587 research outputs found
The Decay of Wall Bounded MHD Turbulence at Low RM
No full textWe have developed a new spectral method to simulate flows with very fine boundary layers present. We apply it to calculate the evolution of freely decaying MHD turbulence between isolating walls. By comparison them with results obtained in fully periodic domain we quantify the influence of the channel walls on the character of freely decaying MHD turbulence
Hall Effects on scale hierarchy in MHD turbulence
No full textDirect numerical simulations of MHD turbulence with and without uniform magnetic field are carried out to study the Hall effects on scale-hierarchy in MHD turbulence. It is observed that vortex and current sheets are filamented either by the Kelvin- Helmholtz instability or magnetic reconnection in case of Hall MHD turbulence, while the filamentation is not observed without the Hall term. We show that the filamentation occurs not only for scales smaller than the ion skin depth, which is indicated by the Hall parameter, but also for scales larger than the ion skin depth, affecting turbulence statistics. It is also shown that the Hall effects can be modelled by a Smagorinsky-type model effectively for high wave number regions
Properties of magnetic energy and magnetic helicity cascades in MHD turbulence
No full textMagnetohydrodynamic (MHD) turbulence is an important part of astrophysical processes, which gives rise to global cosmic magnetic fields. Over the last few decades, the peculiarities of MHD turbulence have attracted the interest of researchers in astrophysics and fluid dynamics, significant attention has been paid to the role of magnetic helicity in fully developed MHD turbulence. Magnetic helicity, together with the energy and cross-helicity, is one of the three integrals of motion in ideal MHD. We show that oppositely directed fluxes of energy and magnetic helicity coexist in the inertial range in fully developed magnetohydrodynamic (MHD) turbulence with small-scale sources of magnetic helicity. Using a helical shell model of MHD turbulence, we study the high Reynolds number magnetohydrodynamic turbulence with well separated scales of energy input, magnetic helicity input and magnetic helicity sink. We obtain three inertial ranges with different scaling properties. In a short range of scales larger than the forcing scale of magnetic helicity, a bottleneck-like effect appears, which results in a local reduction of the spectral slope. The slope changes in a domain with a high level of relative magnetic helicity, which determines that part of the magnetic energy related to the helical modes at a given scale. In the infrared part of the spectra we observe simultaneous inverse cascade of energy and magnetic helicity. Our results indicate that a large-scale dynamo can be affected by the magnetic helicity generated at small scales. The kinetic helicity, in particular, is not involved in the process at all
DC to dc converter: Buck-Boost converter / Mohd Hairul Helmi Mhd Idris
Get PDFThis thesis presents Buck-Boost converter. This is a type of DC converter that can either step up or step down voltage input. It is a class of switching-mode power supply (SMPS) containing at least two semiconductor switches (a diode and a transistor) and at least one energy storage element. The characteristic and performance of the buck-boost converter was proved with the results and findings from conducted experiment with the Buck Boost converter model and the simulation. Circuit simulation has been carried out using PSIM software 7.1.2 version. Result from theoretical, simulation experiment and has been compared to each others
Magnetic condensate in 2D MHD
No full textBy means of numerical simulations, we investigate the phenomenon of self-organization of the magnetic field in a large-scale coherent structure, which occurs in two-dimensional Magneto-Hydro-Dynamic (2D MHD) in presence of a magnetic forcing. We show that the magnetic condensate is not able to induce a large-scale motor effect on the velocity field
The 2D/3D dynamics of wall-bounded low-Rm magnetohydrodynamic (MHD) turbulence
No full textWith this experimental study, we give evidence that the dynamics of low-Rm MHD turbulence depends on the diffusion length l_z, which corresponds to the distance over which the Lorentz force is able to diffuse momentum before it is balanced by inertia
Sidewall flow stability in the MHD channel flows
No full textThe velocity distribution between two sidewalls is; M-shaped for the MHD channel flows with rectangular cross section and thin conducting walls in a strong transverse magnetic field. Assume that the dimensionless numbers R(m) much less than 1, M, N much greater than 1, and sigm
The global L-2 stability of solutions to three dimensional MHD equations
No full textIn this paper, we mainly study the global L-2 stability for large solutions to the MHD equations in three-dimensional bounded or unbounded domains. Under suitable conditions of the large solutions, it is shown that the large solutions are stable. And we obtain the equivalent condition of this stability condition. Moreover, the global existence and the stability of two-dimensional MHD equations under three-dimensional perturbations are also established
MHD Casson fluid flow over a non-linear stretching/shrinking sheet with suction and slip boundary condition
Get PDFA problem of steady laminar magnetohydrodynamic (MHD) Casson flow over a non-linear stretching/shrinking sheet with suction and slip boundary condition is considered. The governing nonlinear partial differential equations are transformed into a system of nonlinear ordinary differential equations using a similarity transformation. The transformed ordinary differential equations are then solved numerically using the bvp4c function in MATLAB software. Dual solutions are found for a certain range of the governing parameter. The effects of the suction parameter and the slip boundary condition on the skin friction and heat transfer coefficients as well as the velocity and temperature profiles are presented and discussed
Sense Making of the Congruence of Comprehension between Two Listeners of the Speech on "Budi Sejahtera Leadership"
No full textYusof Ismail
Dzuljastri Abdul Razak
Suhaimi Mhd Sarif
Receiving information from indirect sources is common in daily lives. This may be due to the time constraint, giving priority to one’s current engagement, physical distance, mandatory non-face-to-face communication, and other factors. In fact, most of an individual’s time is spent on processing indirect information whether one deals with his office work or family matters. This chapter shows the extent of congruence that is identified by a co-author based on the description of the other two co-authors who attended the talk on the topic of “Budi,” “Sejahtera,” and “Leadership.” The lead author created and sent an attachment that contains a combination of dichotomous and open-ended questions related to the three-terminology theme to the other co-authors for their independent views. He analyzed their textual opinions and produced his analysis of the converging and diverging themes based on the opinions provided. This case study helps people become aware of the varying amount and depth of information acquired by listeners to a public lecture, moreover via online platform rather than among the audience of a lecture in a hall. In this case, only two listeners are involved, making content analysis easy.
Keywords: Budi, Communication, Comprehension, Information, Islam, Listening, Malay, Sejahtera
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