  This paper describes work carried out within the European Union (EU)-Russia
Buterfli project to look at the control of transition-causing "target"
stationary cross flow vortices, by the use of distributed plasma actuation to
generate sub-dominant "killer" modes. The objective is to use the "killer"
modes to control the "target" modes through a non-linear stabilizing mechanism.
The numerical modelling and results are compared to experimental studies
performed at the TsAGI T124 tunnel for a swept plate subject to a favorable
pressure gradient flow. A mathematical model for the actuator developed at
TsAGI was implemented in a linearized Navier Stokes (LNS) solver and used to
model and hence predict "killer" mode amplitudes at a measurement plane in the
experiment. The LNS analysis shows good agreement with experiment, and the
results are used as input for non-linear PSE analysis to predict the effect of
these modes on crossflow transition. Whilst the numerical model indicates a
delay in transition, experimental results indicated an advance in transition
rather than delay. This was determined to be due to actuator induced
unsteadiness arising in the experiment, resulting in the generation of
travelling crossflow disturbances which tended to obscure and thus dominate the
plasma stabilized stationary disturbances.
