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The usefulness of the supersonic jet is inhabitable in the Aerospace industry. However, control of the supersonic jet is important for efficient mixing and noise attenuation. Particularly, asymmetric jets are better than axisymmetric jets in rapid mixing. Considering this, the experimental investigation has been carried out for the vortex generators or tab-controlled Mach 1.6 elliptic jet. To compare the impact of the locations of the vortex generators, they are deployed at the diametrically opposite locations of the nozzle outlet along the major or longest axis and the minor or shortest axis, respectively. The investigations have been carried out using the centerline pressure distributions employing the Pitot probe and the Schlieren flow visualizations. A maximum of 66.43% reduction in supersonic length has been observed from the centerline pressure distributions for the vortex generator placed along the shortest axis. In addition, the Schlieren flow visualizations confirm substantial distortions in the shock cell structures when the vortex generators are placed along the shortest axis which results in noise mitigation. The study concluded that the impact of the vortex generator, placed along the shortest axis, is superior in the manipulation of shock cell structure, efficient mixing, and thereby noise mitigation than those placed along the longest axis.

This study experimentally evaluated the mixing augmentation of twin tabs mounted along a diameter at the outlet of a convergent-divergent Mach 1.62 circular nozzle. The usefulness of the plain and grooved tabs is examined at various expansion levels prevailing at nozzle outlet. The tab's performance is assessed through pitot pressure distribution measured along and perpendicular to the jet centerline at different nozzle pressure ratios (NPRs). The shadowgraph technique visualized the shocks and expansion fans in uncontrolled and controlled jets. With the introduction of uncorrugated or plain tabs at the nozzle outlet operating under overexpanded conditions corresponding to NPR 4, the supersonic length (SL) was decreased only by 35.4%. On the other hand, the corrugated or grooved tabs under similar conditions decreased the SL substantially. Interestingly, the performance of grooved tabs was best at underexpanded conditions associated with NPR 6, where the SL was reduced by about 88%. The pressure profiles also established the superiority of tabs with grooved edges in mixing augmentation without introducing any significant asymmetry to the flow field. In addition, the Shadowgraph images also confirmed the weakening of shock strength and reduction of shock-cell length in the case of grooved tabs at the nozzle exit compared to the plain nozzle.

Mixing characteristics of jet emerging from a subsonic nozzle exit has been experimented and the results are compared with uncontrolled jet and controlled jet configurations. The mixing enhancement was achieved using a passive method of jet control in which tandem tabs arrangement with rectangular cross section are fixed at the nozzle exit. Two Tab configurations, the Tandem tab (TT) and Stepped Tandem Tab (STT) are used to enhance the mixing characteristics of the jet, the aspect ratio (length /width) of the tabs was 1.67 offering a blockage ratio of 9.55% to the nozzle exit. The blockage ratio of TT and STT configurations are maintained to be equal so that the mixing characteristics can be compared. The axial and radial jet spread are compared for nozzle exit Mach numbers of 0.6, 0.8 and 1.0. The TT controlled jet offered a potential core reduction of 63%, 78% and 82% for Mach numbers 0.6, 0.8 and 1.0 respectively. The STT controlled jet offered a potential core reduction of 89%, 90% and 85% for Mach numbers 0.6, 0.8 and 1.0 respectively. The radial spread of uncontrolled jet, controlled jet with TT and STT are plotted at several X/D locations and found that the controlled jets have more jet spread in both radial directions. A simulation is conducted for jets with exit Mach number 0.8 and the results are validated with the experimental findings. Based on the preliminary experimentation and computation, the STT controlled jet achieved better jet mixing through more potential core reduction and radial spread characteristics as compared to the TT configuration and base nozzle.

