Numerical Investigation of Flexible Airfoil Aerodynamics

A commercial CFD solver is used to simulate the unsteady aerodynamics performance of rigid and flexible wing airfoils for a high-performance jet trainer aircraft. The configuration used in the computational analysis is NACA 64012. In the numerical simulations the turbulence is modeled by enhancing Spalart-Allmaras turbulence model. To simulate the fluttering motion of the upper surface, an algorithm written in C computer language is integrated with the Fluent. The program controls the oscillation of the upper suction surface to specific defined displacement and the mesh dynamic that adjacent to the moving surface of the airfoil. The numerical experiments for both, rigid and flexible airfoils are carried out at flight speed of 85 m/s and angle of attack from zero to 18 degree. In order to verify the results of numerical simulation, the solver is validated against prior experiment of a lift coefficient. In comparison between rigid and flexible airfoils, the aerodynamic forces produced by a flexible airfoil shows that the lift coefficient is increased by 10% for angle of attack ranging from the incidence degree to 10 degree and then decreased slightly till the stall angle located at 16 degree. The flow separation in rigid airfoil is predicted at 7.5% of airfoil chord, whereas in the flexible airfoil it is at 59% of the airfoil chord

Aerodynamic Coefficients Investigation of GRAD Rocket Using Computational Fluid Dynamics

The article provides an aerodynamic characteristics investigation of GRAD Rocket using the computational fluid dynamic method. Computational analysis has been performed to predict the Aerodynamic characteristics of the GRAD rocket. A commercial software ANSYS FLUENT is used to simulate the unsteady aerodynamic characteristics of the missile while the Missile DATCOM software is used to confirm and validate the results. The simulations have been conducted out for a range of Mach number 0.4 to 3 versus angle of attack from 0° to 9°, through the sideslip angle 0° to 9°. The results represent that the Drag Coefficient is highly sensitive to the angle of attack and velocity region. The total drag of the missile is mainly generated from the missile's body, where they wrap around fins contribute only 18.45 percent of a total drag coefficient. In contrast, the lift coefficient increases with an increased angle of attack, but it decreases with changes of the region from subsonic to supersonic. The flow visualization of the static and dynamic pressure contours is illustrated. The Shock wave is captured at the nose and fins entrance. To verify the results, the simulations were carried out for two missile models. The first model represents the cylindrical body of the fin-less missiles, and the second one represents the rocket body with fins

Primary cultures of chick osteocytes retain functional gap junctions between osteocytes and between osteocytes and osteoblasts

The inaccessibility of osteocytes due to their embedment in the calcified bone matrix in vivo has precluded direct demonstration that osteocytes use gap junctions as a means of intercellular communication. In this article, we report successfully isolating primary cultures of osteocytes from chick calvaria, and, using anti-connexin 43 immunocytochemistry, demonstrate gap junction distribution to be comparable to that found in vivo. Next, we demonstrate the functionality of the gap junctions by (1) dye coupling studies that showed the spread of microinjected Lucifer Yellow from osteoblast to osteocyte and between adjacent osteocytes and (2) analysis of fluorescence replacement after photobleaching (FRAP), in which photobleaching of cells loaded with a membrane-permeable dye resulted in rapid recovery of fluorescence into the photobleached osteocyte, within 5 min postbleaching. This FRAP effect did not occur when cells were treated with a gap junction blocker (18 alpha-glycyrrhetinic acid), but replacement of fluorescence into the photobleached cell resumed when it was removed. These studies demonstrate that gap junctions are responsible for intercellular communication between adjacent osteocytes and between osteoblasts and osteocytes. This role is consistent with the ability of osteocytes to respond to and transmit signals over long distances while embedded in a calcified matrix. </p

３次元培養されたMC3T3-E1細胞と骨細胞の突起におけるアクチンおよび微小管細胞骨格について

Cell shape is the most critical determinant of cell function and is potentially influenced by the organization of a cell's cytoskeletal components. It has been reported that three-dimensionally cultured osteoblasts have a morphology that closely resembles that of osteocytes, most notably including formation of processes. We have previously shown the critical differences between cytoskeletal components in osteoblasts and osteocytes in two-dimensional culture. We have now extended that investigation to the cytoskeletal components of 3D-cultured osteoblasts and osteocytes using 3D cultures of the osteoblast cell line, MC3T3-E1, and primary osteocytes grown in collagen gel. Three-dimensional fluorescent image reconstructions for actin, fimbrin, alpha-actinin, myosin, tropomyosin, and microtubules were made using IMARIS software. Actin, fimbrin, alpha-actinin, myosin, and tropomyosin all appeared in the processes of both cell types, but fimbrin and myosin showed differences in their distribution patterns between cell types. Microtubules were limited in distribution to the proximal region of osteocyte processes but extended the entire length of MC3T3-E1 cell processes. Microtubules were essential for the integrity and formation of MC3T3-E1 cell processes, but osteocyte processes were dependent on actin. These results showed that there are significant differences between the actin and microtubule cytoskeletons in the processes of 3D-cultured MC3T3-E1 cells and in the processes of 3D-cultured primary osteocytes. These differences in the cytoskeleton of the processes of 3D-cultured osteoblasts and of osteocyte dendrites suggest that osteoblast processes may have a different functional role than the osteocyte dendritic network

Hidden structure in the randomness of the prime number sequence?

We report a rigorous theory to show the origin of the unexpected periodic behavior seen in the consecutive differences between prime numbers. We also check numerically our findings to ensure that they hold for finite sequences of primes, that would eventually appear in applications. Finally, our theory allows us to link with three different but important topics: the Hardy-Littlewood conjecture, the statistical mechanics of spin systems, and the celebrated Sierpinski fractal.Comment: 13 pages, 5 figures. New section establishing connection with the Hardy-Littlewood theory. Published in the journal where the solved problem was first describe