Secondary Velocity Research Articles

Optimization of secondary air operation parameters of waste incineration boiler based on response surface methodology

To reduce the NOx emission concentration of waste incineration boilers and improve the thermal efficiency of incinerators, the combustion process of a 600 t/d incineration boiler was numerically investigated. First, the influences of the secondary air injection angle, velocity and temperature on the NOx concentration at the waste incineration boiler outlet and the thermal efficiency of the incinerator were analyzed through a single factor simulation test. Then, coupling optimization of key operating parameters, including the secondary air injection angle, velocity and temperature, was conducted via the response surface design method to obtain the specific functional relationships between outlet NOx concentration, incinerator thermal efficiency, front wall secondary air injection angle, rear wall secondary air velocity and secondary air temperature, as well as the optimal operating parameters for the boiler. The results showed that when the secondary air injection angle of the front wall ranges from 68°∼80° and the secondary air injection angle of the back wall is 67°, the minimum NOx concentration is 142.23 mg/m3, and the maximum thermal efficiency of the incinerator reaches 85.51 %. When the secondary air velocity at the front wall is 42 m/s and the secondary air velocity at the back wall ranges from 42 ∼ 66 m/s, the NOx concentration at the outlet is the lowest at 140.05 mg/m3, and the thermal efficiency of the incinerator is the highest at 85.63 %. When the secondary air temperature ranges from 297.16 ∼ 309.16 K, the NOx concentration at the outlet is the lowest at 155.45 mg/m3, and the thermal efficiency of the incinerator is the highest at 84.64 %. The secondary air injection angle, velocity and temperature impose significant effects on the NOx concentration at the outlet and thermal efficiency of the incinerator. The optimal parameters, as determined in the multifactor simulation test, include a 77° secondary air injection angle of the front wall, 69 m/s secondary air velocity at the back wall, and 297.15 K secondary air temperature. Under these conditions, the NOx concentration at the outlet is 134.98 mg/m3, and the thermal efficiency of the incinerator reaches 86.11 %. This study has important guiding significance for reducing pollution and improving the efficiency of waste incineration boilers.

Impact of active and passive control of nanoparticles in ternary nanofluids across a rotating sphere

The anticipation around future technologies has sparked a keen interest in the study of fluid flows, which include the intricate interplay of several aspects. The design of rotating machinery, cooling of rotating machinery parts, and fiber coating, among other applications, have all given practical importance to the issue of fluid flow from rotating surfaces. This study examines the behavior of a ternary nanofluid over a rotating sphere. Combining Tiwari and Das’s model with Buongiorno’s model is considered for the flow model. When combined with the condition of non-zero normal flux, the zero normal flux of nanoparticles at the surface aims to push the particles away from the surface. Boundary layer equations are used to formulate the physical flow problem, and after that, by using the appropriate variables, these equations are transformed into dimensionless forms. Additionally, mathematical computation software helps in obtaining a numerical solution. Utilizing graphs, it has been determined how different physical flow parameters affect the profiles of velocity, temperature, and concentration. Further, the wall’s heat and mass transfer rates and the skin friction coefficient are graphically assessed and discussed. The outcomes show that increasing acceleration and rotational parameters increases primary velocity and surface drag force while decreasing secondary velocity, temperature, and concentration profiles. The concentration is reduced by Brownian and Schmidt's numbers while increasing for thermophoresis constraint. In both active and passive management of nanoparticles, the mass distribution rate improves for thermophoresis and Brownian parameters. Solid volume fraction improves the thermal distribution while declines the concentration.

Computation of couple stress electroconductive polymer from an exponentially stretching sheet

Magnetic polymer processing involves multiple physical phenomena and requires simultaneous consideration of rheological, hydromagnetic and thermal characteristics. Inspired by new developments in functional magnetic coating dynamics, the present article investigates the viscous magnetohydrodynamic non-Newtonian boundary layer flow of an incompressible, electrically conducting, couple stress, electroconductive polymer from an exponentially stretching sheet. The nonlinear boundary value problem is solved numerically by adopting shooting technique and bvp4c algorithm available in MATLAB software. Validation with the Adams-Moulton 2-step predictor corrector algorithm is included. The effects of non-Newtonian couple stress parameter, magnetic interaction number, mixed convection parameter, slip parameter, Prandtl and Eckert number on the primary and secondary velocities and temperature fields are visualized graphically. Greater hydrodynamic slip effect initially boosts the primary velocity near the wall but thereafter induces a decrement in it. However, a consistent improvement in secondary velocity is computed for greater slip parameter. Increasing Hall parameter strongly accelerates the secondary flow but only weakly accelerates the primary flow. Increasing magnetic interaction number decelerates the primary and secondary flow. Elevating magnetic number promotes the thermal boundary layer thickness and also the temperature. Couple stress effects generally accelerate both the primary and secondary flow.

