Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session X16: CFD: IBM |
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Chair: Bryan Lewis, Brigham Young University - Idaho Room: 155 F |
Tuesday, November 26, 2024 8:00AM - 8:13AM |
X16.00001: A systematic computational study of debris cluster impact on the performance of utility-scale marine hydrokinetic turbines under mobile bed conditions Mustafa M Aksen, Hossein Seyedzadeh, Mehrshad Anjiraki, Jonathan Craig, Kevin Flora, Christian Santoni, Fotis Sotiropoulos, Ali Khosronejad Tidal and riverine flows offer reliable sources for energy production. Still, the installation and operation of marine hydrokinetic (MHK) turbines might alter sediment transport processes, and interactions with debris could negatively affect flow as well as turbine performance. Therefore, assessing the potential impact of debris accumulation on turbine performance and sediment transport is crucial. This study couples large-eddy simulations with a bed morphodynamics model to study the performance of a utility-scale horizontal-axis MHK turbine with various debris clusters over the upstream face of the turbine tower. The geometry of turbine components, waterway, sand waves, and woody debris are modeled directly using the immersed boundary method. Our findings demonstrate the effect of debris accumulation and sediment dynamics on the wake recovery and turbine performance. |
Tuesday, November 26, 2024 8:13AM - 8:26AM |
X16.00002: Improving the conditioning of the immersed boundary projection method Diederik Beckers, Srikumar Balasubramanian, Andres Goza, H. Jane Bae The immersed boundary projection method (IBPM) is a continuous forcing variant of the immersed boundary method, used to model flow over arbitrary surfaces that do not conform to the underlying computational fluid grid. This method offers several advantages, such as the ability to use fast solvers and avoid the need for re-meshing. However, the IBPM is generally limited by its first-order spatial accuracy, the presence of numerical noise in the surface forcing, and the computational expense associated with non-stationary surfaces. This work aims to address the issue of ill-conditioning of IBPM's formulation, which causes the noise in the surface forcing. We introduce higher-order Taylor expansion terms within the support of the smooth delta functions used in the governing and constraint equations. This modification allows the unknown surface forcing to be incorporated into the constraint equation, transforming the governing equation for the forcing from an ill-posed Fredholm equation of the first kind into a well-posed Fredholm equation of the second kind. This approach not only improves the conditioning of the system but also increases the accuracy of the method in one-dimensional cases from first to second order, with ongoing investigations into its efficacy in higher dimensions. We demonstrate the effectiveness of our approach through its application to Dirichlet Poisson problems and discuss its extension to the incompressible Navier-Stokes equations. |
Tuesday, November 26, 2024 8:26AM - 8:39AM |
X16.00003: High Reynolds number immersed boundary method for turbulent flows Shang-Gui Cai In this talk, we focus on the immersed boundary method with the application to high Reynolds number wall-bounded turbulent flows. The immersed boundary method is a great tool to simulate flows over complex geometries on simple Cartesian grid. But the isotropic grid refinement of the Cartesian grid limits its use at high Reynolds number, due to the unaffordable grid numbers to resolve the very thin turbulence boundary layer. The coupling of turbulence wall models and immersed boundaries is a very promising path to overwhelm the grid limitation. However, spurious oscillations have been frequently observed with respect to the wall surface quantities, especially for the surface pressure and the skin friction. These unphysical oscillations have a significant impact on the estimation of drag and lift forces. Therefore, we will present new near wall treatments for reducing these spurious oscillations. Additionally, developments on the explicit wall models and the dynamic hybrid RANS-LES technologies constrained by the Reynolds stress will be presented along with the immersed boundary technique. A wide range of benchmark flows are performed to validate the proposed models and discussions will be finally given. |
Tuesday, November 26, 2024 8:39AM - 8:52AM |
X16.00004: A high order sharp immersed method for the simulation of moving bodies interacting with fluid flows Xinjie Ji, Wim M. van Rees We demonstrate a third order accurate algorithm for solving the incompressible Navier-Stokes equations with moving immersed boundaries. Our approach relies on high-order finite-difference operators applied on a collocated grid, where the immersed geometries are taken into account using a sharp immersed method. This method has been shown to achieve high-order accuracy in space and time for moving immersed bodies. To handle the full Navier-Stokes equations, we present a pressure projection approach that retains high-order convergence of pressure and velocity in the infinity norm. Using an implementation of the algorithm in a 2D Julia code, we show convergence results, solutions to benchmark problems, and performance comparisons with our existing vorticity-velocity flow solver. In addition, we show preliminary results of the algorithm implemented in our in-house HPC solver 'murphy' to generate high-order results of 3D flows with embedded geometries. |
Tuesday, November 26, 2024 8:52AM - 9:05AM |
X16.00005: Simulation of multiple propellers using a GPU-optimized overset grid-based Immersed Boundary method. Debajyoti Kumar, Somnath Roy Overset grid-based Immersed Boundary methods effectively concentrate finer mesh near the body while keeping a coarse background mesh. This reduces the total grid required for achieving |
Tuesday, November 26, 2024 9:05AM - 9:18AM |
X16.00006: Boundary conditions for reaction-diffusion systems in an Immersed Boundary framework Owen Lewis, Robert D Guy, Brittany Jae Leathers The Immersed Boundary Method (IBM) is widely used in the simulation of systems involving fluid-structure interaction. The ability to simulate problems involving complex geometry using a simple, Eulerian grid has led to the use of the IBM for the study of many biomechanical and biophysical systems. However, the study of chemical systems often necessitates the ability to impose Neumann or Robin boundary conditions at irregular locations on the Eulerian grid. Here, we present a method for imposing Neumann and Robin boundary conditions within an IBM framework. The method requires solving a larger, augmented linear system. However, this sytem is well-conditioned and can be solved with a small number of iterations of a standard Kylov method without preconditioning. We also present applications and limitations of our methodology. |
