The Experts below are selected from a list of 43377 Experts worldwide ranked by ideXlab platform
Parviz Moin - One of the best experts on this subject based on the ideXlab platform.
-
wall modeled Large Eddy Simulation of turbulent boundary layers with mean flow three dimensionality
APS Division of Fluid Dynamics Meeting Abstracts, 2020Co-Authors: Minjeong Cho, Parviz Moin, Adrian Lozanoduran, George Ilhwan ParkAbstract:We examine the performance of wall-modeled Large-Eddy Simulation (WMLES) to predict turbulent boundary layers (TBLs) with mean-flow three-dimensionality. The analysis is performed for an ordinary-d...
-
trailing edge noise reduction using derivative free optimization and Large Eddy Simulation
Journal of Fluid Mechanics, 2007Co-Authors: Alison L. Marsden, Meng Wang, J E Dennis, Parviz MoinAbstract:Derivative-free optimization techniques are applied in conjunction with Large-Eddy Simulation (LES) to reduce the noise generated by turbulent flow over a hydrofoil trailing edge. A cost function proportional to the radiated acoustic power is derived based on the Ffowcs Williams and Hall solution to Lighthill's equation. Optimization is performed using the surrogate-management framework with filter-based constraints for lift and drag. To make the optimization more efficient, a novel method has been developed to incorporate Reynolds-averaged Navier–Stokes (RANS) calculations for constraint evaluation. Separation of the constraint and cost-function computations using this method results in fewer expensive LES computations. This work demonstrates the ability to fully couple optimization to Large-Eddy Simulation for time-accurate turbulent flow. The results demonstrate an 89% reduction in noise power, which comes about primarily by the elimination of low-frequency vortex shedding. The higher-frequency broadband noise is reduced as well, by a subtle change in the lower surface near the trailing edge.
-
Large Eddy Simulation of reacting turbulent flows in complex geometries
Journal of Applied Mechanics, 2006Co-Authors: Krishnan Mahesh, George Constantinescu, Sourabh V Apte, Gianluca Iaccarino, Frank Ham, Parviz MoinAbstract:Large-Eddy Simulation (LES) has traditionally been restricted to fairly simple geometries. This paper discusses LES of reacting flows in geometries as complex as commercial gas turbine engine combustors. The incompressible algorithm developed by Mahesh et al. (J. Comput. Phys., 2004, 197, 215-240) is extended to the zero Mach number equations with heat release. Chemical reactions are modeled using the flamelet/progress variable approach of Pierce and Moin (J. Fluid Mech., 2004, 504, 73-97). The Simulations are validated against experiment for methane-air combustion in a coaxial geometry, and jet-A surrogate/air combustion in a gas-turbine combustor geometry.
-
Large Eddy Simulation of realistic gas turbine combustors
AIAA Journal, 2006Co-Authors: Parviz Moin, Sourabh V ApteAbstract:Large-Eddy Simulation is a promising technique for accurate prediction of reacting multiphase flows in practical gas-turbine combustion chambers involving complex physical phenomena of turbulent mixing and combustion dynamics. Development of advanced models for liquid fuel atomization, droplet evaporation, droplet deformation and drag, and turbulent combustion is discussed specifically for gas-turbine applications. The nondissipative, yet robust numerical scheme for arbitrary shaped unstructured grids developed by Mahesh et al. (Mahesh, K., Constantinescu, G., and Moin, P., "A New Time-Accurate Finite-Volume Fractional-Step Algorithm for Prediction of Turbulent Flows on Unstructured Hybrid Meshes," Journal of Computational Physics, Vol. 197, No. 1, 2004, pp. 215-240) is modified to account for density variations due to chemical reactions. A systematic validation and verification study of the individual spray models and the numerical scheme is performed in canonical and complex combustor geometries. Finally, a multiscale, multi physics, turbulent reacting flow Simulation in a real gas-turbine combustor is performed to assess the predictive capability of the solver.
-
a numerical method for Large Eddy Simulation in complex geometries
Journal of Computational Physics, 2004Co-Authors: Krishnan Mahesh, George Constantinescu, Parviz MoinAbstract:We discuss the development of a numerical algorithm, and solver capable of performing Large-Eddy Simulation in the very complex geometries often encountered in industrial applications. The algorithm is developed for unstructured hybrid grids, is non-dissipative, yet robust at high Reynolds numbers on highly skewed grids. Simulation results for a variety of flows are presented.
Thijs Heus - One of the best experts on this subject based on the ideXlab platform.
-
Large Eddy Simulation of organized precipitating trade wind cumulus clouds
Atmospheric Chemistry and Physics, 2013Co-Authors: Axel Seife, Thijs HeusAbstract:Abstract. Trade wind cumulus clouds often organize in along-wind cloud streets and across-wind mesoscale arcs. We present a benchmark Large-Eddy Simulation which resolves the individual clouds as well as the mesoscale organization on scales of O(10 km). Different methods to quantify organization of cloud fields are applied and discussed. Using perturbed physics Large-Eddy Simulation experiments, the processes leading to the formation of cloud clusters and the mesoscale arcs are revealed. We find that both cold pools as well as the sub-cloud layer moisture field are crucial to understand the organization of precipitating shallow convection. Further sensitivity studies show that microphysical assumptions can have a pronounced impact on the onset of cloud organization.
