Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session L38: Computational Fluid Dynamics: ApplicationsCFD
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Chair: Ali Khosronejad, Stony Brook University Room: 304 |
Monday, November 20, 2017 4:05PM - 4:18PM |
L38.00001: Unsteady flow separation from the surface of two square cylinders arranged in series in shear flow using structural bifurcation analysis. Atendra Kumar, Rajendra K. Ray A numerical study of two-dimensional(2D) shear flow past two equal sized square cylinders arranged in series at Reynolds number(\textit{Re) }100 with shear parameter values ($K)$ ranging from 0.0 to 0.2 is presented here. To describe the flow phenomenon, two different gap ratios, $s$/$d =$ 1, 3 are considered, where $d $is the side length of the cylinder and $s $is separation between the cylinders. The flow is computed using a higher order compact (HOC) scheme for stream-function vorticity form of the 2D Navier--Stokes equations. In this study, we basically want to understand the shear effect on vertex shedding phenomena using topology based structural bifurcation analysis. This analysis exactly predicts the location and the time of the occurrence of the flow separation from the surface of the square cylinders. No such study has been done till date for this problem. Shear rates affect the flow phenomena significantly. The instantaneous stream-function and vorticity contours are presented for different $K $values to confirm the theoretical study. All our computed results very efficiently reproduce the complex flow phenomena and structural bifurcation analysis confirms the flow separation from the surface of the cylinders. [Preview Abstract] |
Monday, November 20, 2017 4:18PM - 4:31PM |
L38.00002: Dynamic Responses of Flexible Cylinders with Low Mass Ratio Abiodun Olaoye, Zhicheng Wang, Michael Triantafyllou Flexible cylinders with low mass ratios such as composite risers are attractive in the offshore industry because they require lower top tension and are less likely to buckle under self-weight compared to steel risers. However, their relatively low stiffness characteristics make them more vulnerable to vortex induced vibrations. Additionally, numerical investigation of the dynamic responses of such structures based on realistic conditions is limited by high Reynolds number, complex sheared flow profile, large aspect ratio and low mass ratio challenges. In the framework of Fourier spectral/hp element method, the current technique employs entropy-viscosity method (EVM) based large-eddy simulation approach for flow solver and fictitious added mass method for structure solver. The combination of both methods can handle fluid-structure interaction problems at high Reynolds number with low mass ratio. A validation of the numerical approach is provided by comparison with experiments. [Preview Abstract] |
Monday, November 20, 2017 4:31PM - 4:44PM |
L38.00003: A fluid-structure interaction model of soft robotics using an active strain approach Andrew Hess, Zhaowu Lin, Tong Gao Soft robotic swimmers exhibit rich dynamics that stem from the non-linear interplay of the fluid and immersed soft elastic body. Due to the difficulty of handling the nonlinear two-way coupling of hydrodynamic flow and deforming elastic body, studies of flexible swimmers often employ either one-way coupling strategies with imposed motions of the solid body or some simplified elasticity models. To explore the nonlinear dynamics of soft robots powered by smart soft materials, we develop a computational model to deal with the two-way fluid/elastic structure interactions using the fictitious domain method. To mimic the dynamic response of the functional soft material under external actuations, we assume the solid phase to be neo-Hookean, and employ an active strain approach to incorporate actuation, which is based on the multiplicative decomposition of the deformation gradient tensor. We demonstrate the capability of our algorithm by performing a series of numerical explorations that manipulate an elastic structure with finite thickness, starting from simple rectangular or circular plates to soft robot prototypes such as stingrays and jellyfish. [Preview Abstract] |
Monday, November 20, 2017 4:44PM - 4:57PM |
L38.00004: CFD Analysis of the Oscillating Flow within a Stirling Engine with an Additively Manufactured Foil Type Regenerator. Songgang Qiu, Laura Solomon The simplistic design, fuel independence, and robustness of Stirling convertors makes them the ideal choice for use in solar power and combined heat and power (CHP) applications. A lack of moving parts and the use of novel flexure bearings allows free-piston type Stirling engines to run in excess of ten years without degradation or maintenance. The key component to their overall efficiency is the regenerator. While a foil type regenerator outperforms a sintered random fiber regenerator, limitation in manufacturing and keeping uniform spacing between the foils has limited their overall use. However, with the advent of additive manufacturing, a robust foil type regenerator can be cheaply manufactured without traditional limitations. Currently, a CFD analysis of the oscillating internal flow within the novel design was conducted to evaluate the flow loses within the system. Particularly the pressure drop across the regenerator in comparison to a traditionally used random fiber regenerator. Additionally, the heat transfer and flow over the tubular heater hear was evaluated. The results of the investigation will be used to optimize the operation of the next generation of additively manufactured Stirling convertors. [Preview Abstract] |
