Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session A1: Fluid Structure Interactions I |
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Chair: Kourosh Shoele, RE Vision Consulting Room: 22 |
Sunday, November 18, 2012 8:00AM - 8:13AM |
A1.00001: Limits of the potential flow model for obstacle detection using a lateral line Audrey Maertens, Gabriel Weymouth, Michael Triantafyllou Fish have a particular sensory system called lateral line through which they measure flow velocity and pressure gradient. Behavioral studies have shown that fish can detect and identify obstacles while gliding using this sensory system alone. Despite a widespread interest of the community in understanding and reproducing this capability, a realistic approach is still missing. Indeed, due to computational constraints, most attempts to date have used potential flow models. The present work aims at revealing the limits of the potential flow model in the case of a vehicle gliding by a cylinder. The understanding thus gained can be used to account for viscous effects in a computationally-efficient fashion. An improvement of the boundary data immersion method provides accurate pressure predictions at the Reynolds numbers considered ($500<$~Re~$<10000$). It is shown how a potential flow-based obstacle detection algorithm fails at locating the cylinder at these Reynolds numbers. It is also shown that a panel method accounting for dynamically changing displacement thickness leads to accurate pressure prediction. This is a first step toward real-time pressure predictions for viscous flows which is needed for efficient obstacle detection and identification algorithms. [Preview Abstract] |
Sunday, November 18, 2012 8:13AM - 8:26AM |
A1.00002: A finite volume algorithm for fluid-structure interaction problems using unstructured meshes Branislav Basara The coupled simulation between multiple fluid and solid domains plays an important role in a wide range of multi-physics problems. A simple method is to calculate different computational domains separately by submitting one or more executable codes for each calculation domain and even for solving different physics, and then exchanging data with the so called coupling server which could use a direct data exchange or in-directly via data files. However, nowadays, sophisticated numerical techniques allow separate domains to be solved with the same computational code within one calculation run. The finite volume method based on the collocated variable arrangement and adopted for the general polyhedral control volume is extended here to solve beside fluid flow problems also deformations and stresses in the solid structure. The performance of the method will be demonstrated on a number of fluid flow and stress analysis test cases. Results show that the method can be used as a useful tool for solving fluid-structure interaction problems. [Preview Abstract] |
Sunday, November 18, 2012 8:26AM - 8:39AM |
A1.00003: A numerical framework for modelling floating wind turbines Axelle Vire, Jiansheng Xiang, Matthew Piggott, John-Paul Latham, Christopher Pain This work couples a fluid/ocean- and a solid- dynamics model in order to numerically study fluid-structure interactions. The fully non-linear Navier-Stokes and solid-dynamics equations are solved on two distinct finite-element and unstructured grids. The interplay between fluid and solid is represented through a penalty force in the momentum balances of each material. The present algorithm is novel in that it spatially conserves the discrete penalty force, when exchanging it between both models, independently of the mesh resolution and of the shape-function orders in each model. This numerical framework targets the modelling of offshore floating wind turbines. Results will be shown for the flow past a moving pile and an actuator-disk representation of a turbine. [Preview Abstract] |
Sunday, November 18, 2012 8:39AM - 8:52AM |
A1.00004: Dynamic evolution of a flow to localized, kinetics-driven ablation or coagulation Daniel Hagan, Ryan Crocker, Yves Dubief This research focuses on the numerical simulation of the ablative creation of a cavity or a coagulative formation at a wall in a flow. The fluid-solid interface is defined by a level set (LS) variable, whose transport equation is driven by the mass-loss or growth process. The boundary conditions at the fluid-solid interface are enforced by a mass and energy-conserving immersed boundary method (IBM) using the ghost-fluid node approach for the latter and for the transport of chemical species. The first application of the LS/IBM algorithm is a channel flow in which both walls are cavity-free, but one wall contains a section made of ablatable material, which could correspond to a hole or gap in a spacecraft thermal protection shield. The second application is a pipe flow in which the wall is capable of accumulating material, which could describe the coagulation of blood at a vessel wall. The solid mass loss or growth is driven by one step kinetics. For both flows, the dynamical interplay between the ablative or coagulative patch is investigated through statistics and flow topology. [Preview Abstract] |