Volker Gravemeier - One of the best experts on this subject based on the ideXlab platform.
-
an algebraic variational multiscale multigrid method for Large Eddy Simulation of turbulent flow
Computer Methods in Applied Mechanics and Engineering, 2010Co-Authors: Volker Gravemeier, Martin Kronbichler, Wolfgang A. WallAbstract:An algebraic variational multiscale–multigrid method for Large Eddy Simulation of turbulent flow
-
scale separating operators for variational multiscale Large Eddy Simulation of turbulent flows
Journal of Computational Physics, 2006Co-Authors: Volker GravemeierAbstract:A general class of scale-separating operators based on combined multigrid operators is proposed and analyzed in this work. The operators of this class are designed for variational multiscale Large Eddy Simulation using a finite volume or finite element method. Two representatives are compared to discrete smooth filters, which are widely used in the traditional Large Eddy Simulation literature; the comparison shows that they are not only theoretically different, but also yield considerable differences in the respective numerical results. Dynamic as well as constant-coefficient-based subgrid-scale modeling is used within the multiscale environment. All of the scale-separating operators are implemented in a second-order accurate energy-conserving finite volume method and tested for the case of a turbulent channel flow. One operator shows particularly remarkable results in the framework of the variational multiscale Large Eddy Simulation, that is, profiles are obtained for velocity and kinetic energy which are considerably closer to the respective profiles from a direct numerical Simulation than are the profiles resulting from the application of the other operators considered in the present study. Furthermore, this particular operator proves to be very efficient with regard to the important aspect of computational cost, that is, a reduction in computing time ranging from about 25% up to about 150% compared to the other operators. The introduction of a substantial amount of subgrid viscosity to the small scales, particularly in the buffer layer of the channel, appears to be crucial for the good results achieved with this method.
Peter G Duynkerke - One of the best experts on this subject based on the ideXlab platform.
-
Large Eddy Simulation of trade wind cumulus clouds
Journal of the Atmospheric Sciences, 1993Co-Authors: J W M Cuijpers, Peter G DuynkerkeAbstract:Abstract A Large Eddy Simulation (LES) model, used for studying the dry convective boundary layer, has been extended with an equation for the total water specific humidity and a condensation scheme to simulate the partly cloudy convective boundary layer. A Simulation has been made based on the observations gathered near Puerto Rico on 15 December 1972. Starting from a clear air situation, the model evolves to a situation with small cumulus clouds. Vertical profiles of variances and fluxes show satisfactory agreement with the experimental data. It will be shown that layer-averaged fluxes and variances within the cloud layer are related to the amount of cloud water.
Robert D. Palmer - One of the best experts on this subject based on the ideXlab platform.
-
ARTICLE Methods for Evaluating the Temperature Structure-Function Parameter Using Unmanned Aerial Systems and Large-Eddy Simulation
2016Co-Authors: Evgeni Fedorovich, Robert D. PalmerAbstract:Abstract Small-scale turbulent fluctuations of temperature are known to affect the propaga-tion of both electromagnetic and acoustic waves. Within the inertial-subrange scale, where the turbulence is locally homogeneous and isotropic, these temperature perturbations can be described, in a statistical sense, using the structure-function parameter for temperature, C2T. Here we investigate different methods of evaluating C2T, using data from a numerical Large-Eddy Simulation together with atmospheric observations collected by an unmanned aerial system and a sodar. An example case using data from a late afternoon unmanned aerial system flight on April 24 2013 and corresponding Large-Eddy Simulation data is presented and discussed
-
Methods for Evaluating the Temperature Structure-Function Parameter Using Unmanned Aerial Systems and Large-Eddy Simulation
Boundary-Layer Meteorology, 2015Co-Authors: Charlotte E. Wainwright, Timothy A. Bonin, Phillip B. Chilson, Jeremy A. Gibbs, Evgeni Fedorovich, Robert D. PalmerAbstract:Small-scale turbulent fluctuations of temperature are known to affect the propagation of both electromagnetic and acoustic waves. Within the inertial-subrange scale, where the turbulence is locally homogeneous and isotropic, these temperature perturbations can be described, in a statistical sense, using the structure-function parameter for temperature, $$C_{T}^2$$ C T 2 . Here we investigate different methods of evaluating $$C_{T}^2$$ C T 2 , using data from a numerical Large-Eddy Simulation together with atmospheric observations collected by an unmanned aerial system and a sodar. An example case using data from a late afternoon unmanned aerial system flight on April 24 2013 and corresponding Large-Eddy Simulation data is presented and discussed.
