Primary Velocity Components Research Articles

Velocity Field due to a Vertical Deformation of the Bottom of a Laminar Free-Surface Fluid Flow

This article investigates the velocity field of a free-surface flow subjected to harmonic deformation of the channel bottom, progressing asymptotically from a flat initial state to a maximum amplitude. Assuming a uniform main flow with the primary velocity component transverse to the bed undulation, analytical solutions are obtained for the three velocity components and free surface distortion using the method of perturbations. The perturbation components of the velocity field, streamlines, and surface deformation depend on a dimensionless parameter that reflects the fluid inertia induced by bed deformation relative to viscous resistance. When viscous effects dominate, a monotonic decay of the perturbations from the bed to the free surface is observed. In contrast, when inertia dominates, the perturbations can exhibit an oscillatory behavior and introduce circulation cells in the plane normal to the main flow. The interplay between inertia and viscosity reveals scenarios where surface and bed deformations are either in or out of phase, influencing vertical velocity components. Figures illustrate these phenomena, providing insights into the complex dynamics of free-surface flows with harmonic bed deformation in the direction normal to the main flow, and amplitude growing with time. The results are limited to small deformations of the channel bottom, as imposed by the linearization of the momentum equations. Even so, to the best of the authors’ knowledge, this problem has not been addressed before.

Effect of line/point heat source and Hall current with induced magnetic field on free convective flow in vertical walls

In this research, the hydromagnetic natural convection of an incompressible fluid with point heat source by considering the influence of Hall current and induced magnetic field between infinite vertical walls is studied. The Laplace transform procedure is utilized to determine the analytical solutions of the acquired mathematical model with the wavelet function. With the derived solution of velocity, induced magnetic field, temperature field, and induced current density, the flow character is investigated with the influence of the physical parameters (namely Hall current, Hartmann number, and point heat source) for the presented boundary conditions. Also, the skin friction and volumetric flow rate are derived through the velocity expression. Numerical and graphical results are introduced to formalize the solution of the model. The valuable result from the investigation is that an increase in the length of the point heat source leads to enhance both components of induced current density, induced magnetic field, and primary velocity profiles. Moreover, it is noticeable that an enhancement in the Hall current has a reverse connection with both components of the induced current density, induced magnetic field, while the direct connection with the primary velocity component. There are numerous engineering applications such as the metal cutting, grinding, welding, laser hardening of metals, and many others in which the calculation of temperature field is modeled as a problem involving a point heat source.

Magnetic Rotating Flow of a Hybrid Nano-Materials Ag-MoS2 and Go-MoS2 in C2H6O2-H2O Hybrid Base Fluid over an Extending Surface Involving Activation Energy: FE Simulation

Numeric simulations are performed for a comparative study of magnetohydrodynamic (MHD) rotational flow of hybrid nanofluids (MoS2-Ag/ethyleneglycol-water (50–50%) and MoS2-Go/ethyleneglycol-water (50–50%)) over a horizontally elongated plane sheet. The principal objective is concerned with the enhancement of thermal transportation. The three-dimensional formulation governing the conservation of mass, momentum, energy, and concentration is transmuted into two-dimensional partial differentiation by employing similarity transforms. The resulting set of equations (PDEs) is then solved by variational finite element procedure coded in Matlab script. An intensive computational run is carried out for suitable ranges of the particular quantities of influence. The primary velocity component decreases monotonically and the magnitude of secondary velocity component diminishes significantly when magnetic parameter, rotational parameter, and unsteadiness parameter are incremented. Both the primary and secondary velocities are smaller in values for the hybrid phase Ag-MoS2 than that of hybrid phase Go-MoS2 but the nanoparticle concentration and temperature are higher for hybrid phase Ag-MoS2. The increased values of parameters for thermophoresis, Brownian motion, shape factor, and volume fraction of ϕ2 made significant improvement in the temperature of the two phases of nano liquids. Results are also computed for the coefficients of skin friction(x, y-directions), Nusselt number, and Sherwood number. The present findings manifest reasonable comparison to their existing counterparts. Some of the practical engineering applications of the present analysis may be found in high-temperature nanomaterial processing technology, crystal growing, extrusion processes, manufacturing and rolling of polymer sheets, academic research, lubrication processes, and polymer industry.

