www.tjprc.org editor@tjprc.org EFFECT OF CHEVRON ON THE DECAY CHARACTERISTICS OF COMPRESSIBLE ROUND JET S. SENTHIL VELAVAN 1 & K. VIJAYARAJA 2 1 Research scholar, Sathyabama University, Chennai, India 2 Professor, KCG College of Technology, Chennai, India ABSTRACT In the present study, the flow fields generated by two jets with a chevron and a conventional circular nozzle exits are studied and compared. Three different nozzle configurations were considered one with no chevron and the other two has 4 and 8 chevrons each. Each configuration, has been studied with two different exit Mach numbers. Centerline velocity decay and turbulent kinetic energy were analyzed and discussed. It is found that the flow field strongly depends on the exit geometry. KEYWORDS: Chevron Nozzle, Noise Suppression Techniques, Subsonic Jets & Jet Decay Received: Oct 27, 2017; Accepted: Nov 18, 2017; Published: Dec 18, 2017; Paper Id.: IJMPERDDEC201776 INTRODUCTION Due to strict regulations and associated environmental problems Aircraft-generated noise is a major concern in the aviation industry. Aircraft engine jet noise is the major source of noise generation, especially during take-offs and landings. As a result of these various attempts were made by the researchers to develop new innovative technologies to reduce the jet noise. This attracts massive amount of investments in the field of aeroacoustics research over the past few decades. In the last decades, a few practical passive flow control techniques for jet noise reduction were developed such as tabbed nozzles, pylon installations, deflector plates, castellated nozzles, multi-lobed mixers, microjets, water injection, contoured plugged nozzle, chevrons, etc. The above techniques were suitable for the application in the commercial aircraft gas turbine engines but, it also associated with thrust losses. It must be minimized in-order to make these configurations a success. Turbulence statistics based acoustic models were essential to predict the jet noise. In-regard to that numerous studies were reported on jet turbulence in the past. Davies et al., (1963) experimentally derived the length and time scales from the space-time measurements of cold, low-speed jets. Bradshaw et. al., (1963) documented the spatial correlations for all six components of the correlation matrix with three-dimensional displacements. Bridges and Wernet (2010) used Particle Image Velocimetry (PIV) to develop a consensus dataset of flow quantities for a range of hot jet including uncertainty bands. They created a catalog of turbulent jet flows that can be compared with other measurement techniques. They used hot-wire anemometry (HWA) to experimentally investigate jet flows. It provides single point spectral analysis of the turbulent flow, due to high sampling rates. (Wernet, 2007 et al)PIV is widely used to measure the large regions of unsteady flow field in sequential frames, but it has a lower frequency than the other measurement techniques such as HWA. The above Original Article International Journal of Mechanical and Production Engineering Research and Development (IJMPERD) ISSN (P): 2249-6890; ISSN (E): 2249-8001 Vol. 7, Issue 6, Dec 2017, 679-686 © TJPRC Pvt. Ltd