Tuesday, November 26, 2024 9:18AM - 9:31AM |
X16.00007: Mass conservation limitations in overset CFD with unsteady moving grids Bryan Lewis, Robert F Kunz Overset grid techniques (also known as Chimera grids, composite grids, or overlapping grids) were introduced in 1966. Overset methods were originally applied to compressible flow simulations for multi-body external aerodynamics. In the early 2010's, overset methods were extended to incompressible underwater and naval surface ship simulations. The use of moving overset grids in incompressible flow simulations poses a unique challenge--how to account for the instantaneous mass conservation imbalance when the grid volume changes. If the body mesh moves by a small amount, relative to the size of the overlapping grid cells, then the fringe-donor interpolation stencils can simply be updated based on the new cell positions. However, if the mesh motion requires current hole cells to be reactivated, or new hole cells removed from the simulation, the total fluid volume contained within all active grid cells changes instantaneously. In an incompressible flow simulations, the instantaneous volume change results in a significant pressure oscillation, due to the pressure-mass coupling inherent in PSIO or SIMPLE based algorithms. To further complicate the issue, reducing the simulation time-step actually increases the amplitude of these pressure oscillations. This presentation will explore this time-step phenomina and show some recent work attempting to overcome this limitation. |
Tuesday, November 26, 2024 9:31AM - 9:44AM |
X16.00008: Numerical Simulations of Stably Stratified Flows around Complex Terrain using the Immersed Boundary Method Ting-Hsuan Ma, Inanc Senocak The Immersed Boundary (IB) method, integrated with the large-eddy simulation technique, has been developed further to model neutrally stratified atmospheric flows over complex terrains. This advancement involves a logarithmic IB reconstruction scheme that accounts for surface parameterization of momentum flux and enhances the subgrid-scale viscosity using a Reynolds-averaged Navier-Stokes (RANS)-based eddy viscosity model. Extending this approach to stably stratified atmospheric flows, however, presents challenges due to the need for simultaneous representation of both momentum and temperature fields using the IB method. In this study, we introduce an IB reconstruction scheme based on an extended version of the Monin-Obukhov Similarity Theory (MOST) and propose a stability-dependent correction to the eddy viscosity model, particularly near the surface. We validate our model against direct numerical simulations of stably stratified flows over both a periodic hill and flat terrain. |
Tuesday, November 26, 2024 9:44AM - 9:57AM |
X16.00009: Hybrid Immersed Boundary-Lattice Boltzmann Method for Compressible Flows Vigneshwaran Rajendran, Jingtao Ma, Li Wang, Sridhar Ravi, John Young, Fangbao Tian This talk presents a numerical method for simulating compressible flows using a penalty immersed-boundary method (IBM) coupled with the lattice Boltzmann method (LBM). The LBM has become a popular alternative to conventional numerical methods due to its ease of implementation and lower computational cost. Because of its intrinsic parallel nature, it stands at the forefront of solving many industrial problems when coupled with IBM. However, traditional LBM struggles with high-speed flows due to the inability of standard lattice models to recover the compressible Navier-Stokes equations. In this study, we developed a hybrid compressible LBM approach, using LBM for the mass and momentum equations and the finite difference method (FDM) for the energy equation, alongside an iterative IBM. To guarantee accuracy and stability, a 4th-order hybrid recursive regularized collision model has been adopted. The errors in the stress tensor of standard LBM for high-speed flows are corrected using a numerical force. A diffuse IBM is adopted due to its better numerical efficiency in handling moving geometries and because it can also handle thermal boundary conditions. For validation, subsonic and supersonic flow over a 2D circular cylinder, as well as transonic flow over a NACA airfoil, are presented. The current findings show good agreement with previously published data derived from alternative methodologies, validating the effectiveness of the current solver in simulating highly compressible flows. |
Tuesday, November 26, 2024 9:57AM - 10:10AM |
X16.00010: High-order non-dissipative overset/cut-cell approach for incompressible flows Uday Howlader, Nek Sharan Practical turbulent flow computations require resolving a wide range of spatial and temporal scales within complex domains. High-order methods reduce the grid point requirements; however, ensuring long-time stability and discrete conservation in bounded domains remains challenging with high-order discretizations. As a result, flows in/around realistic geometries are commonly simulated using low-order schemes or artificial dissipation/numerical filters to address stability issues. This talk will present a high-order cut-cell discretization that is provably stable for linearized flow problems using non-dissipative centered schemes. The cut-cell scheme is combined with an energy-stable overset approach to simplify mesh generation and selectively refine the grid over complex/moving geometries. The proposed overset/cut-cell treatment employs a finite-difference (FD) discretization with colocated variables, which, by design, is dimensionally split. The theoretical stability proof guarantees primary and secondary conservation, and the small-cell issue is addressed by selecting flux point spacings that do not vanish even when grid points coincide at the cut-cell boundary, thus avoiding ad hoc procedures that are challenging to automate. The proposed method is applied to perform a series of inviscid and viscous incompressible flow simulations, including three-dimensional flow-induced vibration calculations over bluff bodies.
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