Numerical simulation of aerodynamic interference between ejected payload and the parent aircraft

The purpose of this paper is to develop reliable methodology for numerical modeling of the interference between parent aircraft and ejectable payload and to investigate the influence of the interference on aerodynamic characteristics of the payload. An appropriate algorithm for the said problem is proposed. A mathematical model for supersonic flow around a solid body as well as its finite volume discretization process is described. In the presented mathematical model, a turbulence model is added to the Navier-Stokes system of equations. Namely, Menter’s SST model was chosen. Coupled solver algorithm is reviewed. Implicit Euler scheme is used for time discretization and Newton’s method is implemented to linearize the system of equations. The specifics of determining the appropriate boundary conditions and nondimensionalization of the aerodynamic coefficients are described. The calculations for the isolated payload were performed on an unstructured grid with 9 million cells and for the payload interfered by the parent aircraft - on a 24 million grid. As a result, the summarized aerodynamic characteristics for the payload were obtained for the isolated payload as well as for the payload in presence of the parent aircraft. The characteristics of the isolated object are compared with the ones of the object in presence of the parent aircraft in two different positions - Y rel = 0 m and Y rel = 0.6 m. The developed method was verified using wind tunnel data. It was identified that in presence of the parent aircraft, the coefficients of normal and side force are not zero as opposed to the isolated payload. Moving away from the parent aircraft decreases the interference and thus the side force, as well as the pitch and yaw torques. The obtained results show that the proposed method could be used in other cases of aerodynamic interference between moving objects

Study of structure and surface morphology of two-layer contact Ti/Al metallization

Ti/Al/Ni/Au metallization widely used in the technology of GaN base devices have a very important imperfection i.e. rough surface. There are different opinions about the causes of this imperfection: balling-up of molten aluminum or the appearance of intermetallic melt phases in the Au–Al system. To check the effect of the former cause, we have studied the formation of rough surface after annealing of Ti/Al metallization which is used as a basis of many metallization systems for GaN. The substrates were made from silicon wafers covered with Si3N4 films (0.15 μm). On these substrates we deposited the Ti(12 nm)/Al(135 nm) metallization system. After the deposition the substrates were annealed in nitrogen for 30 s at 850 °С. The as-annealed specimens were tested for metallization sheet resistivity, appearance and surface morphology. We have shown that during annealing of the Ti/Al metallization system, mutual diffusion of the metals and their active interaction with the formation of intermetallic phases occur. This makes the metallization system more resistant to subsequent annealing, oxidation and chemical etching. After annealing the surface of the Ti/Al metallization system becomes gently matted. However, large hemispherical convex areas (as in the Ti/Al/Ni/Au metallization system) do not form. Thus, the hypothesis on the balling-up of molten aluminum on the surface of the Ti/Al metallization system has not been confirmed

Round-the-World Voyage of the Threespine Stickleback (Gasterosteus aculeatus): Phylogeographic Data Covering the Entire Species Range

A total of 205 COI sequences and 310 cyt b sequences of the threespine stickleback (Gasterosteus aculeatus) from basins of all seas throughout the vast range of this species were analyzed. Median networks of haplotypes constructed in this study, combined with the results of reconstruction of paleogeographic conditions, led to the conclusion that the threespine stickleback emerged as a species in the Pacific Ocean basin and spread to Europe from the south, populating the system of water bodies that existed in the Oligocene. The main water body was the Paratethys Ocean (Sea), which existed 5–34 Mya. In the area of the modern North Sea, stickleback populations, part of which later migrated to the eastern and western coasts of North America, gave rise to the group of haplotypes that has the widest distribution in northern Europe. The stickleback populations belonging to the lineage that dispersed along the Arctic and western coasts of North America displaced the carriers of the haplotypes of the ancient phylogenetic lineage that inhabited the Pacific coast. The ancestors of G. wheatlandi dispersed from the Pacific to the Atlantic Ocean via the Arctic to meet G. aculeatus, which circled the globe from east to west

Round-the-World Voyage of the Threespine Stickleback (<i>Gasterosteus aculeatus</i>): Phylogeographic Data Covering the Entire Species Range

A total of 205 COI sequences and 310 cyt b sequences of the threespine stickleback (Gasterosteus aculeatus) from basins of all seas throughout the vast range of this species were analyzed. Median networks of haplotypes constructed in this study, combined with the results of reconstruction of paleogeographic conditions, led to the conclusion that the threespine stickleback emerged as a species in the Pacific Ocean basin and spread to Europe from the south, populating the system of water bodies that existed in the Oligocene. The main water body was the Paratethys Ocean (Sea), which existed 5–34 Mya. In the area of the modern North Sea, stickleback populations, part of which later migrated to the eastern and western coasts of North America, gave rise to the group of haplotypes that has the widest distribution in northern Europe. The stickleback populations belonging to the lineage that dispersed along the Arctic and western coasts of North America displaced the carriers of the haplotypes of the ancient phylogenetic lineage that inhabited the Pacific coast. The ancestors of G. wheatlandi dispersed from the Pacific to the Atlantic Ocean via the Arctic to meet G. aculeatus, which circled the globe from east to west