Natural convection flow of third-grade fluid along an oblique permeable micro-channel with Hall effects: an irreversibility analysis

The third-grade fluid model is one of the unique models in all the non-Newtonian fluids, which is evolved for its particular implementation in petrochemical engineering, confectionaries, earth science and lubricating systems. Hence, the current work scrutinises the entropy generation and thermal analysis of non-Newtonian fluid in a permeable oblique microchannel. The effects of heat generation, thermal radiation and Hall effects on fluids in a microchannel have been explored. The rheological expressions of third-grade fluid are considered. By considering the desirable similarity variables the equation of motion was reduced to nonlinear ordinary differential equations. The Runge–Kutta-Fehlberg’s fourth-fifth-order technique along with the shooting method was adopted to solve these dimensionless expressions. The repercussion of this investigation upholds that the enhancement of distance parameters augments the thermal field. The amplification of the porosity parameter occurs with a decrement in the thermal profile. The secondary velocity profile declines with an enhanced value of the Hall parameter and seen improvement in the primary velocity profile.

A numerical study on MHD Cu-Al2O3/H2O hybrid nanofluid with Hall current and cross-diffusion effect

A numerical investigation has been performed to analyze an unsteady magnetohydrodynamic gravity-driven flow of a Newtonian hybrid nanofluid (Cu-Al2O3/H2O) along an impermeable vertical plate with linearly accelerated temperature and concentration. The Hall current, nanoparticle volume fraction, inclined magnetic field, and Soret effect on water-based Cu-Al2O3 hybrid nanofluid are incorporated into the flow model. The model's governing nonlinear partial differential equations are formulated and transformed into a non-dimensional form by introducing suitable variables and parameters. The finite difference method is implemented via the MATLAB solver fsolve to resolve the model equations numerically. The evolution of the primary and secondary velocities, temperature, and species concentration profiles is discussed via graphical illustration. Furthermore, a comparative analysis is performed on the coefficient of skin friction, rate of heat, and mass transport for hybrid nanofluid and nanofluid through tabular values. The novelty of the investigation reveals that a deceleration in the primary velocity and acceleration in the secondary velocity with the increasing magnetic field inclination parameter exists. The rising value of Cu nanoparticle volume fraction augments the primary, secondary skin friction coefficients, and the heat and mass transport rates at the plate. The Dufour number stimulates a reduction in the heat transport rate, while an enhancement occurs with the Soret number. The present investigation demonstrates that the heat transfer rate for water-based Cu-Al2O3 hybrid nanofluid is higher than that for water-based Cu nanofluid. The current research can be implemented to augment the efficiency of the cooling mechanism of heat exchangers, solar collectors, nuclear reactors, and many more.

Retrofit of a 600 MW Down-Fired Pulverized-Coal Furnace for Low NOx Emission

Aiming at solving the problem of high NOx emissions of a down-fired boiler, a new combustion system has been proposed by means of the numerical simulation using Ansys Fluent. The coal-lean stream (tertiary air), which was originally mixed with a separated overfired air (SOFA) stream on the front and rear walls of the upper furnace, was relocated to the lower zone of the furnace after retrofit. The secondary-air slots were transformed into a new annular port type, which was injected into the furnace with a down-tilt angle to increase the residence time of the coal stream. Furthermore, the effect of secondary air distribution and velocity of coal stream on performance was studied. After retrofitting the combustion system, the NO emissions were effectively controlled, decreasing from 906 mg Nm−3 to 576 mg Nm−3, but the carbon content of fly ash increased from 2.46% to 5.78%. Aiming at decreasing the carbon content of fly ash, the effect of coal/primary air velocity on the arch was studied. Less carbon content in fly ash can be observed for the lower arch airflow velocity. The results showed that the NO emissions can be controlled below 595 mg Nm−3, and the carbon content of fly ash was reduced to 3.39% when the velocity was decreased to 18 m s−1.

