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Purpose The purpose of this paper is to examine the electro-magnetohydrodynamic behavior of a third-grade non-Newtonian fluid, flowing between a pair of parallel plates in the presence of electric and magnetic fields. The flow medium between the plates is porous. The effects of Joule heating and viscous energy dissipation are studied in the present study. Design/methodology/approach A semi-analytical/numerical method, the differential transform method, is used to obtain solutions for the system of the nonlinear differential governing equations. This solution technique is efficient and may be adapted to solve a variety of nonlinear problems in simple geometries, as it was confirmed by comparisons between the results using this method and those of a fully numerical scheme. Findings The results of the computations show that the Darcy–Brinkman–Forchheimer parameter and the third-grade fluid model parameter retards, whereas both parameters have an inverse effect on the temperature profile because the viscous dissipation increases. The presence of the magnetic field also enhances the temperature profile between the two plates but retards the velocity profile because it generates the opposing Lorenz force. A graphical comparison with previously published results is also presented as a special case of this study. Originality/value The obtained results are new and presented for the first time in the literature.

It is crucial to comprehend ternary hybrid nanofluids, which are composed of three distinct types of nanoparticles with varying densities and shapes, in order to properly administer heat in automobiles. In the automotive industry, temperature control and optimal engine performance depend on efficient heat transfer. By enabling exact customization of heat transfer properties, ternary hybrid nanofluids offer a unique advantage that improves cooling, lowers energy consumption, and boosts engine performance. The article describes a ternary hybrid nanofluid's flow, mass, and heat transmission between the porous parallel plates by incorporating a magnetic field, heat sink/source, activation energy, chemical reactions, and quadratic thermal radiation. The governing continuity, momentum, heat, and mass partial differential equations are converted into related, nonlinear systems of ordinary differential equations (ODE) via similarity transformations and solved using RKF-45 method. The Response Surface Methodology (RSM)'s face-centered Central Composite Design is used to calculate the transfer of heat flux at the wall. This approach accounts for the interplay between the heat radiation, magnetic parameter, and squeezing number. Further, sensitivity analysis is used to examine the heat transfer flux, skin friction, and Sherwood number of the ternary nanofluid to understand better how these variables interact with other system properties. It is noted that the local Nusselt number is more sensitive to the magnetic and squeezing factors than the local Sherwood number, although the latter is more sensitive to the former.

In the last two decades, academicians have concentrated on the nanofluid squeezing flow between parallel plates. The increasing energy demands and their applications have seen the focus shifted to the hybrid nanofluid flows, but so much is still left to be investigated. This analysis is executed to explore the symmetry of the MHD squeezing nanofluid (MoS2/H2O) flow and the hybrid nanofluid (MoS2–SiO2/H2O–C2H6O2) flow between the parallel plates and their heat transport property. The heat transport phenomenon is analyzed with the magnetic field, thermal radiation, heat source/sink, suction/injection effect, and porous medium. In the present model, the plate situated above is in the movement towards the lower plate, and the latter is stretching with a linear velocity. The prevailing PDEs depicting the modeled problem with the aforementioned effects are transformed via similarity transformations and solved via the “bvp4c” function, which is an inbuilt function in MATLAB software. The control of the factors on the fields of velocity and temperature, heat transfer rate, velocity boundary layer patterns, and streamlines is investigated. The solution profiles are visually shown and explained. Furthermore, the Nusselt number at the bottom plate is larger for the (MoS2–SiO2/H2O–C2H6O2) hybrid nanofluid than for the (MoS2/H2O) nanofluid flow. In the presence of suction/injection, the streamlines appear to be denser. In addition, the magnetic field has a thinning consequence on the velocity boundary layer region. The results of this study apply to several thermal systems, engineering, and industrial processes, which utilize nanofluid and hybrid nanofluid for cooling and heating processes.

Future space-based far-infrared astrophysical observatories will require exquisitely sensitive detectors consistent with the low optical backgrounds. The PRobe far-Infrared Mission for Astrophysics (PRIMA) will deploy arrays of thousands of superconducting kinetic inductance detectors (KIDs) sensitive to radiation between 25 and 265 μ m. Here, we present laboratory characterization of prototype, 25–80- μ m wavelength, low-volume, aluminum KIDs designed for the low-background environment expected with PRIMA. A compact parallel plate capacitor is used to minimize the detector footprint and suppress TLS noise. A novel resonant absorber is designed to enhance response in the band of interest. We present noise and optical efficiency measurements of these detectors taken with a low-background cryostat and a cryogenic blackbody. A microlens-hybridized KID array is found to be photon noise limited down to about 50 aW with a limiting detector NEP of about 6.5 × 10 - 19 W/Hz 1 / 2 . A fit to an NEP model shows that our optical system is well characterized and understood down to 50 aW. We discuss future plans for low-volume aluminum KID array development as well as the testbeds used for these measurements.

Understanding the influence of magnetic fields on the rheological behavior of flowing cement paste is of great importance to achieve active rheology control during concrete pumping. In this study, the rheological properties of cementitious paste with water-to-cement (w/c) ratio of 0.4 and nano-Fe3O4 content of 3% are first measured under magnetic field. Experimental results show that the shear stress of the cementitious paste under an external magnetic field of 0.5 T is lower than that obtained without magnetic field. After the rheological test, obvious nanoparticle agglomeration and bleeding are observed on the interface between the cementitious paste and the upper rotating plate, and results indicate that this behavior is induced by the high magnetic field strength and high-rate shearing. Subsequently, the hypothesis about the underlying mechanisms of nanoparticles migration in cementitious paste is illustrated. The distribution of the nanoparticles in the cementitious paste between parallel plates is examined by the magnetic properties of the powder as determined by a vibrating sample magnetometer. It is revealed that the magnetization of cementitious powders at different sections and layers provides a solid verification of the hypothesis.

