Presence Of Channels Research Articles

Robust Adaptive Control Based on Incremental Nonlinear Dynamic Inversion for a Quadrotor in Presence of Partial Actuator Fault

This paper presents a novel nonlinear robust adaptive trajectory tracking control architecture for stabilizing and controlling a quadrotor in the presence of actuator partial faults. The proposed control strategy utilizes an Incremental Nonlinear Dynamic Inversion (INDI) algorithm as the baseline controller in the inner loop and augments a nonlinear model reference adaptive controller in the outer loop to ensure robustness against unmodeled faults. Additionally, a modified PID controller is introduced in the most outer-loop to track the desired path. The effects of actuator faults are modeled by considering sudden variations in motor thrust and torques. To enhance the control algorithm's robustness, a projection operator is employed in the robust adaptive structure. Comparative performance evaluations with a previous successful algorithm implemented on a quadrotor model demonstrate that the proposed controller achieves full controllability of the faulty quadrotor in pitch, roll, and yaw channels in the presence of actuator partial faults up to 50%.

Linear stability analysis of MHD mixed convection flow of a radiating nanofluid in porous channel in presence of viscous dissipation

PurposeThis paper aims to investigate the hydrodynamic instability properties of a mixed convection flow of nanofluid in a porous channel.Design/methodology/approachThe treated single-phase nanofluid is a suspension consisting of water as the working fluid and alumina as a nanoparticle. The anisotropy of the porous medium and the effects of the inclination of the magnetic field are highlighted. The effects of viscous dissipation and thermal radiation are incorporated into the energy equation. The eigenvalue equation system resulting from the stability analysis is processed numerically by the spectral collocation method.FindingsAnalysis of the results in terms of growth rate reveals that increasing the volume fraction of nanoparticles increases the critical Reynolds number. Parameters such as the mechanical anisotropy parameter and Richardson number have a destabilizing effect. The Hartmann number, permeability parameter, magnetic field inclination, Prandtl number, wave number and thermal radiation parameter showed a stabilizing effect. The Eckert number has a negligible effect on the growth rate of the disturbances.Originality/valueLinear stability analysis of Magnetohydrodynamics (MHD) mixed convection flow of a radiating nanofluid in porous channel in presence of viscous dissipation.

Heat and Mass Transfer on Non-Newtonian Peristaltic Flow in a Channel in Presence of Magnetic Field: Analytical and Numerical Analysis

Heat and Mass Transfer on Non-Newtonian Peristaltic Flow in a Channel in Presence of Magnetic Field: Analytical and Numerical Analysis

MHD Couette flow and heat transfer in a rotating channel in presence of viscous dissipation and heat source/sink

The fully developed steady flow of an electrically conducting as well as heat-generating/absorbing fluid, in a horizontal rotating channel in the presence of viscous dissipation, has been studied. Further, the flow is subjected to shearing impact due to the motion of the upper plate. The effects of various parameters characterizing the translating and rotating flow and heat transfer phenomena, based on analytical solutions, are depicted with the help of graphs and tables. The solution of the boundary value problem has been carried out analytically and computations thereof with MATLAB code. The outcomes of the present study find applications in the motion of the rotor blade and turbine. The important findings are: the moderate speed of rotation gives rise to inconsistency in heat transfer, a transition state between low and moderately high speed, hence speed of the channel is to be taken care of for smooth and consistent heat transfer; the effect of entire values of Eckert number persists on the temperature distribution; the higher magnetic field intensity gives rise to convex type of temperature field (rise in temperature) resulting thicker thermal boundary layer; whereas the reverse is the case in the presence of sink. Most importantly, the inconsistency of heat transfer at the bounding surface is due to the interaction of electromagnetic force with the rotation of the channel.

Magnetohydrodynamic flow in a vertical annular channel in presence of a uniform axial magnetic field

we have discussed the flow of an electrically conducting fluid in a tall vertical closed annular channel under magnetic field along the decreasing direction of gravitational acceleration. The expression for nondimensional axial velocity and temperature are obtained and shown graphically for varying values of ratio of two radii. we have discussed flow of a viscous incompressible electrically conducting fluid in a tall vertical closed annular channel in the presence of uniform magnetic field in vertical direction.

