### Abstract

It is shown that the pressure signal measured at the outer edge of a jet mixing layer is entirely hydrodynamic in nature and provides a good measure of the large-scale structure of the turbulent flow. Measurement of the pressure signal provides a unique opportunity to utilize proper orthogonal decomposition (POD) to deduce the streamwise structure. Since pressure is a scalar, a significant reduction in the numerical and experimental complexity inherent in the analysis of velocity vector fields results. The POD streamwise eigenfunctions show that the structure associated with any frequency-azimuthal mode number combination displays the general characteristics of amplification-saturation-decay of an instability wave, all within about three wavelengths. High-frequency components saturate early in x and low-frequency components saturate further downstream, indicative of the inhomogeneous character of the flow in the streamwise direction. Application of the POD technique allows the phase velocity to be determined taking into account the inhomogeneity of the flow in the streamwise direction. The phase velocity of each instability wave (POD eigenvector) is constant and equal to 0.58U_{j}, indicating that the jet structure is non-dispersive. Using the shot-noise decomposition, a characteristic event is constructed. This event is found to contain evidence of both pairings and triplings of vortex structures. The tripling results in a rapid increase in the first asymmetric (m = 1) component. On average, pairing occurs once every four U_{j}/D while tripling occurs once every 13U_{j}/D.

Original language | English (US) |
---|---|

Pages (from-to) | 1-33 |

Number of pages | 33 |

Journal | Journal of Fluid Mechanics |

Volume | 340 |

State | Published - Jun 10 1997 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Computational Mechanics
- Mechanics of Materials
- Physics and Astronomy(all)
- Condensed Matter Physics

### Cite this

*Journal of Fluid Mechanics*,

*340*, 1-33.

**The proper orthogonal decomposition of pressure fluctuations surrounding a turbulent jet.** / Arndt, R. E A; Long, D. F.; Glauser, Mark N.

Research output: Contribution to journal › Article

*Journal of Fluid Mechanics*, vol. 340, pp. 1-33.

}

TY - JOUR

T1 - The proper orthogonal decomposition of pressure fluctuations surrounding a turbulent jet

AU - Arndt, R. E A

AU - Long, D. F.

AU - Glauser, Mark N

PY - 1997/6/10

Y1 - 1997/6/10

N2 - It is shown that the pressure signal measured at the outer edge of a jet mixing layer is entirely hydrodynamic in nature and provides a good measure of the large-scale structure of the turbulent flow. Measurement of the pressure signal provides a unique opportunity to utilize proper orthogonal decomposition (POD) to deduce the streamwise structure. Since pressure is a scalar, a significant reduction in the numerical and experimental complexity inherent in the analysis of velocity vector fields results. The POD streamwise eigenfunctions show that the structure associated with any frequency-azimuthal mode number combination displays the general characteristics of amplification-saturation-decay of an instability wave, all within about three wavelengths. High-frequency components saturate early in x and low-frequency components saturate further downstream, indicative of the inhomogeneous character of the flow in the streamwise direction. Application of the POD technique allows the phase velocity to be determined taking into account the inhomogeneity of the flow in the streamwise direction. The phase velocity of each instability wave (POD eigenvector) is constant and equal to 0.58Uj, indicating that the jet structure is non-dispersive. Using the shot-noise decomposition, a characteristic event is constructed. This event is found to contain evidence of both pairings and triplings of vortex structures. The tripling results in a rapid increase in the first asymmetric (m = 1) component. On average, pairing occurs once every four Uj/D while tripling occurs once every 13Uj/D.

AB - It is shown that the pressure signal measured at the outer edge of a jet mixing layer is entirely hydrodynamic in nature and provides a good measure of the large-scale structure of the turbulent flow. Measurement of the pressure signal provides a unique opportunity to utilize proper orthogonal decomposition (POD) to deduce the streamwise structure. Since pressure is a scalar, a significant reduction in the numerical and experimental complexity inherent in the analysis of velocity vector fields results. The POD streamwise eigenfunctions show that the structure associated with any frequency-azimuthal mode number combination displays the general characteristics of amplification-saturation-decay of an instability wave, all within about three wavelengths. High-frequency components saturate early in x and low-frequency components saturate further downstream, indicative of the inhomogeneous character of the flow in the streamwise direction. Application of the POD technique allows the phase velocity to be determined taking into account the inhomogeneity of the flow in the streamwise direction. The phase velocity of each instability wave (POD eigenvector) is constant and equal to 0.58Uj, indicating that the jet structure is non-dispersive. Using the shot-noise decomposition, a characteristic event is constructed. This event is found to contain evidence of both pairings and triplings of vortex structures. The tripling results in a rapid increase in the first asymmetric (m = 1) component. On average, pairing occurs once every four Uj/D while tripling occurs once every 13Uj/D.

UR - http://www.scopus.com/inward/record.url?scp=0031153868&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031153868&partnerID=8YFLogxK

M3 - Article

VL - 340

SP - 1

EP - 33

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -