Faculty by Research AreaAerodynamics Lab Facilities
- A. Alexeenko
- Research is in computational rarefied gas dynamics and its application to micro- and nanofluidics, high-altitude aerothermodynamics, plume-atmosphere interactions and spacecraft surface contamination and thermal radiation. The principal goals of the research are the development of accurate and robust numerical modeling tools for gas flow phenomena in regimes from continuum to free molecular, and their application to a wide range of practical problems from low-speed gas flows in micro- and nanodevices to high enthalpy flows near space vehicles.
- G. A. Blaisdell
- Current research interests involve the study of transitional and turbulent fluid flows using computational fluid dynamics (CFD) as an investigative tool. Most flows of engineering interest are turbulent and turbulence has a significant impact on the performance of engineering systems. The drag on a body is generally much greater if the boundary layer is turbulent. Turbulence also increases heat transfer between a fluid and a surface. In addition, turbulent mixing is important to combustion. The physics of basic turbulent flows are studied using direct numerical simulations (DNS) and large-eddy simulations (LES). With LES the motion of the largest eddies are solved for directly while the effects of the unresolved small scale eddies are modeled. In contrast, with DNS all the relevant length scales within the turbulence are resolved and no modeling is needed. The results of the simulations are used to increase our understanding of turbulence and to test and improve turbulence models. Parallel computing and advanced numerical methods is another area of interest.
- S. H. Collicott
Low-gravity fluid dynamics and capillary fluid physics are the focus of two-phase fluids research. A collaborative aero-elastic study of failures of High-Mast Lighting Towers is underway, led by Professor Connor in Purdue’s School of Civil Engineering. Sprays and internal flows in spray systems plus oil-air flows in turbine engines remain of interest too.
Capillary effects dominate liquid positioning in the weightless portions of spaceflight and in small-scale two-phase fluids systems on Earth. Beginning with work in support of the Gravity Probe-B satellite in 1993, Professor Collicott has become the leading expert in the use of the capillary fluids statics code, Surface Evolver, for both research and real-world engineering in two-phase fluids problems. Research includes designing the “Vane-Gap” experiments for the Capillary Fluids Experiment (CFE) presently in the second set of tests in orbit in the International Space Station, exploring the existence and stability of water droplets in lung passages, designing and building a three-dimensional critical wetting experiment - one of the first experiments to fly on Blue Origin’s New Shepard rocket, and many others. Engineering solutions that have grown from research include the best on-orbit propellant-gauging service available for satellites and presently available for owners and operators of satellites.
Novel spray control and spray formation methods have grown from research, started by an NSF-Career Award, that probes the internal flow with specialized optics to uncover the physics of cavitation. Small-scale non-equilibrium unsteady cavitation exists, the behavior of which can not presently be predicted to any useful extent. Coordination with Professor Heister's simulations with pseudo-density models for non-equilibrium cavitating flows has been crucial to understanding the internal flow fields.
Hypersonic boundary layer transition is a critical event on high speed flight vehicles, including the Space Shuttle during re-entry. Sporadic collaborations with Professor Schneider's experiments involve both an optical perturber and optical diagnostics. The perturber has been developed and is in regular use. High-sensitivity, high bandwidth Laser Differential Interferometry is being applied to detect and measure instability waves in millimeter and thinner boundary layers in flows at speeds in excess of one-half of a kilometer per second.
- A. S. Lyrintzis
- Dr. Lyrintzis' research can be divided mainly into two areas:
- The Use of Integral Techniques in Computational Aeroacoustics:
Dr. Lyrintzis has made significant contributions in the use of integral techniques Computational Aeroacoustics (CAA). CAA is concerned with the prediction of the aerodynamic sound source and the transmission of the generated sound starting from the time-dependent governing equations. The goal is to improve the state-of-the-art predictive techniques, so that aircraft and rotorcraft noise can be reduced. Dr. Lyrintzis has pioneered the use of integral techniques, (i.e. the Kirchhoff method and the porous Ffowcs Williams Hawkings [FWH] equation) for describing noise propagation. The methods are attractive because they utilize surface integrals (over a source region) to determine far-field acoustics, as opposed to the memory intensive volume integrals found in traditional acoustic analogy methods.
Rotorcraft Impulsive Noise: In recent years the increasing use of helicopters and the projected use of tiltrotor aircraft has drawn attention to the noise that they generate. Among the several types of helicopter and tilt rotor noise, that due to helicopter impulsive noise is the most important. Dr. Lyrintzis has introduced the application of Kirchhoff's methodology for rotorcraft impulsive noise prediction. The details of the noise mechanisms are studied extensively and analogies to other unsteady motions are drawn. Both full potential as well as Euler/Navier Stokes codes are employed for the aerodynamic near-field prediction. Dr. Lyrintzis also investigates ideas for noise reduction (e.g. blade tip shape).