Background: Partial breast reconstruction with a pedicled chest wall perforator flap (CWPF) enables breast conservation in a higher tumour: breast volume ratio scenario. Since there is limited evidence, this retrospective cohort study aimed to ascertain immediate (30-days) and medium-term (follow-up duration) surgical outcomes. Methods: STROBE-compliant protocol ascertained CWPF outcomes between March 2011–March 2021. UK centres known to perform CWPF were invited to participate if they performed at least 10 cases. Data were retrospectively collected, including patient demographics, tumour and treatment characteristics, and surgical and oncological outcomes. Statistical analysis (R™) included multivariable logistic regression and sensitivity analysis. Results: Across 15 centres, 507 patients with median age (54 years, IQR; 48–62), body mass index (25.4 kg/m2, IQR; 22.5–29), tumour size (26 mm, IQR; 18–35), and specimen weight (62 g, IQR; 40–92) had following flap types: LiCAP (54.1%, n = 273), MiCAP/AiCAP (19.6%, n = 99), LiCAP + LTAP (19.8%, n = 100) and TDAP (2.2%, n = 11). 30-days complication rates were in 12%: haematoma (4.3%, n = 22), wound infection (4.3%, n = 22), delayed wound healing (2.8%, n = 14) and flap loss (0.6%, n = 3; 1 full) leading to readmissions (2.6%, n = 13) and re-operations (2.6%, n = 13). Positive margins (n = 88, 17.7%) led to 15.9% (n = 79) re-excisions, including 7.5% (n = 37) at the planned 2nd of 2-stage surgery and 1.8% (n = 9) mastectomy. At median 23 months (IQR; 11–39) follow-up, there were 1.2% (n = 6) symmetrisations; recurrences: local (1%), regional/nodal (0.6%) and distant (3.2%). Conclusions: This large multicentre cohort study demonstrates acceptable complication and margin re-excision rates. CWPF extends the range of breast conservation techniques. Further studies are required for long-term oncological outcomes.

This study experimentally explores the effect of tabs with asymmetric projections on the mixing effectiveness of jets at different nozzle exit Mach numbers with subsonic ranges of 0.4, 0.6, and 0.8. The results obtained with the tab-controlled jet are compared with those of uncontrolled jets. In this experimental investigation, a pair of identical tabs is deployed along a diameter of a convergent nozzle with inlet and exit cross sections of a circle, where each tab has two triangular projections configured at locations offset to each other at a distance of 1 mm on a plain rectangular stem. The geometrical blockage due to the presence of both tabs is maintained at 5.09% to minimize the thrust loss incurred due to tabs. The counter-rotating vortices generated at different locations of the tabs, caused instability or shear distortions at the nozzle exit, promoting jet mixing and eventually leading to rapid velocity decay along the jet axis and accentuating the reduction of the potential core. Compared to plain jet, reductions in core length of about 70%, 76%, and 81% at Mach 0.4, 0.6, and 0.8, respectively, are observed with the tab-controlled jets. The total pressure decay characteristics in the radial profile along the tab and normal-to-tab orientations have shown significant distortion in the jet structure, making it asymmetrical again owing to the asymmetrical positioning of projections on the tabs. Besides, in comparison with the plain nozzle, the total pressure decay characteristics in the radial profiles of tab-controlled jets are significantly different along the axial locations in the downstream direction due to the same reason of the asymmetrical positioning of triangular projections on the tabs. The primary research goal of this experimental investigation with asymmetrical tabs is to promote jet mixing asymmetrically to achieve thrust vectoring of jets.

The generation of shock waves and their repercussions in high-speed vehicles are inevitable. Particularly, the hot plume from the aircraft exhaust ejecting at a high speed, as well as the emitted aeroacoustic noise, have several consequences. Besides, the occurrence of the supersonic core length and the emission of high screech noise are mostly due to the shock cells, prevailing in high-speed jets. Therefore, understanding the shock cell structures developed at the exit of aircraft or rocket nozzles is vital in improving mixing and thereby the noise characteristics. Essentially, non-circular nozzle shapes are well known for enhancing entrainment characteristics and mitigating the noise due to their differential spreading over the nozzle's perimeter. The current study examines the shock structures of circular, elliptic, and square jets at various sonic underexpansion levels. In this investigation, the nozzle geometries are considered to have the same exit area. The Nozzle Pressure Ratio (NPR) was adjusted to 3, 4, and 5 to achieve moderate and highly underexpansion conditions. The shadowgraph visualization method is used to study the development of shock cells from axisymmetric and asymmetric nozzles. It is interesting to observe that the incident and reflected shock structures exist only at moderate and high underexpansion levels. Besides, the elliptic and the square jets have distinctive flow patterns along their different axis planes. The intercepting shock appears on the elliptic jet in the minor axis rather than the major axis direction. The curvature of the intercepting shock wave was found to be greater for the elliptic jet than that for the circular jet. In addition, the square jet in the symmetry plane diverges from the jet centerline, but the jet in the diagonal direction converges. Moreover, the estimated shock cell lengths using shadowgraph images were compared to a theoretical model where the experimentally obtained results are in good agreement with the theoretical values.

This present investigation inspects the mixing promoting the efficacy of two short delta tabs which is axis-symmetric, mounted circumferentially antipodal at the end for a Mach number 1.8 convergent-divergent circular nozzle computationally with the nozzle pressure ratios (NPRs) ranging from 4 to 8 with a unit step of one that covers all the critical states of the jet i.e., the overexpanded, the correctly-expanded and the underexpanded states of the jet. In order to minimize thrust loss, the geometric blockage offered by each delta tab is kept within 2.5%. The computational assessment is conducted by adopting and employing ANSYS-FLUENT which is a comprehensive engineering simulation software. Further, the entire steady flow computations are carried out on a three-dimensional numerical enclosure by implementing Reynolds-averaged Navier-Stokes equations along with the κ-omega shear stress transport turbulence model. Interestingly, vital plots including the centerline pressure decay as well as the pressure profiles are depicted for uncontrolled and controlled jets accordingly. Also, numerically obtained schlieren illustrations are adopted for visualization of the shock cell structure, expansion fan, and the Mach wave structure existing in the stream field. Furthermore, Mach variations are also depicted for the varied nozzle pressure ratios in the form of contours. The shock-strength, shock-length, and the progressive disparity found in the shock structures are reasonably demonstrated by the Mach contours. The results of this research are discovered to be in sensible concurrence with the earlier established exploratory results. A maximum core length reduction of 70.81% is observed in underexpanded condition at the nozzle pressure ratio of 6. Absorbingly, a controlled jet has been seen to get split in equal proportion along the succeeding direction of the nozzle exit at a distance of approximately 5De, De indicating the exit diameter of the nozzle. Moreover, it was appealing to detect the development of jet dispersion along the succeeding direction of the nozzle exit periphery. The short delta tabs also performed satisfactorily in diminishing the waves and reducing the shock cell length as depicted via numerical schlieren images.

The attitude control of a rocket engine using the control surfaces becomes cumbersome particularly in larger rockets with high payload. In such cases, a more effective means of producing forces for controlling the flight is the deflection of exhaust gases, referred to as the gas-dynamic steering or the thrust vector control. In this study, the effect of a strut on the exhaust gas deflection, deployed at the locations; 0.62 L, 0.72 L and 0.8 L in the divergent-portion of a Mach 1.84 nozzle at over-expanded, correctly-expanded and under-expanded states of the jet, has been experimentally investigated. The level of expansion at the nozzle exit is varied by changing the settling chamber pressures from 4 bar to 8 bar, in steps of 2 bar. Further, to study the effect of aspect ratio, the height of strut is varied as 1.5 mm, 2.5 mm and 3.5 mm. The strut of height 3.5 mm, deployed at x/L = 0.72, is found to be the most effective thrust vector control at overexpanded conditions; with a maximum jet deflection of about 3.6o, obtained at a settling chamber pressure of 4 bar. The Schlieren flow visualization images confirm the findings of wall static pressure data.

The existence of bubble nuclei identified by the central depletion in nucleonic density is studied for the conventional magic N (Z) = 8, 20, 28, 40, 50, 82, 126 isotones (isotopes) and recently speculated magic N = 164, 184, 228 superheavy isotones. Many new bubble nuclei are predicted in all regions. Study of density profiles, form factor, single particle levels and depletion fraction (DF) across the periodic chart reveals that the central depletion is correlated to shell structure and occurs due to unoccupancy in s-orbit (2s, 3s, 4s) and inversion of (2s, 1d) and (3s, 1h) states in nuclei upto Z ≤ 82. Bubble effect in superheavy region is a signature of the interplay between the Coulomb and nn-interaction where the depletion fraction (DF) is found to increase with Z (Coulomb repulsion) and decrease with isospin. Our results are consistent with the available data. The occupancy in s-state in 34Si increases with temperature which appears to quench the bubble effect. Keywords: Relativistic mean-field plus BCS approach, Bubble nuclei, Statistical theory for hot nuclei, Magic nuclei, Temperature effect on bubble

Two-proton radioactivity with 2p halo is reported theoretically in light mass nuclei A=18â34. We predict 19Mg, 22Si, 26S, 30Ar and 34Ca as promising candidates of ground state 2p-radioactivity with S2p0. Observation of extended tail of spatial charge density distribution, larger charge radius and study of proton single particle states, Fermi energy and the wave functions indicate 2p halo like structure which supports direct 2p emission. The Coulomb and centrifugal barriers in experimentally identified 2p unbound 22Si show a quasi-bound state that ensures enough life time for such experimental probes. Our predictions are in good accord with experimental and other theoretical data available so far. Keywords: Relativistic mean-field theory, Nilson Strutinsky approach, Two-proton radioactivity, One- and two-proton separation energy, Halo nuclei, Proton drip-lines