Magnetohydrodynamic Hybrid Research Articles

Effect of asymmetrical heat rise/fall on the film flow of magnetohydrodynamic hybrid ferrofluid

The movement of the ferrous nanoparticles is random in the base fluid, and it will be homogeneous under the enforced magnetic field. This phenomenon shows a significant impact on the energy transmission process. In view of this, we inspected the stream and energy transport in magnetohydrodynamic dissipative ferro and hybrid ferrofluids by considering an uneven heat rise/fall and radiation effects. We studied the Fe3O4 (magnetic oxide) and CoFe2O4 (cobalt iron oxide) ferrous particles embedded in H2O-EG (ethylene glycol) (50–50%) mixture. The flow model is converted as ODEs with suitable similarities and resolved them using the 4th order Runge-Kutta scheme. The influence of related constraints on transport phenomena examined through graphical illustrations. Simultaneous solutions explored for both ferro and hybrid ferrofluid cases. It is found that the magnetic oxide and cobalt iron oxide suspended in H2O-EG (ethylene glycol) (50–50%) mixture effectively reduces the heat transfer rate under specific conditions.

Modeling and numerical simulation for flow of hybrid nanofluid (SiO2/C3H8O2) and (MoS2/C3H8O2) with entropy optimization and variable viscosity

PurposeThe purpose of this paper is to investigate the entropy optimization in magnetohydrodynamic hybrid nanomaterials flows toward a stretchable surface. The energy expression is modeled subject to dissipation, heat generation/absorption and Joule heating. Here silicon dioxide (SiO2) and molybdenum disulfide (MoS2) as nanoparticles and propylene glycol (C3H8O2) as base fluid, respectively. Furthermore, the authors discussed the comparative study of molybdenum disulfide and silicon dioxide diluted in propylene glycol. The total entropy optimization rate is computed through implementation of the second law of thermodynamics.Design/methodology/approachThe nonlinear partial differential system is reduced to an ordinary one through implementation of transformation. Newton built-in shooting method is used for computational results for the given system. Influences of various flow variables on the temperature, Bejan number, velocity, concentration and entropy generation rate are examined graphically for both nanoparticles (SiO2 and MoS2). Gradients of velocity and temperature are computed numerically for various physical parameters. Also, take the comparison between the present and previously published results in tabulated form.FindingsFor higher estimation of ϕ both temperature and velocity are enhanced. Entropy optimization and Bejan number have the opposite outcome for viscosity parameter. Temperature and velocity have opposite behaviors for larger values of magnetic parameter. Molybdenum disulfide (MoS2) is more efficient than silicon dioxide (SiO2).Originality/valueNo such work is yet published in the literature.

Study of Al2O3/copper–water nanoparticle shape, slip effects, and heat transfer on steady physiological delivery of MHD hybrid nanofluid

This paper contains the analytical investigation of magnetohydrodynamic (MHD) flow of copper/Al2O3–water hybrid nanofluid with unstable peristaltic motion. Three different geometries (bricks, cylinder, and platelets) along with velocity and thermal slip conditions are studied in detail to reach the precise solution. Flow geometry of a non-uniform tube of finite length, experimental values of base fluid, and considered nanoparticles are taken into account to examine the theoretical investigation of formulated equations. Dimensionless control equations, which are subject to physically realistic boundary conditions, are closely studied to obtain precise results. The shape effects of nanoparticles on velocity, temperature distribution, and heat transfer on the length of the non-uniform tube with variation of the various flow parameters are discussed in a graphical description to understand the theoretical aspects to validate the medical analysis. The observations from the analysis state that copper/Al2O3–water carry maximum velocity for smaller values of slip parameter. Temperature distributions for heat absorption parameter are more significant as fluid flow accelerates when large values are chosen. Large values of thermal slip parameter yield enhancement in pressure gradient and Cu–water nanofluid has higher impact than hybrid nanofluid. Platelet-shaped nanoparticles of hybrid nanofluid have more significant effect on pressure gradient than cylinder- and brick-shaped nanoparticles of Cu–water nanofluid. An intrinsic property of peristaltic transport (i.e., trapping) is also discussed. The trapped bolus decreases for platelets and cylinder-shaped nanoparticles, whereas, the size of the trapped bolus increases for brick-shaped nanoparticles. This model is applicable to a drug delivery system and to design the micro-peristaltic pump for transporting nanofluids.

