Abstract:
the aim of the present work is the development of a method based on the momentum transfer law to obtain the solution of confined jet diffusion flames. the reichardt's equation is used to approximate the flow/mixture fraction and it is discretized based on the second order finite difference technique. all thermochemical variables are determined by the mixture fraction as the sandia flame c, used to check the results, is close to equilibrium. the semi-analytical/numerical results compare reasonably with the experimental data indicating that the method contributes to solve some jet flames at low cost.

Abstract:
The aim of the present work is the development of a method based on the momentum transfer law to obtain the solution of confined jet diffusion flames. The Reichardt's equation is used to approximate the flow/mixture fraction and it is discretized based on the second order finite difference technique. All thermochemical variables are determined by the mixture fraction as the Sandia Flame C, used to check the results, is close to equilibrium. The semi-analytical/numerical results compare reasonably with the experimental data indicating that the method contributes to solve some jet flames at low cost.

Abstract:
Employing the standard k-ε turbulent model and slipping grid technique, distributions of velocity and dynamic pressure and mixing time was numerically investigated to research the gasoline flow features and mixing efficiency in a gasoline mixture tank with a rotary jet mixing (RJM) system installed at the bottom center. The simulation results showed that the RJM system can achieve fully circular stir without blind corner, reaching high mixing efficiency in the mixing process of gasoline from different refining line. The mixing density difference met the mixing requirement for the first time at 31.2.s and then showed a tendency of deterioration. It met the requirement again at 58.2.s with the mixing density difference meeting the mixing criterion of 3‰. Employing the standard k-ε turbulent model and slipping grid technique, distributions of velocity and dynamic pressure and mixing time was numerically investigated to research the gasoline flow features and mixing efficiency in a gasoline mixture tank with a rotary jet mixing (RJM) system installed at the bottom center. The simulation results showed that the RJM system can achieve fully circular stir without blind corner, reaching high mixing efficiency in the mixing process of gasoline from different refining line. The mixing density difference met the mixing requirement for the first time at 31.2.s and then showed a tendency of deterioration. It met the requirement again at 58.2.s with the mixing density difference meeting the mixing criterion of 3‰.

Abstract:
The ac response of a slab of material with electrodynamic characteristics $E\sim j^{\kappa+1}$, $\kappa\geq0$, is studied numerically. From the solutions of the nonlinear diffusion equation, the fundamental and higher-order components of the harmonic susceptibility are obtained. A large portion of the data for every $\kappa$ can be scaled by a single parameter, $\xi$ =$t^{1/(\kappa+2)}\cdot H_0^{\kappa/(\kappa+2)}/D$, where $t$ is the period of the ac field at the surface, $H_0$ is its amplitude and $D$ is the slab thickness. This is, however, only an approximate scaling property: The field penetration into a nonlinear medium is a more complex phenomenon than in the linear case. In particular, the susceptibility values are not uniquely defined by a set of only two parameters, such as $\kappa$ and $\xi$, while one parameter, i.e. $t^{1/2}$/D, is sufficient to describe the electrodynamic response of a linear medium.

Abstract:
The mixing flow field around a reentry capsule with a counter-flow jet from its front stagnation point in supersonic flow is numerically studied by solving the axisymmetric Navier-Stokes equation coupled with k-ε turbulence model using the Van Leer’s flux vector splitting spatial discretion scheme. With the jet Mach number and total temperature fixed, the effects of jet total-pressure ratio on the flow structure, drag and heat flux on the body are investigated. The results show that two classical flow modes exist in the mixing flow field, one is long penetration mode and the other is short penetration mode. The drag on the blunt body is reduced significantly because of counter-flow jet. Considering the exhaustion of jet thrust, the effect of drag reduction is better when flow is in LPM than in SPM. It is found that the maximum drag reduction can reach as high as 55.8% for the cases studied. Blunt body heat flux can also be reduced significantly and can even be negative when jet total pressure ratio is high enough. The results may have some significance for the engineering application of supersonic blunt body counter-flow jet technology.

Abstract:
A numerical simulation on confined impinging circular jet working with a mixture of water and Al2O3 nanoparticles is investigated. The flow is turbulent and a constant heat flux is applied on the heated plate. A two-phase mixture model approach has been adopted. Different nozzle-to-plate distance, nanoparticle volume concentrations and Reynolds number have been considered to study the thermal performances of the system in terms of local, average and stagnation point Nusselt number. The local Nusselt number profiles show that the highest values within the stagnation point region, and the lowest at the end of the heated plate. It is observed that the average Nusselt number increases for increasing nanoparticle concentrations, moreover, the highest values are observed for H/D=5, and a maximum increase of 10% is obtained at a concentration equal to 5%.

