Wake deviation of yawed wind turbine by Large-Eddy Simulation

International audienceKeywords: Large Eddy Simulation, yaw and wake interaction According to the current energetic and environmental challenges, maximizing the electric power generated in windfarms is a societal concern. New strategies such as involving wind turbine yaw angle seem relevant to reduce wake interaction and associated power losses [1]. Therefore, yawed turbine aerodynamics is modified and remains a challenging investigation topic. Since experimental data on actual windfarm scales are not affordable and given the constant growth of computational resources, high order numerical simulations tend to be a promising approach [2]. The goal of this study is to evaluate a highly resolved numerical model under yaw condition in a wind tunnel before applying it to actual windfarm. The blade modeling is performed using an Actuator Line Method [3] (ALM), coupled to the low Mach-number massively-parallel finite-volume Large-Eddy Simulation (LES) flow solver on unstructured meshes, called YALES2 [4] [5]. The Blind Test 5 experimental configuration led at NTNU [6], gathering numerous experimental data, is reproduced in this study. After the study of a yawed turbine wake interaction with downstream turbine the study of a single yawed turbine (+30 o and 0 o) will be presented. The computational domain of these cases will be the NTNU wind tunnel, involving a turbulence grid aiming to create a fully turbulent sheared inflow [6]. The grid will be modeled using multiple Actuator Lines (to mimic the turbine blades) with dedicated polars [7] [8]. Each computational case is performed on a unstructured mesh with around 150.10 6 tetrahedra. An instantaneous velocity field of the yawed turbine wake interaction is presented on Figure 1. Figure 1: Instantaneous streamwise velocity field of wake interaction between two turbines in the NTNU wind tunnel with unstructured mes

Turbulent Combustion of Polydisperse Evaporating Sprays with Droplet Crossing: Eulerian Modeling and Validation in the Infinite Knudsen Limit

The accurate simulation of the dynamics of polydisperse evaporating sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. The difficulties encountered by the usual Lagrangian approaches make the use of Eulerian models attractive, aiming at a lower cost and an easier coupling with the carrier gaseous phase. Among these models, the multi-fluid model allows for a detailed description of the polydispersity and size-velocity correlations for droplets of various sizes. The purpose of the present study is twofold. First, we extend the multi-fluid model in order to cope with crossing droplet trajectories by using the quadrature method of moments in velocity phase space conditioned by size. We identify the numerical difficulties and provide dedicated numerical schemes in order to preserve the velocity moment space. Second, we conduct a comparison study and demonstrate the capability of such an approach to capture the dynamics of an evaporating polydisperse spray in a 2-D free jet configuration. We evaluate the accuracy and computational cost of Eulerian models and related discretization schemes vs. Lagrangian solvers and show that, even for finite Stokes number, the standard Eulerian multi-fluid model can be accurate at reasonable cost

Spray vaporization in nonpremixed turbulent combustion modeling: a single droplet model

International audienceThe injection of liquid fuel is a common procedure in turbulent combustion devices operating in the nonpremixed regime. Various numerical models may be found in the literature to calculate such turbulent flames, using either Reynolds averaged Navier-Stokes techniques (RANS) or large eddy simulation (LES). The typical inputs of nonpremixed turbulent combustion modeling are the mean and the fluctuations of the mixture fraction. In computational fluid dynamics codes, the mean source of mixture fraction may be provided by Euler-Lagrange spray modeling. However, the sources of fluctuations of mixture fraction due to vaporization require more closures. Direct numerical simulation (DNS) provides a way of estimating these sources and, using DNS of droplets evaporating in a turbulent flow, it is described how they play an important role in the time evolution of fuel/air mixing in a dilute spray. The statistical properties of the spray and of the scalar field are analyzed to propose a single droplet model (SDM) to evaluate these sources. SDM calculates mean values of the Eulerian source of fuel conditioned on the mixture fraction

Large Eddy Simulation of a Cavitating Multiphase Flow for Liquid Injection

cited By 1; Conference of 9th International Symposium on Cavitation, CAV 2015 ; Conference Date: 6 December 2015 Through 10 December 2015; Conference Code:118001International audienceThis paper presents a numerical method for modelling a compressible multiphase flow that involves phase transition between liquid and vapour in the context of gasoline injection. A discontinuous compressible two fluid mixture based on the Volume of Fluid (VOF) implementation is employed to represent the phases of liquid, vapour and air. The mass transfer between phases is modelled by standard models such as Kunz or Schnerr-Sauer but including the presence of air in the gas phase. Turbulence is modelled using a Large Eddy Simulation (LES) approach to catch instationnarities and coherent structures. Eventually the modelling approach matches favourably experimental data concerning the effect of cavitation on atomisation process

London Hotel Ardlethan card 2 side 2

The Noel Butlin Archives Centre also holds property and manager files for this hotel

Vapor mixing in turbulent vaporizing flows

International audienc