Propagation of sound waves through a blade row: II. Analysis based on the acceleration potential method
TL;DR: In this paper, the effect of blade spacing on sound propagation through a blade row with finite blade spacing is investigated theoretically, in which the kernel function of the aerodynamic integral equation is expressed by several series of the exponential functions, under which many circumferential modes propagate as the transmitted wave and reflected wave for one mode of incident waves.
About: This article is published in Journal of Sound and Vibration.The article was published on 1970-03-01. It has received 113 citations till now. The article focuses on the topics: Acoustic wave & Blade element theory.
Citations
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TL;DR: In this paper, an analytical expression for the unsteady loading, acoustic mode amplitude, and sound power output of a three-dimensional rectilinear cascade of blades with finite chord excited by a three dimensional gust was obtained.
168Â citations
TL;DR: In this article, a single acoustic resonance, excited by vortex shedding from the trailing edge of a flat plate, has been studied in detail, where the mode was traversed at resonance and the modal shape and natural frequency were found to agree well with computations.
105Â citations
TL;DR: In this paper, the authors present a survey of recent advances in the theoretical and computational modeling of turbomachinery unsteady flows through blade rows, including the use of Euler and Navier-Stokes simulations.
Abstract: Introduction T HE unsteady aerodynamic analyses intended for turbomachinery aeroelastic and aeroacoustic predictions must be applicable over wide ranges of blade-row geometries and operating conditions and unsteady excitation modes and frequencies. Also, because of the large number of controlling parameters involved, there is a stringent requirement for computational efficiency. To date these requirements have been met only to a limited extent. As a result, aeroelastic and aeroacoustic design predictions are, for the most part, still based on the classical linearized unsteady aerodynamic analyses developed in the early 1970s. During the past decade, significant advances in unsteady aerodynamic prediction capabilities have been achieved. In particular, researchers have developed efficient linearized analyses that account for the effects of important design features, such as real blade geometry, mean blade loading, and operation at transonic Mach numbers, on the unsteady aerodynamic response of the blading to imposed structural and external aerodynamic excitations. The improvements in physical modeling that such linearizations allow are motivating their current implementation into aeroelastic and aeroacoustic design prediction systems. Also, considerable progress has been made on developing time-accurate Euler and Navier-Stokes simulations of nonlinear unsteady flows through blade rows. Although not yet suitable for design use, such analyses offer opportunities for an improved understanding of the unsteady aerodynamic processes associated with blade vibration and noise generation. These recent advances in the theoretical and computational modeling of turbomachinery unsteady flows are reviewed in the present survey.
101Â citations
TL;DR: In this paper, an analytical and numerical analysis for the interaction and scattering of incident acoustic and vortical disturbances by an unloaded annular cascade in a swirling flow is presented. And the results indicate that the swirl changes the physics of the scattering in three major ways: (i) it modifies the number of acoustic modes in the duct, (ii) it changes their duct radial profile, and (iii) it causes significant amplitude and radial phase variations of the incident disturbance.
Abstract: Analytical and numerical analyses are developed for the interaction and scattering of incident acoustic and vortical disturbances by an unloaded annular cascade in a swirling flow. The mathematical formulation uses the Euler equations linearized about an axial and swirling mean flow. The incident disturbances are decomposed into nearly sonic and nearly convected disturbances using the results of a normal-mode analysis, namely the unsteady pressure is predominantly associated with the former. Exact non-reflecting inflow/outflow conditions are derived in terms of the normal modes using the group velocity to segregate the modes propagating downstream and upstream. An inflow condition is also derived for the nearly convected disturbances. An explicit primitive-variable scheme is implemented and validated by comparison with the uniform flow and narrow annulus limits. Acoustic and aerodynamic results are presented to examine how swirl modifies the scattering from that of the uniform flow and narrow annulus limits and to determine the conditions leading to strong scattering. The results indicate that the swirl changes the physics of the scattering in three major ways: (i) it modifies the number of acoustic modes in the duct, (ii) it changes their duct radial profile, and (iii) it causes significant amplitude and radial phase variations of the incident disturbance. The results also show that when the radial phase of the incident disturbance is different from that of the duct modes, weak scattering into the duct acoustic modes occurs. These results suggest that analysis of the radial variation of the incident disturbance and duct modes can provide an indication of the efficiency of the scattering process.
101Â citations
TL;DR: In this article, the rotor-stator interaction was studied theoretically, taking into account the effect of compressibility of fluid and the non-compact source distribution over the blades.
95Â citations
References
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TL;DR: In this article, the transmission and reflection coefficients of axial-flow compressor ducts were studied theoretically using semi-actuator disk theory, and the effects of flow Mach number, angle of incidence, wavelength and stagger angle on sound propagation were investigated.
95Â citations
01 Feb 1958
36Â citations
28Â citations
TL;DR: In this paper, the effect of the presence of the walls is shown to be very significant near the resonant frequency and, for certain conditions, to be large even at frequencies well removed from resonance.
Abstract: The problem of the determination of the air forces on an oscillating airfoil between plane walls has, until recently, been treated only for incompressible flow. The present paper is concerned with the important effects of compressibility, which may be of significance in such problems as the measurement of oscillating air forces or of wing flutter characteristics in wind tunnels, and in the flutter of airfoils in cascade. The possibility of the existence of an acoustic resonance phenomenon under certain critical conditions is discussed. The integral equation for the compressible case, as obtained by Runyan and Watkins in NACA T N 2552, is reviewed briefly and a method of solving the equation is given. The procedure is applied to a number of selected cases at various Mach numbers and tunnel heights. The effect of the presence of the walls is shown to be very significant near the resonant frequency and, for certain conditions, to be large even at frequencies well removed from resonance.
25Â citations