E298 Fluid Mechanics Seminar

Tuesday, June 6,  2006 at   4:15 pm
Building 300, Room 300

Donghyun You

Stanford University



Large-Eddy Simulation of Flow Separation Control Using Synthetic Jets


ABSTRACT: In recent years control methods employing synthetic jets, or
zero-net-mass-flux oscillatory jets, have shown good promise for controlling
flow separation in industrial applications. An accurate prediction, not to
mention control, of unsteady flow separation at high Reynolds numbers is a
challenging task for numerical simulations. Large-eddy simulation (LES)
provides an attractive alternative to the conventional Reynolds-averaged
Navier-Stokes (RANS) approaches for predicting and analyzing the unsteady
flow dynamics and optimizing control strategies. In this study, a LES
technique with a non-dissipative, energy-conserving numerical scheme and a
dynamic subgrid-scale (SGS) model is applied to predict aerodynamic flow
control with synthetic jets in two different flow configurations.   

The flow over a wall-mounted hump, which is one of the test cases considered
in the NASA Langley Workshop on CFD validation of Synthetic Jets and
Turbulent Separation Control, is first considered to establish the merits of
the present LES technique. The present LES with a dynamic SGS model is shown
to be consistently more accurate than the other LES with a constant
coefficient Smagorinsky model, detached-eddy simulation (DES), and RANS
simulations in predicting the experimentally measured flow quantities.

The second flow configuration to be discussed is the flow over an airfoil
with a high angle of attack. LES of separated turbulent flows over a NACA
0015 airfoil with and without synthetic jet actuators has been performed.
Synthetic jets with a momentum coefficient of 0.2% are found to
significantly reduce flow separation and to increase the lift force more
than 70%.

 

Refreshments served at 4:00 pm