1,721,256 research outputs found
AEROELASTIC ANALYSIS OF MULTIBLADED HINGELESS ROTORS IN HOVER
No full textThe coupled flap-lag-torsion aeroelastic response and stability of multibladed hingeless rotors in the hovering flight condition are investigated. The vortex lattice method, with a three-dimensional prescribed wake geometry, is used for the prediction of unsteady airloads of multibladed rotors undergoing disturbed dynamic motions. Interblade unsteady wake effects due to vortex-phasing phenomena beneath a rotor are numerically calculated by the phase control of wake vortices shed from each blade. The aeroelastic equations of motion of the rotor blade are formulated using a finite element beam model that has no artificial restrictions on the magnitudes of displacements and rotations due to the degree of nonlinearity. Numerical results of the steady equilibrium deflections and the lead-lag damping and frequency are presented for two-, three-, and four-bladed stiff-inplane rotors, and are compared with those obtained from a two-dimensional quasisteady strip theory with steady and uniform inflow
SUPERSONIC FLUTTER ANALYSIS OF CLAMPED SYMMETRICAL COMPOSITE PANELS USING SHEAR DEFORMABLE FINITE-ELEMENTS
No full textTHE flutter analysis of composite panels in supersonic flow has been performed by the finite element method based on the first-order shear deformable theory. The computational results of the vibration and flutter analysis agree well with the results given in the available references. Flutter boundaries have been obtained for both cross-ply and angle-ply composite plates. Also, the flutter analysis has been performed for both rectangular and trapezoidal plates with clamped edges. The plate aspect ratio, flow direction, and fiber orientation affect greatly the flutter boundaries
AEROELASTIC STABILITY OF HINGELESS ROTOR BLADE IN HOVER USING LARGE DEFLECTION THEORY
No full textThe coupled flap-lag-torsion aeroelastic stability of a hingeless rotor blade in hover is investigated using finite elements based on large deflection beam theory. The finite element equations of motion for beams arbitrary large displacements and rotations, but small strains, are obtained from Hamilton's principle. The stability boundary is calculated assuming blade motions to be small perturbations about the nonlinear steady equilibrium deflections, which are obtained through an iterative Newton-Raphson method. The p-k modal flutter analysis based on coupled rotating natural modes is used. Various unsteady two-dimensional strip theories am used to evaluate the aerodynamic loads. The sensitivity of the stability boundary to these aerodynamic assumptions is examined. Numerical results of the steady deflections and stability boundaries are presented for some representative blade configurations and also compared with those given in previous moderate deflection type theories
FINITE-ELEMENT ANALYSIS OF COMPOSITE PANEL FLUTTER
No full textThe finite element method based on the shear deformable theory is developed to analyze the composite panel flutter in supersonic flow. The computational results of the vibration and flutter analysis agree well with those given in the available references. Guyan reduction and the normal mode method are used to reduce the computational time. The plate length ratio, the flow direction and the fiber orientation greatly affect the flutter boundaries of trapezoidal laminated plates. Flutter boundaries have been calculated for both simply supported and clamped boundaries in order to determine the effect of boundary conditions
Decomposition of volatile organic compounds by a microwave plasma discharge process at atmospheric pressure
No full textThe application of a microwave plasma process operated at atmospheric pressure to the decomposition of volatile organic compounds has been investigated. This microwave plasma system consists of a 2.45 GHz magnetron detached from a household microwave oven, a directional coupler, a three-stud tuner, a tapered waveguide terminated by a movable plunger, and plasma flame section where a quartz tube with a copper nozzle is located. In this system, the organic compounds such as toluene and trichloroethylene can be decomposed in the way of thermal incineration as well as by the reactions with a variety of active species formed during plasma discharge. The effect of feed gas flow rate on the decomposition was significant because it changed the gas temperature, but the initial concentration of the organic compound in the range of 210-2,100 ppm did not largely affect the decomposition efficiency. The principal byproduct was nitrogen oxides because this system was operated at high temperature. To improve the decomposition of the organic compounds, argon was used as a plasma-assisting gas, together with the air-like feed gas mixture. Large enhancement in the decomposition efficiency of the organic compounds was achieved by the use of argon.X11sciescopu
Particle-in-cell simulation of power coupling of the grill of the KSTAR 5.0-GHz LHCD launcher
No full textThe 5.0-GHz, 2.0-MW KSTAR, Lower-Hybrid Current Drive (LHCD) system is under design for steady-state operation of the KSTAR, tokamak. The launcher structure is designed as a grill (4 rows by 32 columns; phased-array waveguide structure) that provides asymmetric power spectra. The KSTAB. tokamak plasma is a high-density and high-temperature plasma with an edge density of similar to 10(18) m(-3). The power coupling to the KSTAR plasma edge depends on the impedance matching between the grill assembly and the lower hybrid (LH) wave in the edge plasma. The coupling and the wave propagation in the KSTAB, plasma are investigated using the 2-dimensional Particle-In-Cell code (XOOPIC-2D code). This paper describes the preliminary result of the LH power-coupling calculation and the characteristics of the wave propagation.1112sciescopuskc
Neutron Total Cross-section Measurements with the Li-6-ZnS(Ag) scintillator (BC702) Employing a Neutron and Noise Separation Technique (vol 64, pg 1290, 2014)
No full textX110Ysciescopu
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