Analysis Of Unsteady Flow Research Articles

Fractional analysis of unsteady radiative brinkman-type nanofluid flow comprised of CoFe2O3 nanoparticles across a vertical plate

Fractional analysis of unsteady radiative brinkman-type nanofluid flow comprised of CoFe2O3 nanoparticles across a vertical plate

Influence of Door Gap on Aeroacoustics and Structural Response of a Cavity

Numerical aeroacoustic analysis using the Shear Stress Transport–Scale Adaptive Simulation turbulence model was conducted on a weapon bay model based on the M219 geometry with doors incorporating radar cross-section reduction features. The effect of the introduction of a gap between the doors and the cavity edge on the aeroacoustic and structural response of the cavity was analyzed at Mach 0.85. The effect of introducing 3 deg of sideslip was also investigated. Both mean and unsteady flow analyses were conducted. The results showed a strong palliative effect of the door gap with and without sideslips. The overall analysis of the spectral signature on the forces and moments acting on the doors indicated the possibility of fluid–acoustic coupling, as all acoustic spectra showed a predominant tone located at the same frequency of the first structural mode.

Uncertainty analysis on flood routing of embankment dam breach due to overtopping failure

The breach risk of reservoir dam exists objectively while exerting benefits. There is great uncertainty in the overtopping breach process of embankment dam and the dam break flood routing which affects the accuracy of dam risk analysis and may cause unnecessary waste in emergency scheduling. However, the uncertainty analysis of the breach process and its consequence is currently inadequate. Therefore, a stratified sampling Monte Carlo method is proposed to simulate uncertain overtopping breach flood of embankment dams. The main sources of uncertainty are analyzed and determined as uncertain dam breach and flood routing processes. The uncertain breach process of dam is studied by presenting a sensitive study between 3 mechanism breach models and 5 parametric breach models. The random dam breach process is restored using HEC-RAS semi-empirical breach model by estimating breach characteristics through multiple common breach models. The random flood routing is carried out through 1D–2D coupled unsteady flow analysis in which the random breach process is adopted as an upper inflow boundary condition. According to the case study results, though parameters have been controlled in a limited range, the flood routing results in the early stage of dam overtopping failure present greater uncertainty. As the flood progresses further downstream, the uncertainty will gradually decrease. This study could serve as a reference for dam breach risk map making.

Heat and Mass Transfer Analysis in An Unsteady Natural Convective Magnet Hydrodynamic Flow of a Nano Fluid under the Presence of Thermal Diffusion and Absorption Radiation

An analysis of unsteady natural convective MHD flow of nanofluid under the presence of thermal diffusion and absorption radiation with the effects of chemical reaction on heat and mass transfer without a porous medium is discussed in the present study. The governing equations were implied and were solved analytically using perturbation technique. The velocity, temperature and concentration fields are obtained. Graphical results were presented for velocity, temperature and concentration profile for various values of parameters.

Dynamic mode decomposition for the tip unsteady flow analysis in a counter-rotating axial compressor

Counter-rotating axial compressor (CRAC) is a promising potential technology to improve the thrust-to-weight ratio of aero-engines, but its special aerodynamic layout usually causes more pronounced flow unsteadiness. Understanding the unsteady flow features and mechanism in the CRAC contributes to the aerodynamic optimization design and flow control strategy organization. A data-driven dynamic mode decomposition method is introduced to investigate the tip flow unsteadiness in a CRAC, and the unsteady features of the tip flow at the design point (DP) and near-stall point (NSP) conditions are revealed. The results show that the 1.0 times blade passage frequency (BPF) and its multi-order harmonic frequency are the dominant frequencies for both rotors at the DP condition. At the NSP condition, the 1.0 BPF is no longer the dominant frequency causing the tip flow unsteadiness, and the low frequency fluctuation of the tip leakage flow becomes the dominant frequency to induce the flow unsteadiness. In the front rotor R1, the unsteady dominant frequency is 1.0 BPF, whereas in the rear rotor R2, the frequency (0.801 BPF and 0.803 BPF) of the tip leakage flow is the dominant frequency. By reconstructing the flow field under the NSP condition, the spatiotemporal evolution of the tip flow during the unsteady stable manifests that the interference effect between the rotors is an important source of the tip flow unsteadiness. The increase in flow unsteadiness leads to an increase in the reconstruction error, indicating that more modes are required to obtain a more accurate reconstruction flow field.