VISCOSITY AND HALL EFFECTS ON UNSTEADY MHD CASSON FLUID FLOW THROUGH A PARALLEL POROUS PLATE

This study investigates the temperature viscosity and Hall effects of a Casson fluid flow through a porous medium of a viscous incompressible fluid bounded by two parallel porous plates under the influence of thermal radiation and chemical reaction. A uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to variable pressure gradient. The transformed conservation equations are solved analytically subject to physically appropriate boundary conditions by using perturbation and Eigenfunction expansion techniques. The influence of a number of emerging non-dimensional parameters namely, variable pressure gradient parameter, suction parameter, radiation parameter and Hartman number are examined. It is observed that the primary velocity profile is increased with increasing temperature dependent viscosity while increase in Hall parameter leads to increase in secondary velocity profile of the flow.

Air distribution and coal blending optimization to reduce slagging on coal-fired boiler water wall based on POD reduced order modeling for CFD

Slagging is a common phenomenon interfering with the safe and efficient operation of coal-fired boilers. Due to the lack of monitoring methods for species and temperature distribution near the water wall, which is critical for slagging formation, it is a tricky problem to detect and reduce the slagging in real time. A method for slagging distribution prediction and anti-slagging optimization of a 330 MW tangentially coal-fired boiler is developed in this paper. Proper orthogonal decomposition (POD) reduced order modeling and support vector machine (SVM) are used to predict the distribution of temperature and O2 near the water wall by taking 15 variables as input parameters (load, coal types, primary air rate, secondary air rate, excess air coefficient, and secondary air velocities). Next, fuzzy comprehensive evaluation (FCE) is employed to quantify the slagging occurrence and distribution on the water wall. Furthermore, the real time slagging prediction is realized with the combination of POD, SVM, and FCE. Finally, the conventional genetic algorithm (CGA) and simulated annealing genetic algorithm (SAGA) are adopted to optimize the air distribution schemes and coal blending schemes to reduce the slagging ratio, and their performances are compared. The results indicate that the predictions of temperature and O2 with POD show a good agreement with CFD simulations. In the optimization process, whether air distribution is optimized alone or both coal blending and air distribution are optimized simultaneously, the performance of SAGA is better than that of CGA. After optimizing the air distribution with SAGA, the slagging ratio of a typical operating condition with a load of 330 MW is reduced from 14.21% to 7.16%. The slagging ratio is further reduced to 5.36% after optimizing air distribution and coal blending schemes simultaneously. The proposed slagging prediction and optimization for anti-slagging opens a new perspective to alleviate slagging of water walls effectively.

Flow and heat transfer performance of bionic heat transfer structures with hybrid triply periodic minimal surfaces

Efficient energy conversion technologies are essential for mitigating the environmental impact of industrial activities. The development and application of high-efficiency heat exchangers are key components in this endeavor. Heat exchangers based on triply periodic minimal surfaces (TPMS) are widely acknowledged for their exceptional thermal-hydraulic performance. However, current research mainly focuses on the design and optimization of heat exchangers with standard TPMS structures. In this study, a hybrid process is utilized to construct ten novel heat exchangers, followed by comprehensive investigations of their internal flow fields using three-dimensional numerical simulations. In order to establish a baseline, five standard TPMS structures are also introduced as reference cases. The results reveal that complex secondary flow distributions and velocity variations are critical factors influencing the thermal-hydraulic performance. Moreover, the influence of different standard TPMS cells on the flow and heat transfer characteristics varies during the hybridization process. Specifically, the inclusion of the Schwarz cell generally leads to an improvement in heat transfer, while the presence of the Lindinoid cell may result in a deterioration of heat transfer. The Diamond and Lindinoid cells have an adverse impact on the flow characteristics, while the Gyroid and Neovius cells enhance the flow characteristics. To evaluate the overall thermal-hydraulic performance of different channels, a comprehensive performance assessment is introduced. The Diamond channel and the Gyroid-Neovius channel show superior overall performance in their respective Reynolds number regions, with the former exhibiting better flow characteristics and the latter has outstanding heat transfer performance.

Chemical reaction and radiation impact on unsteady free convective flow through a porous medium past an infinite oscillatory vertical plate

AbstractThe current investigation is concerned with the effect of chemical reactions and radiation on unsteady free convective flow through a porous medium via an infinitely oscillating vertical plate. The primary goal of this study is to investigate the effects of first‐order homogeneous chemical reactions and thermal radiation on mass flow and heat transmission characteristics. The closed‐form Laplace transformation method is used to obtain exact solutions to the governing equations for concentration, energy and momentum. The impact of various non‐dimensional parameters on fluid velocity, temperature and concentration is graphically depicted. Furthermore, 3‐dimensional surface plots for the Nusselt number and Sherwood number are provided, and the equation for skin friction is derived and demonstrated in tabular form. Investigation simulates that the skin friction increases as the chemical reaction parameter hikes, whereas the fluid concentration reduces as the chemical reaction parameter increases. Further, it was revealed that the augmentation of the radiation parameter decreased the temperature and velocity pattern. It is seen that the primary and secondary velocities reduce due to the increment of the chemical reaction parameter.

Effect of additional periodic motion on gas-liquid two-phase secondary flow behavior in inclined pipes

Secondary flow significantly changes the flow structure and increases flow resistance. The pipeline motion further contributes to the evolution of secondary flow. This study aims to elucidate the characteristics of two-phase secondary flow in inclined pipelines under additional periodic motion conditions. Based on the CFD technique, three-dimensional oscillating two-phase flow fields were simulated using the VOF model and dynamic mesh method. The focus was on four common flow patterns observed in inclined pipes, namely stratified flow, slug flow, turbulence flow, and transitional flow. The impact mechanisms of swaying, heaving, and coupling motion on the structural evolution, velocity profile, and relative intensity of secondary flow were analyzed. The results indicate that additional periodic motion exhibits a significant dominant behavior on secondary flow when the amplitude exceeds 1.0D. Heave motion has a more pronounced effect on the secondary flow structure. Additional periodic motion induces periodic evolution of secondary flow structure in stratified flow, with the evolution period aligning with the period of the additional motion. Under additional periodic motion, there is no one-to-one correspondence between secondary flow velocity and axial velocity. Additional motion significantly suppresses the axial velocity of slug flow. Furthermore, additional periodic motion significantly increases the relative intensity of secondary flow, exceeding 10%. When the amplitude is less than 1.5D, additional motion suppresses the relative intensity of secondary flow in turbulence flow and transitional flow.

Transport Features on Bidirectional Nanofluid Flow with Convective Heating and Variable Darcy Regime

The performance of Au and nanoparticles in Casson flow propelled by the rotational effect subject to convective heating and variable Darcy phenomenon is presented. As a means to contribute significantly to the biomedical industry for proper prediction and treatment of diseases like cancer, stenosis, et cetera, the Casson fluid model and magnetohydrodynamic effect are employed in this study to investigate the bidirectional-rotating boundary layer flow of blood since Casson rheology best describe the mammalian blood flow dynamics and that blood is electrically conducting in nature. The enormous performance of nanoparticles made them extremely useful; hence, they gained recognition over the conventional refrigerants and were widely used by scientists, modelers, and researchers for controlling and treating diseases via drug targeting (chemotherapy), etc. In the three-dimensional plane, the assumed electrically conducting fluid conveying nanoparticles is properly mixed through the Coriolis force, thus rotating with angular velocity across the variable porous medium. A numerical tool, Chebyshev Collocation Method (CCM) with pseudo-spectral approach, is deployed on the resulting transformed ODEs. Profile distributions of respective boundary layers to distinct responses of model parameters, including the Eckman, Darcy, and Biot numbers on Au and nanoparticles, are analyzed and discussed. The dominance of nanoparticles on both velocities is revealed, while Au nanoparticles demonstrated a higher thermal performance rate. A rise in the Darcy parameter has a diametrically opposed behavior on the primary and secondary velocities.

