An Evaluation of Linear Instability Waves as Sources of Sound in a Supersonic Turbulent Jet

Mohseni, Kamran; Colonius, Tim; Freund, Jonathan B.

Mach wave radiation from supersonic jets is revisited to better quantify the extent to which linearized equations represent the details of the actual mechanism. To this end, we solve the linearized Navier-Stokes equations (LNS) with precisely the same mean flow and inflow disturbances as a previous direct numerical simulation (DNS) of a perfectly expanded turbulent M = 1.92 jet. We restrict our attention to the first two azimuthal modes, n = 0 and n = 1, which constitute most of the acoustic field. The direction of peak radiation and the peak Strouhal number matches the DNS reasonably well, which is in accord with previous experimental justification of the linear theory. However, it is found that the sound pressure level predicted by LNS is significantly lower than that from DNS. In order to investigate the discrepancy, individual frequency components of the solution are examined. These confirm that near the peak Strouhal number, particularly for the first helical mode n = 1, the amplification of disturbances in the LNS closely matches the DNS. However, away from the peak frequency (and generally for the azimuthal mode n = 0), modes in the LNS are damped while those in the DNS grow at rates comparable to those at the peak Strouhal number.

Document ID

20020048662

Acquisition Source

Glenn Research Center

Document Type

Other

Authors

Date Acquired

September 7, 2013

Publication Date

May 6, 2002

Subject Category

Funding Number(s)

Distribution Limits

Public

Work of the US Gov. Public Use Permitted.

Available Downloads

Name

Type

20020048662.pdf

STI

No Preview Available

NTRS

NTRS - NASA Technical Reports Server

Available Downloads

Related Records