Quantifying and Modeling the Force Variation Within Random Arrays of Spheres

2016 ◽  
Author(s):  
G. Akiki ◽  
T. L. Jackson ◽  
S. Balachandar
Keyword(s):  
Lateral Force ◽  
Point Particle ◽  
Immersed Boundary ◽  
Immersed Boundary Methods ◽  
Lateral Forces ◽  
Random Arrays ◽  
Force Variation ◽  
Drag Models ◽  
Boundary Methods ◽  
Arrays Of Spheres

In this study, we perform fully-resolved direct numerical simulations (DNS) of a flow past random arrays of spheres using immersed boundary methods (IBM). These simulations are used to quantify the error arising from point-particle (PP) force models which assumes equal drag and zero lateral forces on all particles. The results show that the rms drag and lateral force fluctuation can be as high as 26% and 15% of the mean drag value, respectively. For each sphere, the hydrodynamic forces are shown to be dependent on the exact location of few neighboring spheres. A pairwise interaction extended point-particle (PIEP) model is then presented. The model can approximate the drag and lateral forces on each sphere by systematically accounting for the location of few of its neighbors. The perturbation from each neighbor is considered separately then linearly superposed to obtain the total variation of the drag and lateral force. Significant error reduction is observed when using PIEP model instead of mean drag models upon comparing to exact forces acquired from the DNS IBM simulations.

Microstructure simulation of early paper forming using immersed boundary methods

TAPPI Journal ◽  
2011 ◽  
Vol 11 (11) ◽  
pp. 23-30 ◽  
Author(s):  
ANDREAS MARK ◽  
ERIK SVENNING ◽  
ROBERT RUNDQVIST ◽  
FREDRIK EDELVIK ◽  
ERIK GLATT ◽  
...  
Keyword(s):  
Early Paper ◽  
Contact Model ◽  
Fiber Suspension ◽  
Beam Equation ◽  
Immersed Boundary ◽  
Paper Machine ◽  
Immersed Boundary Methods ◽  
Element Discretization ◽  
Microstructure Simulation ◽  
Boundary Methods

Paper forming is the first step in the paper machine where a fiber suspension leaves the headbox and flows through a forming fabric. Complex physical phenomena occur as the paper forms, during which fibers, fillers, fines, and chemicals added to the suspension interact. Understanding this process is important for the development of improved paper products because the configuration of the fibers during this step greatly influences the final paper quality. Because the effective paper properties depend on the microstructure of the fiber web, a continuum model is inadequate to explain the process and the properties of each fiber need to be accounted for in simulations. This study describes a new framework for microstructure simulation of early paper forming. The simulation framework includes a Navier-Stokes solver and immersed boundary methods to resolve the flow around the fibers. The fibers were modeled with a finite element discretization of the Euler-Bernoulli beam equation in a co-rotational formulation. The contact model is based on a penalty method and includes friction and elastic and inelastic collisions. We validated the fiber model and the contact model against demanding test cases from the literature, with excellent results. The fluid-structure interaction in the model was examined by simulating an elastic beam oscillating in a cross flow. We also simulated early paper formation to demonstrate the potential of the proposed framework.

Volume preserving immersed boundary methods for two-phase fluid flows

2011 ◽  
Vol 69 (4) ◽  
pp. 842-858 ◽  
Author(s):  
Yibao Li ◽  
Eunok Jung ◽  
Wanho Lee ◽  
Hyun Geun Lee ◽  
Junseok Kim
Keyword(s):  
Fluid Flows ◽  
Immersed Boundary ◽  
Immersed Boundary Methods ◽  
Two Phase ◽  
Boundary Methods ◽  
Phase Fluid ◽  
Volume Preserving

Hybrid immersed interface-immersed boundary methods for AC dielectrophoresis

2014 ◽  
Vol 270 ◽  
pp. 640-659 ◽  
Author(s):  
Mohammad Robiul Hossan ◽  
Robert Dillon ◽  
Prashanta Dutta
Keyword(s):  
Immersed Boundary ◽  
Immersed Boundary Methods ◽  
Immersed Interface ◽  
Boundary Methods

Interfacial Interactions

2010 ◽  
pp. 128-177
Author(s):  
Wei Ge ◽  
Ning Yang ◽  
Wei Wang ◽  
Jinghai Li
Keyword(s):  
Temporal Distribution ◽  
Gravitational Potential Energy ◽  
Immersed Boundary ◽  
Immersed Boundary Methods ◽  
Additional Information ◽  
Mesoscale Structures ◽  
Computational Fluid Dynamics Cfd ◽  
Spatio Temporal ◽  
Drag Models ◽  
The Stability

The drag interaction between gas and solids not only acts as a driving force for solids in gas-solids flows but also plays as a major role in the dissipation of the energy due to drag losses. This leads to enormous complexities as these drag terms are highly non-linear and multiscale in nature because of the variations in solids spatio-temporal distribution. This chapter provides an overview of this important aspect of the hydrodynamic interactions between the gas and solids and the role of spatio-temporal heterogeneities on the quantification of this drag force. In particular, a model is presented which introduces a mesoscale description into two-fluid models for gas-solids flows. This description is formulated in terms of the stability of gas-solids suspension. The stability condition is, in turn, posed as a minimization problem where the competing factors are the energy consumption required to suspend and transport the solids and their gravitational potential energy. However, the lack of scale-separation leads to many uncertainties in quantifying mesoscale structures. The authors have incorporated this model into computational fluid dynamics (CFD) simulations which have shown improvements over traditional drag models. Fully resolved simulations, such as those mentioned in this chapter and the subject of a later chapter on Immersed Boundary Methods, can be used to obtain additional information about these mesoscale structures. This can be used to formulate better constitutive equations for continuum models.

scholarly journals A Numerical Scheme Based on an Immersed Boundary Method for Compressible Turbulent Flows with Shocks: Application to Two-Dimensional Flows around Cylinders

2014 ◽  
Vol 2014 ◽  
pp. 1-21 ◽  
Author(s):  
Shun Takahashi ◽  
Taku Nonomura ◽  
Kota Fukuda
Keyword(s):  
Turbulent Flows ◽  
Aerodynamic Force ◽  
Flow Region ◽  
Immersed Boundary ◽  
Immersed Boundary Methods ◽  
Two Dimensional ◽  
Symmetric Form ◽  
Present Scheme ◽  
Shock Region ◽  
Boundary Methods

A computational code adopting immersed boundary methods for compressible gas-particle multiphase turbulent flows is developed and validated through two-dimensional numerical experiments. The turbulent flow region is modeled by a second-order pseudo skew-symmetric form with minimum dissipation, while the monotone upstream-centered scheme for conservation laws (MUSCL) scheme is employed in the shock region. The present scheme is applied to the flow around a two-dimensional cylinder under various freestream Mach numbers. Compared with the original MUSCL scheme, the minimum dissipation enabled by the pseudo skew-symmetric form significantly improves the resolution of the vortex generated in the wake while retaining the shock capturing ability. In addition, the resulting aerodynamic force is significantly improved. Also, the present scheme is successfully applied to moving two-cylinder problems.

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