Jet Noise: Jet noise prediction is a very important part of aircraft noise. Dr. Lyrintzis has employed Kirchhoff's method in jet noise prediction, as well. He introduced an important extension to the method in order to include non-linear flow regions that exist downstream of the Computational Fluid Dynamics (CFD) domain. Dr. Lyrintzis proved the equivalence of Acoustic Analogy methods (based on the Ffowcs Williams Hawkings [FWH] equation) and Kirchhoff's methods, as part of the extensions of the Kirchhoff method. He also added mean flow refraction corrections (downstream of the control surface) in the methodology. A new high-order accurate three-dimensional Large Eddy Simulation (LES) CFD code has been developed (with Professor Blaisdell) to provide accurate input data for the Kirchhoff and FWH equation methods. This was part of a large-scale effort in jet noise reduction in collaboration with Rolls-Royce, Indianapolis.
Dr. Lyrintzis' research demonstrates that a simple set of versatile portable Kirchhoff/Acoustic Analogy subroutines can be developed to analyze and reduce noise generation in a number of applications including fans, propellers, air-conditioning units etc. This work has been funded by NASA Langley Research Center, NASA Glenn Research Center, Sikorsky Aircraft Company and the Indiana 21st Research and Technology Fund, and the Aeroacoustics Research Consortium.
- Efficient Parallel Methods for Transonic Flow Calculations.
Dr. Lyrintizis is also investigating the development of efficient computational techniques for the calculation of unsteady transonic flow on parallel machines. The goal is to improve efficiency and parallelization of legacy CFD codes. Dr. Lyrintzis studies unsteady three-dimensional problems in rotorcraft aerodynamics to enhance the computational efficiency of impulsive rotorcraft noise calculations. THe algorithm methodologies developed are general and can be readily applied to several existing CFD codes. This work has been funded by NASA Ames Research Center.
- The Use of Integral Techniques in Computational Aeroacoustics:
- S. P. Schneider
- High-speed laminar-turbulent transition is critical for applications including missiles for survivable time-critical strike, hypersonic reconnaissance vehicles, thermal protection for re-entry vehicles, drag reduction on supersonic transports, and flow noise and heat transfer above IR windows on interceptor missiles. Unfortunately, nearly all existing high-speed experimental results are contaminated by facility noise, such as that radiating from the turbulent boundary layers normally present on the test-section walls of supersonic tunnels. Just as at low speeds, reliable experimental progress requires low-turbulence wind tunnels with noise levels comparable to those in flight. Mechanism-based prediction methods are being developed to reduce the uncertainty in predicting transition on future flight vehicles. Measurements of the instability mechanisms leading to transition are being carried out to support the development and validation of these new methods. However, no single wind tunnel can simultaneously simulate all aspects of transition in flight, including Mach number, Reynolds number, enthalpy, freestream disturbances, surface ablation and so on. Furthermore, although computational advances are critical, all computations require models that must be based on experimental results. Effective progress requires cooperation between theory, computation and experiment, and also between system designers and researchers. Prof. Schneider's primary experimental facility is described at the following websites, which also contains recent papers from his research group and general information about hypersonics: Boeing/AFOSR Mach-6 Quiet Tunnel and General Hypersonics Information
- T. Shih
- Mathematical modeling of fluid mechanics, heat transfer, and combustion problems.
- Develop numerical methods and codes (grid generation and "Navier-Stokes" solver) that can be used to study complex steady and unsteady, multidimensional fluid flow problems that can be laminar or turbulent, reacting or nonreacting, single- or multi-phase. Current focus is on high-order compact schemes for reacting flows, verification and validation issues in CFD, and methods that provide á posteriori estimates of errors in CFD solutions.
- Computational study of problems in aerodynamics (airfoils and wings with ice accretion, shock-wave/boundary-layer interactions with bleed, and turbojet inlets); energy, power, and propulsion systems (gas turbine combustors, piston and rotary engines, automotive torque converters, thermoelectric power generators); cooling of gas-turbine hot section (blade-passage/endwall aerodynamics and heat transfer; internal and film cooling of turbine vanes, blades, and "edges"; conjugate heat transfer); two-phase flows (free-surface flows, objects impacting from gas into liquids, electrodeposition of colloidal particles; particle/particle and particle/fluid interactions in particle-laden flows, and atomization and sprays); materials processing (thermal spray forming, cold spray forming); and multifunction materials (thermal-fluid issues and energy harvesting).
- J. P. Sullivan
- Current research interest is in the area of experimental aerodynamics with particular emphasis on comparison of experimental data with computational analysis. Work continues on developing instrumentation for shear stress measurement and pressure and temperature paint for: Wind tunnels - low speed to hypersonic, gas turbine engines and flight tests
- M. H. Williams
- The determination of aeroelastic stability and forced response characteristics of flight vehicles requires methods for predicting the unsteady aerodynamic loads that are induced by structural deformation and/or free stream disturbances. Current research is directed at developing such methods for transonic flight and for rotating machinery. Much of this work has been done for advanced propfan applications. These engines are intended for use on medium range commercial transports, which operate at low transonic Mach numbers. In order to maintain high operating efficiency and low noise, the blades are very thin and flexible. Therefore they are subject to substantial static and dynamic deformations which alter the aerodynamic loads on the blades. Computational methods have been developed to predict these loads, both for single and counter rotating systems. Flutter boundaries and forced vibration amplitudes have been successfully predicted for a variety of current propfan designs. The most successful schemes developed so far have been based on linearized aerodynamic models. Work is under way on including nonlinear transonic effects through three dimensional potential formulation with moving grids.