Interpolation Method for Visual Simulation of Engine Exhaust Flame

Propulsive force and exhaust fluid temperature are important indicators in the performance of an engine. An investigation of the effects of propellant composition, plane flight conditions, and engine operating environment on rocket thrust and the range of smoke plume temperature can provide references in the design of engine mechanics at the optimization of propellant composition, in monitoring of target identification and in the evolving of stealth of stealth technology. In order to understand the characteristics of the engine tail flame, a visual simulation of the engine tail flame was carried out by combining the engine operating conditions with the tail flame conditions. Based on the advantages of the bicubic spline interpolation algorithm and the Kriging interpolation algorithm, this paper proposes a hybrid interpolation algorithm, which performs color mapping and three-dimensional space separation in the engine plume data set and model, and visualizes the engine and engine plume. The simulation realizes real-time monitoring of the functions of various engine components through characteristic colors. The research results show that the hybrid interpolation method can effectively visualize the engine exhaust flame. The simulated plume has a relatively obvious temperature peak at 0.7 m, and the temperature of the plume flow field is significantly higher than that of the frozen plume flow field by about 200 ~1000 K. This shows that the algorithm in this paper helps to visualize the expression of engine tail flame information.

Variability of the Red River Plume in the Gulf of Tonkin as Revealed by Numerical Modeling and Clustering Analysis

We study the daily to interannual variability of the Red River plume in the Gulf of Tonkin from numerical simulations at high resolution over 6 years (2011–2016). Compared with observational data, the model results show good performance. To identify the plume, passive tracers are used in order to (1) help distinguish the freshwater coming from different continental sources, including the Red River branches, and (2) avoid the low salinity effect due to precipitation. We first consider the buoyant plume formed by the Red River waters and three other nearby rivers along the Vietnamese coast. We show that the temporal evolution of the surface coverage of the plume is correlated with the runoff (within a lag), but that the runoff only cannot explain the variability of the river plume; other processes, such as winds and tides, are involved. Using a K-means unsupervised machine learning algorithm, the main patterns of the plume and their evolution in time are analyzed and linked to different environmental conditions. In winter, the plume is narrow and sticks along the coast most of the time due to the downcoast current and northeasterly wind. In early summer, the southwesterly monsoon wind makes the plume flow offshore. The plume reaches its highest coverage in September after the peak of runoff. Vertically, the plume thickness also shows seasonal variations. In winter, the plume is narrow and mixed over the whole water depth, while in summer, the plume can be detached both from the bottom and the coast. The plume can deepen offshore in summer, due to strong wind (in May, June) or specifically to a recurrent eddy occurring near 19°N (in August). This first analysis of the variability of the Red River plume can be used to provide a general picture of the transport of materials from the river to the ocean, for example in case of anthropogenic chemical substances leaked to the river. For this purpose, we provide maps of the receiving basins for the different river systems in the Gulf of Tonkin.

Study on a calculation model of infrared radiation characteristics of rocket engine plume

In order to study the infrared radiation (IR) characteristics of rocket engine plume in the mid infrared band, a calculation model for IR transfer of rocket engine plume was built. The flow field data are calculated by software FLUENT. Based on HITRAN database, the IR characteristic parameters are calculated after spectral line correction. The Line of Sight (LoS) is used to solve the radiation characteristics in the plume flow field, and the IR characteristics distribution of the plume in the mid infrared band is obtained, which agree well with the results from open literature. The method has the advantages of simple model, less parameters and fast calculation speed in this paper.

Numerical evaluation of the exhaust-direction effects on plume flow and helicopter infrared radiation under hover and cruise statuses

Purpose This study aims to investigate the effects of exhaust direction on exhaust plume and helicopter infrared radiation in hover and cruise status. Design/methodology/approach Four exhaust modes are concerned, and the external flow field and fuselage temperature field are calculated by numerical simulation. The infrared radiation intensity distributions of the four models in hovering and cruising states are computed by the ray-tracing method. Findings Under the hover status, the exhaust plume is deflected to flow downward after it exhausts from the nozzle exit, upon the impact of the main-rotor downwash. Besides, the exhaust plume shows a “swirling” movement following the main-rotor rotational direction. The forward-flight flow helps prevent the hot exhaust plume from a collision with the helicopter fuselage generally for the cruise status. In general, the oblique-upward exhaust mode provides moderate infrared radiation intensities in all of the viewing directions, either under the hover or the cruise status. Compared with the hover status, the infrared radiation intensity distribution alters somewhat in cruise. Originality/value Illustrating the influences of exhaust direction on plume flow and helicopter infrared radiation and the differences of helicopter infrared radiation under hover and cruise statuses are identified. Finally, an appropriate exhaust mode is proposed to provide a better IR signature distribution.

