Engineering Commons^™

Laminar/Turbulent Oscillating Flow In Circular Pipes, Kyung H. Ahn, Mounir B. Ibrahim

Mechanical Engineering Faculty Publications

A two-dimensional oscillating flow analysis was conducted simulating the gas flow inside Stirling engine heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re_max = 1,920 (Va = 80), 10,800 (Va = 272), 19,300 (Va = 272), and 60,800 (Va = 126). The results are here compared with experimental results of previous investigators. Predictions of the flow regime on present oscillating flow conditions are also checked by comparing velocity amplitudes and phase difference with those from laminar theory and quasi-steady profile. A high Reynolds number k-ε turbulence model was used for turbulent oscillating pipe flow. …

Effect Of Operating Conditions On Gearbox Noise, Fred B. Oswald, James J. Zakrajsek, Dennis P. Townsend, William Atherton, Hsiang Hsi Lin

Mechanical Engineering Faculty Publications

Low-contact-ratio spur gears were tested in the NASA gear noise rig to study the noise radiated from the top of the gearbox. The measured sound power from the gearbox top was obtained from a near-field acoustic intensity scan taken at 63 nodes just above the surface. The sound power was measured at a matrix of 45 operating speeds and torque levels. Results are presented in the form of a spectral speed map and as plots of sound power versus torque (at constant speed) and as sound power versus speed (at constant torque) Because of the presence of vibration modes, operating …

Comparison Of Analysis And Experiment For Gearbox Noise, Fred B. Oswald, A. F. Seybert, T. W. Wu, William J. Atherton

Mechanical Engineering Faculty Publications

Low-contact-ratio spur gears were tested in the NASA gearnoise rig to study the noise radiated from the top of the gearbox. Experimental results were compared with a NASA acoustics code to validate the code for predicting transmission noise. The analytical code is based on the boundary element method (BEM) which models the gearbox top as a plate in an infinite baffle. Narrow-band vibration spectra measured at 63 nodes on the gearbox top were used to produce input data for the BEM model. The BEM code predicted the total sound power based on this measured vibration. The measured sound power was …

Data Communication Between An Expert System Shell And A Conventional Algorithmic Program With Application To Cam Motion Specification, Paul P. Lin, An-Jen Yang

Mechanical Engineering Faculty Publications

Although more and more expert system shells have begun to provide communication interfaces to conventional procedural languages, the interfaces are basically shell- and language-dependent. This paper presents a simple, shell- and language-independent data communication technique between a shell and a procedural language via a concept analogous to the handshake data transmission used in microprocessors. A control file is used for the action of handshake. The communication interface is between two data files in two different language environments. A program written in a LISP-based expert system shell, OPS 5, and one written in a procedural language, FORTRAN, were …

A Turbulence Model For The Heat Transfer Near Stagnation Point Of A Circular Cylinder, Mounir B. Ibrahim

Mechanical Engineering Faculty Publications

A one-equation low-Reynolds number turbulence model has been applied successfully to the flow and heat transfer over a circular cylinder in turbulent cross flow. The turbulence length-scale was found to be equal 3.7y up to a distance 0.05δ and then constant equal to 0.185δ up to the edge of the boundary layer (wherey is the distance from the surface and δ is the boundary layer thickness).

The model predictions for heat transfer coefficient, skin friction factor, velocity and kinetic energy profiles were in good agreement with the data. The model was applied for Re ≤250,000 and Tu_{∞ …}

Automated Acoustic Intensity Measurements And The Effect Of Gear Tooth Profile On Noise, William J. Atherton, Adam Pintz, David G. Lewicki

Mechanical Engineering Faculty Publications

Acoustic intensity measurements were made at NASA Lewis Research Center on a spur gear test apparatus. The measurements were obtained with the Robotic Acoustic Intensity Measurement System developed by Cleveland State University. This system provided dense spatial positioning, and was calibrated against a high quality acoustic intensity system. The measured gear noise compared gearsets having two different tooth profiles. The tests evaluated the sound field of the different gears for two speeds and three loads. The experimental results showed that gear tooth profile had a major effect on measured noise. Load and speed were found to have an effect on …