Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session C16: CFD: Immersed Boundary Methods I |
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Chair: Peter Brady, LANL Room: 4c3 |
(Author Not Attending)
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C16.00001: An h-adaptive immersed boundary method for simulating fluid–structure interaction Pan Zhang Fluid-structure interaction (FSI) problems is encountered in many scientific and engineering applications. As an important calculation model in the field of computational fluid dynamics, immersed boundary method is commonly used to deal with FSI problems. And the method has a wide range of applications. However, for FSI of moving boundary problems for large-scale motion, the moving boundary problem of large-scale motion, the immersed boundary method on uniform grid or non-uniform grid has limitations. This work combines the flexibility of adaptive mesh refinement methods, specially for uniform Cartesian grids, and the immersed boundary method requirements for uniform Euler mesh. Based on the common characteristics of these two methods, the adaptive mesh refinement method is applied to the immersed boundary method and an adaptive immersed boundary method is presented to adapt to the calculation of the moving boundary problem of large-scale motion. [Preview Abstract] |
Sunday, November 24, 2019 8:13AM - 8:26AM |
C16.00002: Flow-Structure Interaction Simulation of Parachute using Immersed Boundary Method with Implicit Aerodynamical Load Hang Yu, Carlos Pantano, Fehmi Cirak A method of flow-structure interaction simulation of the thin structure is presented. The immersed boundary method is used to incorporate the dynamics of the fluid and thin structure. A Cartesian background grid is used for compressible flow simulation and the thin structure is represented by Lagrangian markers immersed in the fluid. Linear operators based on the delta function is used for the interpolation and spreading. The boundary condition is enforced with a singular force $f$ that is supported on the thin shell $S$ which serves as boundary representation. Analog to the projection method for incompressible flow, the singular force is regarded as a Lagrangian multiplier to enforce boundary condition. A splitting method is used. The singular force is calculated implicitly by solving a symmetric system, which scales as number of Lagrangian markers. Furthermore, with the interpolation operator acting on the momentum equation, the implicit singular force can be subsequently translated as the aerodynamical load for the thin shell. Therefore, separate calculation of pressure and viscosity load is no longer needed. Lagrangian markers are dynamically removed or added to prevent leakage, unphysical oscillation, or the implicit force equation being underdetermined. [Preview Abstract] |
Sunday, November 24, 2019 8:26AM - 8:39AM |
C16.00003: An Immersed Boundary Formulation for Fluid-Structure-Interaction in Multiphase Flows Elizabeth Gregorio, Akash Dhruv, Megan C. Leftwich, Elias Balaras Immersed boundary methods have been widely used to study single-phase flow problems involving complex geometries. However, the extension of existing techniques to multiphase flows is not trivial. When employing direct forcing schemes, the treatment of the level-set function near an immersed boundary is challenging and may result in non-physical mass gain or loss near the interface. In addition, most existing methods adopt a static contact line treatment, which is not suitable for many practical applications. In the present work, we propose a numerical formulation, which uses a moving least squared based forcing for the physical variables and a ghost-cell approach for the level-set function to satisfy a dynamic contact angle boundary condition at the immersed boundary. The method is well suited to model multiphase flow around moving immersed boundaries. A hydrodynamic stress model is also implemented to accurately compute the forces on the body from both the liquid and gas phases. We will establish that the proposed formulation does not introduce mass errors. Comparison with experimental and reference numerical simulations for falling droplets and entry-body problems will demonstrate accuracy and robustness. [Preview Abstract] |
Sunday, November 24, 2019 8:39AM - 8:52AM |
