Showing papers on "Incompressible flow published in 2021"
TL;DR: This research work develops mathematical modeling for steady magnetized two-dimensional incompressible flow of Jeffrey nanofluid over a stretched curved surface with combined characteristics of activation energy, Brownian motion, viscous dissipation, nonlinear mixed convection, magnetohydrodynamics, Joule heating and thermophoresis diffusion.
108 citations
TL;DR: In this article, a 2D steady, laminar and incompressible flow of magneto-cross nanofluid towards the region of moving thin needle in the occurrence of Darcy-Forchheimer porous medium, Ohmic and viscous dissipation with chemical reaction and mixed convection.
Abstract: Nanofluids have exposed a significant promise in the thermal development of several industrial systems, and at the same time, the flow via needle has major applications in modern construction systems including microstructure electric gadgets and microscale cooling gadgets for thermal migration applications. According to these applications, the current investigation concentrates to deliberate on 2D steady, laminar and incompressible flow of magneto-Cross nanofluid towards the region of moving thin needle in the occurrence of Darcy–Forchheimer porous medium, Ohmic and viscous dissipation with chemical reaction and mixed convection. The new dimensionless similarity variables are introduced to convert the nonlinear expressions governing the flow and transfer of heat. The change in velocity, thermal and concentration profiles for various non-dimensional parameters is deliberated briefly and illustrated with the help of suitable plots. Further, analysis of skin friction and rate of heat transfer is done through graphs. The results obtained are validated by existing works and are found to have a good agreement. The result outcome reveals that advanced values of magnetic parameter and Weissenberg number slowdown the fluid velocity motion. Also, upshot in Brownian motion and thermophoresis parameters improves the thermal profile.
69 citations
TL;DR: In this article, the effect of magnetite nanofluid taking into account water as the base fluid, over a rotating disk in the presence of external magnetic field was analyzed. And the Von Karman transformations of the Navier-Stokes equations were used to obtain the non-dimensional forms of the governing equations, and then fourth order finite difference scheme was used to find the numerical solutions using Noumerov's discretization.
59 citations
TL;DR: In this paper, the authors considered the numerical approximation of the flow-coupled multi-phase-field elastic bending energy model of lipid vesicles and proposed a novel numerical method to construct an effective scheme that is fully decoupled, linear, unconditionally energy stable, and second-order time-accurate.
46 citations
TL;DR: In this article, the authors proposed a novel decoupling method, which only needs to solve several decoupled linear elliptic equations with constant coefficients at each time step to obtain a numerical solution with second-order time accuracy.
41 citations
TL;DR: In this paper, a second-order time-accurate and fully-decoupled scheme for the flow-coupled phase-field model with the incompressible flow was proposed.
33 citations
TL;DR: In this paper, a combined technique was developed for studying free convection of magnetohydrodynamic unsteady incompressible flow in a square cavity that partially heated from lower wall and regular cooling f...
26 citations
TL;DR: In this article, the authors present a review of featured works in the field of hydrodynamics with the main aim to clarify the ways of understanding the algorithms for solving the Navier-Stokes equations.
26 citations
TL;DR: In this article, a discretization of the Navier-Stokes equation that advects mass and momentum in a consistent manner is considered. But the method is not suitable for flow with large density contrasts.
25 citations
TL;DR: In this article, the development of disturbances in the boundary-layer transition (BoLT) flight experiment flowfield is investigated using a recently developed "quiet direct numerical simulation (DNS)" approach.
Abstract: The development of disturbances in the boundary-layer transition (BoLT) flight experiment flowfield is investigated using a recently developed “quiet direct numerical simulation (DNS)” approach. By...
25 citations
TL;DR: The resulting POD-DL-ROMs are shown to provide accurate results in almost real-time for the flow around a cylinder benchmark, the fluid-structure interaction between an elastic beam attached to a fixed, rigid block and a laminar incompressible flow, and the blood flow in a cerebral aneurysm.