Analysis of unsteady non-Newtonian Jeffrey blood flow and transport of magnetic nanoparticles through an inclined porous artery with stenosis using the time fractional derivative

In the present study, a Caputo–Fabrizio (C–F) time-fractional derivative is introduced to the governing equations to present the flow of blood and the transport of magnetic nanoparticles (MNPs) through an inclined porous artery with mild stenosis. The rheology of blood is defined by the non-Newtonian visco-elastic Jeffrey fluid. The transport of MNPs is used as a drug delivery application for cardiovascular disorder therapy. The momentum and transport equations are solved analytically by using the Laplace transform and the finite Hankel transform along with their inverses, and the solutions are presented in the form of Laplace convolutions. To display the solutions graphically, the Laplace convolutions are solved using the numerical integration technique. The study presents the impacts of different governing parameters on blood and MNP velocities, volumetric flow rate, flow resistance, and skin friction. The study demonstrates that blood and MNP velocities boost with an increase in the fractional order parameter, Darcy number, and Jeffrey fluid parameter. The volumetric flow rate decreases and flow resistance increases with enhancement in stenosis height. The non-symmetric shape of stenosis and the rheology of blood decrease skin friction, whereas enhancement in MNP concentration increases skin friction. A comparison of the present result with the previous work shows excellent agreement. The present study will be beneficial for the field of medical science to further study atherosclerosis therapy and other similar disorders.

Modeling unsteady and steady 1D hydrodynamics under different hydraulic conceptualizations: Model/Software development and case studies

The stage-discharge relationship is affected by hysteresis, especially in 1D river cross-sections with very mild slopes, and/or where backwater effects occur. To model these cases, hydraulic property (HP) estimations (e.g., hydraulic radius and conveyance) are usually required as closed-form functions of stage. However, these are typically unavailable for complex cross-sections with overbanks. For no sediment-laden flows, we created the HydroHP - 1D tool to solve the 1D Saint Venant Equations aided by the cross-section HP stored in tables. It also simulates irregular and composite hydraulic cross-sections, allows hydrodynamic simulation using the single-channel method (SCM), and proposes the divided channel method (DCM) for steady and unsteady flow analysis. A wide range of applications in rivers such as the Little Washita River and the Upper Negro River, and comparisons with NOAA normal depth solver, HEC-RAS, and with an analytical solution shows a promising scenario of applying HydroHP - 1D to estimate 1D steady and unsteady hydrodynamics.

Fluid flow analysis of unsteady cavitating flow over MHKF-180s hydrofoil

This study focuses on the fluid flow behavior of three-dimensional unsteady cavitating flow on MHKF-180s hydrofoil at an angle of attack 11° with cavitation number ranging from 0.1 to 1.2. The numerical investigation for this study is carried out in Ansys Fluent. For this purpose, the Zwart-Gerber-Belamri (ZGB) model for cavitation with the RNG k-∊ model for turbulence are used. The hydrofoil's hydrodynamic characteristics are studied by analyzing the lift coefficient, drag coefficient, and Strouhal number, at various cavitation numbers. It has been found that when transitioning from a supercavitating region to a non-cavitating region, both the lift coefficient and the frequency at which the cavitation is shedding increase for an angle of attack of 11°.

