Unsteady Low Reynolds Number Aerodynamics

Situations involving unsteady aerodynamics are common for marine, land and
aerospace vehicles of all sizes. Gusts are frequently experienced by aircraft and
automobiles due to atmospheric turbulence and the flow structures shed by nearby
buildings at low altitudes. Further illustrations of unsteady aerodynamics include
bodies undergoing large accelerations and flapping wings. The unsteady
phenomena can have a significant detrimental impact on the performance and safe
operation of these vehicles. This is particularly important for smaller flying vehicles
travelling at low speeds where the relative flow unsteadiness is higher, leading to
larger changes in incidences and relative loading.
Despite the clear importance and numerous applications, understanding of unsteady
aerodynamics is greatly limited in comparison to that of steady aerodynamics. This
is partly due to the increased complexity of unsteady flow as well as the fact that
steady and quasi-steady state assumptions are routinely used in design processes.
It is becoming increasingly necessary, however, to improve our understanding of
unsteady flows, as the use of smaller unmanned air vehicles becomes more
prevalent.
Existing models for unsteady flow include those developed by Kussner and Wagner.
These models divide the unsteady aerodynamic loading into circulatory and noncirculatory components; vorticity and added-mass. Unfortunately, the application of
these models is severely restricted by the associated assumptions which include
small angles of incidence and enforcement of the Kutta condition.
This project will utilise experimental facilities to investigate the nature of unsteady,
low Reynolds number fluid flows. The research will look to improve understanding of
conditions with significant added mass and vortex dynamics effects. This research
falls within the EPSRC research area "Fluid dynamics and aerodynamics".