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The theoretical finding of the Sanal-flow-choking [PMCID: PMC7267099] and streamtube flow choking (V.R.Sanal Kumar et al., Physics of Fluids, Vol.33, No.3, 2021, DOI: 10.1063/5.0040440) are methodological advancements in predicting the deflagration-to-detonation-transition (DDT) in the real-world-fluid flows (continuum/non-continuum) with credibility.[1,2] Herein, we provide a proof of the concept of the Sanal-flow-choking and streamtube-flow-choking causing DDT in wall-bounded and free-external flows. Once the streamlines compacted, the considerable pressure difference attains inside the streamtube and the flow gets accelerated to the constricted region for satisfying the continuity condition set by the conservation law of nature. If the shape of the streamtube in the internal/external flow is similar to the convergent-divergent (CD) duct the phenomenon of the Sanal-flow-choking and supersonic flow development occurs at a critical-total-to-static pressure ratio (CPR) in yocto to yotta scale systems and beyond, which leads to shock wave generation or detonation as the case may me. At the lower critical detonation or hemorrhage index, the CPR of the reacting flow and the critical blood-pressure-ratio (BPR) of the subjects (human being/animal) are unique functions of the heat-capacity-ratio (HCR) of the evolved gas in the CD duct (V.R.Sanal Kumar et al., Global Challenges, Wiley Publication, January 2021, DOI: 10.1002/gch2.202000076, PMCID: PMC7933821; Sanal Kumar V.R et al. Stroke, Vol. 52, Issue Suppl_11 March 2021, doi.org/10.1161/str.52.suppl_1.P804). In silico results are presented herein to establish the proof of the concept of the Sanal-flow-choking and streamtube-flow-choking causing shock-wave/detonation in diabatic flow systems and asymptomatic-hemorrhagic-stroke in biological systems. The physics of detonation chemistry presented herein sheds light for exploring environmental and supernova explosions.[107] In silico results reported herein provide an authentic answer to many unresolved research questions in Physics in general and aerospace, mechanical, biological, chemical, energy, environmental, nano and material sciences in particular.

The theoretical finding of the Sanal-flow-choking [PMCID: PMC7267099] is a methodological advancement in predicting the deflagration-to-detonation-transition (DDT) in the real-world-fluid flows (continuum/non-continuum) with credibility.[1,2] Herein, we provide a proof of the concept of the Sanal-flow-choking and streamtube-flow-choking causing DDT in wall-bounded and free-external flows. Once the streamlines compacted, the considerable pressure difference attains inside the streamtube and the flow gets accelerated to the constricted region for satisfying the continuity condition set by the conservation law of nature. If the shape of the streamtube in the internal/external flow is similar to the convergent-divergent (CD) duct the phenomenon of the Sanal-flow-choking and supersonic flow development occurs at a critical-total-to-static pressure ratio (CPR) in yocto to yotta scale systems and beyond, which leads to shock wave generation or detonation as the case may me. At the lower critical detonation or hemorrhage index, the CPR of the reacting flow and the critical blood-pressure-ratio (BPR) of the subjects (human being/animal) are unique functions of the heat-capacity-ratio (HCR) of the evolved gas in the CD duct. In silico results are presented herein to establish the proof of the concept of the Sanal-flow-choking and streamtube-flow-choking causing shock-wave/detonation in diabatic flow systems and asymptomatic-hemorrhagic-stroke in biological systems. The physics of detonation chemistry presented herein sheds light for exploring supernova explosions.[107]

The theoretical discoveries of the Sanal flow choking [V. R. Sanal Kumar et al., “Sanal flow choking: A paradigm shift in computational fluid dynamics code verification and diagnosing detonation and hemorrhage in real‐world fluid‐flow systems,” Global Challenges 4, 2000012 (2020)] and streamtube flow choking [V. R. Sanal Kumar et al., “Deflagration to detonation transition in chemical rockets with sudden expansion/divergence regions,” AIAA Paper No. 2020-3520, 2020] achieved significant contemplation in all branches of science and engineering for resolving various unanswered scientific questions brought onward from the beginning of this era [V. R. Sanal Kumar et al., “A closed-form analytical model for predicting 3D boundary layer displacement thickness for the validation of viscous flow solvers,” AIP Adv. 8, 025315 (2018)]. The applications of these flow choking phenomena are more significant in aerospace industries [V. R. Sanal Kumar et al., “Nanoscale flow choking and spaceflight effects on cardiovascular risk of astronauts—A new perspective,” AIAA Paper No. 2021-0357, 2021] and medical sciences [V. R. Sanal Kumar et al., “Lopsided blood-thinning drug increases the risk of internal flow choking leading to shock wave generation causing asymptomatic cardiovascular disease,” Global Challenges 2021, 2000076]. Herein, as an offshoot of the Sanal flow choking phenomena, the proof of the concept of boundary-layer-blockage (BLB) persuaded external-flow-choking (EFC) at aircraft-in-ground (AIG)-effect is presented. When the aircraft's ground clearance is relatively low, the evolving BLB factor from both planes (the bottom surface of the aircraft and the ground) creates a transient fluid-throat, leading to the Sanal flow choking and supersonic flow development in the duct flow region. In this physical situation, the pressure ratio (Ptotal/Pstatic) at the external flow choking region is exclusively a function of the specific heat ratio of the fluid. The EFC is more prone for the low wing aircraft flying in the near vicinity to the ground and/or sea with relatively high subsonic Mach number and low angle of attack. At this flying condition, the underside of the aircraft (fuselage and/or wing) and the ground creates the convergent-divergent duct flow effect leading to the EFC at the critical total-to-static pressure ratio. The accurate estimation of the BLB factor at the location of the EFC at AIG effect is presented in this manuscript as a universal yardstick for two-dimensional (2D) in silico simulation. For establishing the proof of the concept of external flow choking and supersonic flow development and shock wave generation, the 2D in silico results are presented for both stationary and moving airfoils in ground effect. In silico results show that the airfoil at stationary position exhibits relatively higher BLB factor and an immediate occurrence of the EFC than the same airfoil moving with the identical inflow Mach number and Reynolds number. We could establish herein that the moving vehicle simulation is inevitable for capturing actual flow physics and further precise examination of the BLB factor and the possibilities of the occurrence of the EFC for credible trajectory optimization of high-speed ground-effect vehicles.

Numerical studies have been carried out to examine the flame spread mechanism and the chamber dynamics of high-performance dual-thrust solid propellant rocket motors during the starting transient period of operation. Using a three-dimensional unsteady, shear-stress transport k–ω turbulence model, detailed parametric studies have been carried out to examine the aerodynamic choking and the existence/non-existence of a fluid throat at the transition region during the startup transient of dual-thrust motors (DTMs). In the numerical study, a fully implicit finite volume scheme of the compressible, density based Navier–Stokes equation is employed. We confirmed that, at the subsonic inflow conditions, there is a possibility of the occurrence of internal flow choking in dual-thrust motors with large length-to-diameter ratio (L/d > 44) due to the formation of a fluid throat at the beginning of the transition region induced by area blockage caused by boundary layerdisplacement thickness. We also confirmed that in such motors the choked flow becomes unchoked flow during the flame spread period due to the mass injection from the wall as a result of the thinning of the boundary layer thickness. We have demonstrated that without altering the grain geometry one can alter the flame spread mechanism by altering the igniter jet turbulence intensity, igniter gas temperature and propellant conductivity. Additionally, the numerical results of inert simulators of dual-thrust motors are compared with that of the case with propellant injection for establishing the physical situations of the choked and unchoked flow conditions during the starting transient period of operation of dual-thrust motors with high-propellant loading density.

In this paper numerical studies have been carried out to examine the intrinsic flow features of cavity based scramjet combustors with backward facing step and forward ramp using 3D, density-based, implicit, SST k-omega turbulence model. The preliminary results show a wide variety of flow features resulting from the interactions between the injector flows, shock waves, boundary layers, and cavity flows. In all the cases the C2H6-CO2-H2O fuel is injected at three different jet angles for the optimization of the jet orientation. Through the 3D numerical simulation we have corroborated that an optimized cavity is a good choice to stabilize the flame in the scramjet combustor as it generates a benign recirculation zone in the scramjet combustor. We comprehended that the cavity based scramjet combustors have a bearing on the source of disturbance for the transverse jet oscillation, fuel/air mixing enhancement, and flame-holding improvement. We concluded that the cavity shaped combustor with backward facing step and 45 o forward ramp having an injector location of 1.6 times of its hydraulic diameter from the inlet facilitating at an angle of injection of 45 o opposing the inlet flow is a good choice to getting relatively higher temperature at the exit.

The noise regulations around the major airports and rocket launching stations due to the environmental concern have made jet noise a crucial problem in the present day aeroacoustics research. Acoustic studies reveal that addition of chevrons to the nozzle reduces the sound pressure level reasonably with acceptable reduction in performance. In this paper three-dimensional jet acoustic characterization and geometry optimization of chevron nozzles have been carried out for getting optimum performance of the propulsion systems by meeting the multifold objectives. The numerical studies have been carried out using a validated steady 3D density based, k-e turbulence models with standard wall functions. In the numerical study, a fully implicit finite volume scheme of the compressible, Navier–Stokes equations is employed. We observed through the parametric analytical studies that a case with round edge chevron nozzle having aerodynamically contoured tips is better than sharp edge chevrons for jet noise reduction in terms of tip effect induced noise. We also observed that round-shaped chevron nozzle could reduce ~ 4 % acoustic level with marginal thrust loss while comparing a case with conventional CD nozzle. We have proved conclusively that the geometry optimization of chevron nozzles with aerodynamically efficient tip contours for facilitating silent exit flow will enable an appreciable reduction of the jet noise at different frequencies and at different range of exit Mach numbers without much compromising on the overall performance of the aerospace vehicles. We also concluded that the chevron with round edge having suitable number of chevrons with aerofoil shaped tip contours, as the case may be, is the best choice for the sound reduction on the order of 6.5 dB with a marginal penalty of ~0.58 % total thrust loss while comparing with those aerospace vehicles having conventional CD nozzle.

In this paper comprehensive studies on chamber dynamics have been carried out to examine the intrinsic flow physics pertaining to the nozzle flow choking time and the liftoff time of dual-thrust solid propellant rockets. Diagnostic investigations have been carried out using a three-dimensional unsteady, double precision, density based, shear-stress transport k–ω turbulence model. This model solves standard k–ω turbulence equations with shear flow corrections using a coupled second-order-implicit unsteady formulation. In the numerical study, a fully implicit finite volume scheme of the compressible, Reynoldsaveraged, Navier–Stokes equations is employed. Numerical studies reveal that narrow port and long flow development ahead of the divergent location of dual-thrust motors (DTMs) are likely to have multiple flow choking and spread rate enhancement. As a result the transition location of the DTM will act like a second throat and/or the upstream port will perform as a second igniter, which will certainly delay significantly the flow choking time of the rocket nozzle due to the delay in establishing the choked flow condition leading to delay in the full development of thrust for takeoff. The internal flow choking can lead to the formation of shock waves inside the DTM. The shock waves and the connected new turbulence features will alter the flamespread and chamber dynamics and will indeed alter the nozzle flow choking time and the liftoff time of dual-thrust rockets with high length to diameter ratio. We conjectured from the parametric analytical studies that the altered variations of the igniter jet impingement angle, igniter jet turbulence level, time and location of the first ignition, flame spread characteristics, flow development history, the overall chamber dynamics and the thermoviscoelastic response of the grain are having the bearing on the starting transient and the nozzle flow choking time for establishing the required full thrust for the rocket liftoff. We concluded that the higher igniter jet turbulence intensity will cause delayed nozzle flow choking warranting delayed liftoff time of dual-thrust solid propellant rockets.

A plethora of systemic and local signaling molecules regulate ovarian function, but how different signaling molecules interact within an ovarian target cell is not known. Here we report that endocrine cells of the ovary express a phosphoprotein, DARPP-32 (dopamine and cyclic AMP-regulated phosphoprotein of Mr 32,000), which integrates signaling molecules in neurons. We thus hypothesized that DARPP-32 might act in a similar way in ovarian endocrine cells and therefore studied whether DARPP-32 gene deletion has consequences for ovarian functions in mice. Reproductive performance of adult mutants did not differ from wild-type females, as judged from numbers of litters and pups delivered. Similar steroid levels in mutant and wild-type mice ruled out gross abnormalities in the hypothalamic-pituitary-ovarian axis. However, an analysis of ovarian morphology, using serially sectioned ovaries, revealed several differences. Ovaries of young adult mutant mice at 2 - 3 months contained luteinized follicles, but fewer corpora lutea. At 5 - 6 months, large cysts were found in mutant mice, as well as reduced numbers of preantral follicles and antral follicles. Interstitial cell hypertrophy and degeneration was marked in all mutant ovaries at this age. Thus, while the lack of DARPP-32 does not overtly alter reproductive performance in adult mice, it is associated with progressive alterations and derangements of growth and development of ovarian follicles, suggesting premature ovarian ageing. This implies that ovarian DARPP-32 is involved in follicular development, presumably by integrating effects of signaling molecules, which act together to ensure efficient follicular development.