A minimal property of cubic splines generated by initial conditions is obtained in order to generate smooth and optimal aerodynamic shape for the aeolian blade profile. [ABSTRACT FROM AUTHOR]
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Posts Tagged ‘AERODYNAMICS’
A minimal property of cubic splines generated by initial conditions is obtained in order to generate smooth and optimal aerodynamic shape for the aeolian blade profile. [ABSTRACT FROM AUTHOR]
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July 14, 2012 Tags: AERODYNAMICS, Cubic, DATA analysis, ERROR analysis (Mathematics), MATHEMATICAL analysis, OPTIMAL designs (Statistics), SPLINE theory, SURFACES
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An innovative aeroacoustic prediction method for Contra-Rotating Open Rotors (CROR) based on the nonlinear harmonic method (NLH) for the CFD computations and on the Ffowcs Williams and Hawkings (FW-H) equations for the far-field acoustic propagation is described. This method is tested on a generic 8 × 8 puller CROR at typical take-off conditions. The outstanding efficiency of the prediction method in terms of CPU cost is demonstrated in this study. An analysis of the aerodynamic interactions between the two rotors as well as of the aeroacoustic field radiated in the far-field is presented, allowing for an improved understanding of noise generation mechanisms. [ABSTRACT FROM AUTHOR]
Read MoreMay 22, 2012 Tags: AEROACOUSTICS, AERODYNAMICS, ELECTRIC machinery, FLUID dynamics, ROTORS
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This work deals with the numerical prediction of the trailing edge noise from rotating blades. A semi-empirical model of the wall pressure spectrum in proximity of the trailing edge is used in connection with an analytical flat-plate aerodynamic response function to compute the acoustic pressure fluctuations on the surface of the blade. Pressure signals with a broadband spectral content are generated by superimposing Fourier components of the blade pressure waves with a stochastic phase distribution. Finally, the far-field noise is computed through a numerical integration of the Ffowcs-Williams and Hawkings equation in the time domain. The hybrid analytical/numerical broadband noise prediction method is verified by computing the trailing-edge noise from a flat plate and comparing its spectrum to the one obtained through a direct analytical extrapolation of the wall pressure spectrum in the frequency domain. The same flat-plate results are then validated against measurements of trailing edge noise spectrum from a NACA-0012 airfoil. The method is finally used to compute the broadband noise from an aircraft propeller and results are compared with analytical results obtained through a blade strip approach. The method and the results described in this paper have been presented at the 14th CEAS-ASC workshop held on 7-8 October 2010 at the Institute of Aviation in Warsaw, Poland. [ABSTRACT FROM AUTHOR]
Read MoreMay 21, 2012 Tags: AERODYNAMICS, AEROFOILS, BLADES, WIND tunnel walls, WIND-pressure
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Abstract: This paper examines the use of eigenvector orientation method to detect the onset of subsonic and supersonic flutter of panels modeled by finite elements. The accuracy of the eigenvector orientation method for prediction of the flutter boundary (indicated by a gradual loss of orthogonality between two eigenvectors) is demonstrated by using the examples of a swept-back cantilever plate model at subsonic speed and a simply supported plate model at supersonic speed. Piezoelectric layers are assumed to be bonded to the top and bottom surfaces of the simply supported plate in order to provide bending moments to control motions of each finite element. An approach of optimal control design is presented to actively suppress the possible flutter based on linear quadratic regulator theory and the nonlinear modal equations of motions. To illustrate the applicability and effectiveness of using the piezoelectric layers as controllers, several cases are studied and presented. The effects of varying locations of control moments are studied so as to fulfill the objective of adjusting the flutter speed to be within a desirable range. The results illustrate that the control moment manipulation can offset the flutter occurrence and additionally generate a lead time for possibly executing flutter control. [Copyright &y& Elsevier]
Read MoreMarch 1, 2012 Tags: AERODYNAMICS, BENDING moment, CANTILEVERS, ECHO suppression (Telecommunication), EIGENVECTORS, EQUATIONS of motion, FLUTTER (Aerodynamics), PIEZOELECTRIC devices, Supersonic
