Studies on high speed jets from nozzles with internal grooves

Elangovan, S.; Rathakrishnan, E.

doi:10.1017/s000192400000498x

Cited by 20 publications

(8 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Passive control methods use geometrical modifications which alter the flow structure. Passive control techniques range from alterations in the exit shape of the nozzle (non-circular nozzles (2) ) to the, implementation of grooves/notches (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39) , tooth like tabs, swirls (40)(41)(42)(43)(44)(45)(46) and chevron nozzles (47)(48)(49)(50)(51)(52)(53) . Many studies have focused on the placement of small tabs at the exit of axisymmetric and asymmetric nozzles.…”

Section: Introductionmentioning

confidence: 99%

Triangular tabs for supersonic jet mixing enhancement

Rathakrishnan

2014

Aeronaut. j. (1968)

Self Cite

View full text Add to dashboard Cite

The mixing promoting capability of right-angled triangular tab with sharp and truncated vertex has been investigated by placing two identical tabs at the exit of a Mach 2 axi-symmetric nozzle. The mixing promoting efficiency of these tabs have been quantified in the presence of adverse and marginally favourable pressure gradients at the nozzle exit. It was found that, at all levels of expansion of the present study though the core length reduction caused by both the tabs are appreciable, but the mixing caused by the truncated tab is superior. The mixing promoting efficiency of the truncated tab is found to increase with increase of nozzle pressure ratio (that is, decrease of adverse pressure gradient). For all the nozzle pressure ratios of the present study, the core length reduction caused by the truncated vertex tab is more than that of sharp vertex tab. As high as 84% reduction in core length is achieved with truncated vertex right-angled triangular tabs at moderately overexpanded level, corresponding to expansion level p e /p a = 0·90. The corresponding core length reduction for right-angled triangular tabs with sharp vertex and rectangular tabs are 65% and 31%, respectively. The present results clearly show that the mixing promoting capability of the triangular tab is best than that of rectangular tabs at identical blockage and flow conditions.

show abstract

Section: Introductionmentioning

confidence: 99%

Triangular tabs for supersonic jet mixing enhancement

Rathakrishnan

2014

Aeronaut. j. (1968)

Self Cite

View full text Add to dashboard Cite

show abstract

“…The effects of internal grooves in high-speed circular jets were studied for the first time by Elangovan and Rathakrishnan (10) . These grooves were observed to improve the jet growth in the plane in which they are introduced thereby weakening the shock-cell structure relative to plain circular jet.…”

Section: Mean Centreline Velocity Decaymentioning

confidence: 99%

Study of jets from rectangular nozzles with square grooves

Kumar¹,

Verma

Elangovan

2011

Aeronaut. j.

Self Cite

View full text Add to dashboard Cite

NOMENCLATURE sside of square groove, mm D e equivalent diameter of rectangular exit, mm l length of square groove, mm m exit mass flow rate at the nozzle exit m j mass flow rate at any axial location along the jet centerline U e mean velocity at nozzle exit, ms -1 U local mean velocity, ms -1 K u mean streamwise velocity decay rate, C u kinematic virtual origin (end of the potential core length non dimensionalised by the nozzle equivalent diameter) u'/U e non-dimensional velocity fluctuation along X-direction v'/U e non-dimensional velocity fluctuation along Y-direction X co-ordinate along the jet axis, mm Y co-ordinate along the horizontal plane, mm Y 0·5 jet half-width along Y axis, mm Z co-ordinate along the vertical plane, mm Z 0·5 jet half-width along Z axis, mm ABSTRACTAn experimental study has been carried out to understand jet flow development from plain and grooved rectangular nozzles of aspect ratio 2:1 using two-component hotwire anemometry. Grooves of square configuration (side 4mm) and length 5mm were introduced in the (i) minor-axis, (ii) major-axis and, (iii) in both minor-and majoraxes directions. The equivalent diameter of the plain rectangular nozzle is 37·5mm. Studies were carried out for a nominal jet exit velocity of 20ms -1 and for Reynolds number based on equivalent diameter of 54,000. The introduction of grooves in either plane does not show any influence on the potential-core length but results in faster jet-decay thereafter. It is observed that the grooves when introduced in minor-axis direction inhibit the jet growth in that plane while promoting the jet growth along major-axis plane and hence, delays the phenomena of axis-switching. However when introduced in major-axis direction, the grooves promote jet growth along majoraxis plane while inhibiting jet-growth in minor-axis plane. Crosssectional contours of mean-velocity suggest that the grooves modify the process of overall jet development significantly in the plane in which they are introduced relative to the plain jet and hence, significantly affect the axis-switching location in each case.