Purpose This study aims to analyse the non-linear losses of a porous media (stack) composed by parallel plates and inserted in a resonator tube in oscillatory flows by proposing numerical correlations between pressure gradient and velocity. Design/methodology/approach The numerical correlations origin from computational fluid dynamics simulations, conducted at the microscopic scale, in which three fluid channels representing the porous media are taken into account. More specifically, for a specific frequency and stack porosity, the oscillating pressure input is varied, and the velocity and the pressure-drop are post-processed in the frequency domain (Fast Fourier Transform analysis). Findings It emerges that the viscous component of pressure drop follows a quadratic trend with respect to velocity inside the stack, while the inertial component is linear also at high-velocity regimes. Furthermore, the non-linear coefficient b of the correlation ax + bx2 (related to the Forchheimer coefficient) is discovered to be dependent on frequency. The largest value of the b is found at low frequencies as the fluid particle displacement is comparable to the stack length. Furthermore, the lower the porosity the higher the Forchheimer term because the velocity gradients at the stack geometrical discontinuities are more pronounced. Originality/value The main novelty of this work is that, for the first time, non-linear losses of a parallel plate stack are investigated from a macroscopic point of view and summarised into a non-linear correlation, similar to the steady-state and well-known Darcy–Forchheimer law. The main difference is that it considers the frequency dependence of both Darcy and Forchheimer terms. The results can be used to enhance the analysis and design of thermoacoustic devices, which use the kind of stacks studied in the present work.

The Balloon Experiment for Galactic INfrared Science (BEGINS) is a concept for a sub-orbital observatory that will operate from λ = 25 to 250 μ m to characterize dust in the vicinity of high-mass stars. The mission’s sensitivity requirements will be met by utilizing arrays of 1840 lens-coupled, lumped-element kinetic inductance detectors (KIDs) operating at 300 mK. Each KID will consist of a titanium nitride (TiN) parallel strip absorbing inductive section and parallel plate capacitor deposited on a Silicon (Si) substrate. The parallel plate capacitor geometry allows for reduction of the pixel spacing. At the BEGINS focal plane, the detectors require optical NEPs from 2 × 10 - 16 to 6 × 10 - 17 W/ Hz from 25 to 250 μ m for optical loads ranging from 4 to 10 pW. We present the design, optical performance and quasiparticle lifetime measurements of a prototype BEGINS KID array at 25 μ m when coupled to Fresnel zone plate lenses. For our optical set up and the absorption efficiency of the KIDs, the electrical NEP requirement at 25 μ m is 7.6 × 10 - 17 W/ Hz for an absorbed optical power of 0.36 pW. We find that over an average of five resonators the the detectors are photon noise limited down to about 200 fW, with a limiting NEP of about 7.4 × 10 - 17 W/ Hz . Future arrays will be coupled to microlens arrays and have higher optical efficiencies.

The current work puts forward a numerical study of non-colloidal suspension flows in a parallel-plate geometry. The inhomogeneous Euler-Euler model applied to the continuity and momentum equations is used to solve the two-phase flow problem. The aim is at the investigation of particle motion in the suspensions flow and its consequence on the measured apparent viscosity. In contrast with prior works that dealt with neutrally buoyant flows, buoyancy is now taken into account. Good agreement was obtained between measured and computed particle distributions. Analysis of this distribution reveals that not only the particle motion but also the apparent viscosity depends on whether the lower or the upper plate is rotating. Comparisons between buoyant and non-buoyant flows were performed to understand the reasons behind the particle motion. Numerical experiments were conducted by rotating the upper or lower parallel plates and varying Reynolds number, particle volume fraction, density ratio and particle size. It can be anticipated that the particle motion in buoyant flows is mainly driven by a combination of gravity and a secondary flow perpendicular to the main circumferential flow.

Flow around a pair of flat plates is a basic hydrodynamics problem. In this paper, the flow and heat transfer characteristics of two parallel plates with different edge shapes are numerically calculated. Under different inclined angles, the influence of chamfered and rounded structures with different sizes at the end-edge on unsteady flow and heat transfer characteristics of two parallel plates are analyzed. It is found that the instability and unsteadiness of flow decrease with the increase of end-edge size, and the non-uniformity of wake velocity of both rounded and chamfered plates decreases gradually. The non-uniformity of wake temperature increases firstly and then decreases at a small inclined angle, and the amplitude becomes the largest when S rou ( S cha )=3, while it basically keeps monotonically increasing at a large inclined angle. Moreover, the global heat transfer performance of the flat plate is obviously affected by the end-edge modification, especially the chamfered structure. With the increase of chamfered size, the global Nusselt number basically shows the decreasing trend. This study provides a theoretical basis for the application of plate-shape structure in engineering fields.

The gap waveguide technology for millimeter waves applications has been recently presented. The new structure is made by generating a parallel plate cut-off region between an artificial magnetic conductor (AMC) and a metallic plate. Propagating waves will be only allowed to follow a metal ridge or groove surrounded by the AMC. The gap waveguide can be made of only metal and does not need any contact between the metal joints compared to standard waveguides. In this study, a study of Q-factors of resonators made in ridge and groove gap waveguides are presented. The resonators are made of copper and the AMC used is a textured surface of metallic pins. Simulated and measured unloaded Qs are presented and compared with Q of a standard rectangular waveguide. High Q-factors are measured for the prototypes presented, approaching 90–96% of the simulated values. Furthermore, it is shown how the lid of pins can easily stop the leakage loss at the joints of the circuit, which is the typical cause of reduced Q-factor of standard waveguides at high frequency.