Accession Number:

ADA604901

Title:

Active Flow Control with Thermoacoustic Actuators

Descriptive Note:

Final rept. 1 Apr-13 Dec 2013

Corporate Author:

FLORIDA STATE UNIV TALLAHASSEE DEPT OF MECHANICAL ENGINEERING

Personal Author(s):

• Taira, Kunihiko

Report Date:

2014-01-31

Pagination or Media Count:

29.0

Abstract:

We numerically examine the effectiveness of thermoacoustic actuators that locally introduce high-intensity acoustic waves for active flow control. In this investigation, we perform LES of flow control with acoustic waves motivated by the recent development in manufacturing graphenecarbon nanotube-based surface compliant loud speakers. The interaction of the acoustic waves and turbulent flow structures is analyzed with high-fidelity LES for compressible flow over a wall-mounted hump at a Reynolds number of 0.5x1000000 and Mach number of 0.25. In the computations, we consider the use of high-frequency actuation at Helmholtz number of 3 based on performance characteristics of the graphene-based thermoacoustic actuators. We observe that the actuation is able to introduce small-scale perturbation to the shear layer in the separated flow and delay the formation of large-scale spanwise vortices. This hence elongates the recirculation zone and shifts the low-pressure region downstream of the hump. As a consequence, the drag on the hump is reduced by approximately 5 for the threedimensional calculation and up to 10 in the two-dimensional flow. The mechanism of drag reduction is different from the one using synthetic jets, which relies on reducing the size of the recirculation zone.

Descriptors:

• *ACTUATORS
• *THERMOACOUSTICS
• ACOUSTIC WAVES
• ACOUSTICS
• COMPRESSIBLE FLOW
• ELASTIC PROPERTIES
• FLOW SEPARATION
• HIGH FREQUENCY
• LOW PRESSURE
• MACH NUMBER
• REYNOLDS NUMBER
• TURBULENT FLOW
• TWO DIMENSIONAL FLOW

Subject Categories:

• Machinery and Tools
• Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE