Analysis Of Incompressible Flow Research Articles

A novel stabilized nodal integration formulation using particle finite element method for incompressible flow analysis

AbstractIn simulations using the particle finite element method (PFEM) with node‐based strain smoothing technique (NS‐PFEM) to simulate the incompressible flow, spatial and temporal instabilities have been identified as crucial problems. Accordingly, this study presents a stabilized NS‐PFEM‐FIC formulation to simulate an incompressible fluid with free‐surface flow. In the proposed approach, (1) stabilization is achieved by implementing the gradient strain field in place of the constant strain field over the smoothing domains, handling spatial and temporal instabilities in direct nodal integration; (2) the finite increment calculus (FIC) stabilization terms are added using nodal integration, and a three‐step fractional step method is adopted to update pressures and velocities; and (3) a novel slip boundary with the predictor–corrector algorithm is developed to deal with the interaction between the free‐surface flow with rigid walls, avoiding the pressure concentration induced by standard no‐slip condition. The proposed stabilized NS‐PFEM‐FIC is validated via several classical numerical cases (hydrostatic test, water jet impinging, water dam break, and water dam break on a rigid obstacle). Comparisons of all simulations to the experimental results and other numerical solutions reveal good agreement, demonstrating the strong ability of the proposed stabilized NS‐PFEM‐FIC to solve incompressible free‐surface flow with high accuracy and promising application prospects.

Experimental and Numerical Analysis of Incompressible Flow over an Iced Airfoil

Determining the aerodynamic characteristics of iced airfoil is an important step in aircraft design. The goal of this work is to study experimentally and numerically an iced airfoil to assess the aerodynamic penalties associated with presence of ice on the airfoil surface. Three iced shapes were tested on NACA 0012 straight wing at zero and non-zero angles of attack, at Reynolds No. equal to (3.36*105). The 2-D steady state continuity and momentum equations have been solved utilizing finite volume method to analyze the turbulent flow over a clean and iced airfoil. The results show that the ice shapes affected the aerodynamic characteristics due to the change in airfoil shape. The experimental results show that the horn iced airfoil consumes more power than the other shapes of ice, its value was (44.4W). The horn iced shape has the worst effect on the airfoil than the other shapes. The present results are compared with previously reported results; it is found there is a very good agreement between them. A comparison between the experimental and computational results of the presented work were pursing the same behavior.

Evaluation of wing performance for NACA 4415 using subparametric finite element transforms

The goal of the current research is to improve the lift performance of an aerodynamic device for commercial application by performing accurate aerodynamic computations and flow analyses of NACA 4-digit airfoil designs. An enhanced aerodynamic characteristic, which has been estimated effectively by interpreting the impacts of Reynolds numbers at various angles of attack, is crucial for a cost-effective airfoil shape. Numerous Reynolds numbers have been used in the analysis of these aerodynamic properties. Investigations were carried out using subparametric finite elements and a unique approach for higher order triangular element meshing in relation to the NACA 4415 airfoil design. This approach provides precise boundary node information for the airfoil design, resulting in improved calculations of the lift coefficient, drag coefficient, and lift-to-drag ratio. Moreover, it effectively addresses the challenges faced in aerospace research pertaining to flow analysis, thereby reducing the complexities involved. The evaluationof the airfoil shape and analysis for incompressible flow over the NACA 4415 airfoil design could improve the overall effectiveness of the aerodynamic vehicle. Any vehicle's aerodynamic surface must go through a number of tests before being launched. Modern technology can be incorporated into the design process to reduce the high costs associated with these testing processes. The current flow analysis and aerodynamic investigations exhibit a high degree of accuracy, and the use of HO elements lowers the expense of the experiment.

Case studies on simulations of flow-induced vibrations of a cooled circular cylinder: Incompressible flow solver for moving mesh problem

The paper presents an in-house code developed for simulating incompressible flow involving moving boundaries. The solver is based on Arbitrarily Lagrangian-Eulerian formulation with Harten Lax and van Leer with Contact for artificial compressibility (ALE-HLLC-AC) method. In the finite volume formulation, the moving boundary problem is taken care of by the arbitrarily Lagrangian-Eulerian formulation, where radial basis function-based interpolation is employed to move the meshes. The Harten Lax and van Leer with -Contact scheme developed to evaluate the convective fluxes in artificial compressibility formulation. High order accuracy is achieved over an unstructured data structure by developing solution-dependent weighted least squares-based gradient calculations. Flow-induced vibrations caused due to the cyclic lift forces over a cooled circular cylinder are simulated and compared with available literature results. For flow-induced vibration of circular cylinder: fluid-structure interaction problem, the elastically mounted cylinder wall temperature is maintained lower than the flowing fluid. The cylinder vibrates transverse to the direction of fluid flow, and its oscillating movement is simulated using a numerical mass-spring-damper system. Both heat transfer scenarios, i.e., without gravity and gravity acting against the flow direction, are simulated. The unsteady, laminar, incompressible flow analysis is carried out at Richardson number (−1, 0) for the cooled circular cylinder with various reduced velocities Ur (3–20). Prandtl number and Reynolds number are Pr = 7.1 and Re = 150, with the fixed mass ratio of 2 and zero damping coefficient. The validation of the results is presented in the literature. It has been noticed that the thermal boundary layer affects the fluid characteristics. The vibration of the cylinder reached the highest amplitude of cylinder dimension, more dominantly in the range of reduced velocities (4–15), showing a galloping kind of flow nature.

Flow Visualization of Golf Ball in Subsonic Incompressible Flow Regime

Golf ball ideal plan has been considered for over a century. Generally, golf balls move at long-distance and high speed. Dimples golf ball have a fundamental impact by streamlined flow properties and also the flight heading. Streamlined highlights the golf ball where it was still incomplete in the appearance of an essential interior information. In the present paper we designed a golf ball and subsonic in-compressible flow analysis is conducted at a speed of 210 m/s, Now, the golf ball drag coefficient is changed because of change in geometry(dimple). In this paper, the results specify depth ratio of dimple increasing or golf ball roughness of surface can move the change to a lesser Reynold’s number and drag coefficient valve regime increases and also it gives an optimistic linear process between relative roughness and drag coefficient.

Reduced conservation error of kinetic energy using a Runge-Kutta algorithm with reduced numerical dissipation

This paper describes an approach that reduces the error in the conservation law of velocity fluctuation intensities and turbulent kinetic energy resulting from a numerical analysis of incompressible flow. The optimized fourth-order Runge-Kutta method used to analyze acoustic problems in previous studies was used here to reduce the numerical dissipation. In order to strictly validate the conservation law of velocity fluctuation intensities and turbulent kinetic energy, the authors used a periodic box filled with an inviscid flow, where velocity fluctuation intensities and turbulent kinetic energy could be analytically held. By using the optimized Runge-Kutta method, the numerical dissipation, which is the error in conservation laws, is of the order of 1/100. The reduction in the numerical dissipation shown in this study increased with an increasing time increment. To investigate the effect of numerical dissipation, higher-order statistics of turbulent kinetic energy were calculated. This study also derived a simple mathematical form to estimate the conservation error of higher-order statistics for turbulent kinetic energy.

A residual-based stabilized finite element formulation for incompressible flow problems in the Arlequin framework

Many fluid flow problems involve localized effects within a larger flow domain, with boundary layers close to solid boundaries being one of the most common. Accurate and realistic computational analysis of such problems requires that the local flow behavior be properly represented by a numerical formulation with affordable computational cost. Among several strategies developed in the computational mechanics to deal with multiscale phenomena, the Arlequin method proposes overlapping a local discretization to a global one, in the neighborhood of localized effects, and gluing both models in an appropriate subzone of the overlap by means of Lagrange multipliers method, being successful in the solid mechanics context, but less explored in CFD analysis. To improve stability and conditioning of the algebraic system of equations and, at the same time ensure more flexibility, we propose a novel residual-based stabilized Arlequin formulation. Following, the proposed formulation is applied to the numerical analysis of incompressible flows. The resulting formulation is tested with selected numerical examples, considering structured and unstructured, coincident and non-coincident finite element discretization, Stokes problems and convection dominated Navier–Stokes problems, steady and transient cases, showing the methodology precision, robustness and flexibility.

Gyrotactic Microorganism Effects on Mixed Convective Nanofluid Flow Past a Vertical Cylinder

The transient mixed convection boundary layer analysis of incompressible flow over an isothermal vertical cylinder is embedded in a saturated porous medium in the vicinity for Gyrotactic microorganism effects. The mathematical model used for the bioconvective nanofluid incorporates the effects of Brownian motion, thermophoresis, and gyrotactic microorganisms. Moreover, the resulting governing nonsimilarity equations are changed into partial differential equations and solved numerically. The results are explained graphically for various physical parameters. It is determined that bioconvection parameter boosts the heat transfer rates and the thickness of the motile microorganism reduces the mass transfer rates. Expanding bioconvection Lewis number leads to decrease in heat transfer rates and the density of the motile microorganism, whereas the mass transfer rates decelerate the flow field. The investigation is pertinent to the nanobiopolymer manufacturing processes.

LES Analysis for Incompressible Flow of Internal Flow in a Box Fan and Computational Aeroacoustics of Radiated Sound from It

LES Analysis for Incompressible Flow of Internal Flow in a Box Fan and Computational Aeroacoustics of Radiated Sound from It

A reduced order model based on Kalman filtering for sequential data assimilation of turbulent flows

A Kalman filter based sequential estimator is presented in this work. The estimator is integrated in the structure of segregated solvers for the analysis of incompressible flows. This technique provides an augmented flow state integrating available observation in the CFD model, naturally preserving a zero-divergence condition for the velocity field. Because of the prohibitive costs associated with a complete Kalman Filter application, two model reduction strategies have been proposed and assessed. These strategies dramatically reduce the increase in computational costs of the model, which can be quantified in an augmentation of 10%–15% with respect to the classical numerical simulation. In addition, an extended analysis of the behavior of the numerical model covariance Q has been performed. Optimized values are strongly linked to the truncation error of the discretization procedure. The estimator has been applied to the analysis of a number of test cases exhibiting increasing complexity, including turbulent flow configurations. The results show that the augmented flow successfully improves the prediction of the physical quantities investigated, even when the observation is provided in a limited region of the physical domain. In addition, the present work suggests that these Data Assimilation techniques, which are at an embryonic stage of development in CFD, may have the potential to be pushed even further using the augmented prediction as a powerful tool for the optimization of the free parameters in the numerical simulation.

The linearized pressure Poisson equation for global instability analysis of incompressible flows

The linearized pressure Poisson equation (LPPE) is used in two and three spatial dimensions in the respective matrix-forming solution of the BiGlobal and TriGlobal eigenvalue problem in primitive variables on collocated grids. It provides a disturbance pressure boundary condition which is compatible with the recovery of perturbation velocity components that satisfy exactly the linearized continuity equation. The LPPE is employed to analyze instability in wall-bounded flows and in the prototype open Blasius boundary layer flow. In the closed flows, excellent agreement is shown between results of the LPPE and those of global linear instability analyses based on the time-stepping nektar++, Semtex and nek5000 codes, as well as with those obtained from the FreeFEM++ matrix-forming code. In the flat plate boundary layer, solutions extracted from the two-dimensional LPPE eigenvector at constant streamwise locations are found to be in very good agreement with profiles delivered by the NOLOT/PSE space marching code. Benchmark eigenvalue data are provided in all flows analyzed. The performance of the LPPE is seen to be superior to that of the commonly used pressure compatibility (PC) boundary condition: at any given resolution, the discrete part of the LPPE eigenspectrum contains converged and not converged, but physically correct, eigenvalues. By contrast, the PC boundary closure delivers some of the LPPE eigenvalues and, in addition, physically wrong eigenmodes. It is concluded that the LPPE should be used in place of the PC pressure boundary closure, when BiGlobal or TriGlobal eigenvalue problems are solved in primitive variables by the matrix-forming approach on collocated grids.

Efficient iterative algorithms for linear stability analysis of incompressible flows

Efficient iterative algorithms for linear stability analysis of incompressible flows

Least squares moving particle semi-implicit method

In this paper, a consistent meshfree Lagrangian approach for numerical analysis of incompressible flow with free surfaces, named least squares moving particle semi-implicit (LSMPS) method, is developed. The present methodology includes arbitrary high-order accurate meshfree spatial discretization schemes, consistent time integration schemes, and generalized treatment of boundary conditions. LSMPS method can resolve the existing major issues of widely used strong-form particle method for incompressible flow—particularly, the lack of consistency condition for spatial discretization schemes, difficulty in enforcing consistent Neumann boundary conditions, and serious instability like unphysical pressure oscillation. Applications of the present proposal demonstrate remarkable enhancements of stability and accuracy.

An explicit finite volume element method for solving characteristic level set equation on triangular grids

Level set methods are widely used for predicting evolutions of complex free surface topologies, such as the crystal and crack growth, bubbles and droplets deformation, spilling and breaking waves, and two-phase flow phenomena. This paper presents a characteristic level set equation which is derived from the two-dimensional level set equation by using the characteristic-based scheme. An explicit finite volume element method is developed to discretize the equation on triangular grids. Several examples are presented to demonstrate the performance of the proposed method for calculating interface evolutions in time. The proposed level set method is also coupled with the Navier-Stokes equations for two-phase immiscible incompressible flow analysis with surface tension. The Rayleigh-Taylor instability problem is used to test and evaluate the effectiveness of the proposed scheme.

LES Analysis of Incompressible Flows around an Automobile in Motion Using ALE Method (4th Report, Unsteady Aerodynamic Analysis around a Simplified Car Model in Pitch Motion)

In order to clarify the relations between vehicle motions and flow fields, LES (Large Eddy Simulation) is conducted for flows around a simplified car model in pitch motions, where an improved discretization scheme in the ALE (Arbitrary Lagrangian-Eulerian) coordinates is employed. The analysis model is the Ahmed model with a rear slant angle of 12.5 degrees. It is forced to oscillate sinusoidally with forcing amplitudes of 0.88 and 3 degrees at two different frequencies of 4 and 8 Hz. The fluctuations of the lift coefficient (CZ) are phase-lead to the pitch angle (Δθ), while those of the pitching moment coefficient (CMY) are phase-lag to Δθ. Especially in the cases of the larger amplitude of 3 degrees, the Lissajous curves of CMY form characteristic teardrop shapes. In addition to the three aerodynamic effects observed in the heave motion, such as flow contraction, relative change of inflow angle, and fluid added mass effect, pressure on the upper and under surfaces of the model fluctuates due to the change of incident angle. It is also revealed that the streamwise vortices which induce flow from the underside to the lateral side, are formed close to the side surfaces of the model when the model is in the pitch-up position. These vortices are closely related to the aforementioned teardrop-shaped Lissajous curves of CMY.

Wavelets with differential relation

Divergence-free wavelets are successfully applied to numerical solutions of Navier-Stokes equation and to analysis of incompressible flows. They closely depend on a pair of one-dimensional wavelets with some differential relations. In this paper, we point out some restrictions of those wavelets and study scaling functions with the differential relation; Wavelets and their duals are discussed; In addition to the differential relation, we are particularly interested in a class of examples with the interpolatory property; It turns out there is a connection between our examples and Micchelli’s work.

A partitioned model for fluid–structure interaction problems using hexahedral finite elements with one‐point quadrature

AbstractA partitioned numerical model for fluid–structure interaction analysis of incompressible flows and structures with geometrically non‐linear behavior is presented in this work. The flow analysis is performed considering the well‐known Navier–Stokes equations for Newtonian fluids and the continuity equation, obtained from the pseudo‐compressibility hypothesis. An explicit two‐step Taylor‐Galerkin scheme is employed in the time discretization procedure of the system of governing equations, which is expressed in terms of an arbitrary Lagrangean‐Eulerian description. The structural subsystem is analyzed using a geometrically non‐linear elastic model and the respective equation of motion is discretized in the time domain employing the Generalized‐α scheme. Fluid–structure coupling is taken into account regarding a new energy‐conserving partitioned scheme with non‐linear effects, which is accomplished by enforcing equilibrium and kinematical compatibility conditions at the solid–fluid interface. Non‐matching meshes and subcycling are also considered in the present model. The finite element method is employed for spatial discretizations using eight‐node hexahedral elements with one‐point integration in both fields. Some numerical examples are simulated in order to demonstrate the applicability of the proposed formulation. Copyright © 2009 John Wiley & Sons, Ltd.

INFLUENCE OF THE INLET SHAPE ON THE PERFORMANCE OF DOUBLE OFFSET TRANSITION S-DUCT WITH DIFFUSION

Transition S-shaped intake duct is a crucial component of dual engine used in modern combat aircrafts. Present flow investigation demonstrates the flow behavior of double offset transition S-duct for different inlet geometries having circular exit (ϕ = 72.5 mm) and uniform roughness. The inlet geometries namely rectangular, square, elliptical, oval, and semicircular have been analyzed for double offset transition S-duct having 300 mm centerline length and an area ratio of 2.0. Incompressible flow analysis carried out for free stream velocity at 30 m/s with RNG k–ε turbulence model has shown that the elliptical inlet shape gives the best performance whereas square inlet gives the worst performance in terms of longitudinal and cross-flow velocity distribution, pressure recovery, total pressure loss, distortion coefficient, and swirl coefficient at the exit of the duct.

Numerical Analysis of Incompressible Flows by the Lattice Boltzmann Method

A lattice Boltzmann method for one-phase incompressible flows is proposed. The conventional lattice Boltzmann equation leads to the compressible Navier-Stokes equations through the Chapman-Enskog expansion. The compressible error is eliminated by applying the Fractional Step method to the conventional LB method. Two particle velocity distribution functions are used in this method : one calculates the momentum, and the other does the pressure in numerical computations. This method is able to compute the fluid flows as the density is constant, that is, the sound velocity is infinity. This method is validated by simulations of the Taylor vortex flow, of the Poiseuille flow, and of the cavity flow. The proposed model eliminates the pressure oscillation observed in the simulations of the Taylor vortex flow. The simulations show that the both errors of the continuity equation and of the fluid velocity reduce to about one-tenth. The numerical results of the proposed model are more accurate than those of the conventional LB method.

Combined adaptive meshing technique and characteristic-based split algorithm for viscous incompressible flow analysis

A combined characteristic-based split algorithm and an adaptive meshing technique for analyzing two-dimensional viscous incompressible flow are presented. The method uses the three-node triangular element with equal-order interpolation functions for all variables of the velocity components and pressure. The main advantage of the combined method is that it improves the solution accuracy by coupling an error estimation procedure to an adaptive meshing technique that generates small elements in regions with a large change in solution gradients, and at the same time, larger elements in the other regions. The performance of the combined procedure is evaluated by analyzing one test case of the flow past a cylinder, for their transient and steady-state flow behaviors.