Impact of viscous dissipation and entropy generation on cold liquid via channel with porous medium by analytical analysis

In the current investigation, it is examined numerically entropy generation (EG) on inherent irreversibility motion of couple stress cold liquid with porous medium via Horizontal channel in presence of viscous dissipation. Present work was studied heat generation on couple stress liquid with porous channel. This work considerable importance in many industrial applications like “Control Mechanism in Material Manufacturing”, “Manufactures of Electronic Chips”, “Crystal Formation”, “Scientific Treatment Problems of Irrigation”, “Soil Erosion and tile drainage” are the present focus of development of channel motion. The formulated physical liquid equations are subsequently calculated by shooting technique with R-K-F (“Runge-Kutta Fehlberg”) scheme. The velocity, temperature as predicted via graphically. we found the velocity dwindle, temperature high production by an escalating statistical value of K (“Couple Stress Parameter”), Ec (“Eckert number”) and Q (“Heat Generation parameter”) respectively. Gradient constraint in addition to improve by an enhancement into Bejan number for various values of “pressure gradient parameter”.

A Study of Licklider Transmission Protocol in Deep-Space Communications in Presence of Link Disruptions

Delay/disruption-tolerant networking (DTN) is widely recognized as a key internetworking technology for implementing a space system of systems (SoS). Aimed at being the main data transport protocol of DTN, Licklider transmission protocol (LTP) is expected to provide reliable data transmission service in a challenging space SoS networking environment regardless of random link disruptions. In this paper, a study of LTP in deep-space communication networks in presence of link disruptions is presented. An analytical framework is developed for the effect of multiple random link disruptions on LTP's reliable data delivery in deep-space networks. The study indicates that the models accurately predict the transmission performance of LTP over a deep-space communication channel in presence of multiple link disruptions. A threshold interval value, obtained from the analytical modeling results, is proposed as a means of determining the reducibility of two successive link disruptions to a single disruption; that threshold value is verified by the experiments.

Robust Trajectory and Resource Optimization in UAV-Enabled IoT Networks under Probabilistic LoS Channel in Presence of Jammers

This paper studies the anti-jamming problem of unmanned aerial vehicle (UAV)-enabled Internet of Things (IoT) communication networks in the presence of a jammer under the accurate probabilistic line-of-sight (LoS) model. Our goal is to maximize the information collection throughput of the system under the assumption that only the jammer's approximate location is known. To this end, we formulate a throughput maximization problem by optimizing the UAV trajectory, the IoT devices' transmit power, and communication scheduling under the accurate real-time probabilistic LoS channel. However, the proposed optimization problem is non-convex and coupled, and hence intractable to be solved. In order to tackle the problem, a robust iterative algorithm is proposed by leveraging the block coordinate descent (BCD) method, the successive convex approximation (SCA) technology, the difference of convex (D.C) programming approach, and the S-procedure. Extensive simulation results show that our proposed algorithm significantly improves the system throughput while achieving a practical anti-jamming effect compared with the benchmark algorithms.

Analysis of two non‐miscible electrically conducting micropolar fluid flow through an inclined porous channel: Influence of magnetic field

AbstractThis work aims to analyse the flow of immiscible micropolar fluid through an inclined porous channel in presence of uniform magnetic field. The flow model have divided in two different porous regions and permeability of each porous region is taken different. The two immiscible electrically conducting micropolar fluids which have different densities and viscosities, take place through these two porous regions. The flow in an inclined porous channel is caused by a constant pressure gradient which acts on entrance section of flow domain. The flow of the micropolar fluids in the respective regions is governed by Brinkman's equation. The governing flow equations of the proposed model are solved analytically by reliable techniques and exact solution of flow field, flow rate and wall shear stress is evaluated by using well‐known boundary conditions. In this work, authors examined the influence of existing parameters such as permeability parameters, Hartmann number, gravitational parameter, viscosity ratio and so forth, which describes the physical significance of the presented model, on velocity profile, flow rate and wall shear stresses and these effect presented by graphs. The results are validated with the findings of past published article.

