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Ray M. Chi - One of the best experts on this subject based on the ideXlab platform.

  • An unsteady Lifting Surface theory for ducted fan blades
    Journal of Turbomachinery, 1993
    Co-Authors: Ray M. Chi
    Abstract:

    A frequency domain Lifting Surface theory is developed to predict the unsteady aerodynamic pressure loads on oscillating blades of a ducted subsonic fan. The steady baseline flow as observed in the rotating frame of reference is the helical flow dictated by the forward flight speed and the rotational speed of the fan. The unsteady perturbation flow, which is assumed to be potential, is determined by solving an integral equation that relates the unknown jump in perturbation velocity potential across the Lifting Surface to the upwash velocity distribution prescribed by the vibratory motion of the blade. Examples of unsteady pressure distributions are given to illustrate the differences between the three-dimensional Lifting Surface analysis and the classical two-dimensional strip analysis. The effects of blade axial bending, bowing (i.e., circumferential bending), and sweeping on the unsteady pressure load are also discussed.

  • An Unsteady Lifting Surface Theory for Ducted Fan Blades
    Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 1991
    Co-Authors: Ray M. Chi
    Abstract:

    A frequency domain Lifting Surface theory is developed to predict the unsteady aerodynamic pressure loads on oscillating blades of a ducted subsonic fan. The steady baseline flow as observed in the rotating frame of reference is the helical flow dictated by the forward flight speed and the rotational speed of the fan. The unsteady perturbation flow, which is assumed to be potential, is determined by solving an integral equation that relates the unknown jump in perturbation velocity potential across the Lifting Surface to the upwash velocity distribution prescribed by the vibratory motion of the blade. Examples of unsteady pressure distributions are given to illustrate the differences between the three dimensional Lifting Surface analysis and the classical two dimensional strip analysis. The effects of blade axial bending, bowing (i.e., circumferential bending) and sweeping on the unsteady pressure load are also discussed.Copyright © 1991 by ASME

Jiunn-jyi Lin - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear hydroelastic behavior of propellers using a finite-element method and Lifting Surface theory
    Journal of Marine Science and Technology, 1996
    Co-Authors: Huei-jeng Lin, Jiunn-jyi Lin
    Abstract:

    A finite-element method coupled with analysis of a noncavitating Lifting Surface was used to assess the performance of a marine propeller, including the thrust, torque, efficiency coefficients, and deflections. The formulation used displacements as unknowns in the structural part and the strength of the vortex as unknowns in the fluid part. A coupled matrix derived from the Bernoulli equation and hydrostatic pressure in terms of the strength, of the vortex enforced coupling between the fluid and the structure. The resulting matrix equation was unsymmetric and nonlinear; a Newton-Raphson procedure was used to solve this equation. The numerical results were compared with test data; computed and measured values agreed satisfactorily. We also investigated the effect of blade thickness on the performance and strength of the propeller. We did not consider the fatigue strengh of the propeller in this analysis.

P. Gasbarri - One of the best experts on this subject based on the ideXlab platform.

  • Lifting Surface in Subsonic Unsteady Regime
    Meccanica, 1999
    Co-Authors: P. Santini, P. Gasbarri
    Abstract:

    The paper refers to the solution of the integral equation for the acceleration (or pressure) potential for the study of subsonic linearized unsteady flow in view of aeroelastic applications. The case considered is relevant to a trapezoidal wing infinitely thin Surface without discontinuities. As is well known [1, 2], the kernel of the integral equation exhibits three singularities, two of which are integrable in elementary form, whereas, for the third one integration in principal part according to Hadamard's rule is necessary. The kernel is therefore reworked in such a way that all the singularities are separated from the regular part, and eventually the discretization is performed in such a way that only the regular part is to be recalculated for each new value of the reduced frequency. Convergence tests, comparison with other methods of solution, and time saving associated with the technique of separation are also shown. Sommario. II lavoro tratta la risoluzione del problema relativo alla equazione integrale nel potenziale di accelerazione (o di pressione) per lo studio di una corrente subsonica linearizzata nonstazionaria, in vista di applicazioni aeroelastiche. Il caso considerato è quello di una superficie alare a pianta trapezoidale in assenza di discontinuità di spessore infinitesimo. Come è noto [1, 2], il nucleo della equazione integrale in parola presenta tre singolarità, due sole delle quali sono integrabili in forma elementare, (o riconducibili ad essa), mentre per la terza è necessario far ricorso alla integrazione in parte principale alla Hadamard. Il nucleo stesso viene quindi rielaborato in modo da isolare tutte le singolarità dalla componente regolare del nucleo; si procede così alla discretizzazione dell' equazione integrale, e, per ogni valore della frequenza ridotta, va ricalcolata solo la parte regolare della matrice risolvente. Vengono poi effettuati tests di convergenza, confronti con altri metodi di soluzione, analisi sui tempi di calcolo e risparmio di tempo di calcolo dovuto alla tecnica di separazione.

Koichi Koyama - One of the best experts on this subject based on the ideXlab platform.

  • Relation between the Lifting Surface theory and the Lifting line theory in the design of an optimum screw propeller
    Journal of Marine Science and Technology, 2013
    Co-Authors: Koichi Koyama
    Abstract:

    A theory on an optimum screw propeller is described. The optimum means optimum efficiency of a propeller, that is, maximizing thrust horse power for a given shaft horse power. The theory is based on the propeller Lifting Surface theory. Circulation density (lift density) of the blade is determined by the Lifting Surface theory on a specified condition in general. However, it is shown that, in the case of optimum condition, the circulation density is not determined by the Lifting Surface theory, although the circulation distribution which is the chordwise integral of the circulation density is determined. The reason is that the governing equation of the optimization by the Lifting Surface theory is reduced to that by the Lifting line theory. This theoretical deduction is the main part of this paper. The importance of the Lifting line theory in the design of the optimum propeller is made clear. Numerical calculations support the conclusion from the deduction. This is shown in the case of freely running propellers and in the case of wake adapted propellers.

R. T. Medan - One of the best experts on this subject based on the ideXlab platform.

  • Boundary condition program for aerodynamic Lifting Surface theory
    2013
    Co-Authors: R. T. Medan, K. S. Ray
    Abstract:

    Users manual for a U.S.A. FORTRAN 4 computer program which determines boundary conditions for a thin wing Lifting Surface program is described. This program, the geometry program, and several other programs are used together in the analysis of Lifting, thin wings in steady, subsonic flow according to a kernel function Lifting Surface theory. The program calculates specific types of boundary conditions automatically such as those necessary to determine pitch and roll damping derivatives. The program also accepts descriptions of the camber or downwash and twist in the form of tables and/or coefficients of equations. The program performs interpolations so that tables and/or coefficients can apply at stations selected by the user and not at stations dictated by the control point locations.

  • Plotting program for aerodynamic Lifting Surface theory
    2013
    Co-Authors: K. S. Ray, R. T. Medan
    Abstract:

    A description of and users manual for a USA FORTRAN IV computer program which plots the planform and control points of a wing are presented. The program also plots some of the configuration data such as the aspect ratio. The planform data is stored on a disc file which is created by a geometry program. This program, the geometry program, and several other programs are used together in the analysis of Lifting, thin wings in steady, subsonic flow according to a kernel function Lifting Surface theory.