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 E29: Turbulence: LES - ApplicationsCFD Turbulence
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Chair: Reza Sheikhi, Dena Scientific Wellesley MA Room: 205 |
Sunday, November 19, 2017 4:55PM - 5:08PM |
E29.00001: Large Eddy Simulation of a Supercritical Turbulent Mixing Layer Reza Sheikhi, Fatemeh Hadi, Mehdi Safari Supercritical turbulent flows are relevant to a wide range of applications such as supercritical power cycles, gas turbine combustors, rocket propulsion and internal combustion engines. Large eddy simulation (LES) analysis of such flows involves solving mass, momentum, energy and scalar transport equations with inclusion of generalized diffusion fluxes. These equations are combined with a real gas equation of state and the corresponding thermodynamic mixture variables. Subgrid scale models are needed for not only the conventional convective terms but also the additional high pressure effects arising due to the nonlinearity associated with generalized diffusion fluxes and real gas equation of state. In this study, LES is carried out to study the high pressure turbulent mixing of methane with carbon dioxide in a temporally developing mixing layer under supercritical condition. LES results are assessed by comparing with data obtained from direct numerical simulation (DNS) of the same layer. LES predictions agree favorably with DNS data and represent several key supercritical turbulent flow features such as high density gradient regions. [Preview Abstract] |
Sunday, November 19, 2017 5:08PM - 5:21PM |
E29.00002: Analysis of flow over an axisymmetric hull-form using Large Eddy Simulation Praveen Kumar, Krishnan Mahesh Large eddy simulations are performed for flow over an idealized axisymmetric hull at a Reynolds number of 1.1 million, based on hull length and freestream velocity. The domain is chosen to minimize confinement effects and the grid is designed to capture the near-wall physics as well as the evolution of turbulent wake. The entire hull is broken up into bow, mid and stern region and analyzed individually before merging them together, to ensure accurate solution on the final grid. The boundary layer is tripped on the bow region of the hull to make it turbulent as done in experiment. The turbulent boundary layer evolves on the mid region of the hull and eventually separates on the stern region due to the adverse pressure gradient, and forms the wake. Results are shown for the flow field and the pressure and skin-friction on the hull. The sensitivity of wake to the boundary layer characteristics on the stern is discussed. [Preview Abstract] |
Sunday, November 19, 2017 5:21PM - 5:34PM |
E29.00003: Comparative Study of Reynolds Averaged and Embedded Large Eddy Simulations of a High-Pressure Turbine Stage Samuel Jones, Thomas Corke, Aleksandar Jemcov An Embedded Large Eddy Simulation (ELES) approach is used to simulate the flow path through a high-pressure turbine stage that includes the entry duct, stationary inlet and exit guide vanes, and a rotor. The flowfield around the rotor is simulated using LES. A Reynolds Averaged Simulation (RAS) is used for the rest of the flow domain. The interface between RAS and LES domains uses the RAS turbulence quantities as a means of obtaining length scales that are used in computing the vorticity required to trigger a proper energy cascade within the LES part of the flow field. The objective is to resolve the unsteady vortical motions that emanate from the gap between the rotor tip and duct walls that are presumably under-resolved in a RAS approach. A comparative analysis between RAS and ELES approaches for this turbomachinery problem is then presented. [Preview Abstract] |
Sunday, November 19, 2017 5:34PM - 5:47PM |
E29.00004: Large Eddy Simulation of Supercritical CO2 Through Bend Pipes Xiaoliang He, Sourabh Apte, Omer Dogan Supercritical Carbon Dioxide (sCO2) is investigated as working fluid for power generation in thermal solar, fossil energy and nuclear power plants at high pressures. Severe erosion has been observed in the sCO2 test loops, particularly in nozzles, turbine blades and pipe bends. It is hypothesized that complex flow features such as flow separation and property variations may lead to large oscillations in the wall shear stresses and result in material erosion. In this work, large eddy simulations are conducted at different Reynolds numbers (5000, 27,000 and 50,000) to investigate the effect of heat transfer in a 90 degree bend pipe with unit radius of curvature in order to identify the potential causes of the erosion. The simulation is first performed without heat transfer to validate the flow solver against available experimental and computational studies. Mean flow statistics, turbulent kinetic energy, shear stresses and wall force spectra are computed and compared with available experimental data. Formation of counter-rotating vortices, named Dean vortices, are observed. Secondary flow pattern and swirling-switching flow motions are identified and visualized. Effects of heat transfer on these flow phenomena are then investigated by applying a constant heat flux at the wall. [Preview Abstract] |
Sunday, November 19, 2017 5:47PM - 6:00PM |
E29.00005: Wall modeled LES of wind turbine wakes with geometrical effects Laurent Bricteux, Pierre Benard, Stephanie Zeoli, Vincent Moureau, Ghislain Lartigue, Axelle Vire This study focuses on prediction of wind turbine wakes when geometrical effects such as nacelle, tower, and built environment, are taken into account. The aim is to demonstrate the ability of a high order unstructured solver called YALES2 to perform wall modeled LES of wind turbine wake turbulence. The wind turbine rotor is modeled using an Actuator Line Model (ALM) while the geometrical details are explicitly meshed thanks to the use of an unstructured grid. As high Reynolds number flows are considered, sub-grid scale models as well as wall modeling are required. The first test case investigated concerns a wind turbine flow located in a wind tunnel that allows to validate the proposed methodology using experimental data. The second test case concerns the simulation of a wind turbine wake in a complex environment (e.g. a Building) using realistic turbulent inflow conditions. [Preview Abstract] |
Sunday, November 19, 2017 6:00PM - 6:13PM |
E29.00006: Relationship between Anisotropy and Dispersive Stress in Wind Plants with Variable Spacing Tamara Dib, Naseem Ali, Gerard Cortina, Marc Calaf, Raul Bayoan Cal Large eddy simulations are considered for wind plants with varied spanwise and streamwise spacing. Data from five different configurations of staggered and aligned LES wind turbine arrays with a neutrally stratified atmospheric boundary layer are employed for analysis. For this study, the flow fields are analyzed by evaluating the anisotropy stress invariants based on the Reynolds shear stresses and dispersive stress tensor. The relationship between quantities are drawn as a function of the wind plant packing. Reynolds stresses and dispersive stresses are investigated alongside a domain altered version of the second and third scalar invariants, $\xi$, $\eta$, as well as the combination of the two invariants described by the function $F=1-27\eta^2+54\xi^3$. $F$ is a measure of the approach to either a two-component turbulence ($F$=1) or an isotropic turbulence ($F$=0). The invariant $\eta$ describes the degree of anisotropy while $\xi$ describes the characteristic shape. For the purposes of this study, the LES data is analyzed to understand the effects of canopy density on the anisotropy of dispersive stresses, adding further insight and detail for future modeling techniques. [Preview Abstract] |
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