Abstract: Simulating fluid flows in different virtual scenarios is of key importance in engineering applications. However, high-fidelity, full-order models relying, e.g., on the finite element method, are unaffordable whenever fluid flows must be simulated in almost real-time. Reduced order models (ROMs) relying, e.g., on proper orthogonal decomposition (POD) provide reliable approximations to parameter-dependent fluid dynamics problems in rapid times. However, they might require expensive hyper-reduction strategies for handling parameterized nonlinear terms, and enriched reduced spaces (or Petrov–Galerkin projections) if a mixed velocity–pressure formulation is considered, possibly hampering the evaluation of reliable solutions in real-time. Dealing with fluid–structure interactions entails even greater difficulties. The proposed deep learning (DL)-based ROMs overcome all these limitations by learning, in a nonintrusive way, both the nonlinear trial manifold and the reduced dynamics. To do so, they rely on deep neural networks, after performing a former dimensionality reduction through POD, enhancing their training times substantially. The resulting POD-DL-ROMs are shown to provide accurate results in almost real-time for the flow around a cylinder benchmark, the fluid–structure interaction between an elastic beam attached to a fixed, rigid block and a laminar incompressible flow, and the blood flow in a cerebral aneurysm.
TL;DR: In this paper, the fluid flow and heat transfer characteristics of a heat exchanger have been improved by various active, passive, and combined methods, and the results showed that active and passive methods were more effective than combined methods.
Abstract: Improving the fluid flow and heat transfer characteristics of a heat exchanger has always been desired for any heat transferring application. Various active, passive, and combined methods were adop...
TL;DR: In this paper, an experimental investigation of a propeller operating at low Reynolds numbers and providing insights into the role of aerodynamic flow features on both propeller performances was presented, and the performance of the propeller was analyzed.
Abstract: This paper presents an experimental investigation of a propeller operating at low Reynolds numbers and provides insights into the role of aerodynamic flow features on both propeller performances an...
TL;DR: In this paper, three-dimensional numerical simulations based on the Volume of Fluid method are conducted to investigate the hydrodynamic behavior of a falling film over horizontal round tubes with diameter and tube-to-tube spacings each of 16 mm.
TL;DR: In this article, the effects of surface roughness on a hypersonic (approximately 7.3 ) flat-plate turbulent boundary layer were investigated. But no significant compressibility effects were apparent in the flow response in that the behavior of the mean velocity and streamwise turbulence profiles was in general accord with similar experiments in incompressible flows.
Abstract: Particle image velocimetry experiments were performed to study the effects of surface roughness on a hypersonic (
$$ M \approx 7.3 $$
), flat-plate turbulent boundary layer. Diamond mesh and square bars of different heights were used to form the roughness. No significant compressibility effects were apparent in the flow response in that the behavior of the mean velocity and streamwise turbulence profiles was in general accord with similar experiments in incompressible flows. The effects of the roughness extended to about one roughness height above the roughness itself and Townsend’s hypothesis were confirmed. Outside of this region, the streamwise lengthscale and the inclination of the spatial correlation contours also showed good agreement with observations on smooth-wall and incompressible flow experiments.
TL;DR: In this article, the concept of the product-like fractal measure introduced by Li and Ostoja-Starzewski in their formulation of fractal continuum media is combined with the fractal time derivative operator to construct a map between the Schrodinger equation which governs the wave function of a quantum-mechanical system and the Navier-Stokes equations that describe the flow of incompressible fluids.
Abstract: In this study, the concept of the product-like fractal measure introduced by Li and Ostoja-Starzewski in their formulation of fractal continuum media is combined with the concept of the fractal time derivative operator. This combination is used to construct a map between the Schrodinger equation which governs the wave function of a quantum–mechanical system and the Navier–Stokes equations, which are the fundamental partial differential equations that describe the flow of incompressible fluids. Several interesting features are found. In particular, for the case of a variable thermal conductivity and special numerical values of the fractal parameters in the theory, it is observed that the entropy density in the semiclassical approximation of any stationary state may be not be constant in time. The decrease in the entropy over time leads in our approach to a decrease in the thermal conductivity with distance, a scenario which takes place in material sciences.
TL;DR: In this paper, a new numerical method to simulate particulate interactions with high-speed transitional boundary-layer flows is presented, using a particulate solver, employing Crowe's correlation.
Abstract: A new numerical method to efficiently simulate particulate interactions with high-speed transitional boundary-layer flows is presented. A particulate solver, employing Crowe’s correlation, is used ...
TL;DR: In this article, a finite element numerical scheme for the Cahn-Hilliard phase-field model of the two-phase incompressible flow system with variable density and viscosity is presented.
