Georgia Tech is teamed with three other universities: Washington University in St. Louis, Missouri; Ohio State University (OSU) in Columbus, Ohio; and Clark Atlanta University (CAU), just a few miles from Georgia Tech in Atlanta, Georgia. Dr. Dave Peters has rotorcraft dynamics test facilities in St. Louis and has been the Associate Director of CERT since 1992. CAU has an excellent Advanced Composites Structural Lab, and Ohio State faculty are well known for their research in rotor wake definition, measurement, experimental, and predicted wakes.

A breakdown of the Georgia Tech CERT faculty (see faculty sidebar) shows the depth of the interdisciplinary team, with all of the critical rotorcraft technologies, including systems design, analysis and integration. From the outset in 1982, the Georgia Tech CERT has made rotorcraft design an integrating focus for its graduate education and research program. Dr. Schrage explains: "From the very beginning, we always felt when you have multiple disciplines and you’re going to be interdisciplinary, you have to look at it from a design view point and try to integrate the disciplines together. And that also is a way of helping to transfer this stuff to industry because the methods and tools that you develop should hopefully help you to design better rotorcraft in the future. So we’ve concentrated on that from the outset." In fact, the GT Aerospace Systems Design Laboratory and Aerial Robotics Laboratory have an integral relationship with the CERT.

With its partner universities, Georgia Tech has a number of world-class facilities used in the CERT research. For aerodynamics and aeroacoustics, CERT has the John J. Harper Wind Tunnel, the 9-Foot Rotor Facility, and the Aerothermodynamics Lab. At Washington University, the CERT uses the Center for Computational Mechanics and the Ground Resonance Dynamic Facility to study rotor dynamics and aeroelasticity. For structures, the CERT uses the Advanced Composite Structures Lab and the Aerospace Engineering Structures Lab at Georgia Tech, as well as the Advanced Composite Structural Lab at Clark Atlanta University. For flight mechanics and controls, CERT has a Flight Mechanics and Control Computer Laboratory, a Flight Simulation Laboratory, and an Unmanned Aerial Vehicle Research Facility. The UAVRF has a number of rotorcraft flying testbeds which are being used for flight mechanics and controls research in CERT and for Software Enabled Control for DARPA.

Georgia Tech also has a Propulsion/Combustion Research Laboratory. Interestingly, however, this is one area not handled under the NRTC RCOE grant, since propulsion, except for drivetrains research, has been excluded from the RCOE efforts. This is because the Army has funded propulsion in other centers. Nonetheless, "propulsion is a very critical part of rotorcraft technology," says Schrage, and Georgia Tech has an ARO Multidisciplinary University Research Initiative (MURI) in Intelligent Turbine Engines (MITE) grant for about $800K per year. Although it is not part of the CERT, it includes some of the same people that work in the CERT, particularly in the controls, aerodynamics, and dynamics areas. "If you have a Center, you should be integrating all the critical disciplines, both horizontally and vertically. Horizontally is across the disciplinary boundaries. Vertically is in system design analysis and integration. But if you look at the disciplines that are funded by the rotorcraft center they don’t include propulsion. With a propulsion system on a rotorcraft there’s so much coupling between the rotor and the engine, especially in the controls and the dynamics interactions."

The 12 basic research tasks that are being funded under the NRTC RCOE program at Georgia Tech are summarized in the sidebar. As mentioned, earlier, however, CERT also has a large number of RITA projects for technology transfer. Dr. Schrage explains: "We’ve concentrated over the years on transferring technologies for industry’s use. So if you go to Sikorsky or Bell or Boeing, they’re using CERT’s CFD [Computational Fluid Dynamics] codes, and beginning to use DYMORE – a nonlinear finite element modeling framework – for addressing tough dynamics and loads problems. So as far as transferring technology that industry’s using, that’s been one of the successes of our Center over the years. Because if you’ve been a center for 18 years, there should be products that have successfully been transferred to industry and government and are advancing the state-of-the-art of rotorcraft technology. That’s why we try to do so much RITA work now." The six current RITA tasks being performed by CERT are:

• Implementation of High Accuracy Aerodynamic and Aeroacoustic Modules in Industry Standard Methodologies/Codes
• Fan-in-Fin Unsteady Aerodynamics
• Advanced Applications of a 3-Axis Sidestick Controller
• Development of Fatigue and Damage Tolerance Models for Sandwich Composites
• Probabilistic and Robust Design Approach for Rotorcraft Affordability Tradeoffs
• Comprehensive Aeromechanical Analysis Using Integrated Analysis Tools

Georgia Tech’s Center of Excellence in Rotorcraft Technology has set the standard for rotorcraft research and technology transfer to industry for nearly 20 years. The NRTC RCOE research grant, coupled with the RITA and ARO MURI grants, make Georgia Tech’s CERT the largest academic rotorcraft research center in the world.