A mathematical model for radiative peristaltic flow of Jeffrey fluid in curved channel with Joule heating and different walls: Shooting technique analysis

The peristaltic phenomenon has intended the researcher’s attention due to its extensive applications in bio-mechanics, industries and biological sciences. The applications of peristaltic transport problems are observed in the transportation of cilia, food mixing in digestive tract, small blood vessels vasomtion, urine transportation etc. Following to such motivating applications in minds, this theoretical analysis presents the peristaltic flow of magnetized Jeffery fluid through accounted by curved channel in presence of heat transfer. The assumed flow is confined by different wave frames. The heat transfer inspection has been performed by utilizing the non-linear thermal radiation and joule heating features. The curvilinear coordinate system is used to model the two dimensional, laminar and incompressible Jeffrey fluid with peristaltic phenomenon. The partial differential equations are transformed into ordinary differential equations in view of appropriate quantities. The implementation of wave length with long magnitude and the assumptions of smaller Reynolds assumptions, the governing system of ordinary system is solved numerically by using shooting technique. The dynamic of involved quantities and physical variables is observed carefully. A declining observation in the temperature in all forms of waves has been noticed for increasing the viscoelastic parameter. The heat transfer coefficient for all waves enhanced for the radius of curvature. Moreover, the velocity of the fluid declines in the lower half of the channel and rises near upper wall of the curved channel due to magnetic parameter.

Error analysis of TAS‐OSTBC assisted downlink NOMA system over generalized η−μ fading Channel

SummaryIncorporation of multiple antennas in downlink non‐orthogonal multiple access (NOMA) system helps in achieving better performance by exploiting different diversity schemes. To this end, we propose a general framework of transmit antenna selection (TAS)‐assisted orthogonal space‐time block code (OSTBC) transmission for multiple NOMA users. We derive exact expressions of probability density function of the TAS‐OSTBC processed signal‐to‐noise ratio (SNR) at the output of maximum‐ratio combiner of the NOMA users. Using well‐known moment generating function approach, we evaluate the error performance of TAS‐OSTBC assisted NOMA users over generalized η−μ fading channel in presence of perfect and imperfect successive interference cancelation. We investigate the proposed system in different multi‐antenna scenarios and accordingly observe better error performance of the users by increasing the number of transmit and receive antennas. We perform their asymptotic analysis leading to full‐diversity order at high SNR. For numerical evaluation, we truncate the infinite series in derived results and examine the upper bound of truncation error. We evaluate nth moment of the output SNR and obtain channel quality estimation index as a performance measure of the proposed NOMA system. Moreover, we investigate the influence of power coefficients and fading parameters, η and μ, on the error performance of TAS‐OSTBC‐assisted NOMA users. We also compare the derived error performances with the existing schemes, wherein we observe that the proposed system shows remarkable improvement in the bit error rate (BER) of the NOMA users. For validation, we execute simulations which closely match with the derived analytical results.

Counterpropagating topological and quantum Hall edge channels

The survival of the quantum spin Hall edge channels in presence of an external magnetic field has been a subject of experimental and theoretical research. The inversion of Landau levels that accommodates the quantum spin Hall effect is destroyed at a critical magnetic field, and a trivial insulating gap appears in the spectrum for stronger fields. In this work, we report the absence of this transport gap in disordered two dimensional topological insulators in perpendicular magnetic fields of up to 16 T. Instead, we observe that a topological edge channel (from band inversion) coexists with a counterpropagating quantum Hall edge channel for magnetic fields at which the transition to the insulating regime is expected. For larger fields, we observe only the quantum Hall edge channel with transverse resistance close to h/e2. By tuning the disorder using different fabrication processes, we find evidence that this unexpected ν = 1 plateau originates from extended quantum Hall edge channels along a continuous network of charge puddles at the edges of the device.

An Analytical Framework for Disruption of Licklider Transmission Protocol in Mars Communications

As one of the main data transport protocols of delay/disruption-tolerant networking (DTN), Licklider transmission protocol (LTP) is designed to provide reliable data delivery in an interplanetary Internet environment characterized by frequent and lengthy link disruptions and extremely long signal propagation delays. Some studies have been done on the performance of LTP in cislunar and Mars communications. However, to date the effect of link disruption on LTP for Mars communications has received little attention. In this paper, an analytical framework is presented for the effect of link disruption on reliable data delivery and performance of LTP in Mars communications. The analysis focuses on how various link disruptions affect the number of transmission attempts, the consequent round-trip time (RTT) of data exchange, and the resulting goodput performance of LTP for reliable data block delivery in Mars communications. The analytical framework is validated by means of realistic data block transmission experiments using a PC-based experimental infrastructure, and it can be used to predict the performance of LTP over a deep-space vehicle communication channel in presence of link disruption.

