Daniel M. Israel

Numerical investigation of turbulent separation control using periodic disturbances

The new Flow Simulation Methodology (FSM) proposed by Speziale (1997) is applied to the separation control experiments of Seifert and Pack (1999). By smoothly ramping between RANS and LES based on the local flow conditions, the FSM allows simulations which capture the unsteady nature of the shear layer without requiring LES resolution in the boundary layer. This makes the FSM ideal for investigations of Active Flow Control (AFC). In the experiments a model simulating the upper surface of a 20% thick airfoil was mounted on the side of a wind tunnel. The flow over this airfoil separates at ~ 64% chord if no control is applied. This model was used to investigate sweep and compressibility effects over a range of Reynolds numbers. The goal of our ongoing research is to implement and validate the FSM in an high-order accurate CFD code capable of simulating these experiments. In this paper we demonstrate the FSM for the experimental geometry with a fully turbulent boundary layer at the domain inflow. The calculations show that the FSM does allow the formation of unsteady structures in the separated region.

A flow simulation methodology for analysis of coherent structures and flow control

The Flow Simulation Methodology (FSM) is evaluated for the case of a separated ow subject to control by oscillatory forcing. The geometry chosen is the hump geometry from the NASA Langley CFD Validation Workshop 2004. In addition to the FSM, Direct Numerical Simulation (DNS) results are also presented. Simulation data for the uncontrolled ow, control by steady suction, and control by unsteady forcing all agree very well with the experimental data for both DNS and FSM. In addition, the ability of the FSM to produce accurate results over a wide variety of model lter widths is demonstrated. Finally, the relative strengths of the two approaches (FSM and DNS) are compared.