermal convection in Navier-Stokes-Voigt fluids with couple stresses saturating a porous medium, focusing on the effects of medium permeability and couple stresses.We employ both nonlinear and linear approaches to analyze the system using energy and normal mode analysis method, respectively. The Rayleigh number is calculated using the Galerkin method, yielding consistent results that indicate global stability and the absence of subcritical regions. Convection is limited to a stationary state, adhering to the principle of exchange of stabilities. Our findings reveal that while the Kelvin-Voigt parameter significantly influences energy decay, it does not affect convection modes. Couple stresses contribute to the stabilization of the fluid system, whereas medium permeability introduces a destabilizing effect. Notably, configurations with rigid-rigid boundary surfaces enhance thermal stability, making them particularly advantageous for convection in this context. This research has important implications across various fields, including petroleum engineering, groundwater hydrology, biomedical engineering, geothermal energy, civil engineering, and environmental engineering.
The thermo-convective stability of a bottom-heated box is strongly related to the eigenvalues of the Helmholtz equation with Neumann boundary conditions. The Helmholtz eigenvalues for shapes bounded by separable coordinates can be easily found, but the basic triangular region has not been fully documented. This work presents exact solutions for some specific triangles, approximations for thin triangles, and an efficient method of eigenfunction expansion and boundary collocation. The eigenvalues are then applied to the determination of the onset of natural convection in an isosceles triangular box filled with fluid-saturated porous medium. The mosaics for critical Rayleigh numbers and incipient modes are determined. Applications, aside from the thermo-convective stability of general triangular boxes, include the onset of convection in narrow crevices, and the tiling of hexagonal convection modes.
This paper investigates randomly distributed streamwise jets generated due to flow through thin open-porous materials and the jet coalescence phenomenon. The pattern and coalescence of jets at the exit of thin porous materials impact their use as membranes, papers and cartons, filters, filtration cakes, porous coatings, fuel cells, textiles, and hygiene products such as wipes and diapers. Computational fluid dynamics (CFD) simulations are performed on the geometry reconstructed using X-ray micro-computed tomography to predict the pressure drop, permeability, and inertial coefficient and validated by measurements. Furthermore, a novel methodology is developed to estimate the jet dimensions by performing a fast Fourier transform of the voxelized streamwise velocity component at the exit of the porous material. Statistical analysis of the resulting spectra reveals the jet length distribution in the flow field and quantitatively confirms jet coalescence. The present work illustrates the jet formation, emergence, and jet coalescence at the exit of a thin porous foam. The proposed methodology allows jet flow characterization and avoids extensive experimentation. Also, the results offer guidelines for jet impingement heat and mass transport augmentation and flow uniformity, and study the impact of flow on sound propagation and mixing.
Tumor treatment using ferrofluids has recently emerged as an appealing therapeutic idea. Ferrofluids are injected inside the vascular system of tumors to produce localized heat for treatment of tumors. However, the complexity of the interaction among the ferrofluid, porous tumor tissue, and surrounding vascular system presents significant challenges to an understanding of the underlying dynamics. Previous studies have often neglected ferrohydrodynamic interactions in porous tumor structures. This study presents a theoretical model for analyzing the steady flow of ferrofluid in a cylindrical vessel encircled by a porous tumor in the presence of magnetic fields, focusing on varying tissue porosity under temperature-dependent viscosity. The nonlinear partial differential equations governing flow, heat, and mass transfer are nondimensionalized using similarity transformations and solved numerically in MATLAB using bvp4c function. This method was chosen due to its accuracy and efficiency in handling nonlinear boundary value problems. Ferromagnetic interaction parameter, tissue porosity, Brownian motion parameter, thermophoresis, Darcy number, and radiation effects are analyzed with respect to the primary flow properties, including velocity distribution, shear stress, skin friction coefficient, and heat transfer rates. Results reveal that increase in tumor porosity enhances fluid motion by reducing resistance to flow, but it simultaneously lowers heat transfer efficiency due to reduced thermal conduction. Additionally, higher values of the ferromagnetic interaction parameter enhance velocity and temperature but decrease concentration, ensuring effective ferrofluid delivery to the tumor site. The interplay between porosity and magnetization provides crucial insights for optimizing ferrofluid-based therapies, such as magnetic drug targeting. Future studies can incorporate blood-based and dual-phase models for more realistic simulations and explore experimental validation to enhance clinical applicability.
The promotion of effective contact between water, chemical agents, and heavy oil improves the efficiency of thermal-chemical flooding in heavy-oil reservoirs. The hydraulic pulse jet technique was integrated with thermal-chemical flooding to form a novel composite enhanced oil recovery technique and improve the contact between oil, water, and chemical agents. Experiments on the heavy-oil thermal-chemical flooding (pre-displacement) assisted by the hydraulic pulse jet (displacement) were carried out in both macroscale and microscale. The recovery enhancement, pressure difference, relative permeability, and oil-water state in the produced fluid were analyzed by considering the different excitation intensities of the hydraulic pulse jet (1, 3, and 5 MPa). The variations in the microscopic oil-water state in different areas of a visual simulation device were assessed. The results revealed that for various excitation intensities, differences were evident in the hydraulic-pulse jet's effect on the thermal-chemical flooding process, both temporally and spatially. The type of oil-water emulsification process of the produced fluid, different from what typically occurs, with oil and water production fluctuating instead of oil being produced first and then steadily changing to water. There were also different forms of displaced oil in different areas. A high intensity of the hydraulic pulse jet was recommended to achieve maximum enhancement of about 6.26% in the experimental heavy-oil recovery. The results of this study are expected to provide theoretical guidance for the development of heavy-oil reservoirs.