C16.00004: An immersed boundary method with mesh refinement for turbulent flow simulations Shao-Ching Huang The immersed boundary method has been one of the preferred approaches for direct numerical simulation of turbulence that involves irregular or moving boundaries in the computational domain. The method not only bypasses curvilinear or body-fitted mesh generation but also enables the possibility of using fast solvers in the solution procedure, such as FFT-based methods for Poisson equation, making the method highly efficient. However, the convenience of immersed boundary method can be plagued by lack of resolution in the regions where truncation error is large due to the nature of the underlying structured mesh; increasing the local resolution to resolve sharp gradients usually results in rapid growth of the required total computational resources. To address this problem and to enable large-scale computations on parallel computers, an immersed boundary method with mesh refinement capability is developed. A tree-based data structure, as opposed to a block-structured one, is considered to manage the mesh refinement. A number of selected flow cases are used to evaluate the method's accuracy and performance, and to compare to its Cartesian-mesh counterpart. [Preview Abstract] |
Sunday, November 24, 2019 8:52AM - 9:05AM |
C16.00005: An improved wall model based on immersed boundary method for large eddy simulation of turbulent flow over complex/moving boundaries Ming Ma, Wei-Xi Huang, Chun-Xiao Xu A hybrid immersed boundary/wall-model based large eddy simulation method is developed to simulate high Reynolds number turbulent flow with complex/moving boundaries. The no-slip boundary condition is imposed by continuous forcing of the immersed boundary (IB) method, so that the filter Navier-Stokes equations can be solved on a regular Cartesian grid. Wall shear on the boundary is obtained by solving thin boundary layer equation on an embedded mesh. Subgrid viscosity near the wall is modified to maintain the viscosity flux at the face adjacent to the wall equal to the modeled wall shear stress. Non-physical correlation caused by IB force oscillation is eliminated by applying viscosity buffer under the wall. This method has been validated by simulating turbulent channel and pipe flows at high Reynolds numbers, up to Re$_{\mathrm{\tau }}=$10$^{\mathrm{5}}$. Furthermore, flows past a circular cylinder at Re$_{\mathrm{D}}=$10$^{\mathrm{4}}$ and $1.4\times10$$^{\mathrm{5}}$ have also been simulated. The numerical results are shown to be in good agreements with previous numerical and experiment data. [Preview Abstract] |
Sunday, November 24, 2019 9:05AM - 9:18AM |
C16.00006: A Direct Forcing Immersed Boundary Method for Simulations of Heat and Mass Transport with Neumann Boundary Conditions Jacob Johnston, Jincheng Lou, Nils Tilton The application of Dirichlet boundary conditions with direct-forcing immersed boundaries is well understood. There is less published work, however, on the application of Neumann conditions, particularly to second-order spatial accuracy in the context of finite volume and projection methods. This issue is important for the simulation of membrane filtration systems in which coupled heat and solute transport occur in the presence of complicated surfaces. Though linear interpolation of the forcing over the grid is sufficient to ensure second-order accuracy of Dirichlet conditions, we find that third-order interpolation is required for the implementation Neumann conditions to second-order accuracy. For semi-implicit simulations, this increases the local stencil such that matrices are no longer banded. We use the method to develop a 2D unsteady finite volume code that simulates heat, mass and momentum transport with the projection method of Choi and Moin (Journal of Computational Physics, 1994). We perform numerical experiments to confirm second-order spatial and temporal accuracy, and then use the method to simulate transport in a membrane filtration system. [Preview Abstract] |
Sunday, November 24, 2019 9:18AM - 9:31AM |
C16.00007: A Parallel Dynamic Overset Grid Framework for Incompressible Flow Simulations Mohammadali Hedayat, Iman Borazjani The overset grid technique enables the flow solvers to handle unsteady moving grid simulations. However, the task of overset grid assembly in parallel for partitioned grid remains challenging. In this study, a new efficient parallel grid assembly and interpolation framework is developed to perform overset grid assembly for structured meshes in a distributed computing environment. This framework is integrated with a sharp interface curvilinear immersed boundary (CURVIB) flow solver to handle multiple overlapping flow domains. To achieve a good parallel performance several steps are implemented in our framework: 1) using oriented bounding boxes (OBB) instead of axis-aligned bounding boxes; 2) using a walking strategy for donor search; 3) directly integrating grid assembly to the flow solver; 4) efficient vectorized implementation for velocity interpolation; and 5) using a general non-inertial frame of reference flow solver to prevent the recomputation of curvilinear grid. The framework verified and validated against experimental and numerical benchmarks. Our results show a good scalability and accuracy for this new framework. In addition, its capabilities are demonstrated by simulating a school of aquatic swimmers in a diamond shape. [Preview Abstract] |