Abstract: We construct a fully-discrete finite element numerical scheme for the Cahn–Hilliard phase-field model of the two-phase incompressible flow system with variable density and viscosity. The scheme is linear, decoupled, and unconditionally energy stable. Its key idea is to combine the penalty method of the Navier–Stokes equations with the Strang operator splitting method, and introduce several nonlocal variables and their ordinary differential equations to process coupled nonlinear terms. The scheme is highly efficient and it only needs to solve a series of completely independent linear elliptic equations at each time step, in which the Cahn–Hilliard equation and the pressure Poisson equation only have constant coefficients. We rigorously prove the unconditional energy stability and solvability of the scheme and carry out numerous accuracy/stability examples and various benchmark numerical simulations in 2D and 3D, including the Rayleigh–Taylor instability and rising/coalescence dynamics of bubbles to demonstrate the effectiveness of the scheme, numerically.
TL;DR: In this paper, the authors investigated how heat and mass transfer impacts the unsteady incompressible flow of the Maxwell fluid and found that adding molybdenum disulfide nanoparticles to the engine oil increased the heat transfer up to 12.899%.
Abstract: The aim of this study is to investigate how heat and mass transfer impacts the unsteady incompressible flow of Maxwell fluid. An infinite vertical plate with ramped and isothermal wall temperature and concentration boundary conditions is considered with the Maxwell fluid. Furthermore, in this study, engine oil has been taken as a base fluid due to its enormous applications in modern science and technologies. To see the importance of nanofluids, we have suspended molybdenum disulfide in engine oil base fluid to enhance its heat transfer rate. To investigate the flow regime, the system of equations was derived in the form of partial differential equations. The exact solutions to the complex system are obtained using the Laplace transform technique. Graphically, the impact of different embedded parameters on velocity, temperature, and concentration distributions has been shown. Through using the graphical analysis, we were interested in comparing the velocity, temperature, and concentration profiles for ramped and isothermal wall temperature and concentration. The magnitude of velocity, temperature, and concentration distributions is greater for an isothermal wall and less for a ramped wall, according to our observations. We observed that adding molybdenum disulfide nanoparticles to the engine oil increased the heat transfer up to 12.899%. Finally, the corresponding skin friction, Nusselt number, and Sherwood number have been calculated and presented in a tabular form.
TL;DR: A 2D fluid–structure interaction (FSI) solver based on Smoothed Particle Hydrodynamics and RKPM and Bernoulli’s principle is established, which is more accurate for the simulation of incompressible FSI problems.
TL;DR: In this article, a leading-edge flow sensing (LEFS) technique was used to detect vortex shedding in unsteady airfoil flows, which can be beneficial in controlling and positively harnessing their effects for increased aerodynamic performance.
Abstract: Sensing of vortex shedding in unsteady airfoil flows can be beneficial in controlling and positively harnessing their effects for increased aerodynamic performance. The time variation of the leading-edge suction parameter (LESP), which is a non-dimensional measure of the leading-edge suction force, is shown to be useful in deducing the various events related to vortex shedding from unsteady airfoils. The recently developed leading-edge flow sensing (LEFS) technique, which uses a few pressures in the airfoil leading-edge region for deducing the aerodynamic state of an airfoil, is adapted to deduce the variation of LESP during an unsteady motion in incompressible flow. For this purpose, the flow over the airfoil is divided into an outer-region flow over the chord, modeled using thin airfoil theory, and an inner-region flow over the leading edge, modeled as a flow past a parabola. By matching these two flows, relations are derived for calculating the LESP from a few pressures at the leading edge. By studying the variations of the LEFS outputs and the calculated LESP for various unsteady motions, guidelines are presented for detecting events related to vortex shedding: initiation, pinch-off, and termination. Computational and experimental results for additional unsteady motions confirm the effectiveness of the LEFS as a sensing technique for events associated with vortex shedding on unsteady airfoils.
TL;DR: In this article, a virtual element discretization for the problem of miscible displacement of one incompressible fluid by another, described by a time-dependent coupled system of nonlinear partial differential equations, is presented.
TL;DR: In this paper, a two-dimensional unsteady incompressible flow of a micropolar cross nanofluid past a linear stretching/shrinking sheet with a magnetic field is investigated.