Monday, November 20, 2017 4:57PM - 5:10PM |
L38.00005: Numerical analysis of heat and mass transfer for water recovery in an evaporative cooling tower Hyunsub Lee, Gihun Son Numerical analysis is performed for water recovery in an evaporative cooling tower using a condensing heat exchanger, which consists of a humid air channel and an ambient dry air channel. The humid air including water vapor produced in an evaporative cooling tower is cooled by the ambient dry air so that the water vapor is condensed and recovered to the liquid water. The conservation equations of mass, momentum, energy and vapor concentration in each fluid region and the energy equation in a solid region are simultaneously solved with the heat and mass transfer boundary conditions coupled to the effect of condensation on the channel surface of humid air. The present computation demonstrates the condensed water film distribution on the humid air channel, which is caused by the vapor mass transfer between the humid air and the colder water film surface, which is coupled to the indirect heat exchange with the ambient air. Computations are carried out to predict water recovery rate in parallel, counter and cross-flow type heat exchangers. The effects of air flow rate and channel interval on the water recovery rate are quantified. [Preview Abstract] |
Monday, November 20, 2017 5:10PM - 5:23PM |
L38.00006: Effect of Material Property Variations at Near Critical Thermodynamic Conditions on Pipe Flow Heat Transfer Rebecca Barney, Robert Nourgaliev, Jean-Pierre Delplanque, Rose McCallen Heat transfer is quantified and contrasted for the Poiseuille flow of a fluid at both subcritical and supercritical thermodynamic conditions in a circular pipe subject to a uniform wall heat flux. The conditions considered are relevant to Supercritical Water Reactor (SCWR) applications. In the supercritical thermodynamic regime, a fluid can exhibit large density variations of density, thermal conductivity, and viscosity, which will affect flow and heat transfer characteristics significantly. An advanced equation of state for supercritical water was implemented in a 2D and 3D Arbitrary Lagrangian-Eurlerian multi-physics simulation tool called ALE3D developed at Lawrence Livermore National Laboratory. A newly developed, robust, high-order in space and time, fully implicit reconstructed discontinuous Galerkin (rDG) method is used to enable the numerical simulation of convective heat transfer with supercritical water. Results demonstrate the capability of this approach to accurately capture the non-linear behavior and enhanced heat transfer with supercritical water. Work is supported by the Integrated University Program Graduate Fellowship. Opinions, findings, conclusions or recommendations expressed are of the authors and do not necessarily reflect the views of DOE office of NE [Preview Abstract] |
Monday, November 20, 2017 5:23PM - 5:36PM |
L38.00007: The numerical model of multi-layer insulation with a defined wrapping pattern immersed in superfluid helium Ziemowit Malecha, Eliza Lubryka The numerical model of thin layers, characterized by a defined wrapping pattern can be a crucial element of many computational problems related to engineering and science. A motivating example is found in multilayer electrical insulation, which is an important component of superconducting magnets and other cryogenic installations. The wrapping pattern of the insulation can significantly affect heat transport and the performance of the considered instruments. The major objective of this study is to develop the numerical boundary conditions (BC) needed to model the wrapping pattern of thin insulation. An example of the practical application of the proposed BC includes the heat transfer of Rutherford NbTi cables immersed in super-fluid helium (He II) across thin layers of electrical insulation. The proposed BC and a mathematical model of heat transfer in He II are implemented in the open source CFD toolbox OpenFOAM. The implemented mathematical model and the BC are compared in the experiments. The study confirms that the thermal resistance of electrical insulation can be lowered by implementing the proper wrapping pattern. The proposed BC can be useful in the study of new patterns for wrapping schemes. [Preview Abstract] |
Monday, November 20, 2017 5:36PM - 5:49PM |
L38.00008: Effect of Substrate Wetting on the Morphology and Dynamics of Phase Separating Multi-Component Mixture Abheeti Goyal, Federico Toschi, Paul van der Schoot We study the morphological evolution and dynamics of phase separation of multi-component mixture~in thin film~constrained by a substrate. Specifically, we have explored the surface-directed spinodal decomposition of multicomponent mixture~numerically by Free Energy Lattice Boltzmann (LB) simulations.~The distinguishing feature of this model over the~Shan-Chen~(SC) model~is that we have explicit and independent control over the free energy functional and EoS of the system. This vastly expands the ambit of physical systems that can be realistically simulated by LB simulations.~We investigate the effect of composition, film thickness and substrate wetting on the phase morphology and the mechanism of growth in the vicinity of the substrate.~The phase morphology and averaged size in the vicinity of the substrate fluctuate greatly due to the wetting of the substrate in both the parallel and perpendicular directions.~Additionally, we also describe how the model presented here can be extended to include an arbitrary number of fluid components. [Preview Abstract] |
