+ Visit NASA.gov + Contact NASA   + Home Collection > NASA  Author > Laurence, James C.  NASA Center > Glenn Research Center  Publication Year > 1951-1960 > 1960  Subject > D-F > Fluid Mechanics And Heat Transfer  Availability Options > Online > PDF  Item/Media Type > NASA Report > Technical Notes (TN)  Item/Media Type > Technical Report  Note: Start a new navigation search by selecting a link above     Previous Record | Next Record + Back to Results   + Printer Friendly Title: Turbulence Studies of a Rectangular Slotted Noise-Suppressor Nozzle Author(s): Laurence, James C. Abstract: The problem of noise suppression of turbojet engines has shown a need for turbulence data within the flow field of various types of nozzles used in ad hoc investigations of the sound power. The result of turbulence studies in a nozzle configuration of four parallel rectangular slots is presented in this report with special attention to the effect of the spacing of the nozzles on the intensity of turbulence, scale of turbulence, spectrum of turbulence, and the mean stream velocity. Taylor's hypothesis, which describes the convection of the turbulence eddies, was tested and found correct within experimental error and certain experimental and theoretical limitations. The convection of the pressure patterns was also investigated, and the value of the convection velocity was found to be about 0.43 times the central core velocity of the jets. The effect of the spacing-to-width ratio of the nozzles upon the turbulence intensity, the scale of turbulence, and the spectral distribution of the noise was found in general to produce a maximum change for spacing-to-width ratios of 1.5 to 2.0. These changes may be the cause of the reduction in sound power reported for similar full-scale nozzles and test conditions under actual (static) engine operation. A noise reduction parameter is defined from Lighthill's theory which gives qualitative agreement with experiments which show the noise reduction is greatest for spacing-to-width ratios of 1.5 to 2.0. NASA Center: Glenn Research Center Publication Date: Sep.1960 Document Source: CASI Online Source: View PDF File Document ID: 19980227304 Publication Information: Number of Pages = 90 Report Number: E-384; NASA-TN-D-294 Price Code: A05 Keywords: NOISE REDUCTION; TURBULENCE; NOZZLES; TURBOJET ENGINES; FLOW VELOCITY; FULL SCALE TESTS; FLOW DISTRIBUTION; VORTICES; SLOTS; ERRORS; Accessibility: Unclassified; No Copyright; Unlimited; Publicly available; Updated/Added to NTRS: 2005-08-25 + Back to Top + Sponsored by the NASA Scientific and Technical    Information Program + 2004 Vision for Space Exploration + Freedom of Information Act + NASA Web Privacy Policy and Important Notices + NASA Disclaimers, Copyright Notice,    and Terms and Conditions of Use NASA Official: Calvin Mackey Page Curator: NASA Center for AeroSpace Information (help@sti.nasa.gov) Last Updated: July 5, 2007