Sunday, November 24, 2019 9:31AM - 9:44AM |
C16.00008: High-Order Ghost-Point Method for Non-Conforming Boundaries Prakash Shrestha, Peter Brady, Vitaliy Gyrya, Daniel Livescu We investigate numerical properties of constrained moving least squares method for numerical implementation of solid boundary conditions (CMLS, an immersed boundary method) by Qu, Shi and Batra (2018) coupled with central finite differences for interior derivatives. This study represents an extension of the original method, which uses first order interpolation / extrapolation for the ghost and image points, as well as dissipative interior discretization. The objectives of the investigation are to determine the suitability of the method for direct numerical simulations of turbulent flows in complex geometries and to find an optimal set of built-in parameters in terms of achieving high order of accuracy and stability of the method for a wide range of canonical test problems. The test problems include a 1-D linear scalar wave equation, for which rigorous stability and conservation properties can be discussed, and 2-D nonlinear tests using Burgers' equation and the compressible Euler equations with manufactured solutions. Preliminary data indicate that the method can achieve good stability and accuracy properties. [Preview Abstract] |
Sunday, November 24, 2019 9:44AM - 9:57AM |
C16.00009: A single-sided direct-forcing diffused immersed boundary method for correct local velocity gradient computation Cheng Peng, Lian-Ping Wang Current algorithms of the immersed boundary method (IBM) based on diffused interfaces are not able to correctly calculate the velocity gradients within the diffused solid-fluid interfaces. This is because the non-zero boundary forcing creates a difference in the actual momentum equation solved in IBM from the physical one described by the Navier-Stokes equations with a sharp fluid-solid no-slip interface. A single-sided direct-forcing IBM algorithm is proposed to remove the boundary forcing from the fluid region. The capability of the proposed algorithm in correctly computing velocity gradients within all fluid region is validated in both laminar and turbulent flows. A technique to speed up the convergence of no-slip enforcement via force iteration is also introduced. This technique works for the proposed algorithm and other IBM algorithms. [Preview Abstract] |
Sunday, November 24, 2019 9:57AM - 10:10AM |
C16.00010: An Immersed Boundary Method Coupled with a Level Set and Dynamic Overlapping Grids Approaches for Free Surface and Moving Bodies Problems Riccardo Broglia, Antonio Posa, Danilo Durante An immersed-boundary (IB) approach was developed within an existing level-set/dynamic overlapping-grids finite-volume solver. An IB strategy is utilized together with curvilinear grids capabilities, keeping cells count under control, a main disadvantage for the classical IB methods using Cartesian grids. Moreover, the IB is identified by an additional level-set function, i.e., a distance function defined at each node of the computational grid, whose zero level represents the fluid/solid interface. One of the main advantages of the proposed approach is the coupling with a dynamic overlapping-grids methodology and a single-phase level-set approach. The former is especially convenient in presence of moving bodies: updating the position of the Lagrangian grid, which discretizes the surface of the body, relative to the Eulerian grid, is not required, since the Eulerian grid attached to a moving IB can follow the body during its motion. The latter is efficiently adopted to handle the presence of an air/water interface. Here the methodology is discussed in detail. Test cases feature stationary and moving bodies as well as complex geometries and free-surface flows. Results from present IB computations are compared with body-fitted solutions and data from literature. [Preview Abstract] |
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