Parametric modeling study for blown-dust secondary pollution and optimal ventilation velocity during tunnel construction

Tunnel construction often relies on drilling and blasting. High dust pollution is one of the primary problems of drilling and blasting construction. The level of secondary blown dust pollution caused by ventilation matches that of dust pollution caused by drilling construction. In this study, a critical flow model and blown dust rate model for deposited dust were established via force analysis, which was validated against the test data. The research results showed that the characteristic airflow velocity for blowing dust particles with a 100 μm diameter reached approximately 0.42 m/s for tunnel diameter is 10 m, and the ventilation Re values under smooth and rough conditions were 2.3 × 105 and 1.4 × 105, respectively. Furthermore, when ventilation Re reached 4 × 105, the blown dust pollution rate caused by ventilation under smooth conditions was approximately 1.8 × 10−2 kg/s. If dust particle size is more or less the critical dust particle size, the characteristic airflow velocity was increased. Moreover, the optimal velocity at which the deposited dust does not flow or move during tunnel construction was related to the tunnel size and roughness. For the smooth tunnel with a diameter of 10 m, the optimal ventilation velocity was 3.5 m/s. When the tunnel roughness was increased from 0.005 to 0.5 m, the optimal ventilation velocity decreased from 3.3 to 1.6 m/s. The deposited dust critical flow model and blown dust pollution rate model established in this study provide a sound theoretical basis for selecting the optimal velocity of tunnel ventilation and recognizing the risks of secondary blown dust pollution due to ventilation.

Performance improvement of CO2 two-phase ejector by combining CFD modeling, artificial neural network and genetic algorithm

The ejector, as one of the core components of the CO2 trans-critical ejection refrigeration system, plays an important role in improving refrigeration capacity and reducing compressor power consumption. Although the ejector can be optimized by experiment and Computational Fluid Dynamics (CFD) simulation to improve its performance, these methods are time-consuming and complicated. This study aims to propose a method to improve the performance of the CO2 trans-critical two-phase ejector assisted by using CFD, artificial neural network (ANN), and genetic algorithm (GA). Firstly, the influence of geometric parameters on ejector efficiency was analyzed by using CFD technology, and the database was generated. Next, the complex and time-consuming CFD model was replaced by the ANN surrogate model established to predict the ejector performance. Finally, the GA method was used to optimize the ejector to maximize the ejector efficiency. The results show that the efficiency of the optimized ejector is 35.39%. The optimized ejector increases the secondary flow velocity and eliminates the vortex in ejector, and the efficiency of the optimized ejector is raised by more than 8% on average than that of initial ejector under different primary and secondary flow conditions. The research shows that the combination of CFD, ANN, and GA has higher reliability and better performance in the optimization design of CO2 two-phase ejector.

Variation of Flow Hydrodynamic Parameters and Prediction of Particle Separation Indices in the Spiral Concentrator with the Regulation of Pitch-Diameter Ratio

The pitch-diameter ratio is an important design indicator affecting the separation performance of spirals. Based on the numerical simulation method, this paper systematically investigated the variation of flow hydrodynamic parameters in the spiral concentrator with the regulation of the pitch-diameter ratio. The radial distribution and variation trend of hematite and quartz particles with different particle sizes are further analyzed. Additionally, the separation indices of hematite and quartz with different particle size combinations were predicted. The results show that the tangential velocity, maximum radial velocity, velocity shear rate, and Reynolds number of fluid in each region decrease with the increase of the pitch-diameter ratio. The range of laminar flow gradually expands as the pitch-diameter ratio increases. There are significant differences in depth of water, ratio of inward and outward flows, and secondary flow velocity in different regions. Some flow hydrodynamic parameters at the inner trough reach relative equilibrium at a pitch-diameter ratio of 0.675. Hematite and quartz particles form a selective distribution in the trough surface, which comprehensively reflects the density effect, particle size effect, following flow effect of fine particles, and the effect of interstitial trickling of high-density fine particles. Fine hematite and coarse quartz form a large amount of misplaced material, and there is a corresponding mixing area. With the increase in pitch-diameter ratio, coarse and fine hematite particles migrate inward and outward, respectively. With the increase in pitch-diameter ratio, the misplaced amount of quartz on the inner trough decreases, but the outward migration distance of coarse quartz is smaller. Increasing the pitch-diameter ratio is beneficial to the separation of combined feedings of coarse hematite and quartz but unfavorable to that of fine hematite and quartz. The maximum separation efficiency of coarse hematite and fine quartz can reach 85.74%, and the iron grade of the inner product can reach 65.96% when the pitch-diameter ratio is 0.675 and the splitter location is 115 mm. The changing trend of separation indices in this feeding is closely related to the variation of fluid parameters and the change in the radial distribution of single mineral particles. The research results can provide references for the structural design of spirals, the selection of feed particle size, and the adjustment of splitter location.

