Faculty — Aerodynamics

Aerodynamics 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. 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.

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 continues to focus on hypersonic transition and the development of quiet tunnels, while also serving as a senior technical expert in aerothermodynamics. Prof. Jewell now leads the Mach-6 quiet tunnel, and Prof. Chynoweth leads the development of the new Mach-8 quiet tunnel. Prof. Schneider has moved into a supporting role as part of a long phased retirement. He is no longer serving as an advisor to new graduate students. Some details are described at the following websites, which also contains general information about hypersonics: Boeing/AFOSR Mach-6 Quiet Tunnel and General Hypersonics Information

T. Shih