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On the lighthill relationship and sound generation from isotropic turbulence
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Zhou, YE Oncley, Steven Praskovsky, Alexander |
| Copyright Year | 1994 |
| Description | In 1952, Lighthill developed a theory for determining the sound generated by a turbulent motion of a fluid. With some statistical assumptions, Proudman applied this theory to estimate the acoustic power of isotropic turbulence. Recently, Lighthill established a simple relationship that relates the fourth-order retarded time and space covariance of his stress tensor to the corresponding second-order covariance and the turbulent flatness factor, without making statistical assumptions for a homogeneous turbulence. Lilley revisited Proudman's work and applied the Lighthill relationship to evaluate directly the radiated acoustic power from isotropic turbulence. After choosing the time separation dependence in the two-point velocity time and space covariance based on the insights gained from direct numerical simulations, Lilley concluded that the Proudman constant is determined by the turbulent flatness factor and the second-order spatial velocity covariance. In order to estimate the Proudman constant at high Reynolds numbers, we analyzed a unique data set of measurements in a large wind tunnel and atmospheric surface layer that covers a range of the Taylor microscale based on Reynolds numbers 2.0 x 10(exp 3) less than or equal to R(sub lambda) less than or equal to 12.7 x 10(exp 3). Our measurements demonstrate that the Lighthill relationship is a good approximation, providing additional support to Lilley's approach. The flatness factor is found between 2.7 - 3.3 and the second order spatial velocity covariance is obtained. Based on these experimental data, the Proudman constant is estimated to be 0.68 - 3.68. |
| File Size | 695354 |
| Page Count | 22 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19950011776 |
| Archival Resource Key | ark:/13960/t3gx97h5q |
| Language | English |
| Publisher Date | 1994-11-01 |
| Access Restriction | Open |
| Subject Keyword | Fluid Mechanics And Heat Transfer High Reynolds Number Stress Tensors Turbulent Flow Atmospheric Boundary Layer Wind Tunnel Tests Aerodynamic Noise Isotropic Turbulence Aeroacoustics Noise Prediction Lighthill Method Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