Tip blade trajectory for the conversion from helicopter to cruise mode
of a Variable Diameter Tilt Rotor

• Director: Daniel P. Schrage
• Associate Director: David A. Peters (Wash. U)
• Aerodynamics & Aeroacoustics: N. Lakshmi Sankar, Narayanan Komerath, A. Terry Conlisk (Ohio State University), Suresh Menon, and Robert Funk
• Dynamics & Aeroelasticity: Olivier Bauchau, David Peters (Wash. U), Dewey Hodges, Marilyn Smith, Robert Loewy
• Structures & Materials: Dewey Hodges, Erian Armanios, George Kardomateas, A. Badir (CAU), Stefan Dancila, Vitali Volovoi
• Flight Mechanics & Controls: J.V.R. Prasad, Anthony Calise, David A. Peters (Wash. U), Daniel Schrage
• Systems Design, Analysis & Integration: Dimitri Mavris, Daniel Schrage, James Craig

2000 NRTC Grant Tasks

Efficient Low Noise Rotors

Active Rotorcraft Blade Tips for Tip Vortex Core Modifications

This project will evaluate the combined concepts of elastic tailoring and active material actuation applicable to rotor blade tips.

First Principles Based Modeling of Rotors in Hover, Forward Flight and Maneuver

The goal of this work is to develop a first-principles based Navier-Stokes methodology capable of efficiently and accurately predicting rotor airloads and noise characteristics in hover, forward flight, and maneuvers.

Simulations of Unsteady Flow-Rotor Interactions to Predict Dynamic Loading in a Turbulent Environment

Georgia Tech will employ large-eddy simulations (LES) to investigate the highly unsteady turbulent flow-rotor interactions in order to determine the impact of unsteady dynamics on the rotor loading.

Affordability

Efficient and Affordable Joining of Composites

This research is directed at improving the joining of composites through better understanding of the fundamental mechanisms leading to their premature failure. A general and reliable framework will then be constructed for developing and implementing improved, cost-effective composite joining concepts.

Low-Vibration Dynamic Systems

Phenomenological and First-Principles Based Models of Complete Helicopters

This project will develop and validate Navier-Stokes methods and improvements that complement existing techniques for modeling complex rotorcraft configurations.

Smart and Composite Structures

Elastically Tailored Smart Composite Rotor Blades

This project seeks to combine the advantages of elastic tailoring with actuation provided by piezoelectric materials in order to improve the performance of rotor blades.

Damage Tolerance Analysis of Stiffened Composites and Rotor Hubs

This task aims at establishing a general framework for damage tolerance analysis in rotorcraft composites by developing a rigorous model that would accurately predict the local stress state and energy release rates. This will help to establish a methodology for damage tolerance analysis of composite structures.

Composite Beam Cross-Sectional Optimization

This effort seeks to develop an easy to use practical tool that would provide an optimized cross-sectional configuration of composite blades and wings with a specified matrix of cross-sectional stiffness coefficients.

Highly Reliable Safe Operations

Wakes of Rotorcraft Maneuvering in Ground Effect

This task will develop detailed physics-based modeling to capture the essential features of ground-effect flows and their effects on rotorcraft, in both quasi-steady state and maneuvers.

Limit Detection and Limit Avoidance Methods for Carefree Maneuvering

Development of robust, real time limit prediction and limit cueing algorithms will be used to overcome the problem of envelope limiting.

Digital-Optical Integrated Flight Controls

Deformable Wake Dynamics for Maneuvering Flight Simulation

This task will refine the GT finite state in-ground-effect inflow models to capture the effect of ground vortices typically present in low speed forward flight close to the ground. It will also combine their ground effect and maneuvering inflow models for understanding of response behavior of a helicopter in nap-of-the-earth operations.

Neural Network Based Adaptive Flight Control

Neural network-based adaptive control in an output feedback setting will be improved and applied to active controls employing smart sensing and smart actuation.

Periodic Wake Rollup in Low Speed Climb