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Huang H.,University of Tennessee at Knoxville | Ekici K.,Mechanical
AIAA Journal | Year: 2014

We investigate the application of a temporal spectral viscosity operator to eliminate aliasing errors associated with the high-dimensional harmonic balance technique, which is an efficient method for modeling nonlinear time-periodic problems. Previous studies have shown that aliasing errors resulting from the discrete Fourier transformation may slow down convergence, trigger a nonlinear instability, or lead to nonphysical solutions. A temporal spectral viscosity operator, similar to that used for pseudospectral methods, is introduced. The temporal spectral viscosity is added to the high-frequency modes of the solution to eliminate aliasing errors so as to ensure the convergence to the physical solution. The implementation of the technique is straightforward and can be incorporated into the high-dimensional harmonic balance solver as a matrix product operator. The accuracy and effectiveness of the modified method is demonstrated for different test cases including a Duffing oscillator and unsteady flow about an oscillating circular cylinder. Finally, the temporal spectral viscosity is applied to a turbomachinery aeroelasticity problem to investigate the effect of added dissipation on the accuracy of unsteady solutions. Copyright © 2013 by Huang Huang and Kivanc Ekici.

Safai N.M.,Mechanical | Thompson C.F.,Salt Lake Community College
ASEE Annual Conference and Exposition, Conference Proceedings | Year: 2012

This paper will cover the ideas and concepts presented to first year civil engineering students through classroom lecture combined with onsite international field study. This paper will allow a case study to be presented that will outline the basis for increasing global awareness of first year civil engineering students by exposing them to more than just simple classroom instruction and textbook reading. In order to create a well-rounded civil engineer, educators and academic institutions will have a need to tie together classroom lecture and global competency through international field study, creating a viable global civil engineering student model. For example, Salt Lake Community College in Salt Lake City, Utah, avidly supports a classroom culture that contains international implications as demonstrated by the acceptance of society level engineering organizations. By combining engineering lecture topics such as The Hoover Dam, nuclear science, and The Colorado River Bridge with actual onsite field study, a distinct connection will be made between the technical subject and reality. Salt lake Community College students have educational requirements to be completed as dictated by their Engineering Department. During engineering courses such as "Special Topics in Engineering" and "Civil Engineering Design," each student is exposed to an endless number of engineering subjects. Each student will then be presented with the possibility to field visit a few select specific topics discussed during these required classroom lectures. Civil Engineering Students have already had the opportunity to visit The Hoover Dam and The Colorado River Bridge. Salt lake Community College Civil Engineering students have visited and received a personalized tour of a TRIGA Nuclear Reactor present on the University of Utah campus. The growth and future outlook of international field study is increased with the possibility of visiting a global engineering sites such as the Panama Canal. Allowing students to validate their educational experience with the combination of classroom lecture and onsite international field study will produce a civil engineering student who will not only increase their global competency and awareness, but they will foster passion for their future professional career. © 2012 American Society for Engineering Education.

Linze N.,Boulevard Dolez | Tihon P.,Mechanical | Verlinden O.,Mechanical | Megret P.,Boulevard Dolez | Wuilpart M.,Boulevard Dolez
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

In this paper we propose a novel kind of quasi-distributed polarimetric vibration sensor. Its functioning is based on the use of mechanical transducers, which transform the mechanical vibration into a birefringence variation, and of fiber Bragg gratings (FBGs), which reflect light from different positions. As it will be shown this sensor can provide the vibration frequency in a quasi-distributed manner. © 2012 SPIE.

Rathay N.W.,Rensselaer Polytechnic Institute | Rathay N.W.,Boeing Company | Boucher M.J.,Boeing Company | Amitay M.,Mechanical | Whalen E.,Boeing Company
50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition | Year: 2012

Active flow control with synthetic jets has been shown to increase aerodynamic efficiency by delaying flow separation. Application of flow control to a vertical stabilizer of an aircraft could enable a significant size reduction of that stabilizer. Wind tunnel experiments were conducted at Rensselaer Polytechnic Institute on a swept back, tapered stabilizer with a 33% chord rudder. Flow control was implemented using eight synthetic jet actuators located just upstream of the hinge-line. The mechanism of enhancement was characterized with surface pressure measurements and stereoscopic particle image velocimetry (SPIV). Using flow control, the side force was increased by up to 20% at moderate rudder deflections with actuators operating at dimensionless frequency O(10). Actuating the synthetic jets with a pulse-modulated waveform yielded superior performance at high rudder deflections. The effect of spanwise spacing was also investigated, as was the relative effect of actuators at different spanwise locations. It was demonstrated that mid-span actuators provide the greatest contribution at moderate rudder deflections, and root (inboard) actuators provide the greatest contribution a high deflections. Given that separation propagates from tip to root as rudder deflection increases, this correlates well with SPIV measurements, which show that the effect of each actuator is predominantly on a region outboard of its own position. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Linze N.,Boulevard Dolez | Tihon P.,Mechanical | Verlinden O.,Mechanical | Megret P.,Boulevard Dolez | Wuilpart M.,Boulevard Dolez
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