Finite Element Analysis of the Dynamics of Power-Law Fluid around an Obstacle in a Channel

Control of fluid forces is an emerging area of research with numerous engineering applications. The uneven wake behind an obstacle causes undesirable structural oscillations, which can lead to fatigue or structural failure. Controlling the wake phenomena could directly benefit a wide range of engineering applications, including skyscrapers, naval risers, bridges, columns, and a few sections of airplanes. This study is concerned with the time dependent simulations in a channel in presence of an obstacle aiming to compute fluid forces. The underlying mathematical model is based on nonstationary Navier–Stokes equations coupled with the constitutive relations of power law fluids. Because the representative equations are complex, an effective computing strategy based on the finite element approach is used. To achieve higher accuracy, a hybrid computational grid at a very fine level is used. Theℙ2−ℙ1elements based on the shape functions of the second and first-order polynomials were used to approximate the solution. The discrete nonlinear system arising from this discretization is linearized by Newton’s method and then solved through a direct linear solver PARADISO. The code validation study is also performed for Newtonian fluids as a special case, and then the study is extended to compute drag and lift forces for other cases of viscosity as described by the power law index. When looking at the phase plot, it can be seen that for the Newtonian case n = 1, there is only one closed orbit after the steady state is reached, whereas forn=0.5, there are multiple periodic orbits. Moreover, the effects of shear rate on the drag-lift phase plot are also discussed.

Role of thermophoresis on unsteady/steady mixed convective flow in a vertical channel having convective boundary conditions

A numerical as well as analytical investigation is performed to study time dependent/steady state mixed convection flow in a vertical channel in presence of thermophoresis having convective boundary conditions. The main objective of this paper is to present exact solutions for steady state mathematical model under relevant boundary conditions and numerical solutions for time dependent situation under relevant initial and boundary conditions. The impact of various controlling parameters such as dimensionless time t, Schmidt number Sc, Biot numbers Bi_{1} and Bi_{2}, buoyancy ratio b and thermophoretic coefficient k have on the flow patterns is discussed. Graphical results show that the effect of increasing two or more of the parameters simultaneously with high mixed convection parameter changes the flow from bi-directional to unidirectional. Also, the occurrence of a flow reversal depends on buoyancy and dimensional time. Furthermore, there exists a convergence of Sherwood number values at the cold plate when thermophoretic values are high.Article HighlightsWhen buoyancy dominates the flow, a decrease of reverse flow at the cold plate is observed as thermophoresis approaches its peak.If Schmidt number increases simultaneously with time, a wider region across the channel where concentration of particles is zero is observed.When thermophoretic values are low, an increment in time reduces Sherwood numbers. Sherwood number values are observed to converge at the cold plate when thermophoretic values are high. These findings have implications in the developments of thermophoretic cells used in biochemical and medical researches because Sherwood numbers imply negative concentration fluxes at boundaries.

Unsteady MHD Squeezing Flow of Casson Fluid Over Horizontal Channel in Presence of Chemical Reaction

The fluid flow with chemical reaction is one of well-known research areas in the field of computational fluid dynamic. It has been acknowledged by many researchers due to its industrial applications in the modelling of flow on a nuclear reactor. Motivated by the implementation of the flow in the industry problems, the aim of this study is to explore the impacts of chemical reaction on magnetohydrodynamic (MHD) squeeze flow of Casson fluid over a permeable medium in the slip condition with viscous dissipation. The flow is induced due to compress of two plates. Transformation of the partial differential equations (PDEs) to ordinary differential equations (ODEs) is performed by imposing similarity variables. The numerical procedure of Keller-box is used to solve the dimensionless equations. Comparison of the numerical results with former studies to validate the current solutions is conducted. It is shown to be in proper agreement. The results show that the velocity and wall shear stress enhance as both plates moving nearer. Moreover, increase in Hartmann and Casson parameters reducing the velocity, temperature and concentration. The temperature and the rate of thermal transfer boosts with the existence of viscous dissipation. Furthermore, the mass transfer rate is discovered boosts in destructive chemical reaction and adverse outcome is noted in constructive chemical reaction.

Flow of Dusty Non-Newtonian Fluid in a Vertical Channel in Presence of Inclined Magnetic Field

A theoretical investigation of the influence of inclined magnetic field on the flow of non-Newtonian fluid with dust in a vertical channel has been considered. The non-Newtonian fluid is characterized by second-order fluid. The governing partial differential equations are obtained and solved analytically. The analytical expression for velocity field, temperature field , shearing stress flow flux at the channel are obtained. The potency of relevant parameters of the problem on velocity , shearing stress and flow flux of both dusty fluid and dust particles have been presented graphically.

