Influences of Zero Mass Flux and Active Conditions on the Predictions of Double Dispersion and Double Diffusive Boundary Layer in Darcy/Non Darcy Nanofluid Flow

Free convective of nanofluid inside dispersive porous medium adjacent to a vertical plate under the effects of the zero mass nanoparticles flux condition and the thermal and solutal dispersions is studied. Buongiorno's model revised is used considering Darcy and non Darcy laminar flows, and isothermal or convective flux outer the wall. Dimensionless governing equations formulated using velocity, temperature, concentration and nanoparticle volume fraction have been solved by finite difference method that implements the 3-stage Lobatto collocation formula. The numerical data obtained with semi or full dispersions cases are compared to predictions made using the non dispersive porous medium. Taking into account the dispersions, the influence of the zero mass nanoparticles flux condition is examined to test the validity of the control active nanoparticle assumption. It is found mainly that the thermal transfers can reach more than 100% in connection with the case where of a semi-dispersion of the porous medium is applied. Realistic condition, i.e. zero mass flux should be addressed for the heat transfer rate rather than the mass transfer rate, discovered markedly different to the active condition. This signifies the importance of considering the zero nanoparticles mass flux and dispersions in the performance characterization of nanofluid flow in porous media.

Back EMF Waveform Comparison and Analysis of Two Kinds of Electrical Machines

In this study, the back electromotive force (EMF) waveforms of a flux switching permanent magnet (FSPM) machine and variable flux memory permanent magnet (VFMPM) machine with same main dimension were researched. Firstly, the simulation result showed that the maximum amplitude of phase back EMF waveform of FSPM machine was 245% larger than that of the VFMPM machine, and this was verified by the experimental result (243%). Secondly, the phase back EMF harmonics of the FSPM machine and VFMPM machine were compared, including the enhance flux condition and weaken flux condition of VFMPM machine. At last, the mutual demagnetization effect, which led to the difference amplitudes of maximum back EMF waveform between FSPM machine and VFMPM machine was analyzed. The comparison and analysis of the back EMF waveform will provide some qualitative advice for the future application research of the FSPM machine and VFMPM machine, such as application selection, optimization control method and so on.

Statistical modeling for bioconvective tangent hyperbolic nanofluid towards stretching surface with zero mass flux condition

This article presents the implementation of a numerical solution of bioconvective nanofluid flow. The boundary layer flow (BLF) towards a vertical exponentially stretching plate with combination of heat and mass transfer rate in tangent hyperbolic nanofluid containing microorganisms. We have introduced zero mass flux condition to achieve physically realistic outcomes. Analysis is conducted with magnetic field phenomenon. By using similarity variables, the partial differential equation which governs the said model was converted into a nonlinear ordinary differential equation, and numerical results are achieved by applying the shooting technique. The paper describes and addresses all numerical outcomes, such as for the Skin friction coefficients (SFC), local density of motile microorganisams (LDMM) and the local number Nusselt (LNN). Furthermore, the effects of the buoyancy force number, bioconvection Lewis parameter, bioconvection Rayleigh number, bioconvection Pecelt parameter, thermophoresis and Brownian motion are discussed. The outcomes of the study ensure that the stretched surface has a unique solution: as Nr (Lb) and Rb (Pe) increase, the drag force (mass transfer rate) increases respectively. Furthermore, for least values of Nb and all the values of Nt under consideration the rate of heat transfer upsurges. The data of SFC, LNN, and LDMM have been tested utilizing various statistical models, and it is noted that data sets for SFC and LDMM fit the Weibull model for different values of Nr and Lb respectively. On the other hand, Frechet distribution fits well for LNN data set for various values of Nt.

Digital fluxgate current sensor based on second harmonic detection

This paper presents a new digital fluxgate current sensor based on second harmonic detection for DC and AC measurement. The sensor utilizes a feedback loop to obtain an almost zero-flux condition, i.e., a balance between the magnetic flux of the primary current and the feedback current, in which way the feedback current is proportional to the primary current. The AC magnetic flux is detected with an induction coil, and the DC zero-flux condition is realized by magnetic saturation effect method, where the magnetic core is periodically magnetized and then the second harmonic of the magnetization current is calculated as an indication of the DC magnetic flux. After theoretical derivation, the operating principle of the sensor was investigated using a numerical simulation model built with Simulink of MATLAB. In addition, a prototype sensor was developed and tested. The experiment results demonstrate that the current sensor works properly for DC and AC measurement. The average error is about 0.06% for DC measurement.