Comprehensive magnetohydrodynamic hybrid simulations of Alfvén eigenmode bursts and fast-ion losses in the Large Helical Device

Comprehensive magnetohydrodynamic (MHD) hybrid simulations with neutral beam injection and collisions were conducted to investigate the Alfvén eigenmode (AE) bursts and the fast-ion losses in the large helical device (LHD) for the realistic conditions close to the experiments. It is found in the simulation of the slowing-down time scale that the AE bursts take place repetitively accompanied by fast-ion redistribution and losses leading to lower saturation levels of stored fast-ion energy than those in a classical calculation where the MHD perturbations are neglected. The fast-ion loss rate caused by the AE burst has the quadratic dependence on AE amplitude, which was observed in the LHD experiment. The majority of the lost fast ions are counter-passing particles whose velocity and pitch-angle are close to those of the beam injection. The second component of the lost fast ions is transit particles whose velocity is close to thermal velocity. The loss of the counter-passing particles occurs mainly during the AE bursts, while the transit particles are lost both during the AE bursts and the quiescent periods with larger loss rate than that in the classical calculation. The initial location of the lost counter-injected particles spreads from the plasma edge to the plasma center, while only the particles initially located in the peripheral region are lost for the co-injected beam.

Comprehensive magnetohydrodynamic hybrid simulations of fast ion driven instabilities in a Large Helical Device experiment

Alfvén eigenmodes (AEs) destabilized by the neutral beam injection (NBI) in a Large Helical Device experiment are investigated using multi-phase magnetohydrodynamic (MHD) hybrid simulation, which is a combination of classical and MHD hybrid simulations for fast ions. The fast ion distribution is simulated with NBI, collisions, and losses in the equilibrium magnetic field in the classical simulation, while the MHD hybrid simulation takes account of the interaction between fast ions and an MHD fluid, in addition to the classical dynamics. It is found in the multi-phase hybrid simulation that the stored fast ion energy is saturated due to the interaction with AEs at a lower level than that of the classical simulation. Two groups of AEs with frequencies close to those observed in the experiment are destabilized alternately at each hybrid simulation. Firstly destabilized are two toroidal Alfvén eigenmodes whose frequency is close to the local minimum of the upper Alfvén continuous spectrum. Secondly destabilized is a global Alfvén eigenmode whose frequency is located well inside the Alfvén continuous spectrum gap. In addition, two AEs whose frequencies are close to that of the ellipticity-induced Alfvén eigenmode are observed with a lower amplitude. When the hybrid simulation is run continuously, the interchange mode grows more slowly than the AEs, but becomes dominant in the long time scale. The interchange mode oscillates with a constant amplitude and a frequency of ∼1 kHz. The interchange mode reduces the stored fast ion energy to a lower level than that of the AEs.

Validation of comprehensive magnetohydrodynamic hybrid simulations for Alfvén eigenmode induced energetic particle transport in DIII-D plasmas

A multi-phase simulation, which is a combination of classical simulation and hybrid simulation for energetic particles interacting with a magnetohydrodynamic (MHD) fluid including neutral beam injection, slowing-down, and pitch angle scattering, is applied to DIII-D discharge #142111 where the fast ion spatial profile is significantly flattened due to multiple Alfvén eigenmodes (AEs). The large fast ion pressure profile flattening observed experimentally is successfully reproduced by these first of a kind comprehensive simulations. Temperature fluctuations due to three of the dominant toroidal Alfvén eigenmodes in the simulation results are compared in detail with electron cyclotron emission measurements in the experiment. It is demonstrated that the temperature fluctuation profile and the phase profile are in very good agreement with the measurement, and the amplitude is also in agreement within a factor of two. This level of agreement validates the multi-phase hybrid simulation for the prediction of AE activity and alpha particle transport in burning plasmas.

Alfvén cascade modes at high β in the National Spherical Torus Experiment

Alfvén cascade (AC) modes are observed in the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] reversed shear plasmas over a wide range (up to ∼25% on axis, or ∼11% at minimum q) of β (ratio of kinetic pressure to magnetic pressure). At low β, the AC mode spectrum shows characteristics similar to conventional tokamaks. At higher β, distinct β and ∇β effects are observed in the spectrum, including a significant reduction in the relative size of the frequency sweep and a toroidal mode number dependence in the minimum mode frequency. AC mode structure is obtained using reflectometry. Fast-ion loss associated with AC mode activity is observed. AC mode polarization at the plasma edge is consistent with expectation. Magnetohydrodynamic (MHD) spectroscopy is shown to be usable to determine qmin at both low β and high β. Observed AC mode structure and frequency are found to be consistent with calculations for the same plasma conditions and geometry using the linear, ideal MHD hybrid kinetic code NOVA-K [C. Z. Cheng, Phys. Rep. 211, 1 (1992)].