Double Diffusion Non-Isothermal Thermo-Convective Flow of Couple Stress Micropolar Nanofluid Flow in a Hall MHD Generator System

Nanofluids are potential liquids that enhance the thermophysical characteristics and the ability to transport heat rather than base liquids. This article discusses the non-isothermal heat transfer of the convective steady flow of magnetohydrodynamic micropolar nanofluid over a non-linear extended wall, considering the effects of Brownian motion and thermophoresis, coupled stress, hall current and viscous dissipation effects. Fluid flow is controlled by a high magnetic field. The system of equations is resolved using the Homotopy Analysis Method (HAM) technique and the results are visualized graphically. The effects of different fluid parameters summarizing the problem behavior on primary, secondary and angular velocity, temperature, volume fraction and nanoparticle concentration profiles are measured using graphs. The primary velocity component decreased throughout the entire flow study with magnetic, couple stress and Hall parameters. The large magnetic field parameter and the smaller couple stress parameter lower the secondary velocity, while the increase of the local Grashof number increases the secondary velocity. The strong magnetic parameter, the local Grashof number and the couple stress parameter reduce the angular velocity as observed. The large magnetic parameter, Grashof number, Hall parameter and radiation parameter reduces temperature, while the temperature increases with the increase in Brinkman number and Prandtl number. Brownian motion and thermophoresis encourage the transfer of heat. Tables are used to highlight the impact of dimensionless parameters on the skin friction coefficient, Nusselt and Sherwood numbers.

Study of the Couple Stress Convective Micropolar Fluid Flow in a Hall MHD Generator System

The steady non-isothermal convective heat transfer in magnetohydrodynamic micropolar fluid flow over a non-linear extending wall is examined. The fluid flow is treated with strong magnetic field. The influence of magnetic field, Hall current, viscous dissipation, and couple stress are mainly focused in this work. The fluid flow problem is solved by analytical method. The impact of developing dimensionless parameters on primary, secondary, and angular velocity components and temperature profile are determined through graphs. The greater magnetic parameter, local Grashof number, Hall parameter, power-law index, Prandtl number, nonlinear wall geometric parameter, and couples stress parameter reduce the primary velocity component while the material parameter, and Eckert number escalates the primary velocity component. The greater local Grashof number, material parameter, power-law index, Prandtl number, and wall geometric parameter reduces the secondary velocity component while the greater magnetic parameter, Hall parameter, Eckert number, and couple stress parameter escalates the secondary velocity component.

An ATCA survey of Sagittarius B2 at 7 mm: chemical complexity meets broad-band interferometry

We present a 30 - 50 GHz survey of Sagittarius B2(N) conducted with the Australia Telescope Compact Array (ATCA) with 5 - 10 arcsec resolution. This work releases the survey data and demonstrates the utility of scripts that perform automated spectral line fitting on broadband line data. We describe the line-fitting procedure, evaluate the performance of the method, and provide access to all data and scripts. The scripts are used to characterize the spectra at the positions of three HII regions, each with recombination line emission and molecular line absorption. Towards the most line-dense of the three regions characterised in this work, we detect ~500 spectral line components of which ~90 per cent are confidently assigned to H and He recombination lines and to 53 molecular species and their isotopologues. The data reveal extremely subthermally excited molecular gas absorbing against the continuum background at two primary velocity components. Based on the line radiation over the full spectra, the molecular abundances and line excitation in the absorbing components appear to vary substantially towards the different positions, possibly indicating that the two gas clouds are located proximate to the star forming cores instead of within the envelope of Sgr B2. Furthermore, the spatial distributions of species including CS, OCS, SiO, and HNCO indicate that the absorbing gas components likely have high UV-flux. Finally, the data contain line-of-sight absorption by $\sim$15 molecules observed in translucent gas in the Galactic Center, bar, and intervening spiral arm clouds, revealing the complex chemistry and clumpy structure of this gas. Formamide (NH$_2$CHO) is detected for the first time in a translucent cloud.

Effects of Velocity Gradients and Secondary Flow on the Dispersion of Solutes in a Meandering Channel

Two contrasting mechanisms, created by channel curvature which strongly affect longitudinal dispersion of solutes in rivers are examined. In natural channels the large cross-sectional variability of the primary velocity component tends to increase longitudinal dispersion by providing a large difference between adjacent fast and slow moving zones of fluid. By contrast secondary circulation tends to decrease longitudinal dispersion by enhancing transverse mixing. A series of tests have been carried out in a very large flume containing a meandering water-formed sand bed channel to measure the longitudinal dispersion coefficient at various locations around a meander. These experimental observations are compared with experimental data obtained from meandering channels with smooth, fixed sides and regular cross-sectional shapes. All the data has been compared against predictions from two current modeling approaches. Finally, the significance of the two competing mechanisms in curved channels is discussed with regard to their relative influence on longitudinal mixing.

Velocity Distribution in Compound Channel Flows by Numerical Modeling

The paper examines the problem of prediction of uniform turbulent flow in a compound channel with the nonlinear k‐ε model. This model is capable of predicting the secondary currents, caused by the anisotropy of normal turbulent stresses, that are important features of the flow in compound channels, as they determine the transverse momentum transfer. The model is applied to reproduce experimental runs available in the literature. The comparison shows that the model predicts with accuracy the distribution of the primary velocity component, the secondary circulation, and the discharge distribution. The numerical results are used to search a subdivision surface between main channel and floodplain on the basis of the flow field and to compare different subdivision surfaces on the basis of the discharge distribution by a simple uniform flow formula. The better subdivision surfaces as predicted by the model are the diagonal surface going from the corner between main channel and floodplain to the free surface on the symmetry plane and the bisector of the same corner.