Flow Bifurcation Phenomena of Shear-Thinning and Newtonian Fluids in a Rectangular Channel in Presence of Intermediate Steps: using Carreau-Yasuda Model

Flow bifurcation transitions of shear-thinning fluid and Newtonian fluid, flow through a two-dimensional rectangular channel in presence of intermediate steps have been considered in this manuscript. Employing SIMPLE algorithm, the governing equations have been solved numerically and using FLUENT software to visualize the simulation results for convenience. The Rheological properties of shear-thinning and Newtonian fluids are described in the light of Carreau-Yasuda model. The result of this formulation has been validated with those of an earlier work. The motivation of this work is to study the bifurcation characteristics for different values of Reynolds numbers in presence of multiple steps in a rectangular channel. Pressure drop characteristic has also been studied for different values of expansion ratio and intermediate steps. For some particular value of expansion ratio (ER), a linear relation between 〖Re〗_crit and the value of n of Carreau-Yasuda model has been shown.

Networked control for linear systems with forward and backward channels in presence of data transmission delays, consecutive packet dropouts and disordering

This paper investigates networked control for discrete-time systems with communication imperfections including data transmission time-varying delays, consecutive packet dropouts and packet disordering. The system states, which are measured by a sensor with periodic sampling period, will be directly transmitted to a sender and further delivered to a remote controller with aperiodic sending time-intervals. Only when the controller receives valid state information, the control signals are calculated and sent to the actuator. Because the data transmission imperfections are simultaneously allowed in the forward and backward communication channels (i.e., sender-to-controller and controller-to-actuator networks), the data transmission procedure from the sensor to the actuator is analyzed in details and the actuator received control command is presented in a time-delay description. Meanwhile, the qualitative relationships between the non-periodical sampling period, time-delay bound, consecutive packet dropout number and disordering are given as well. A delay-independent Lyapunov functional is employed while the sufficient delay-dependent stability condition is obtained. By the proposed method, not only system asymptotical stability of the closed-loop system can be achieved but also the network imperfections can be tolerated. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed method.

Direct measurement of the effect of non-submerged rigid vegetation-induced flow cross-section area variations on flow force in compound channel

In this experimental work, flow force in compound channel in presence of non-submerged vegetation was obtained via direct measurement method. The direct measurement method was used to address the inefficiency of the conventional energy-based methods for measuring the force within the body of highly rough flows. On this basis, the study was performed using a specially designed flume called knife-edge flume with a length of 14 m, a width of 1.07 m, and a height of 1.05 m at a stream bed grade of 10-3. The flow force measurements were performed directly using a load cell in absence of the common errors that were otherwise associated with velocity measurement by inserting an external body into the flow. In this study, we examined non-submerged rigid vegetation layers with five different diameters (i.e., 20, 25, 30, 40, and 50 mm), three values of crossline spacing (i.e., 6, 8, and 10 cm), five values of crossline spacing (i.e., 8, 10, 12, 15, and 20 cm), and two different arrangements (i.e., ordered and non-ordered or cruciform) at three different positions (i.e., in the floodplain, in the main channel, and simultaneously in the floodplain and the main channel) by performing a total of 451 tests. The flow force exhibited the highest sensitivity to the increase in vegetation volume under the non-ordered arrangement. In this respect, the improvement in the flow force with increasing the percent volume of vegetation was much larger when the vegetation was arranged in a non-ordered rather than ordered fashion, with the effect of the vegetation been even more pronounced in the floodplain rather than the main channel. In addition, at a certain percent change of the flow force, the trough-vegetation flow velocity was higher under the ordered arrangement rather than the non-ordered arrangement, reflecting the more difficulty encountered by the flow as it passed through the non-ordered vegetation. Based on the analysis results, it was found that the flow force would change by 060% when the vegetation had grown in the floodplain with λ* values in the range of 0–1. In cases where the vegetation had grown in the main channel and simultaneously in the main channel and the floodplain, the flow force variations increased to 10–70% and 20–80% as the λ* changed from 0 to 10, respectively. Analyzing the results of the experiments and the vegetation-modified Reynolds number, a relationship was further presented for calculating the flow force in presence of non-submerged rigid vegetation in a compound channel.