A Large Eddy Simulation Of Turbulent Flow Within A Progressively Thinned Loblolly Pine Forest

Forest thinning has been going on for decades for reasons such as removing dead trees, controlling potential wildfires and controlling invasive bark beetle infestations. However more needs to be done in the way of examining the effects of the thinning on canopy flow. This research presents the results of a large-eddy simulation (LES) analysis of flow within and above a loblolly pine forest. The simulations represent an actual forest where the US Forest Service engaged in a project to measure canopy flow properties while progressively thinning the forest vegetation. The LES model is compared to an eddy-viscosity model as well as data from the forest thinning. It was found that the number of large coherent structures decreased as the canopy density decreased. The spacing between the structures increased with decreasing canopy density. As the forest was thinned the velocity in the lower canopy increased but the average velocity profile continued to show an inflected shape. The height of the inflection remaining unchanged with the change in canopy densities examined. Zero displacement height tracked linearly with the percentage of density reduction and it also proved to be a good reference point for validating reestablishment of transitioning flow. Studies of canopy edge flow where the flow transitions from dense forest to open ground indicate a distance of approximately 15 canopy heights before the flow completes its transition and behaves as if there had been no canopy present. When the flow transitions to a thinned canopy instead of bare ground the presence of the canopy has a measureable effect on the distance required to reestablish steady state flow. The denser the canopy the more quickly the flow is reestablished. The thinner the canopy, the higher the downward sweeps of velocity occur to reestablish the flow. Research into flow transitioning from canopy to bare ground found a recirculating zone at the transition edge for some canopy densities. No recirculation zone was found at the transition edge from the fully dense canopy to the three different thinnings examined here.

Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.

First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."

Large eddy simulation (LES) seeks to simulate the large structures of a turbulent flow. This is the first monograph which considers LES from a mathematical point of view. It concentrates on LES models for which mathematical and numerical analysis is already available and on related LES models. Most of the available analysis is given in detail, the implementation of the LES models into a finite element code is described, the efficient solution of the discrete systems is discussed and numerical studies with the considered LES models are presented.

The LES-method is rapidly developing in many practical applications in engineering The mathematical background is presented here for the first time in book form by one of the leaders in the field

First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."

It is a truism that turbulence is an unsolved problem, whether in scientific, engin eering or geophysical terms. It is strange that this remains largely the case even though we now know how to solve directly, with the help of sufficiently large and powerful computers, accurate approximations to the equations that govern tur bulent flows. The problem lies not with our numerical approximations but with the size of the computational task and the complexity of the solutions we gen erate, which match the complexity of real turbulence precisely in so far as the computations mimic the real flows. The fact that we can now solve some turbu lence in this limited sense is nevertheless an enormous step towards the goal of full understanding. Direct and large-eddy simulations are these numerical solutions of turbulence. They reproduce with remarkable fidelity the statistical, structural and dynamical properties of physical turbulent and transitional flows, though since the simula tions are necessarily time-dependent and three-dimensional they demand the most advanced computer resources at our disposal. The numerical techniques vary from accurate spectral methods and high-order finite differences to simple finite-volume algorithms derived on the principle of embedding fundamental conservation prop erties in the numerical operations. Genuine direct simulations resolve all the fluid motions fully, and require the highest practical accuracy in their numerical and temporal discretisation. Such simulations have the virtue of great fidelity when carried out carefully, and repre sent a most powerful tool for investigating the processes of transition to turbulence.

This book addresses both the fundamentals and the practical industrial applications of Large Eddy Simulation (LES) in order to bridge the gap between LES research and the growing need to use it in engineering modeling.