Numerical Analysis of unsteady Non-linear mixed convection flow of Reiner-Philippoff nanofluid along Falkner-Skan wedge with new mass flux condition

The main goal of this research focuses on the theoretical examination of the melting and nonlinear mixed convection mechanisms in unsteady Falkner-Skan wedge flow of Reiner-Philippoff nanofluid with nonlinear thermally radiative, nanoparticle mass flux condition, uniform heat source/sink, chemically reactive, and Arrhenius activation energy effects are considered. The nanoparticle concept includes thermophoretic and Brownian motion. Arrhenius activation energy idea is adopted in the concentricity equation. Appropriate transformations are employed to obtain non-linear ordinary differential equations. The outcoming non-linear (ODEs) are then computationally implemented through R-K 4th order approach based on shooting method. We investigate and discuss the impacts of various physical parameters on thermal, velocity, solutal, skin friction, heat transport, and streamlines field. A comparative examination is presented between the present findings and available date and displayed to be in excellent agreement. Velocity field diminished against escalating valuations of concentration buoyancy and wedge angle parameters, respectively. Concentricity field has opposite trend for augmenting thermophoretic and non-linear solutal convection parameters, respectively.

Heat transfer analysis of unsteady MHD slip flow of ternary hybrid Casson fluid through nonlinear stretching disk embedded in a porous medium

The original article's purpose is to assess transfer of heat exploration for unsteady magneto hydrodynamic slip flow of ternary hybrid Casson fluid via a nonlinear flexible disk placed within a perforated medium of a magnetic field in the presence. Unsteady nonlinearly stretched disk inside porous material causes flow to occur. In the investigation, convective circumstances on wall temperature are also considered. The governing equations (PDEs) are transformed into ordinary differential equations (ODEs) using appropriate transformations, and the Keller-box technique is employed for their solution. In forced convection, the variable radiation has no direct impact on fluid velocity, but it is noticed that in the case of aiding flow, fluid velocity rises with an increase in radiation parameter, and the opposite is true in the case of opposing flow. Furthermore, it is experiential that fluid concentration and velocity goes up in creative chemical reactions, and both profiles decrease in detrimental chemical reactions. Moreover, a slightly greater unsteadiness characteristic lowers fluid, concentration, temperatureand velocity. Physical parameters' effects on fluid temperature, concentration, and velocity, as well as on wall shear stress, energy, and mass transfer rates, are studied.

Mathematical modeling of unsteady convective flow analysis of water and nano-encapsulated phase change particles in composite enclosure subject to rotation

Free convection heat transfer in water and hybrid particles in an enclosure is studied. A layer of porous material with various thickness and permeability is attached to the enclosure. Both fluid and porous layers rotate with a specific speed. Hybrid particles are formed by a polyurethane (PU) and an N-nonadecane (ND). PU acts as shell and ND goes through a phase change and it capables of preserving and releasing a considerable amount of latent heat. The enclosure movement can be controlled through a rotation speed. The Brinkman-Forchheimer extended Darcy model is used for governing the flow within a fully saturated porous layer. The governing equations for the convective flow and phase change heat transfer, including specific heat capacity and permeability, were introduced and solved by FEM. The impact of the porous thickness, permeability, fusion temperature and rotation speed on the heat capacity ratio, streamline and isotherms structures were investigated. The results showed that a high Darcy number and thin porous thickness were a good candidate for the improvement of average heat transfer rate since reinforcing the melting process and heat transmitting.

Heat transfer analysis of unsteady nanofluid flow between moving parallel plates with magnetic field: Analytical approach

Heat transfer analysis of unsteady nanofluid flow between moving parallel plates with magnetic field: Analytical approach

An adjoint-based drag reduction technique for unsteady flows

A framework based on a continuous adjoint-based analysis of steady and unsteady flows to predict and control the drag force due to surface morphing is presented. By establishing a relation between perturbations in the body shape and in the boundary condition on a certain geometry, we derive an analytical expression of the sensitivity to changes in the geometry of the body and its relation to the sensitivity to the perturbation of the boundary conditions. The methodology is evaluated on the incompressible flow around a cylinder for steady and unsteady flows. A reduction of the drag coefficient was obtained and investigated by several surface deformations, conducted in the direction of the sensitivity vector field obtained by solving the derived adjoint problem. In unsteady flows, the sensitivity field is computed by integrating the unsteady adjoint problem backward in time from the unsteady flow solution. Two different types of deformations based on the calculated sensitivity were applied: time-averaged deformation and time-dependent. Attempting the latter, a deformation at each time step, did not yield the same satisfactory results as the time-averaged in terms of expected drag reduction. We provide a theoretical reasoning for the difference between both methodologies, together with an insight into the physics of the sensitivity vector field distribution relating it to the drag force sources.

