Study of hybrid air vehicles stability using computational fluid dynamics

This paper uses Computational Fluid Dynamics to predict aerodynamic damping of airships or hybrid air vehicles. This class of aircraft is characterised by large lifting bodies combining buoyancy and circulatory lift. Damping is investigated via forced oscillations of the vehicle in pitch and yaw. The employed method is verified using data for lighter than air vehicles. The use of fins and stabilisers was found to be beneficial. The rear part of the body was dominated by separated flow that containedmore frequencies than the forcing frequency imposed on the body. The final design is seen to be dynamically stable across a range of conditions for small pitch angles

Computational fluid dynamics challenges for hybrid air vehicle applications

This paper begins by comparing turbulence models for the prediction of hybrid air vehicle (HAV) flows. A 6 : 1 prolate spheroid is employed for validation of the computational fluid dynamics (CFD) method. An analysis of turbulent quantities is presented and the Shear Stress Transport (SST) k-ω model is compared against a k-ω Explicit Algebraic Stress model (EASM) within the unsteady Reynolds-Averaged Navier-Stokes (RANS) framework. Further comparisons involve Scale Adaptative Simulation models and a local transition transport model. The results show that the flow around the vehicle at low pitch angles is sensitive to transition effects. At high pitch angles, the vortices generated on the suction side provide substantial lift augmentation and are better resolved by EASMs. The validated CFD method is employed for the flow around a shape similar to the Airlander aircraft of Hybrid Air Vehicles Ltd. The sensitivity of the transition location to the Reynolds number is demonstrated and the role of each vehicle£s component is analyzed. It was found that the ¦ns contributed the most to increase the lift and drag

Tiltrotor CFD part II: aerodynamic optimisation of tiltrotor blades

This paper presents aerodynamic optimisation of tiltrotor blades with high-fidelity computational fluid dynamics. The employed optimisation framework is based on a quasi-Newton method, and the required high-fidelity flow gradients were computed using a discrete adjoint solver. Single-point optimisations were first performed, to highlight the contrasting requirements of the helicopter and aeroplane flight regimes. It is then shown how a trade-off blade design can be obtained using a multi-point optimisation strategy. The parametrisation of the blade shape allowed to modify the twist and chord distributions, and to introduce a swept tip. The work shows how these main blade shape parameters influence the optimal performance of the tiltrotor in helicopter and aeroplane modes, and how a compromise blade shape can increase the overall tiltrotor performance. Moreover, in all the presented cases, the accuracy of the adjoint gradients resulted in a small number of flow evaluations for finding the optimal solution, thus indicating gradient-based optimisation as a viable tool for modern tiltrotor design

(E)-3-Heteroarylidenechroman-4-ones as potent and selective monoamine oxidase-B inhibitors

A series of (E)-3-heteroarylidenechroman-4-ones (1a-r) was designed, synthesized and investigated in vitro for their ability to inhibit the enzymatic activity of both human monoamine oxidase (hMAO) isoforms, hMAO-A and hMAO-B. All the compounds were found to be selective hMAO-B inhibitors showing IC50 values in the nanomolar or micromolar range. (E)-5,7-Dichloro-3-{[(2-(dimethylamino) pyrimidin-5-yl]methylene}chroman-4-one (1c) was the most interesting compound identified in this study, endowed with higher hMAO-B potency (IC50 ¼ 10.58 nM) and selectivity (SI > 9452) with respect to the reference selective inhibitor selegiline (IC50 ¼ 19.60 nM, IC50 > 3431). Molecular modelling studies were performed for rationalizing at molecular level the target selective inhibition of our compounds, revealing a remarkable contribution of hydrogen bond network and water solvent

Optimisation of Transonic Circulation Control Devices

Gradient based optimisation of a Coanda surface for a transonic, supercritical circulation control aerofoil is presented. Design variable updates are driven by a Sequential Least Squares Quadratic Programming (SLSQP) algorithm, using gradients provided by the solution of the Adjoint equations in discrete formulation. Surface sensitivities of the lift coefficient relative to local variations on the Coanda shape are shown, which indicate that the effects due to under-expansion of the jet have a significant influence on the circulation control efficiency. It is also shown that a 16\% improvement in the augmented lift coefficient compared with a simple circular shape can be achieved with minor alterations of an initial quasi-elliptical design. A gain in lift coefficient of $C_l = 0.09$ was achieved relative to this initial shape

Peroxidase activity of dimanganese(III) complexes with the [Mn2(μ-OAc)(μ-OR)2]3+ core

Catalytic activity of three dinuclear MnIII complexes of general formula [Mn2(μ-OAc)(μ-OMe)(L)]BPh4 (H3L = 1,5-bis[(2-hydroxy-5-X-benzyl)(2-pyridylmethyl)amino] pentan-3-ol, 1: X = H, 2: X = OMe, 3: X = Br) in the oxidation of phenol, 2,6-dimethoxyphenol and wood pulp by H2O2 has been investigated. The role of pH, electronic properties of the ligand and metal coordination environment on the ability of these complexes to activate H2O2 has been examined. The three catalysts showed similar activity independently of the aromatic substituent in the ligand and were found to be 2-3 times more active at pH 9.00 than at neutral pH. Bleaching of Kraft pulp by H2O2 activated by 1 in alkaline media decreased the kappa number of the pulp by 16%, at room temperature and low catalyst concentration, without damage of cellulose fibers. It was found that the exchange of the methoxo- and acetato-bridges by an oxo-bridge reduces the catalytic activity of these compounds, probably by direct binding of phenolate to a vacant site on the metal center.Fil: Biava, Hernan Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Signorella, Sandra Rosanna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

A cellular automaton model of laser-plasma interactions

This paper deals with the realization of a CA model of the physical interactions occurring when high-power laser pulses are focused on plasma targets. The low-level and microscopic physical laws of interactions among the plasma and the photons in the pulse are described. In particular, electron–electron interaction via the Coulomb force and photon–electron interaction due to ponderomotive forces are considered. Moreover, the dependence on time and space of the index of refraction is taken into account, as a consequence of electron motion in the plasma. Ions are considered as a fixed background. Simulations of these interactions are provided in different conditions and the macroscopic dynamics of the system, in agreement with the experimental behavior, are evidenced