Monday, November 20, 2017 5:49PM - 6:02PM |
L38.00009: Towards a Numerical Simulation of the Blue Whirl Xiao Zhang, Joseph Chung, Ryan Houim, Carolyn Kaplan, Elaine Oran The blue whirl is a newly observed flame structure shown to evolve from a fire whirl. A new computational model is being developed to simulate this phenomenon and help explain the transition and structure. A three-dimensional numerical model was constructed to solve the partially compressible, reactive Navier-Stokes equations. The fourth-order Flux- Corrected Transport (FCT) algorithm is used for convection and the Barely Implicit Correction (BIC) is applied to remove the time step restriction imposed by the sound speed. A simplified chemical-diffusive (CD) model accounts for the chemical-energy release. The diffusion process models the mass diffusion, heat conduction, and viscous diffusion. The CD chemical model implemented here allows for variable equivalence ratios, allowing for computations of both premixed and non-premixed systems without the additional numerical cost of solving a multi-step chemical model and tracking many intermediate species. The implementation of these methods and models along with various test problems are presented. [Preview Abstract] |
Monday, November 20, 2017 6:02PM - 6:15PM |
L38.00010: Direct numerical simulation of reactive flow and modeling of pore-scale transport phenomena in porous media Mohammad Nomeli, Amir Riaz Direct numerical simulation of reactive flow and a long-term geochemical modeling of CO$_{\mathrm{2}}$ sequestration is carried out in a fractured media to investigate its impact on CO$_{\mathrm{2}}$ transport and storage capacity. The fracture is modeled by considering flow of CO$_{\mathrm{2}}$ between finite plates. We study the physics and the critical time of blockage for a fracture to interpret the results. To this end, we employ direct numerical simulation tools and algorithms to simulate incompressible flow along with necessary transport equations that capture the kinetics of relevant chemical reactions. The numerical model is based on a finite volume method using a sequential non-iterative approach. It is found that the reactive transport of minerals has an important effect on reservoir porosity and permeability. According to the simulations, the flow of injected CO$_{\mathrm{2}}$ in the fracture is controlled by changes in the pore-scale permeability. The fracture ceases to be a fluid channel due to geochemical reactions of minerals. In addition, using parameter analysis we also determine the effect of various reaction kinetics on permeability of porous media. [Preview Abstract] |
Monday, November 20, 2017 6:15PM - 6:28PM |
L38.00011: Simulation of Oxy-Fuel Pulse Detonation using a Space-Time CESE Method Shashank Karra, Jeremiah Hauth, Sourabh Apte Pulse detonation system using oxy-fuel combustion can be used for direct power extraction especially when combined with magnetohydrodynamics (MHD). In the present work, we investigate use of a space-time conservation element-solution element (CE/SE) method for simulation of oxy-methane pulse detonation waves. A CE/SE method results in a consistent multi-dimensional formulation for unstructured tetrahedral meshes by providing flux conservation in space and time, and eliminating the need for complex Reimann solvers to capture shocks. As the first step, a CE/SE method solving the Euler equations is implemented and verified for standard sod shock-tube problem to show very good predictive capability. The Euler solver is extended to account for single-step as well as reduced reaction mechanisms for oxy-fuel combustion. A revised Jones-Lindstedt (JL-R) reaction mechanism accounting for radicals such as O, OH, and H is used as a reduced mechanism to simulate detonation waves from methane-oxygen combustion. Detailed verification and validation is conducted to evaluate the effectiveness of the CE/SE method. The approach is being further developed for simulation of compressible reacting flows on unstructured grids. [Preview Abstract] |
Monday, November 20, 2017 6:28PM - 6:41PM |
L38.00012: Simulations of High Speed Fragment Trajectories Peter Yeh, Stephen Attaway, Srinivasan Arunajatesan, Travis Fisher Flying shrapnel from an explosion are capable of traveling at supersonic speeds and distances much farther than expected due to aerodynamic interactions. Predicting the trajectories and stable tumbling modes of arbitrary shaped fragments is a fundamental problem applicable to range safety calculations, damage assessment, and military technology. Traditional approaches rely on characterizing fragment flight using a single drag coefficient, which may be inaccurate for fragments with large aspect ratios. In our work we develop a procedure to simulate trajectories of arbitrary shaped fragments with higher fidelity using high performance computing. We employ a two-step approach in which the force and moment coefficients are first computed as a function of orientation using compressible computational fluid dynamics. The force and moment data are then input into a six-degree-of-freedom rigid body dynamics solver to integrate trajectories in time. Results of these high fidelity simulations allow us to further understand the flight dynamics and tumbling modes of a single fragment. Furthermore, we use these results to determine the validity and uncertainty of inexpensive methods such as the single drag coefficient model. [Preview Abstract] |
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