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Abstract: As the speed of high-speed train (HST) increases continuously, aerodynamic noise has become more remarkable compared with the wheel/rail noise, which affects the inhabited environment along the railway and the riding comfort. This paper preliminarily investigates the feasibility of using open-cell metal foam covering layer to reduce the low Mach number aerodynamic noise generated by the flow around a circular cylinder which is the typical section of pantographs. The aerodynamic noises radiated from the circular cylinder with and without metal foam are calculated. The hybrid method combining two-dimensional large eddy simulation (LES) with Ffowcs Williams–Hawkings (FW–H) equation is employed. The calculated Strouhal number, time-averaged drag coefficient, base pressure and overall sound pressure level agree well with some available experimental data. Then, the influences of metal foam porosity, pore density, thickness of covering layer and the speed of train on the aerodynamic noise and the aerodynamic forces are investigated, and some detailed comparisons of flow field are made. The numerical results indicate that as a passive scheme, the open-cell metal foam with high porosity can modify the flow, adjust the vortex shedding frequency and regularize the wake, leading to a significant reduction of aerodynamic noise. The results are expected to provide useful information for the control of aerodynamic noise using this new material. [Copyright &y& Elsevier]
Read MoreMarch 1, 2012 Tags: AERODYNAMIC noise, AERODYNAMICS, HIGH speed trains, MACH number, METAL foams, NUMERICAL analysisLARGE eddy simulation models, PANTOGRAPH, Supersonic
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Abstract: Recently, the requirement for developing high-performance centrifugal fans exists due to increasing system resistance and space limitation on computer devices. Also, performance evaluation of fan design under different operating conditions is evidently in great demand for practical engineering applications. Therefore, this comprehensive investigation is aimed at offering the overall technical information for thoroughly evaluating fan performance. An 80mm-diameter backward-inclined centrifugal fan is chosen to serve as the research subject for demonstration purposes. Numerical results are utilized to perform detailed flow visualization, torque calculation, efficiency estimation, and noise analysis. The results indicate that the fan performance curve and the sound pressure level (SPL) spectrum of the experiment agree with those of numerical simulations. In addition, this study proposes two modification alternatives based on the flow visualization at each operating point, having verified the successful enhancement of fan performance via numerical calculation. Consequently, this study establishes an integrated aerodynamic, acoustic, and electro-mechanical evaluation scheme that can be used as an essential tool for fan designers. [Copyright &y& Elsevier]
Read MoreAbstract: The computation of flow sensitivities for shape optimization in flow problems using continuous adjoint-based boundary integrals reduces the computational costs and makes the scheme independent of the numerical solvers. However, certain analytic manipulations involved in the boundary formulation of the gradients do not hold valid at the discrete level near geometric singularities and lead to inconsistencies in the sensitivities, which add to already known mesh sensitivity issues at the same locations. Both questions appear to be relevant for inviscid flow problems only. These matters are examined and detailed numerical testing is performed on several conventional flow configurations. [Copyright &y& Elsevier]
Read MoreMarch 1, 2012 Tags: AERODYNAMICS, BOUNDARY layer, INVISCID flow, NUMERICAL analysis, SENSITIVITY analysis, SINGULARITIES (Mathematics), STRUCTURAL optimization
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The SuperSonics will move to Oklahoma City for the 2008-9 N.B.A. season as part of a settlement with the city of Seattle, ending a contentious relationship that resulted in a trial in which the judge was due to issue her ruling Wednesday. The settlement calls for the owner of the Sonics, Clay Bennett, and the Professional Basketball Club LLC to pay up to $75 million to the city in exchange for the termination of the KeyArena lease between the team and the city.
Read MoreJuly 3, 2008 Tags: ACTIONS & defenses (Law), AERODYNAMICS, STRUCTURED financial settlements, Supersonic
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