Sunday, November 18, 2012 8:52AM - 9:05AM |
A1.00005: High Order Solution of the Incompressible Navier-Stokes Equations in Immersed Domains Jean-Christophe Nave, Alexandre Marques, Ruben Rosales The Correction Function Method (CFM) is a general framework that can be used to devise highly accurate discretizations for diffusion dominated phenomena in the presence of immersed interfaces or boundaries. In previous work, the authors presented the CFM for the solution of the Poisson equation. In this talk, we discuss the application of the CFM to time-dependent problems, with emphasis on the incompressible Navier-Stokes equations. Fourth-order accurate results are presented. [Preview Abstract] |
Sunday, November 18, 2012 9:05AM - 9:18AM |
A1.00006: Numerical Capture of Wing-tip Vortex Using Vorticity Confinement Baili Zhang, Jing Lou, Chang Wei Kang, Alexander Wilson, Johan Lundberg, Rickard Bensow Tracking vortices accurately over large distances is very important in many areas of engineering, for instance flow over rotating helicopter blades, ship propeller blades and aircraft wings. However, due to the inherent numerical dissipation in the advection step of flow simulation, current Euler and RANS field solvers tend to damp these vortices too fast. One possible solution to reduce the unphysical decay of these vortices is the application of vorticity confinement methods. In this study, a vorticity confinement term is added to the momentum conservation equations which is a function of the local element size, the vorticity and the gradient of the absolute value of vorticity. The approach has been evaluated by a systematic numerical study on the tip vortex trailing from a rectangular NACA0012 half-wing. The simulated structure and development of the wing-tip vortex agree well with experiments both qualitatively and quantitatively without any adverse effects on the global flow field. It is shown that vorticity confinement can negate the effect of numerical dissipation, leading to a more or less constant vortex strength. This is an approximate method in that genuine viscous diffusion of the vortex is not modeled, but it can be appropriate for vortex dominant flows over short to medium length scales where viscous diffusion can be neglected. [Preview Abstract] |
Sunday, November 18, 2012 9:18AM - 9:31AM |
A1.00007: Implementation of a Phase-Lagged Boundary Condition for Turbomachinery Alex Wouden, John Cimbala, Bryan Lewis One factor that contributes significantly to the cost of a time-dependent CFD simulation is the size and scope of the computational domain. Common approximations, such as periodic and symmetric boundary conditions, have the advantage of reducing the domain proportional to its periodicity or symmetry. However, turbomachinery applications featuring multiple blade rows render the periodic boundary condition unphysical because the adjacent blade rows are designed with dissimilar blade counts. Though the meshes of adjacent blade rows can be modeled independently and data can be interpolated across a grid interface, applying the standard periodic definition to the coupled faces leads to an over-constrained situation: a failure to reconcile two governing relations imposed on the same cell. A phase-lagged boundary condition (PLBC) relaxes the over-constraint problem and provides a more correct assumption for the resulting flow field. PLBC is available in a limited number of private CFD codes and is only briefly documented in the literature. The present work expands upon its development by implementing PLBC in OpenFOAM\textregistered{}, an open-source CFD software package. Its performance is demonstrated for basic turbomachinery applications through comparisons with full-wheel simulation. [Preview Abstract] |
Sunday, November 18, 2012 9:31AM - 9:44AM |
A1.00008: Characterization of the Boundary Conditions at the Test Section Inlet for a Combustion Rig Christopher Ruscher, John Dannenhoffer, III, Mark Glauser, Balu Sekar, Vincent Belovich Large eddy simulations are sensitive to boundary conditions and therefore it is important to characterize the boundary conditions. The boundary conditions for the test section inlet of a combustion rig have been calculated using a computational fluid dynamic (CFD) simulation. A simulation was performed in lieu of experimental testing due to the complexity and cost of placing sensors in the upstream portions of the rig. The mean and RMS profiles for velocity as well as auto-spectrum are computed for the inlet. The calculated values will be used in future simulation work for this combustion rig. [Preview Abstract] |
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