Generation of sound by rotor-stator interaction
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.
About: This article is published in Journal of Sound and Vibration.The article was published on 1970-11-01. It has received 95 citations till now. The article focuses on the topics: Sound pressure & Stator.
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.
168 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.
101 citations
Cites background from "Generation of sound by rotor-stator..."
...The linearized governing equations of the scattered field have constant coefficients and thus the problem can be formulated in terms of a singular integral equation (Kaji & Okazaki 1970b; Goldstein 1976; Atassi 1994)....
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...Numerical solutions have been obtained for the unsteady pressure distribution on the blades and the acoustic radiation upstream and downstream (Kaji & Okazaki 1970a; Smith 1971; Atassi & Hamad 1981)....
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TL;DR: In this article, an unsteady lifting surface theory for a rotating subsonic annular cascade has been developed to predict the blade forces and the acoustic power generation caused by interaction of blades with inlet distortions or wakes.
81 citations
TL;DR: In this article, an unsteady three-dimensional lifting surface theory to predict the sound field of a stator with leaned, i.e., nonradial, vanes in an annular duct is presented.
Abstract: An unsteady three-dimensional lifting surface theory to predict the sound field of a stator with leaned, i.e., nonradial, vanes in an annular duct is presented. The duct carries a uniform subsonic main flow and is assumed to be anechoic. The sound is generated by the interaction of velocity disturbances with the stator vanes. The problem is formulated as an integral equation for the pressure jump across the vanes. This equation is solved by a Fourier series expansion, followed by a collocation procedure. The effect of vane lean on the sound field of a typical stator exposed to the viscous wake system of a rotor is studied. The modal distribution proves to be very sensitive to lean variation. Unless the rotor speed is very low (one mode cut-on), no reduction in the acoustic power at the blade passing frequency is found for any lean angle. On the contrary, even a moderate amount of lean raises the power significantly.
73 citations
TL;DR: The history of research on rotating blade noise is reviewed in this paper, from early studies of propeller radiation to current work on aircraft-engine fans, with emphasis on fundamental aspects of aerodynamic sound generation by blades.
65 citations
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1,138 citations
TL;DR: In this paper, the configuration of viscous wakes of cascade blades is approximated from single airfoil experiments and the unsteady force and moment on a downstream blade passing through such wakes is calculated on the basis of the theory of isolated thin airfoils in nonuniform motion.
Abstract: The configuration of viscous wakes of cascade blades is approximated from single airfoil experiments. The unsteady force and moment on a downstream blade passing through such wakes is then calculated on the basis of the theory of isolated thin airfoils in nonuniform motion. The results indicate that the force is nearly proportional to the profile-drag coefficient of the upstream blades. For typical values of this coefficient and conventional cascade geometry the unsteady forces arising from passage through viscous wakes are of about the same size as those due to aerodynamic interference between the moving blade rows, previously estimated.
139 citations
119 citations
TL;DR: In this paper, an approximate theory of waves in annular ducts gives a physical picture of sound waves in any duct mode; mode shapes and cut-off frequencies are predicted with sufficient accuracy for many purposes.
119 citations
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.
113 citations