The effect of water on coking and heat transfer inhomogeneity of supercritical aviation kerosene in a curved mini-channel

Water addition to aviation kerosene draws increasing attention in increasing heat sink and suppressing coke formation for regenerative cooling of scramjet engines. However, the effect of water on flow, reaction and heat transfer, particularly the thermal inhomogeneity in curved cooling channel is rarely reported. In the present study, the effect of water on coking and heat transfer inhomogeneity characteristics of China aviation kerosene, RP-3 studied in a uniformly heated curved mini-channel. A transient three-dimensional numerical simulation model with hybrid pyrolysis and steam reforming reactions of RP-3 is established and validated. The results show that there exists serious mass and thermal stratification in the curved mini-channel due to secondary flow and species diffusion. Specifically, RP-3 and water are diffused to concentrate at the bottom heating wall surface while coke deposition and light gaseous species, e.g., H2, CH4, CO are concentrated at the top heating wall surface. The thermal difference between the top and bottom heating walls is significant. Temperature and coke content of the top heating wall are much higher than those of the bottom heating wall. The gas film and coke deposition formed at the top heating wall surface lead to serious heat transfer deterioration. Therefore, the heat transfer coefficient at the bottom wall of the curved channel is much higher than that of the top wall. Water addition enhances secondary flow and thus exacerbates the coking and heat transfer inhomogeneity in the curved cooling channel. With water content increasing from 0 to 15 wt%, the secondary flow velocity increases by 288.2%, the conversion of RP-3 increases by 114.8% and the average coke content on the heating walls decreases by 40%. Meanwhile, the average heat transfer coefficient increases by 33.9% at the bottom heating wall but decreases by 18.0% at the top heating wall with the increase of water content.

Geological modeling of diagenetic logs of the Sarvak reservoir in Dezful Embayment, southwestern Iran: implications for geostatistical simulation and reservoir quality assessment

Reservoir quality in carbonate reservoirs is significantly influenced by diagenetic processes. Although diagenesis is studied as a common reservoir quality damaging/enhancing process in many previous studies, literature is limited about the spatial modeling of diagenesis processes using advanced geostatistical algorithms. In the current study, 3D models of the main diagenetic processes which affect the reservoir quality of the Sarvak reservoir in an Iranian oilfield located in the north Dezful Embayment were constructed using geostatistics. According to the petrographic studies, a total of 10 microfacies were identified. In addition, the significant diagenetic processes in this reservoir include dolomitization, cementation, dissolution, and compaction. In this study, diagenetic electrofacies were determined using the “multi-resolution graph clustering” method based on the quantitative results of the petrographic studies. The results of spatial modeling and provided average maps were used to investigate the lateral variation of those properties and their relationship with effective porosity. It shows that trends of the secondary porosity and velocity deviation log (VDL) maps are generally correlatable with the effective porosity maps confirming the impact of dissolution as a main significant diagenetic process on reservoir quality enhancement. The most impact of the dissolution on porosity is observed in Lower Sarvak-E2 zone where the correlation coefficient is 0.75. The correlation coefficient between porosity and VDL in some zones is high indicating the effect of diagenesis on reservoir quality as it exceeds 0.61 in Lower Sarvak-A1 zone. In the occurrence of dolomitization, it has dual constructive and destructive effects on the reservoir quality. The most constructive and destructive effects of dolomitization were observed in Lower Sarvak-E1 and Lower Sarvak-F zones in which the correlation coefficients were 0.476 and − 0.456, respectively. In addition, low porosity zones are correlatable with developing cementation, stylolites, and solution seams.