In this paper we propose a novel kind of quasi-distributed vibration sensor based on the measurement of the polarization state of light. Its principle is based on the combination of mechanical transducers -which transform the mechanical perturbation into a birefringence variation- with fiber Bragg gratings. We show that several vibrations can be detected and localized at each transducer position with a frequency resolution of 1.25 Hz. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Sreenivasulu A.,Mechanical | Venkatachalapathi N.,Velammal Engineering College | Prasanthi G.,P.A. College
Journal of Advanced Manufacturing Systems | Year: 2015

The aim of this paper is to deal with a simulation study on effect of part launching, part sequencing at central buffer and tool selection rules on a flexible manufacturing system (FMS) involving tool movement along with part movement policy. A typical FMS is selected for a study of discrete event simulation model. Simulation experiments are conducted on various combinations of decision rules and it is found to be good in evaluated performance measures. © 2015 World Scientific Publishing Company.

Vande Cavey M.,Mechanical | Helsen L.,Mechanical | Tant J.,ESAT | Geth F.,ESAT | Driesen J.,ESAT
IET Conference Publications | Year: 2013

This paper presents real-time control strategies for peak shaving and voltage control provided by a Battery Energy Storage System in a low voltage grid. Two performance indices, one for peak shaving and one for voltage control, are proposed to quantify the results. The strategies are compared with a benchmark which is calculated as an ex post optimization that solves the control problem together with the sizing problem. First, a rule-based strategy for peak shaving is presented which only injects active power. Afterwards, the strategy is extended with voltage control through reactive power injection. In the latter case, an optimization problem is solved at each time step to decide at which rate active and reactive power should be injected.

Perez D.,Mechanical | Bevilacqua R.,Mechanical
Advances in the Astronautical Sciences | Year: 2013

An atmospheric differential drag based adaptive Lyapunov controller, originally proposed by the authors in previous work for spacecraft rendezvous, is here generalized allowing for the tracking of reference trajectories or dynamics. Differential drag is based on the ability to vary a satellite's cross wind surface area, and it represents a propellant-free alternative to thrusters to control relative motion of low Earth orbiting spacecraft. The interest in autonomous propellant-less maneuvering comes from the desire of reducing costs of performing formation maneuvering. Formation maneuvering opens up a wide variety of new applications for spacecraft, such as on-orbit maintenance missions and refueling. The control technique is successfully tested using Systems Tool Kit simulations for re-phase, fly-around, and rendezvous maneuvers, proving the feasibility of the proposed approach for a real flight. © 2013 2013 California Institute of Technology.

Perschke R.F.,Mechanical | Ramachandran R.C.,Mechanical | Raman G.,Mechanical
Journal of Sound and Vibration | Year: 2015

The acoustic properties of a wall jet over a hard-walled backward-facing step of aspect ratios 6, 3, 2, and 1.5 are studied using a 24-channel microphone phased array at Mach numbers up to M=0.6. The Reynolds number based on inflow velocity and step height assumes values from Reh=3.0×104 to 7.2×105. Flow without and with side walls is considered. The experimental setup is open in the wall-normal direction and the expansion ratio is effectively 1. In case of flow through a duct, symmetry of the flow in the spanwise direction is lost downstream of separation at all but the largest aspect ratio as revealed by oil paint flow visualization. Hydrodynamic scattering of turbulence from the trailing edge of the step contributes significantly to the radiated sound. Reflection of acoustic waves from the bottom plate results in a modulation of power spectral densities. Acoustic source localization has been conducted using a 24-channel microphone phased array. Convective mean-flow effects on the apparent source origin have been assessed by placing a loudspeaker underneath a perforated flat plate and evaluating the displacement of the beamforming peak with inflow Mach number. Two source mechanisms are found near the step. One is due to interaction of the turbulent wall jet with the convex edge of the step. Free-stream turbulence sound is found to be peaked downstream of the step. Presence of the side walls increases free-stream sound. Results of the flow visualization are correlated with acoustic source maps. Trailing-edge sound and free-stream turbulence sound can be discriminated using source localization. © 2014 Elsevier Ltd. All rights reserved.

Ramachandran R.,Mechanical | Raman G.,Mechanical | Dougherty R.,Optinav, Inc.
Wind Engineering | Year: 2012

Locating the dominant noise sources on a wind turbine is an important problem in designing and developing low noise wind turbines. Previously very large microphone arrays were used to locate these sources. The primary focus of this paper is to show that using a compact and mobile microphone array with advanced beamforming algorithms, the noise sources can be successfully located and quantified. The results from the qualification experiments on the microphone array conducted in laboratory using synthetic noise sources show the differences between the various beamforming algorithms used in this study (both frequency and time domain algorithms). The initial experimental results on a full scale wind turbine reveal that it is indeed possible to locate the noise sources using a compact microphone array by successfully locating the two dominant noise sources on the wind turbine namely, aerodynamic noise near the blade tip and mechanical noise from nacelle.

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