Entropy analysis of unsteady MHD nanofluid flow over a stretching surface with effects of variable viscosity and nonuniform heat generation

An unsteady two-dimensional nanofluid flow across a permeable stretched sheet is examined in terms of thermodynamic analysis. Water is utilized as the basic fluid, together with four distinct types of nanoparticles: copper (Cu), copper oxide (CuO), aluminum oxide (Al2O3), and titanium dioxide (TiO2). An external source is used to describe the heat transfer phenomena. The effects of heat generation and absorption are also taken into account. The nonlinear partial differential equations are transformed into a system of nonlinear ordinary differential equations via a similarity transformation. The spectral quasi-linearization approach is then used to numerically integrate the altered equations. Except when otherwise noted, the findings are provided for copper nanoparticle situations. A visual and detailed explanation of the effects of several physical factors on the profiles of dimensionless velocity, temperature, average entropy generation function, skin friction, and the Nusselt number are discussed. As exceptional circumstances of the current findings, there is a strong agreement between the current conclusion and the findings of the other researchers. The average entropy generation number, temperature, and velocity profiles are shown to be strongly influenced by regulating factors. It is concluded that the average entropy generation decreased in the presence of a temperature- and space-dependent heat source/sink, but it improves with enhanced viscosity parameter. The significance of the present study has frequent applications in the major area of heat transfer enhancement in renewable energy systems, industrial thermal management, and also materials processing.

Mathematical analysis of unsteady blood flow through bifurcated abdominal aorta featured aneurysm

An abdominal aortic aneurysm (AAA) is a localized dilatation of abdominal aorta. This study investigates a 2-dimensional unsteady and laminar flow through a bifurcated artery with an aneurysm that is computationally and mathematically simulated using 3-dimensional geometry. The fluid used in this simulation is blood which is Newtonian for high shear rate. The computational technique is used to solve the equations that governs due to the flow. The flow of blood is analyzed with the assist of cut planes of pressure and velocity in the abdominal aortic aneurysm (AAA) for t=1s and t=4s. The pressure on the wall and complete velocity profile are also displayed with the assist of graphs. The streamlines are also shown with the help of graphs for t=1s and t=4s. The results can be used in the treatment of abdominal aortic aneurysm.

Fractional modeling and analysis of unsteady squeezing flow of Casson nanofluid via extended He-Laplace algorithm in Liouville-Caputo sense

The objective of this manuscript is to model the fully fractional unsteady Casson nanofluid flow between two parallel plates influenced by magneto hydrodynamic forces and Darcian effects in both slip and no-slip case. Casson nanofluid model is fractionally transformed through mixed similarity transformations into a non-dimensional fully fractional model. In modeled fluid problem the continuity equation is identically satisfied and fractional order highly non-linear momentum equation is obtained. The obtained fractional model is further validated by putting α=1 and obtaining the integer order Casson fluid model already existing in literature. In order to solve the flow problem, a hybrid of homotopy perturbation method and Laplace transform, namely He-Laplace method (HLM) is utilized. The obtained results are validated with existing results in literature and through residual errors and average error plots with increasing order of approximation. It is observed that results obtained through HLM are better in terms of accuracy than existing results. Moreover, the errors reduce substantially as order of approximation in HLM increases, depicting the convergence of proposed scheme. Graphical analysis is also performed to analyze the behavior of normal and radial velocity. Furthermore, contour plots are presented for flow rate and skin friction of Casson nanofluid. It is observed that fluid parameters present different behavior incase of fractional environment when compared with existing integer order results. Also, the behavior of velocity profile in no-slip case is in contrast to the behavior noted in slip case of Casson nanofluid. These finding confirm the importance of fractional modeling in terms of capturing more generalized physical phenomena.

Comparative analysis of unsteady flow of induced MHD radiative Sutterby fluid flow at nonlinear stretching cylinder/sheet: Variable thermal conductivity

Unsteady incompressible Sutterby fluid model is considered. The comparative results of stretching cylinder and sheet have been studied. The induced magnetic field is considered in the presence of thermal slip. Darcy resistance and viscos dissipation impacts have been studied. The thermal conductivity of liquid has considered as variable under the thermal radiation. The governing model of presence study have been developed under boundary layer approximation in term of partial differential equations. The differential equation become dimensionless by means of transformations. The dimensionless system have been solved through numerical procedure. Involving factor of physical influence presented in the form of tabular as well as graphical. Fluid temperature boosted up due to larger values of variable thermal conductivity. Physically, the thermal conductivity of liquid increased as well as variable thermal conductivity liquid enhanced as the temperature of fluid improved. The momentum layer thickness of stretching cylinder achieved mover than stretching sheet. The fluid velocity curves achieved higher thickness for boosting values of Darcy resistant factor. The velocity fluid curves revealed declining by increasing the Sponginess factor. Fluid temperature boosted up due to larger values of Eckert number.

Fractional Analysis of Unsteady Slip Flow of Viscous Fluid Confined to the Boundaries of an Annulus Driven by Exponentially Decaying/Growing Time-Dependent Pressure Gradient

Fractional Analysis of Unsteady Slip Flow of Viscous Fluid Confined to the Boundaries of an Annulus Driven by Exponentially Decaying/Growing Time-Dependent Pressure Gradient

Analysis of unsteady thin film flows over the porous and moving surfaces of variable thickness: Unsteady and non-linear kinematics of sheet

Thin film flows over porous and moving sheets of variable thickness have been reconsidered here. New and multiple dimensions of classical problems of such type flow are analyzed. Here, we categorically emphasized on the nature and kinds of injection (suction) and moving velocities of the sheet, whereas, variable size of the sheet is also taken into account. We formed and investigated different cases and checked different options for kinematics of sheet, variable sizes of thin film and that of sheet. All possible cases of exact similarities are noticed by which the system of partial differential equations and boundary conditions are exactly transformed into ordinary differential equations. The final systems of exact equations are solved by bvp4c technique. The present simulations are exactly matched with the previously published analyses for special choices of functions and parameters. Strict behavioral changes have been observed in the velocity profiles by changing the nature of sheet’s kinematics.

Influence of dual-axial swirler configuration on hydrodynamic stability in combustor

To improve hydrodynamic stability in a combustor, an unsteady flow analysis method is needed. Hence, the proper orthogonal decomposition (POD) method based on a large eddy simulation (LES) unsteady flow field and corresponding experimental verification were utilized to analyze and assess the influence of the precession vortex core (PVC) motion law on the pulsation downstream of different swirler configurations. The pulsation outcomes of the unsteady simulation match the experimental data quite well, with case 1 having the highest pulsation quantity. The POD analysis reveals that the majority of pulsation energy is concentrated in the first two modes. The results of the motion state, regularity of the time coefficient, and frequency characteristics also demonstrate that the combustor's PVC features are compatible with modes 1 and 2. There is an optimum value of swirl number, 0.72, for which the flow field's stability has the lowest degree of disturbance. Moreover, the airfoil vane's stability is beyond that of the straight vane. The mean flow field and the coherent flow field in the pulsation flow field of case 3 are the most beneficial factors concerning combustion stability, and the unstable aspects of the transition flow field and the turbulent flow field are the least in shape and energy ratio. The data procured from the experiment certify that there is no characteristic frequency of pulsation within 5000 Hz that exists in case 3.