Van Allen Probes Observations of Oxygen Ions at the Geospace Plume

The geospace plume couples the ionosphere, plasmasphere, and magnetosphere from sub-auroral regions to the magnetopause, on polar field lines, and into the magnetotail. We describe Van Allen Probes observations of ionospheric O+ ions at altitudes of 3–6 RE in the near vicinity of the geospace plume in the noon and post-noon sector. The temporal variation of warm ion fluxes observed as a function of time on a moving spacecraft is complicated by changing spacecraft position and complex ion drift paths and velocities that are highly sensitive to ion energy, pitch angle and L value. In the “notch” region of lower density plasma outside the morning-side plasmapause, bi-directionally field aligned fluxes of lower energy (<5 keV) ions, following corotation-dominated drift trajectories from the midnight sector, are excluded from geospace plume field lines as they are deflected sunward in the plume flow channel. In general, O+ at ring current energies (∼10 keV) is bi-directionally field aligned on plume field lines, while lower energy O+ (<3 keV) are absent. The observation of ion plumes with energies increasing from ∼1 keV–>20 keV in the dusk sector outer plasmasphere is interpreted as evidence for localized ionospheric O+ outflow at the outer edge of the geospace plume with subsequent O+ acceleration to >50 keV in <30 min during the ions’ sunward drift.

Using video images to study Haima cold seep bubble plumes

<p>Cold seep is a widespread geological process mainly caused by hydrocarbon fluid migration. Methane bubble plumes released from cold seeps are often observed at the seafloor. These methane bubbles might be released into the atmosphere and have a huge effect on climate changes. It is of great significance for understanding the fate of these methane bubble plumes.</p><p>Many kinds of methods have been used to observe the methane bubble plumes, e.g., acoustical, geochemical, and optical methods. Video imaging is a kind of optical methods widely used in methane bubble plume studies. Compared to other methods, video imaging is a non-intrusive, high-resolution, and quick-collected method. Many studies have estimated bubbles' size, rise velocities, behavior, and the fate of bubbles by analyzing video images manually. However, manual analysis is time-consuming, one dimension, and has not been able to determine temporospatial changes in a two-dimension profile perspective.</p><p>In this study, we applied the manual analysis method and the particle image velocimetry (PIV) method to analyze in-situ video image sequences of Haima cold seep bubble plumes, a newly discovered, active cold seep in the Qiongdongnan Basin of the northern South China Sea during 2019. Quantitative and temporospatial change information about the plume flow filed is obtained. The results show that the sizes of bubbles in the plume range from 2.556 ~ 4.624 mm, with a rising velocity of ~ 0.26 m/s. The flux for an individual bubble stream is ~ 94.8 ml/min. The flow velocity field of the bubble plume is consistent with the manual analysis, and it reveals that the bubble plume's flow field is a multiscale turbulent flow field. The bubble plumes are usually V-shaped. Through carrying the adjacent water column, the bubble plumes swell and change rapidly. The direction and velocity of the bubble plume flow change with time, and its streamlines are sinuous. The max velocity of the bubble plume flow field changes at a 6.6 s period cycle.</p><p>Although there is some indetermination, our results show that the PIV method is feasible for calculating the bubble plume flow field and that it has some unique advantages, e.g., it is fast, non-invasive, it provides two-dimension temporospatial change images, and it has a high resolution. The images of the bubble plume flow field provide a new perspective to observe the cold seep systems. We hope that this method can be improved and widely applied in cold seep plume studies in the future.</p>

Causes and consequences of asymmetric lateral plume flow during South Atlantic rifting

Volcanic rifted margins are typically associated with a thick magmatic layer of seaward dipping reflectors and anomalous regional uplift. This is conventionally interpreted as due to melting of an arriving mantle plume head at the onset of rifting. However, seaward dipping reflectors and uplift are sometimes asymmetrically distributed with respect to the subsequent plume track. Here we investigate if these asymmetries are induced by preexisting lateral variations in the thickness of continental lithosphere and/or lithospheric stretching rates, variations that promote lateral sublithospheric flow of plume material below only one arm of the extending rift. Using three-dimensional numerical experiments, we find that South Atlantic rifting is predicted to develop a strong southward asymmetry in its distribution of seaward dipping reflectors and associated anomalous relief with respect to the Tristan Plume that “drove” this volcanic rifted margin, and that the region where plume material drains into the rift should experience long-lived uplift during rifting—both as observed. We conclude that a mantle plume is still needed to source the anomalously hot sublithospheric material that generates a volcanic rifted margin, but lateral along-rift flow from this plume, not a broad starting plume head, is what controls when and where a volcanic rifted margin will form.