Abstract: The present work concentrates on two-dimensional unsteady incompressible flow of a micropolar cross nanofluid past a linear stretching/shrinking sheet with a magnetic field. The Cattaneo–Christov diffusion theory with heat and mass fluxes is incorporated into the study. Famous Buongiorno model featured by Brownian motion and thermophoresis accounting for nanoparticle diffusion is included. The shooting method is employed to obtain numerical solutions of the transformed system of non-linear equations. The influence of the governing parameters on the dimensionless velocity, temperature, micro-rotation, nanoparticle concentration, skin friction, heat and mass transfer rates, entropy generation rate, Bejan number, irreversibility ratio, streamlines and finally isotherms are incorporated. The significant outcomes of the current investigation are that increment in micropolar parameter uplifts flow velocity, microrotation, while that peters out fluid temperature. Irreversibility ratio augments due to increment in stretching/shrinking strength parameter. Streamlines/Isotherms diverge/converge more and more from/to an origin accordingly.
TL;DR: A ghost node-based field extension technique provides an efficient way to improve mass conservation and as a result, reduces not only spurious oscillations but also increases temporal accuracy.
Abstract: This study presents a robust, sharp interface immersed boundary (IBM) framework for moving body problems. The in-house solver makes use of a density-based finite volume framework for solving unsteady, 3D Favre averaged Navier Stokes equation in a generalized curvilinear coordinate system. The immersed boundary formulation is capable of handling arbitrarily complex three-dimensional bodies. The sharp interface approach allows for the exact imposition of boundary conditions at the immersed surface by reconstructing the flow field along its local normal. The implemented reconstruction schemes maintain second-order accuracy. The study focuses on issues of mass conservation and spurious temporal oscillations (pressure as well as force) that the sharp interface IBM approach typically faces when encountering moving body problems. A ghost node-based field extension technique provides an efficient way to improve mass conservation and as a result, reduces not only spurious oscillations but also increases temporal accuracy. Flow past both bluff body (triangular, circular and spherical), as well as streamlined body (airfoil), is presented here as validation studies. The ability of the present formulation to deal with moving body problems in the laminar incompressible flow regime is demonstrated by presenting cases that involve motions such as pitching and in-line oscillation. The predictions are found to be in good agreement with the published results and measurements as well.
TL;DR: A sharp interface method to simulate fluid-structure interaction (FSI) involving rigid bodies immersed in viscous incompressible fluids and relies on an immersed interface method (IIM) for discrete geometries, which enables the accurate determination of both velocities and stresses along complex internal interfaces.
08 Feb 2021
TL;DR: In this article, the Navier-Stokes equations were solved analytically and numerically for specific physical conditions using Fα-calculus, and the fractal form of Navier Stokes equations, which describes the laminar flow of incompressible fluids, was solved using two groups of general solutions.
Abstract: Navier–Stokes equations describe the laminar flow of incompressible fluids. In most cases, one prefers to solve either these equations numerically, or the physical conditions of solving the problem are considered more straightforward than the real situation. In this paper, the Navier–Stokes equations are solved analytically and numerically for specific physical conditions. Using Fα-calculus, the fractal form of Navier–Stokes equations, which describes the laminar flow of incompressible fluids, has been solved analytically for two groups of general solutions. In the analytical section, for just “the single-phase fluid” analytical answers are obtained in a two-dimensional situation. However, in the numerical part, we simulate two fluids’ flow (liquid–liquid) in a three-dimensional case through several fractal structures and the sides of several fractal structures. Static mixers can be used to mix two fluids. These static mixers can be fractal in shape. The Sierpinski triangle, the Sierpinski carpet, and the circular fractal pattern have the static mixer’s role in our simulations. We apply these structures just in zero, first and second iterations. Using the COMSOL software, these equations for “fractal mixing” were solved numerically. For this purpose, fractal structures act as a barrier, and one can handle different types of their corresponding simulations. In COMSOL software, after the execution, we verify the defining model. We may present speed, pressure, and concentration distributions before and after passing fluids through or out of the fractal structure. The parameter for analyzing the quality of fractal mixing is the Coefficient of Variation (CoV).
TL;DR: In this paper, three-dimensional high-fidelity numerical simulations of a Mach 5 hypersonic ramjet intake are performed combining a high-order and time-accurate large-eddy-simulation model with a sharp interface.
Abstract: Three-dimensional high-fidelity numerical simulations of a Mach 5 hypersonic ramjet intake are performed combining a high-order and time-accurate large-eddy-simulation model with a sharp-interface ...
TL;DR: It is demonstrated how ML models can be used to model the time‐varying characteristics of the proper orthogonal decomposition (POD) coefficients, and that the locally interpolating models such as regression trees and k‐nearest neighbors seem to be better for such models than other models like support vector regression or long‐short term memory networks.