No description available.

No description available.

Thesis (Ph. D.)--University of Hong Kong, 1993.

Thesis (PH. D.)--Michigan State University. Mechanical Engineering, 2008. / Title from PDF t.p. (viewed on Sept. 8, 2009) Includes bibliographical references (p. 104-108). Also issued in print.

Noise prediction methods are necessary in aspects of aerodynamic and hydrodynamic engineering. Predictive models of noise from rotating machinery ingesting turbulence is of much interest and relatively recently studied. This thesis presents a numerical method processed in a series of three codes that was written and edited to receive input for geometrical features of rotating machinery, as well as, adjustments to turbulent operating conditions. One objective of this thesis was to create a platform of analysis for any rotor design to obtain five parameters necessary for noise prediction; 1) the hydrodynamic inflow angle to each blade section, 2) chord length as a function of radius, 3) the cylindrical radius of each blade section, 4) & 5) the leading edge as a function of span in both the rotor-plane and as a function of axial distance downstream. Another objective of this thesis was to use computational fluid dynamics (CFD), specifically by using a Reynold’s-Averaged Navier-Stokes (RANS) Shear Stress Transport (SST) 𝑘 − 𝜔 model simulation in ANSYS Fluent, to obtain the turbulent kinetic energy distribution, also necessary in the noise prediction method presented. The purpose of collecting the rotor geometry data and turbulent kinetic energy data was to input the values into the first of the series of codes and run the calculation so that the output spectra could be compared to experimental noise measurements conducted at the Stability Wind Tunnel at Virginia Tech. The comparison shows that the prediction method results in data that can be reliable if careful attention is payed to the input parameters and the length scale used for analysis. The significance of this research is the noise prediction method presented and used simplifies the model of turbulence by using a correlation function that can be determined by a one-dimensional function while also simplifying the iterations completed on rotor blade to calculate the unsteady forces. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

No description available.

A linear model based on the wave-envelope technique is used to study the propagation of axisymmetric and spinning acoustic modes in hard-walled and lined nonuniform circular ducts carrying near sonic mean flows. This method is valid for large as well as small axial variations, as long as the mean flow does not separate. The wave-envelope technique is based on solving for the envelopes of the quasiparallel acoustic modes that exist in the duct instead o£ solving for the actual wave, thereby reducing the computational time and the round-off error encountered in purely numerical techniques. The influence of the throat Mach number, frequency, boundary-layer thickness and liner admittance on both upstream and downstream propagation of acoustic modes is considered. A numerical procedure, which is stable for cases of strong interaction, for analysis of nonlinear acoustic propagation through nearly sonic mean flows is also developed. This procedure is a combination of the Adams-PECE integration scheme and the singular value decomposition scheme. It does not develop the numerical instability associated with the Runge-Kutta and matrix inversion methods for nearly sonic duct flows. The numerical results show that an impedance condition can be satisfied at the duct exit and a corresponding solution obtained. The numerical results confirm that the nonlinearity intensifies the acoustic disturbance in the throat region, reduces the intensity of the fundamental frequency at the duct exit, and increases the reflections. This implies that the mode conversion properties of variable area ducts can reflect and focus the acoustic signal to the vicinity of the throat in high subsonic flows. Also the numerical results indicate that a shock develops if certain limits on the input parameters are exceeded. / Ph. D.

A computational study of the air flow in a helical rocket pump inducer has been performed using a 3-D elliptic flow procedure including viscous effects. The inlet flow is considered turbulent and fully developed. The geometric, definition of the inducer blade shape and the calculation grid are first presented, followed by a discussion of the flow calculation results displayed in various new graphical representations. The general characteristics expected from previous experimental and analytical work appear in the simulation and were quantitatively studied. The tip leakage flow observed has velocities of the order of the blade tip speed and is partially convected across the entire passage. The important boundary layer development on the blade pressure side and suction side creates radial outward flows, whereas a radial inward motion develops in the core region, with velocities of same order, and from shroud to hub. Secondary and tip leakage flows combine to give a region of high flow losses and blockage near the shroud wall, and the secondary flow pattern is nearly fully developed by the inducer exit. Original details were also resolved in the flow calculation. A circumferential vortex develops near the shroud, immediately upstream of the suction side of the swept-back leading edge. A simplified air-LH2 analogy permitted the prediction of cavitation inception in the liquid hydrogen pump, and the results obtained correspond qualitatively well with water flow visualizations. The accordance of the model with available air test data at the inlet and exit of the inducer is generally very good, with the total pressure losses in excellent agreement. / Master of Science

A study was conducted to determine the effect of strut position on the aerodynamic and acoustic performance of a supersonic inlet. The investigated inlet was a prototype 1/14 scale model of a mixed compression, axisymmetric supersonic inlet designed for the high speed civil transport aircraft. A 10.4 cm (4.1 in.) turbofan engine simulator was used in conjunction with the inlet to provide the typical noise signature of a high bypass turbofan engine. Two inlet configurations were investigated in this study. The first configuration was the standard inlet design where the struts are located immediately upstream of the fan. The new configuration has the struts located 3.3 chord length upstream of the fan. The purpose for relocating the strut position was to reduce the flow distortion and radiated noise level. The experiment was conducted at various fan operating conditions in order to simulate aircraft approach. The inlet was tested statically without simulating the inflight speed effects. Steady state measurements were made in order to evaluate the aerodynamic performance of the inlet. The aerodynamic results show that the movement of the struts to a new location allowed the strut wake to diffuse significantly before reaching the fan. This reduced the circumferential distortion parameter by a factor of 2.4, without affecting the pressure recovery of the inlet at a fan Abstract speed of 30,000 rpm (40 PNC). Acoustic measurements were taken in the far field in the 0°-110°sector from the inlet axis. The new configuration of the inlet showed an improved acoustic performance over the standard design. Relocating the struts upstream reduced the blade passing tone by an average of 8 dB (0°-110°) sector, and the overall sound pressure level was lowered by an average of 2.6 dB at a fan speed of 30,000 rpm (40 PNC). / Master of Science

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy