Stagnation Region Research Articles

Numerical analysis of ternary hybrid nanofluid flow over a stagnation region of stretching/shrinking curved surface with suction and Lorentz force

In recent years, there has been a lot of interest in studying stagnation point flow. This is because stagnation point flow is used in many technological applications, such as cooling spinning machinery segments and nuclear reactors. This study analyzes the potential practical applications of the ternary (Cu-Fe3O4-SiO2/SA) hybrid nanofluid as it flows through a stagnation zone of a stretching or shrinking curved surface under the impact of suction and Lorentz force. To acquire numerical solutions, the governing PDEs are first altered into a system of ODEs and then entered into the MATHEMATICA program. We compare findings for validation purposes and illustrate the consequences of specific characteristics that will be planned for the physical quantities that are of interest. When magnetic field and suction are present, velocity improves, but the inverse is true for curvature and nanoparticle volume fraction for both stretching and shrinking surfaces. Temperature increases against nanoparticle volume fraction, magnetic field, and heat source/sink and decreases against suction and curvature parameters for both stretching and shrinking cases. When the values of the suction parameters were changed from 2.0 to 2.5, the heat transfer rates rose by an increase ranging from 34% to 39% may be determined. Improved velocity and temperature distributions may be attributed to the presence of ternary hybrid nanofluids. This research gives scientists and engineers a head start in adjusting the relevant parameters to get the best possible results in the associated practical applications.

Stability Analysis of Unsteady Mixed Convection Flow Near the Stagnation Point with Buoyancy Effect

This numerical study investigates the behaviour of the unsteady mixed convection flow and heat transfer near the stagnation region past a vertical plate in Al2O3-Cu/H2O hybrid nanofluids. By choosing an appropriate similarity transformation, an ordinary differential equations system is obtained, hence scrutinized via the bvp4c package embedded in the MATLAB program. The results show that as the nanoparticle volume fraction and unsteadiness parameter increase, the fluid's skin friction coefficient also increases. Also, an increase in the nanoparticle volume fraction and unsteadiness parameter has broadened the range of solutions hence, delayed the progress of boundary layer separation. In addition, the presence of the unsteadiness parameter provides a significant result in the thermal system. The first solution is declared stable by the stability analysis.

Study of thermophoresis and Brownian motion phenomena in radial stagnation flow over a twisting cylinder

This article deals with the analysis of nanofluid flow and its thermal energy transport in the stagnation region, impinged radially on a rotating circular cylinder with magnetohydrodynamic (MHD) effect. The swirling flow is driven by the rotational motion of a circular cylinder along the z -direction. A two-phase nanofluid model, namely the Buongiorno model is utilized to determine the thermal characteristics of nanoparticles, which highlights the influence of Brownian diffusion and thermophoresis on temperature and concentration distributions. Numerical outcomes are computed by applying the built-in program bvp5c in MATLAB. The focus of this manuscript is to determine the numerical interpretations of wall stresses with their asymptotic behavior, Nusselt number, and Sherwood number against relevant parameters. The axial and azimuthal wall stress parameters are obtained as a function of twist rate at various values of Reynolds number. Furthermore, the asymptotic behavior for small Reynolds number is compared with their corresponding numerical solutions. The comparison of our result as a special case for non-electrically conducting flow is found in exact agreement with the ones in the literature. It is noticed that wall stresses are greatly affected due to an increment in Reynolds number. The thermal and mass transport phenomena is reduced due to increment in the twisting rate of the cylinder. However, the momentum of the system is inclined, and consequently, an increase in the axial and azimuthal velocities is observed. Moreover, the numerical values of heat and mass transfer rates deteriorate because of thermophoresis; however, owing to the Brownian diffusion, the former declines, and the latter progress significantly.

Experimental and analytical study on local heat transfer distribution between smooth flat plate and free surface impinging jet from a circular straight pipe nozzle

The present study describes the heat transfer characteristics of free surface single-phase circular liquid jet impinging on a thin smooth flat surface subjected to uniform heat flux. The experimental setup is developed to measure the local temperature of a thin stainless steel metal foil using the infrared thermography technique. The effects of nozzle diameter (d = 2.5 to 10.8 mm), nozzle to plate spacing (z/d = 2 to 10), and Reynolds number (Re = 5000 to 24,000) on the local Nusselt number (Nu) distributions are studied. The local Nu is maximum in the stagnation region, and it decreases in the downstream flow following the stagnation region. The nozzle with a larger diameter shows maximum Nu compared to other nozzles. For a given z/d of 2 and a Reynolds number of 15,000, a maximum increment of 67% in local Nu is observed for a 10.8 mm nozzle in comparison to a 2.5 mm nozzle. The local Nu in the viscous boundary layer is found to be a function of the Reynolds number, Prandtl number, dimensionless r/d, and Weber number. The Nu increases with an increase in Reynolds number, however, the effect of the nozzle to plate spacing is negligible. The off-stagnation peak is observed for the 10.8 mm nozzle in the region of 0≤r/d≤0.7. The existing correlations reported in the literature are not able to capture the measured local Nusselt number distribution. Therefore, in the present study, an effort has been made to propose semi-empirical correlations for local Nu in the stagnation and viscous boundary layer region which will incorporate the diameter effect of the nozzle. The proposed correlations are able to predict the local Nusselt number distribution within the maximum deviation of 20%. The comparison between the free surface and submerged jet has been made which suggests that the local Nu for the submerged jet is higher compared to the free surface jet.

On the impingement of heat transfer using swirled air jets

Experimental analyses were conducted under identical experimental conditions on the heat transfer between a constant heat flux flat plate and a round air jet for both conventional and swirled jets. Vane-type swirl generators inserted at the nozzle exit were used to produce a swirl. The experimental measurements were performed at a fixed Reynolds number value (Re = 23,000) calculated on the jet tube’s inside diameter. A comparison between conventional air jets and swirl jets with swirl numbers of S = 0, 0.19, 0.42, and 0.72 was presented for the different nozzle-to-plate spacings Z/D = 2, 6, and 10. The results show that heat transfer to the plate decreases when the nozzle-to-plate distance increases. In addition, increasing the swirl number S increases heat transfer uniformity but decreases global heat transfer. At the low plate-to-jet distance Z/D = 2, the point of maximum heat transfer is shifted to a radial position depending on the swirl number. Also, for both Z/D = 6 and 10, the stagnation point and stagnation region heat-transfer enhances only for swirl numbers 0 and 0.19.

The effect of drainage cannula tip position on risk of thrombosis during venoarterial extracorporeal membrane oxygenation

Background and objectivesVenoarterial extracorporeal membrane oxygenation (VA ECMO) is able to support critically ill patients undergoing refractory cardiopulmonary failure. It relies on drainage cannulae to extract venous blood from the patient, but cannula features and tip position may impact flow dynamics and thrombosis risk. Therefore, this study aimed to investigate the effect of tip position of single-stage (SS) and multi-stage (MS) VA ECMO drainage cannulae on the risk of thrombosis. MethodsComputational fluid dynamics was used to model flow dynamics within patient-specific geometry of the venous vasculature. The tip of the SS and MS cannula was placed in the superior vena cava (SVC), SVC-Right atrium (RA) junction, mid-RA, inferior vena cava (IVC)-RA junction, and IVC. The risk of thrombosis was assessed by measuring several factors. Blood residence time was measured via an Eulerian approach through the use of a scalar source term. Regions of stagnant volume were recognised by identifying regions of low fluid velocity and shear rate. Rate of blood washout was calculated by patching the domain with a scalar value and measuring the rate of fluid displacement. Lastly, wall shear stress values were determined to provide a qualitative understanding of potential blood trauma. ResultsThrombosis risk varied substantially with position changes of the SS cannula, which was less evident with the MS cannula. The SS cannula showed reduced thrombosis risk arising from stagnant regions when placed in the SVC or SVC-RA junction, whereas an MS cannula was predicted to create stagnant regions during all tip positions. When positioned in the IVC-RA junction or IVC, the risk of thrombosis was higher in the SS cannula than in the MS cannula due to both high and low shear flow. ConclusionTip position of the drainage cannula impacts cannula flow dynamics and, subsequently, the risk of thrombosis. The use of MS cannulae can reduce high shear-related thrombosis, but SS cannulae can eliminate stagnant regions when advanced into the SVC. Therefore, the choice of cannula design and tip position should be carefully considered during cannulation.

Status, Trends, and Drivers of Harmful Algal Blooms Along the Freshwater-to-Marine Gradient in the San Francisco Bay–Delta System

Harmful algal blooms (HABs) are on the rise worldwide. Known drivers for the proliferation and intensification of HAB events include increasing nutrient pollution, climate change, regulation and modification of hydrological flow, and the combined effect of climate drivers and nutrient pollution. The San Francisco Bay–Delta system has largely been immune to severe or acute HAB events, but there is both a potential and realized threat which has been underestimated and under-reported, in part because of the lack of coordinated sampling and data reporting. There is also increasing evidence that HABs must be considered in the context of a freshwater-to-marine continuum, and that the physical and political boundaries separating components of the Bay–Delta system are porous barriers to HABs and their toxins. Much remains to be learned about the ecology and physiology of HAB organisms in this system, but five primary environmental drivers can be identified: temperature, salinity, irradiance, nutrients, and stratification/residence time. All these drivers are responding rapidly to climate change, but nutrients are the primary variable that is largely under human control. Plans for the development of a comprehensive monitoring, prediction, and mitigation strategy across the freshwater-to-marine continuum have been documented; effectively following through on these plans provides a roadmap toward identifying the drivers and threats—and reducing the potential consequences now and in the future. While HABs alone are not a sufficient motivator for potentially costly and extensive mitigation efforts, there is strong evidence that decreasing nutrient loads, maintaining hydrological connectivity while minimizing stagnant regions, and managing the biota to maintain biodiversity of the Bay–Delta system will result in multiple co-benefits, including reduction of the HAB threat potential.

Large eddy simulation of impinging heat transfer of pulsed chevron jet on a semi-cylindrical concave plate

This study employs large eddy simulation to investigate the impinging heat transfer of the pulsed chevron jet on a semi-cylindrical concave plate at f = 20 Hz and H/d = 4. The instantaneous temperature of the target plate is highly associated with the behavior of the pulsed jet. The temperature sharply decreases once it is covered by the cooling wall jet and then sharps increase only when the jet injection is off. The pulsation plays a significant role in the formation and evolvement of the coherence structure. At the time of t = 0.1φ, the pulsed jet has covered the stagnation region. The stripe-shaped coherence structure is vertical to the ring-shaped secondary vortex. The secondary vortex becomes broken and unsteady as moving downstream. When the jet is off, the wall jet moves downstream because of inertia. There is no remnant cooling wall jet covering the target plate. There is no recirculation zone along the curvilinear direction during the duty cycle, while the recirculation zone is formed only when the jet injection is off. The hot wall jet along the curvilinear direction is entrained through large-scale recirculation and then returns to the target plate. The influencing area of the recirculation zone of the pulsation becomes larger and more closed to the jet mainstream compared with the steady jet. The existence of pulsation enlarges the spreading width of the jet core compared with a steady jet. The proportion of velocity and pressure in primary frequency dominates the pulsed jet, and the proportion in higher order can be neglected.

Two‐Dimensional Modeling of Colloid‐Facilitated Contaminant Transport in Groundwater Flow Systems With Stagnant Zones

AbstractA mathematical model has been developed for the contaminant transport with colloids in groundwater flow systems with stagnant zones to investigate the effect of stagnant zones on the transport of contaminants with colloids. In the present study, colloids and contaminants are supposed to drift via two coexisting homogeneous regions. The critical limitation of the mobile‐immobile (MIM) model is to deal with the number of parameters used upon application to larger scales for both mobile and immobile regions when a series of transport mechanisms are involved. Therefore, the present model is the first attempt model of the equilibrium approach for mobile‐immobile regions to avoid complexities in the model. The present study includes the effect of the stagnant zone on the plume movement in mobile regions for steady‐state flow conditions, and it is discerned that the plume moves faster in the presence of immobile regions. However, when dispersion, velocity, and pulse duration are decreased, tailing is noticed in the breakthrough profiles. Stagnant regions enhance the transport of contaminants in the porous media and produce augmented breakthrough curves by increasing the velocity in the mobile regions where colloids and contaminants migrate simultaneously. The transport of contaminants can be enhanced in the presence of colloids. However, sensitivity analyses indicate that the combination of different distribution coefficients controls the mobility of contaminants even in the presence of colloids. The proposed model has been validated using experimental data of the single‐porosity model in the presence of colloids and the MIM model in the absence of colloids.

A Study of the Velocity Field During Mitigation of Vortex Breakdown in Model Francis Turbine at High Load

Abstract Off-design operation leads to the development of flow instabilities like vortex breakdown phenomenon which manifests as an enlarged vortex core in the draft tube at high load operating conditions. These flow instabilities are known to potentially have detrimental effects on turbine performance necessitating investigations on their formative and mitigation mechanisms. This work clarifies the evolving velocity maps characterizing vortex breakdown seen in a model Francis turbine draft tube during the transition from high load to best efficiency point. Velocity measurements have been performed inside a draft tube cone using a 2D particle image velocimetry system. Results show a wake-like velocity profile characterizing the vortex core in the draft tube cone at high load condition. The vortex core is a centrally located flow feature embodying a quasi-stagnant flow with recirculation regions. Surrounding the core, an axial outflow is seen with shear layers arising at the interface of core and outflow due to a substantial velocity gradient. Mitigation of this vortex core through a load rejection operation was further investigated. It is seen that as the flowrate approaches the best efficiency point, the shear layers between the outflow and central stagnation region break. The breakup leads to an axially dominated and streamlined flow. This is enabled by the reduction of the swirl until no central flow separation at the stagnation point occurs. The flow at the best efficiency point is thus devoid of the vortex core due to the absence of flow stagnation, the primary instability causing the core development.

Computational flow and heat transfer study on impingement cooling in a turbine blade leading edge using an innovative convergent nozzles

The present paper discusses a detailed numerical study performed to investigate flow and heat transfer characteristics of impingement cooling of the leading edge of a HP gas turbine blade model. An array of innovative converging shape nozzles are used as jets which strike the surface to be cooled. A comprehensive study is presented investigating various parameters which effect impingement cooling. These parameters include varying Mach number of the flow as 0.2 to 0.8, converging ratio of the nozzle varied as 2 to 8 at two different minor diameters of 0.25–0.5 mm of the jet, pitch distance is changed from 3 to 5 mm, and inter-jet distance changed from 3 mm to 6 mm. Each parameter is independently scrutinized keeping other parameters constant. The results indicate the formation of primary stagnation region where Nusselt number augmentation is maximum compared to secondary stagnation region. Cross-flow effect plays a significant role in reducing peak values in the Nusselt number in the downstream region. Enhancement in peak Nusselt number value is greater for high values of Mach number of the flow, lower jet-to-target distances and the higher converging ratio at a lower value of jet diameter. Average Nusselt number is found to be higher for lower values of pitch distance.

A passive control strategy of a micropolar hybrid nanofluid flow over a convectively heated flat surface

In this report, the authors have presented a semi-analytical analysis on thermal convective magnetohydrodynamic flow of a water-based micropolar hybrid nanofluid comprising of Ag and CuO nanoparticles over a stagnant point region of a surface. Thermal convection and mass flux conditions are taken in flow problem. Additionally, the impacts of Brownian motion, chemical reaction, thermophoresis, heat source, and viscous dissipation are taken into account. Also, the Cattaneo-Christovo flux model is used to analyze the transportations of heat and mass. The problem formulation is transformed into dimensionless form by means of suitable similarity transformations. The homotopy analysis technique (HAM), which is semi-numerical approach that does not require small or large factors, is applied. The convergence of each profile of the flow functions are demonstrated in pictorial form. The code has been utilized in the MATHEMATICA 12.0 software. The results show that the growing micropolar factor reduces the velocity and micro-rotational distribution. Also, the coefficient of skin friction is a decreasing function of the magnetic factor. The growing magnetic factor upsurges the velocity distribution, where a dual impact of the magnetic factor on microrotation distribution is observed. The heat transfer rate is a reducing function of Eckert number, magnetic, Brownian as well as thermophoretic factors. Mass transportation rate has declined with growth in Brownian and thermophoresis factors.

An Aerodynamic Property Investigation of an Unmanned Aerial Vehicle (UAV) in case of Forward Flight by Numerical Approach

In the golden era of digitalization, flow calculation research based on a numerical approach has become increasingly popular in the scientific world and has played a vital role in revealing the aerodynamic characteristics of various aircraft models. This paper, belonging to computational fluid dynamics, describes the process and results of a numerical simulation approach using the software OpenFOAM for an unmanned aerial vehicle (UAV) in the case of forwarding flight with a low Reynolds number. With regard to the numerical approach, the aerodynamic properties are investigated through the turbulence model k-ω-SST (shear stress transport), which is a part of the turbulence calculation approach Reynolds average Navier–Stokes (RANS). Furthermore, the entire process of mesh generation and the numerical calculation process by simpleFoam in OpenFOAM, which is the solver using the semi-implicit method for pressure-linked equations (SIMPLE) algorithm for steady, incompressible flow, are also depicted in this paper. In addition, the characteristics of the flow field surrounding the model and the characteristic aerodynamic coefficients (drag coefficient, lift coefficient, lift-to-drag ratio versus angle of attack and pressure coefficients, and skin-friction coefficients for special positions on the wing) of the model are also clearly illustrated. Finally, the simulation illustrations in ParaView, including the velocity field, pressure field and vortices in the stagnation region, are shown. The process description and results contribute a clear picture of the numerical execution steps in OpenFOAM and aerodynamic knowledge for a particular unmanned aerial vehicle model to the computational fluid dynamics field in the aerospace industry.

Substrate Characteristics of Multiple Arrays of Turbulent Swirling Impinging Jets

This research investigates the flow aspects and thermal behavior of multiple air jet impingements on a flat plate through two different geometrical arrangements. A variety of flow conditions and geometrical parameters are considered including Reynolds number, swirl number, impingement distance, and jet-to-jet separation. A numerical approach is adopted to conduct the analysis using the SST k-ω turbulence model in the commercial CFD software package ANSYS Fluent v17. Results reveal that the static pressure is uniformly distributed on the impingement surface for the higher nozzle-to-surface distance at a strong swirl flow, while for no-swirl and medium-swirl configurations, the static pressure is accumulated at the stagnation regions. A lower impingement distance ameliorates the cooling performance while a higher impingement distance accelerates the consistency in temperature distribution. Moreover, the staggered nozzle arrangement is found superior in terms of generating integrity in thermal cooling. Overall, the pressure coefficient enhances up to 126% for medium swirl (S = 0.3) and 67% for high swirl (S = 0.75) cases, and in terms of Reynolds number (Re), the pressure coefficient decreases by 12% and 15% for Re = 24600 and 35000, respectively, compared to Re = 11600. Besides, the average Nusselt number amplifies by 8% and 17% for medium (S = 0.3) and high swirl (S = 0.75) flow, respectively, while compared to Re = 11600, the average Nusselt number raises by 58% and 98% for Re = 24600, and 35000, respectively. The eddy viscosity increases strongly with the growth of swirl intensity, while a monotonous vorticity distribution is achieved at high swirl conditions.

Helium plasma jet interaction with different target materials and the plasma characteristics on the irradiation area

The experimental study on the dynamic behavior of helium atmospheric pressure plasma jet exposed on the surface of different conductivity is reported in this article. Electrical, optical, and gas dynamics characteristics are monitored using a high voltage probe, current probe, and imaging technique. The turbulence-free plasma jet length is estimated from the image of the plasma jet and correlated with the length estimated through the Electrohydrodynamic number (Ehd number). It has been shown that plasma species strongly modify the gas dynamics on the contact surface. The irradiation area on agar gel, metal, and Teflon is observed and the different flow regimes (free jet, stagnant region, and accelerating region) are identified. The irradiation area is significantly broadened for the polymer-like substrate and intensity is higher close to the stagnant region. The excited nitrogen and OH intensity is higher than the other observed chemical species on the target surface. The turbulence is higher near the outer radius of the irradiated surface, and it increases with operating voltage. The chemistry of the water changes with the presence of the metal probe inside the water.

AEROTHERMODYNAMICS OF COMBINED SPIKE AND COUNTERFLOW JET TECHNIQUE FOR REACTING HYPERSONIC FLOWS

Computational investigation is carried out to estimate the drag force and surface heating load for hypersonic reacting flows. An in-house viscous nonequilibrium finite volume-based reacting gas solver has been utilized. This solver is capable of investigating 11 chemical elementary reactions and temperature-dependent specific properties to reveal the effect of lower as well as higher freestream stagnation enthalpy conditions. Initially, the calorically perfect-gas and real-gas model-based simulations are carried out to understand the real-gas effects in the presence of a metallic spike. Computed surface pressure and heat flux are compared for the freestream stagnation enthalpy of 2 MJ/kg. The real-gas model predicts a 5% higher drag and 57.21 kW/m<sup>2</sup> higher peak heat flux compared to the perfect-gas model. However, lower enthalpy conditions predict almost the same drag force for any spike length. Further, a counterflowing jet is installed at the root of the spike, and flow field alterations are studied for this proposed integrated configuration. The root jet further pushes the conical shock in the upstream direction and provides an extra-large recirculation zone. Here, the possibility of drag and surface heat flux reduction is very much evident due to the decrease in surface pressure and presence of low-temperature jet gas in the vicinity of the object. Various freestream stagnation enthalpies, as well as the jet pressures, are considered to investigate the performance alterations by the combination technique. It is observed that the drag and surface heat load reduction efficiency of the combined configuration decreases with an increase in the freestream stagnation enthalpy. Moreover, it increases when increasing the root jet pressure for given enthalpy conditions. Hence, instead of attaching a long spike at the stagnation region of a blunt-shaped object, the use of a short spike and low-pressure root jet is recommended for a better reduction in drag and surface heat load.

Study on convective heat transfer characteristics of inclined jet impinging cylindrical target surface in the confined space

• Heat transfer of cylinder surface with flow confinement is experimentally tested. • The effects of jet angle and Reynolds number on heat transfer have been studied. • The mechanism of heat transfer for different jet angles is analyzed in detail. In this study, the convective heat transfer characteristics of a cylinder with flow confinement under the impingement of a circumferentially arranged turbulent inclined circular air jet array are experimentally studied. This jet configuration can be effectively applied in the cooling/heating of rotating machinery, such as cooling of the steam turbine shaft, cement rotary kiln cooling, and textile drying. The purpose of the study is to elucidate the effect of the jet angle ( θ ) and the jet Reynolds number ( Re d ) on the heat transfer behaviors of the cylindrical target surface. The jet Reynolds number varies from 20,000 to 35,000, and three different jet angles ( θ =20°,30°,45°) are adopted. The local Nusselt number distribution of the region of interest on the cylindrical target surface is experimentally measured by applying the transient thermochromic liquid crystal technique. Numerical studies are conducted to obtain details of flow patterns in the confined space, so as to analyze the convective heat transfer mechanisms. The results show that for small jet angles ( θ =20°,30°), due to the intense circumferential cross-flow, the overall distribution of the Nusselt number is relatively uniform. As the jet angle increases to 45 °, the Nusselt number in the middle of the target surface increases significantly because of the formation of the stagnation region. As the jet angle increases from 30 ° to 45 °, the heat transfer uniformity on the cylindrical surface decreases significantly. The maximum difference of the variation coefficient of the Nusselt number is 26.6% at Re d = 35 , 000 . As the jet Reynolds number increases, the local Nusselt number on the cylindrical target surface increases as a whole. The average Nusselt number with Re d = 35 , 000 increases by 64.3%-74.9% compared with the cases of Re d = 20 , 000 .

BepiColombo mission confirms stagnation region of Venus and reveals its large extent

The second Venus flyby of the BepiColombo mission offer a unique opportunity to make a complete tour of one of the few gas-dynamics dominated interaction regions between the supersonic solar wind and a Solar System object. The spacecraft pass through the full Venusian magnetosheath following the plasma streamlines, and cross the subsolar stagnation region during very stable solar wind conditions as observed upstream by the neighboring Solar Orbiter mission. These rare multipoint synergistic observations and stable conditions experimentally confirm what was previously predicted for the barely-explored stagnation region close to solar minimum. Here, we show that this region has a large extend, up to an altitude of 1900 km, and the estimated low energy transfer near the subsolar point confirm that the atmosphere of Venus, despite being non-magnetized and less conductive due to lower ultraviolet flux at solar minimum, is capable of withstanding the solar wind under low dynamic pressure.

Dynamics of angularly colliding laser-produced plasmas in air and argon ambient

The effects of ambient gas pressure on the dynamics of angularly colliding laser-produced plasmas are investigated in air and Ar ambient. Fast formation of intense stagnation region is observed even in the low-pressure regime, and the tendency of interpenetration is also greater because of the involvement of the fast forward expansion velocity of seed plasmas. An intense and spherical stagnation region is observed at an intermediate pressure regime of Ar ambient. At higher pressure regime, shock front interaction in air ambient and at 10−1 mbar of Ar ambient is due to the regular reflection of shock waves. At 1 mbar of Ar ambient, a channel is formed at the collision front, and its width increases with time which is due to the Mach reflection of shock waves. Increasing inter-plume separation or the increase of angle between the targets significantly influences the shock wave reflections. Mach reflection of shock waves is observed even at 10−1 mbar of Ar ambient in higher angular separation. A peculiar plume splitting is also observed at 750 ns in 10−1 mbar of Ar ambient. Optical emission spectroscopic analysis was also done to understand the spectral emission from interaction region and its variation with ambient gas pressure.

Significance of Buongiorno’s model on viscoelastic MHD flow over a heated lubricated surface subject to Joule heating

Lubrication theory has attained attention lately due to its practical applications, such as the formation of thin films, adhesives, and lubrication of components of machines. Jeffrey’s nanofluid flow over the stagnation region past a power-law lubricated surface is presented in this study. Buongiorno’s model is employed to scrutinize the effects of thermophoresis and Brownian motion phenomena with constant wall and prescribed surface temperature (PST) and effects of heat source/sink, chemical reaction, and Joule heating. Due to the continuity of shear stress of fluid-lubricant and velocity at the interface, interfacial conditions are generated. By similarity conversions, ordinary differential equations are obtained and their solutions are computed numerically. For power-law index equaling [Formula: see text], local similarity solutions are calculated by adopting a finite difference scheme, viz. bvp4c in MATLAB. The energy profiles for constant and prescribed temperatures are monitored. The effects of pertinent parameters on the flow, thermal, and mass distributions are scrutinized and illustrated in graphs. Flow field decreases significantly by raising slip parameter as the aptitude of power-law lubricant to improve the velocity of the bulk fluid. The numerical comparison of wall stress and Nusselt number is also presented. The slip and Jeffrey’s material parameters raise the numerical outcomes of the wall shear stress. In addition, increment in Prandtl number enhances the numerical value of the Nusselt number; however, it reduces for relaxation-to-retardation times ratio.