show abstract

“…Iso-baric contours of arc-tab facing-in creates more asymmetry as It is seen that the arc-tab facing-in performs consistently better than arc-tab facing-out and rectangular tab configurations. This may be attributed to the fact that the strong streamwise vortices having longer life span, shed by the arc-tab facing-in, causes an inward indentation of the ambient air into the jet core increasing mass entrainment and hence, enhanced mixing at the same blockage level [8].…”

Section: Iso-baric Contoursmentioning

confidence: 99%

“…This limit is known as Rathakrishnan limit [3,4]. Elangovan and Rathakrishanan [8] studied the jet issuing from circular nozzle with grooved exit. They found that for correctly and under-expanded sonic jets, the shock-cell structure was weakened with the introduction of grooves at the nozzle exit.…”

Section: Introductionmentioning

confidence: 99%

Influence of tab geometry and its orientation on under-expanded sonic jets

Thanigaiarasu

Jayaprakash

Elangovan

et al. 2008

Proceedings of the Institution of Mechanical Engineers, Part G:

View full text Add to dashboard Cite

The effect of tab geometry and its orientation placed at the nozzle exit on the evolution of an axi-symmetric sonic under-expanded and fully expanded jet was investigated experimentally. The tab used was a hollow semi-circular tube. The near jet flow field was studied for two configurations of the tab, namely, the concave surface facing the flow exiting nozzle (arc-tab facing-in) and convex surface facing the flow (arc-tab facing-out) for three different protrusions of the tab corresponding to blockages of 3.82, 7.64, and 11.46 per cent (z 1 , z 2 , and z 3 , respectively). The results were compared with that obtained for a plain rectangular tab of the same blockage and a plain circular nozzle. The jet was found to decay at a faster rate in the case of arc-tab facing-in configuration at all blockage levels as compared with the other two configurations. With arc-tab facing-in, the core length was reduced by 80 per cent and the corresponding reduction was 40 per cent for the jet with arc-tab facing-out and rectangular tabs. For the under-expanded sonic jet at the nozzle pressure ratio (NPR) 2, 3, and 5, the arc-tab facing-in configuration was found to reduce the potential core length and weaken the shock structure significantly as compared with the other two configurations as indicated by the lesser amplitude in pitot pressure variations. The shadowgraph pictures showed that the shock-cell structure was significantly perturbed and length of the cells was reduced considerably. This effect was found to be more pronounced at higher blockages. The iso-baric contours indicate that the jet spread is faster and wider in the direction normal to the tab revealing that the streamwise vortices shed by the tabs cause an inward indentation of the ambient air into the jet core and outward ejection of the jet core to the ambient. The geometry and orientation of the tab along with the level of blockage seem to have a profound influence on the development of the jet in the near field.

show abstract

Studies on high speed jets from nozzles with internal grooves

Cited by 20 publications

References 15 publications

Triangular tabs for supersonic jet mixing enhancement

Triangular tabs for supersonic jet mixing enhancement

Study of jets from rectangular nozzles with square grooves

Influence of tab geometry and its orientation on under-expanded sonic jets

Contact Info

Product

Resources

About