Melting rheology of three-dimensional Maxwell nanofluid (graphene-engine-oil) flow with slip condition past a stretching surface through Darcy-Forchheimer medium

Nanofluid has numerous industrial and engineering applications, especially for the improvement of heat transmission. Engine oil is a highly versatile lubricant that is extensively used across diverse industries and engineering fields for a wide range of applications. The applications of engine oil are the aerospace industry, automotive industry, marine industry, power generation, construction and mining, manufacturing and machinery, railroad and transportation, agriculture, etc. Therefore, in the existing problem, 3D flow of Maxwell nanoliquid along the stretched sheet through the porous medium with a melting heat transport mechanism is studied. Nanofluid is made by a mixture of graphene nanoparticles in the engine oil base liquid. Additionally, the physical significance of the Darcy-Forchheimer is discussed on the flow behavior. The computation for heat and mass transference is performed due to the applications of thermal radiation, heat source/sink, Brownian and thermophoresis diffusivity, and chemical reaction. Simulation of the existing model is made by using the idea of velocity slip conditions along with convective boundary and zero mass concentration conditions. In the flow analysis, the magnetic effect is applied normally to the surface, therefore, the features of the magnetic field are studied. On the basis of flow assumptions, the current flow problem is modeled in the system of highly nonlinear PDEs. Appropriate similarity transformation is exploited for the conversion of these PDEs into ODEs. By using the concepts of the Homotopic method (HAM), the attained coupled nonlinear higher-order ODEs are simulated. The graphs are used to discuss how numerous physical factors affect the flow profile, highlighting their distinctive characteristics. Several noteworthy findings of this study are that both primary and secondary velocities declined due to the Lorentz force by using the applications of magnetic impact. Also, it is distinguished that the nanoliquid thermal profile is amplified for the thermal Biot number. Also, the nanoliquid concentration is lesser for the greater Schmidt number. The present nanofluid problem is also investigated for its significant practical applications. Further, it is examined that the Nusselt number is greater for the thermal Biot number.

Mathematical Modelling and Fluidic Thrust Vectoring Control of a Delta Wing UAV

Pitch control of an unmanned aerial vehicle (UAV) using fluidic thrust vectoring (FTV) is a relatively novel technique requiring no moving control surfaces, such as elevators. In this paper, the authors’ previous work on the characterization of a static co-flow FTV rig is further validated using the free to pitch dynamic test bench. The deflection of a primary jet after injection of a high-velocity secondary jet was captured using the tuft flow visualization technique, along with the experimental recording of subsequent normal force impinged on the Coanda surface resulting in the pitching moment. The effect of primary and secondary flow velocities on exhaust jet deflection, as well as on the pitch angle of the aircraft, is examined. Aerodynamic gain as well as the inertia of a delta wing UAV test bench are computed through experiments and fed into the equation of motion (e.o.m). The e.o.m developed aided in the design of a model-based PID controller for pitch motion control using the multi-parameter root locus technique. The root locus tuned controller serves as a benchmark controller for performance evaluation of the genetic algorithm (GA) and particle swarm optimization (PSO) tuned controllers. Furthermore, the frequency domain metric of gain and phase margins were also employed to reach a robust control design. Experiments conducted in a simulation environment reveal that PSO-PID results in a better response of the UAV in comparison to the baseline pitch controller.

Effect of heart rate on the hemodynamics in healthy and stenosed carotid arteries

Stenosis in the internal carotid arteries is a serious cardiovascular condition. It is well-reported that low and oscillatory wall shear stress enhances the risk of stenosis progression. However, the effects of increased heart rates in highly stenosed arteries are not well explored. A detailed understanding of the flow features and stress distribution in stenosed carotid arteries at different heart rates may help clinicians to prescribe better exercise schedules for patients. In this study, we probe the effects of elevated heart rates on the hemodynamics in healthy and stenosed carotid arterial geometries using an immersed boundary method-based computational framework. Our results reveal that a strong recirculation, secondary velocity, and oscillatory shear index (OSI) zone develop inside a severely stenosed carotid artery at normal heart rate. Higher heart rates may potentially improve arterial health by reducing OSI only for the healthy and mild stenosis carotid arteries. However, the increased heart rates worsen the arterial health of severely stenosed arteries by onsetting flow instabilities, enhancing the spread and severity of the recirculation zone and the magnitude of the secondary velocity, the pressure drops across the stenosis, and the spread of high OSI (≥0.2) zone downstream. Furthermore, in the case of severe stenosis, the wall shear stress at the stenosis throat rises significantly, which can contribute to plaque rupture and thrombus development. Here, we report in detail the behavior of stress levels and pressure fluctuations in the carotid artery model at different stenosis levels for normal and elevated heart rates.