Numerical investigation of tandem-cylinder noise reduction using plasma-based flow control

Abstract

The noise of flow over tandem cylinders at Re D = 22 000 and its reduction using single dielectric barrier discharge (SDBD) plasma actuators are simulated numerically both to confirm and extend experimental results. The numerical approach is based on large-eddy simulation (LES) for the turbulent flow field, a semi-empirical plasma actuation model, and Lighthill's theory for acoustic calculation. Excellent agreement between LES and experimental results is obtained for both the baseline flow and flow with plasma control in terms of wake velocity profiles, turbulence intensity, and frequency spectra of pressure fluctuations on the downstream cylinder. The validated flow-field results allow an accurate acoustic analysis based on Lighthill's equation, which is solved using a boundary-element method. The effectiveness of plasma actuators for reducing noise is clearly demonstrated. In the baseline flow, the acoustic field is dominated by the interaction between the downstream cylinder and the upstream wake. Through suppression of vortex shedding from the upstream cylinder, the interaction noise is reduced drastically by the plasma flow control, and the vortex-shedding noise from the downstream cylinder becomes equally important. At a free-stream Mach number of 0.2, the peak sound pressure level is reduced by approximately 16 dB. This suggests the viability of plasma actuation for active aeroacoustic control of airframe noise.

Modelling of Dielectric Barrier Discharge Plasma Actuators for Direct Numerical Simulations

“…It provides a body force distribution from the solution of a Laplace's equation for electric potential due to the voltage applied to the electrodes and a Poisson-like 2nd order partial differential equation for the charge density of the ionized working fluid. We have chosen this model because of its simplicity, but also for the fact that it takes a physical approach starting from the Lorentz force equation, and for its ability to mimic the time-averaged effect of real life DBD plasma actuators (1,2,16,17). The derivation starts with the assumption, that the magnetic force is negligible and the electrohydrodynamic (EHD) force can be expressed as:…”

“…The most popular of those models are the Orlov model (14), the Shyy model (15) and the Suzen & Huang model (1,2) because of their relative simplicity and ability to mimic the time-averaged effects of a DBD actuator on the ambient fluid. Those three models have been tested in various flow configurations: boundary-layer separation control for the Orlov model (14), turbine blades (1,2), channel flow (16) and tandem of cylinders (17) for the Suzen & Huang model and channel flow (18) and transition control around an airfoil (19) for the Shyy model. These models have two major drawbacks.…”

The importance of controlling the upstream body wake in tandem cylinders system for noise reduction

“…Comparing equation (9) with equation (5), it can be seen that the derived aerodynamics mass-spring-damper model has the accelerated velocity term and velocity term on the left hand side and the force term on the right hand side of equation (9). However, there is no displacement term in equation 9, because the cylinder is assumed to be rigid and fixed.…”

“…The strong unsteady aerodynamics forces on the DC consequently cause severe vibration and noise problem. Therefore, tandem structures flow has been extensively studied over the past four decades, [2][3][4][5][6][7][8][9] involving aerodynamics, aeroacoustics, and aero-elasticity. For the aerodynamics noise of tandem cylinders system, the broadband noise originates from the interaction of upstream wake with the DC while the tonal noise originates primarily from the vortex shedding itself.…”

Multi-Electrode Plasma Actuator to Improve Performance of Flow Separation Control

“…Flow reattachment was achieved by using a plasma actuator for Mach numbers up to 0.4 in the wind tunnel at the University of Notre Dame [6] . Outstanding results have also been obtained numerically and experimentally in the investigation of noise reduction using a plasma actuator from the tandem-cylinder similar to the landing gear configuration of an aircraft [7] . Tip flow-control in the jet engine using plasma actuators has been investigated by GE.…”