61-63 of 63 results

  • ACTIVE CONTROL OF SUPERSONIC JET NOISE VIA BI-MODAL EXCITATION



    Jet noise is a major problem for both military and commercial aircraft, and there is a lot of interest in ways to reduce it.  In this research project sponsored by the Office of Naval Research, the objective is to implement active control in rectangular jets to reduce the noise.  This is to be done by exciting the jet at a fundamental frequency as well as either a harmonic or subharmonic frequency.  The amplitudes of the excitation are small, thus there should be minimal impact of excitation on aircraft performance.  In doing this, we can manipulate the large-scale structures in the jet, which is the dominant noise source.  The working principle here is that energy from the fundamental mode is transferred to the subharmonic or harmonic, which results in a reduction of the peak noise. 

    In order to compute the noise sources, High-Fidelity Large Eddy Simulations (LES) is done by modifying a code originally developed by the Air Force Research Laboratory, which uses high-order numerical schemes.  However, LES is very computationally expensive and can take weeks to obtain results when running on a supercomputer.  Choosing the wrong excitation parameters can result in zero noise reduction or even enhancement of the noise.  To predict optimal excitation parameters, a Reduced-Order Model (ROM) has been derived to predict the propagation of noise sources in a jet.  Inputs to the ROM can come from linear methods such as Linear Stability Analysis or the Linearized Euler Equations.  Once the ROM is set up, a set of nonlinear differential equations can be solved numerically.  By comparison, this takes only a matter of seconds and does not require the use of a supercomputing cluster.  Using these results, we can observe the damping effect on the dominant noise source, and optimal excitation parameters can be chosen as inputs into LES.

    Current work is focused on performing LES on a Mach 1.5 planar jet, which approximates the flow in the minor plane of a rectangular jet.  This is being done to validate open-loop control using results from the ROM.  Both the symmetric and asymmetric modes will be studied.  Future work will involve performing LES on a Three-dimensional rectangular jet, which will be more representative of a real jet.  Here, closed-loop control can also be implemented.  By measuring the noise signal near the exit of the jet, parameters can be inputted to the ROM to give optimal excitation parameters thereby maximizing the noise reduction.


    Categories: Faculty-Staff

  • The S-Band Array for Bistatic Electromagnetic Ranging (SABER)

    CO-I Brian Butka

    Faculty in the Electrical, Computer, Software, and Systems Engineering Department at Embry-Riddle are developing new radar that may alter the paradigm of locating aircraft.



    Unlike standard radars that generate high-power radio pulses and listen for the return echoes indicating aircraft, the SABER system has no transmitter of its own. Instead, the researchers use weak echoes of signals from existing satellites high above the Earth to locate their quarry.Passive radars exploiting environmental signals are not uncommon and systems using television and radio stations have been known for more than a decade; however, systems using satellites are unique. Satellite signals are much weaker than ground-based signals, and are often considered too weak to be useful. The key, says Barott, is in the signal processing, which is able to identify the very weak echoes - and thus the aircraft - among the sea of radio noise and interfering signals.

    Passive radars exploiting environmental signals are not uncommon and systems using television and radio stations have been known for more than a decade; however, systems using satellites are unique. Satellite signals are much weaker than ground-based signals, and are often considered too weak to be useful. The key, says Barott, is in the signal processing, which is able to identify the very weak echoes - and thus the aircraft - among the sea of radio noise and interfering signals.The researchers envision many applications for passive radars using satellite-based signals. To start with, a network of inexpensive stations could supplement existing systems for tracking low-altitude aircraft, and provide coverage in mountainous regions where little radar coverage currently exists. “It's a similar idea to why you might get satellite television,” says Barott. “Remote locations and rough terrain might block ground-based signals, but are no problem for satellites sending their signals down from orbit.” Other applications include rapid deployment radars and approach radars for remote airfields. The researchers also note potential applications utilizing the covert and stealth-detecting aspects of this type of radar

    Categories: Faculty-Staff

  • GAANN

    CO-I William Engblom

    CO-I J. Gordon Leishman

    This project is sponsored by the Department of Education Graduate Assistance in Areas of National Need (GAANN) fellowship program to support six to 10 Ph.D. students of high ability and financial need in the Department of Aerospace Engineering at Embry-Riddle Aeronautical University.

    This project is sponsored by the Department of Education Graduate Assistance in Areas of National Need (GAANN) fellowship program to support six to 10 Ph.D. students of high ability and financial need in the Department of Aerospace Engineering at Embry-Riddle Aeronautical University. The purpose of the program is to enhance and diversify the pool of U.S. citizens who are qualified to teach and pursue research careers in the field of aerospace engineering.

    Embry-Riddle's Aerospace Engineering Department is among the top aerospace engineering programs in the nation. It is currently ranked 32nd for its graduate programs and 8th for its undergraduate program by U.S. News and World Report. The department currently has 34 faculty comprised of distinguished researchers and teachers in the fields of aerodynamics and propulsion, dynamics and control, as well as structures and materials.

    GAANN Fellows will participate in a formal training/teaching program, which will allow them to learn, observe experienced teachers and gain hands-on experience in teaching. Fellows will receive instruction on effective teaching techniques and will be evaluated formally on their teaching. A far-reaching recruitment plan will allow Embry-Riddle to identify outstanding and eligible students, especially from traditionally underrepresented groups. Embry-Riddle is contributing matching funds in the form of tuition and fee assistance. 

    If you are interested in being supported as a GAANN Fellow, please contact Dr. Lyrintzis at lyrintzi@erau.edu.

    Categories: Faculty-Staff

61-63 of 63 results