Abstract:
We study the formation of coronal jets through numerical simulation of the emergence of a twisted magnetic flux rope into a pre-existing open magnetic field. Reconnection inside the emerging flux rope in addition to that between the emerging and pre-existing fields give rise to the violent eruption studied. The simulated event closely resembles the coronal jets ubiquitously observed by Hinode/XRT and demonstrates that heated plasma is driven into the extended atmosphere above. Thermal conduction implemented in the model allows us to qualitatively compare simulated and observed emission from such events. We find that untwisting field lines after the reconnection drive spinning outflows of plasma in the jet column. The Poynting flux in the simulated jet is dominated by the untwisting motions of the magnetic fields loaded with high-density plasma. The simulated jet is comprised of spires of untwisting field that are loaded with a mixture of cold and hot plasma and exhibit rotational motion of order 20 km/s and match contemporary observations.

Abstract:
In the solar atmosphere, the jets are ubiquitous and found to be at various spatia-temporal scales. They are significant to understand energy and mass transport in the solar atmosphere. Recently, the high-speed transition region jets are reported from the observation. Here we conduct a numerical simulation to investigate the mechanism in their formation. Driven by the supergranular convection motion, the magnetic reconnection between the magnetic loop and the background open flux occurring in the transition region is simulated with a two-dimensional magnetohydrodynamics model. The simulation results show that not only a fast hot jet, much resemble the found transition region jets, but also a adjacent slow cool jet, mostly like classical spicules, is launched. The force analysis shows that the fast hot jet is continually driven by the Lorentz force around the reconnection region, while the slow cool jet is induced by an initial kick through the Lorentz force associated with the emerging magnetic flux. Also, the features of the driven jets change with the amount of the emerging magnetic flux, giving the varieties of both jets. These results will inspire our understanding of the formation of the prevalence of both the fast hot jet and slow cool jet from the solar transition region and chromosphere.

Abstract:
Brownian dynamics simulations require the connection of a small discrete simulation volume to large baths that are maintained at fixed concentrations and voltages. The continuum baths are connected to the simulation through interfaces, located in the baths sufficiently far from the channel. Average boundary concentrations have to be maintained at their values in the baths by injecting and removing particles at the interfaces. The particles injected into the simulation volume represent a unidirectional diffusion flux, while the outgoing particles represent the unidirectional flux in the opposite direction. The classical diffusion equation defines net diffusion flux, but not unidirectional fluxes. The stochastic formulation of classical diffusion in terms of the Wiener process leads to a Wiener path integral, which can split the net flux into unidirectional fluxes. These unidirectional fluxes are infinite, though the net flux is finite and agrees with classical theory. We find that the infinite unidirectional flux is an artifact caused by replacing the Langevin dynamics with its Smoluchowski approximation, which is classical diffusion. The Smoluchowski approximation fails on time scales shorter than the relaxation time $1/\gamma$ of the Langevin equation. We find the unidirectional flux (source strength) needed to maintain average boundary concentrations in a manner consistent with the physics of Brownian particles. This unidirectional flux is proportional to the concentration and inversely proportional to $\sqrt{\Delta t}$ to leading order. We develop a BD simulation that maintains fixed average boundary concentrations in a manner consistent with the actual physics of the interface and without creating spurious boundary layers.

Abstract:
the traditional welding flux development has been by cost, material, time and labour intensive experiments. the extensive and expensive trial and error experimentation is needed because it is often difficult to know a priori how the flux ingredients interact to determine the operational characteristics of the flux and the final performance of the welded structure. the limitation of the traditional approach includes: (1) long lead-time (2) expensive experiments in terms of materials and energy consumption and labour requirements (3) the flux developed can not be guaranteed to be optimal and (4) inability to identify and quantify direct and interaction effects of flux ingredients. these constraints are due to the paucity of statistical modelling tools in welding flux technology. since prediction models are derived from designed experiments, flux researchers need other methods by which flux experiments may be designed. this paper discusses a statistical modelling tool known as mixture experiment which has the potential to revolutionize welding flux development technology. mixture design is discussed but not fully developed. the procedure of mixture experiment, analytical model forms and the sequence of model fitting are discussed. areas of welding flux research where the various mixture designs may be useful are suggested.