Along-wind dispersion by horizontal turbulent jets in the upper ocean

Dispersion processes in the ocean surface boundary layer (OSBL) determine marine material distributions such as those of plankton and pollutants. Sheared velocities drive shear dispersion, which is traditionally assumed to be due to mean horizontal currents that decrease from the surface. However, OSBL turbulence supports along-wind jets; located in near-surface convergence and downwelling regions, such turbulent jets contain strong local shear. Through wind-driven idealized and large eddy simulation (LES) models of the OSBL, this study examines the role of turbulent along-wind jets in dispersing material. In the idealized model, turbulent jets are generated by prescribed cellular flow with surface convergence and associated downwelling regions. Numeric and analytic model solutions reveal that horizontal jets substantially contribute to along-wind dispersion for sufficiently strong cellular flows and exceed contributions due to vertical mean shear for buoyant surface-trapped material. However, surface convergence regions also accumulate surface-trapped material, reducing shear dispersion by jets. Turbulence resolving LES results of a coastal depth-limited ocean agree qualitatively with the idealized model and reveal long-lived coherent jet structures that are necessary for effective jet dispersion. These coastal results indicate substantial jet contributions to along-wind dispersion. However, jet dispersion is likely less effective in the open ocean because jets are shorter lived, less organized, and distorted due to spiraling Ekman currents.

3D Integrated Modeling of Supersonic Coherent Jet Penetration and Decarburization in EAF Refining Process

The present study proposes a complete 3D integrated model to simulate the top-blown supersonic coherent jet decarburization in the electric arc furnace (EAF) refining process. The 3D integrated model avoids the direct simulation of the supersonic coherent jet interacting with the liquid steel bath and provides a feasible way to simulate the decarburization in the liquid steel-oxygen two-phase reacting flow system with acceptable computational time. The model can be used to dynamically predict the details of the molten bath, including 3D distribution of in-bath substances, flow characteristics and bath temperature and provide a basis for optimizing the decarburization rate or other required parameters during the refining process.

Effect of Lance Structure on Behavior of Coherent Jet in EAF Steelmaking Process

During the electric arc furnace steelmaking process, the coherent jet technology was widely used to protect the kinetic energy of the supersonic oxygen jet and achieve better mixing effects. Comparing with the conventional oxygen lance, the coherent lance could increase the surface area of impaction cavity, resulting in a better stirring effect and higher reaction rate. However, there was limited research about the effect of restriction structure for the coherent lance tip on the flow field characteristic of the main oxygen jet. In this research, three kinds of restriction structures have been investigated by numerical simulation and combustion experiment at room and high ambient temperature conditions. Then an optimum restriction structure would be tested in a 75 t electrical arc furnace steelmaking process to verify its metallurgical property.

On the Fluid Dynamical Effects of Synchronization in Side-by-Side Swimmers

In-phase and anti-phase synchronization of neighboring swimmers is examined experimentally using two self-propelled independent flexible foils swimming side-by-side in a water tank. The foils are actuated by pitching oscillations at one extremity—the head of the swimmers—and the flow engendered by their undulations is analyzed using two-dimensional particle image velocimetry in their frontal symmetry plane. Following recent observations on the behavior of real fish, we focus on the comparison between in-phase and anti-phase actuation by fixing all other geometric and kinematic parameters. We show that swimming with a neighbor is beneficial for both synchronizations tested, as compared to swimming alone, with an advantage for the anti-phase synchronization. We show that the advantage of anti-phase synchronization in terms of swimming performance for the two-foil “school” results from the emergence of a periodic coherent jet between the two swimmers.

Characteristics of the Supersonic Combustion Coherent Jet for Electric Arc Furnace Steelmaking

Herein, a supersonic combustion coherent jet is proposed based on current coherent jet technology to improve the impact capacity of a coherent jet and increase the stirring intensity of the electric arc furnace (EAF) bath. Further, numerical simulations and an experimental analysis are combined to study the supersonic combustion coherent jet characteristics, including the Mach number, dynamic pressure, static temperature, vorticity, and turbulence intensity, in the EAF steelmaking environment. The results show that the supersonic combustion coherent jet exhibits stable combustion in a high-temperature EAF steelmaking environment. The supersonic combustion flame generated by the supersonic shrouding fuel gas can envelop the main oxygen jet more effectively than current coherent jets. Furthermore, the velocity attenuation, vorticity, and turbulence intensity performances of the supersonic combustion coherent jet are better when compared with those of the current coherent jet. The velocity core length of the main oxygen jet for the supersonic combustion coherent jet is 30% longer than that of the current coherent jet, resulting in an improved impact capacity and stirring intensity of the molten bath.

Investigation on the Impact and Penetration Performance of the Particulated Jet into Concrete Targets

In this study, the performance of titanium alloys (TC21, TC1), nickel-titanium (Ni-Ti) alloy, and zirconium-niobium (Zr-Nb) alloy lined shaped charge impact and penetration into concrete targets are investigated experimentally. Shaped charge jet radiographs reveal that the resulting jets of titanium alloys and Ni-Ti alloy exhibit particulate, radially dispersed behaviors, whereas that of the Zr-Nb alloy is coherent. Cavity diameters, penetration depths and parameters of the impact craters generated by the jets were analyzed using the depth of penetration (DOP) experiment method. Data indicate that the particulated jet causes more extensive damage to the surface of the concrete targets compared to the coherent jet. The penetration depth decreases to some degree, but the cavity diameter increases significantly. Penetration efficiency varies with degree of dispersion of the particulated jet and, as such, is also sensitive to stand-off distance.

Research on coherent jet oxygen lance in BOF steelmaking process

The properties of conventional supersonic oxygen jet and coherent jet were simulated by Fluent in this paper. Their velocity field and jet radius were analyzed comparatively. The attenuation of gas jet was slowed down by the coherent jet oxygen lance. Besides, the effects of annular flow rate on the central oxygen jet velocity were also researched. It is showed that the core of the jet is gradually prolonged with the increase of annular gas flow rate. Based on the simulations, the designed coherent jet oxygen lance was experimented in 35 ton converter. It is found that the end-point phosphorus content is decreased from 0.024 to 0.016%, and dephosphorization rate is increased significantly, the average consumption of steel material is reduced by 3.4 kg/t, and iron-loss of slag is also reduced, which is favorable to improve oxygen utilization and metallic yield. This research provides good foundation for coherent jet technology promotion and application in Basic Oxygen Furnace (BOF).