Experimental investigation on mixing characteristics of high speed co-flow jets by using tabbed chevron nozzle

The present study investigates the effect of chevron with tab (Tabbed chevron) fixed at the exit of the co-flowing primary nozzle on the mixing characteristics in subsonic and sonic jets. The experiment was conducted for the jet Mach number 0.6 and 0.8. The centerline Mach number decay was calculated for all these jet Mach numbers for the co-flow baseline nozzle, nozzle with chevrons and tabbed chevron (primary flow) nozzle respectively. It was found that tabbed chevron was effective in reducing the potential core length by 88.23% as compared to the chevron nozzle with baseline nozzle. The radial profile also shows that the mixing enhancement by tabbed chevron is better than chevron nozzle.

Experimental investigation on mixing characteristics of high speed co-flow jets by using tabbed chevron nozzle

The present study investigates the effect of chevron with tab (Tabbed chevron) fixed at the exit of the co-flowing primary nozzle on the mixing characteristics in subsonic and sonic jets. The experiment was conducted for the jet Mach number 0.6 and 0.8. The centerline Mach number decay was calculated for all these jet Mach numbers for the co-flow baseline nozzle, nozzle with chevrons and tabbed chevron (primary flow) nozzle respectively. It was found that tabbed chevron was effective in reducing the potential core length by 88.23% as compared to the chevron nozzle with baseline nozzle. The radial profile also shows that the mixing enhancement by tabbed chevron is better than chevron nozzle.

Acoustic and Flow Aspects of Synthetic Jet Actuators with Chevron Orifices

The use of a chevron nozzle/orifice is one of the methods of heat transfer enhancement and noise reduction. In the case of synthetic jets, the number of papers on this topic is small. Therefore, a synthetic jet actuator with three different chevron orifices and one circular orifice is investigated. The aim of this study is to find the impact of orifice shape on centerline velocity (measured with a hot-wire anemometer) and determine if the chevron orifice reduces the generated noise. The sound pressure level was strongly dependent on the input actuator’s power, and only one chevron orifice ensured noise reduction for low power (p = 6; 8 W). At real power p = 12 W, the sound pressure level was lower for each chevron orifice actuator than in the case of the circular orifice actuator. It is shown that the application of a chevron nozzle does not have to provide noise reduction. It is important in the case of the design of new actuators that are to operate in places where noise levels should be limited (e.g., offices).

Computational Analysis of Co-Flow Potential Core Degradation of a Chevron Nozzle

In this paper, the characteristics of co-flowing jet in circular and chevron nozzle was studied. Three-dimensional chevron nozzle was designed with the saw tooth pattern to reduce the exhaust noise and infrared signature. Co-flow analysis of the nozzles was carried out using ANSYS CFX software. The jet performance of chevron nozzle was compared with that of a circular nozzle. The potential core decay length of co-flow circular and chevron nozzle was studied at two different Mach number of 0.6 and 1. The results shown that the potential core decay reduced for co-flow chevron nozzle along axial and radial directions.

Numerical predictions of the flow characteristics of subsonic jet emanating from corrugated lobed nozzle

Purpose The purpose of this study is to investigate the aerodynamic characteristics of subsonic jet emanating from corrugated lobed nozzle. Design/methodology/approach Numerical simulations of subsonic turbulent jets from corrugated lobed nozzles using shear stress transport k-ω turbulence model have been carried out. The analysis was carried out by varying parameters such as lobe length, lobe penetration and lobe count at a Mach number of 0.75. The numerical predictions of axial and radial variation of the mean axial velocity, u′u′ ¯ and v′v′ ¯ have been compared with experimental results of conventional round and chevron nozzles reported in the literature. Findings The centreline velocity at the exit of the corrugated lobed nozzle was found to be lower than the velocity at the outer edges of the nozzle. The predicted potential core length is lesser than the experimental results of the conventional round nozzle and hence the decay in centreline velocity is faster. The centreline velocity increases with the increase in lobe length and becomes more uniform at the exit. The potential core length increases with the increase in lobe count and decreases with the increase in lobe penetration. The turbulent kinetic energy region is narrower with early appearance of a stronger peak for higher lobe penetration. The centreline velocity degrades much faster in the corrugated nozzle than the chevron nozzle and the peak value of Reynolds stress appears in the vicinity of the nozzle exit. Practical implications The corrugated lobed nozzles are used for enhancing mixing without the thrust penalty inducing better acoustic benefits. Originality/value The prominent features of the corrugated lobed nozzle were obtained from the extensive study of variation of flow characteristics for different lobe parameters after making comparison with round and chevron nozzle, which paved the way to the utilization of these nozzles for various applications.

EXPERIMENTAL STUDY OF INFLUENCE OF THE CHEVRONS ON JET-FLAP INTERACTION NOISE

The interaction noise of turbulent jet with deflected flap is considered. The test objects are small-scale models of turbulent jet and flap in scale 1:6. To compare the effect of chevrons on the interaction noise level, experiments are carried out for two types of conical nozzles: conventional and chevron. It is also used conventional flap and chevron flap. Noise measurements in acoustic far field are carried out in the PNRUP acoustic chamber for directions from 15 to 105 degrees with a step of 15 degrees. The flap deflection angle varied from 0 to 45 degrees in increments of 5 degrees. The results are compared with each other. It was found that the use of chevrons for nozzle and for flap has the effect of some reduction in the interaction noise. Moreover, the jet outflowing from the chevron nozzle, when interacting with chevron flap, gives lower noise level than when interacting with conventional flap.