CaltechTHESIS
  A Caltech Library Service

Large-eddy simulations of fully developed turbulent channel and pipe flows with smooth and rough walls

Citation

Saito, Namiko (2014) Large-eddy simulations of fully developed turbulent channel and pipe flows with smooth and rough walls. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:02142014-112419793

Abstract

Studies in turbulence often focus on two flow conditions, both of which occur frequently in real-world flows and are sought-after for their value in advancing turbulence theory. These are the high Reynolds number regime and the effect of wall surface roughness. In this dissertation, a Large-Eddy Simulation (LES) recreates both conditions over a wide range of Reynolds numbers Reτ = O(102)-O(108) and accounts for roughness by locally modeling the statistical effects of near-wall anisotropic fine scales in a thin layer immediately above the rough surface. A subgrid, roughness-corrected wall model is introduced to dynamically transmit this modeled information from the wall to the outer LES, which uses a stretched-vortex subgrid-scale model operating in the bulk of the flow. Of primary interest is the Reynolds number and roughness dependence of these flows in terms of first and second order statistics. The LES is first applied to a fully turbulent uniformly-smooth/rough channel flow to capture the flow dynamics over smooth, transitionally rough and fully rough regimes. Results include a Moody-like diagram for the wall averaged friction factor, believed to be the first of its kind obtained from LES. Confirmation is found for experimentally observed logarithmic behavior in the normalized stream-wise turbulent intensities. Tight logarithmic collapse, scaled on the wall friction velocity, is found for smooth-wall flows when Reτ ≥ O(106) and in fully rough cases. Since the wall model operates locally and dynamically, the framework is used to investigate non-uniform roughness distribution cases in a channel, where the flow adjustments to sudden surface changes are investigated. Recovery of mean quantities and turbulent statistics after transitions are discussed qualitatively and quantitatively at various roughness and Reynolds number levels. The internal boundary layer, which is defined as the border between the flow affected by the new surface condition and the unaffected part, is computed, and a collapse of the profiles on a length scale containing the logarithm of friction Reynolds number is presented. Finally, we turn to the possibility of expanding the present framework to accommodate more general geometries. As a first step, the whole LES framework is modified for use in the curvilinear geometry of a fully-developed turbulent pipe flow, with implementation carried out in a spectral element solver capable of handling complex wall profiles. The friction factors have shown favorable agreement with the superpipe data, and the LES estimates of the Karman constant and additive constant of the log-law closely match values obtained from experiment.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Turbulence, Roughness, Modeling, LES
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Pullin, Dale I.
Thesis Committee:
  • Meiron, Daniel I. (chair)
  • Pullin, Dale I.
  • McKeon, Beverley J.
  • Colonius, Timothy E.
Defense Date:31 January 2014
Non-Caltech Author Email:namiko12 (AT) icloud.com
Funders:
Funding AgencyGrant Number
National Science FoundationCBET-1235605
Record Number:CaltechTHESIS:02142014-112419793
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:02142014-112419793
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8077
Collection:CaltechTHESIS
Deposited By: Namiko Saito
Deposited On:24 Mar 2014 17:04
Last Modified:30 Jan 2015 23:24

Thesis Files

[img]
Preview
PDF - Final Version
See Usage Policy.

5Mb

Repository Staff Only: item control page