of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The dynamic subgrid-scale eddy viscosity model of Germano et al. [Phys. Fluids A 3, 1760 (1991)] (DSM) is modified by employing the mixed model of Bardina et al. [Ph.D dissertation, Stanford University (1983)] as the base model. The new dynamic mixed model explicitly calculates the modified Leonard term and only models the cross term and the SGS Reynolds stress. It retains the favorable features of DSM and, at the same time, does not require that the principal axes of the stress tensor be aligned with those of the strain rate tensor. The model coefficient is computed using local flow variables. The new model is incorporated in a finite-volume solution method and large-eddy simulations of flows in a lid-driven cavity at Reynolds numbers of 3200, 7500, and 10 000 show excellent agreement with the experimental data. Better agreement is achieved by using the new model compared to the DSM. The magnitude of the dynamically computed model coefficient of the new model is significantly smaller than that from DSM.
This paper reports on a series of large-eddy simulations of a round
jet issuing normally
into a crossflow. Simulations were performed at two jet-to-crossflow velocity
ratios,
2.0 and 3.3, and two Reynolds numbers, 1050 and 2100, based on crossflow
velocity
and jet diameter. Mean and turbulent statistics computed from the simulations
match experimental measurements reasonably well. Large-scale coherent structures
observed in experimental flow visualizations are reproduced by the simulations,
and
the mechanisms by which these structures form are described. The effects
of coherent
structures upon the evolution of mean velocities, resolved Reynolds stresses,
and
turbulent kinetic energy along the centreplane are discussed. In this paper,
the
ubiquitous far-field counter-rotating vortex pair is shown to originate
from a pair of
quasi-steady ‘hanging’ vortices. These vortices
form in the skewed mixing layer that
develops between jet and crossflow fluid on the lateral edges of the jet.
Axial flow
through the hanging vortex transports vortical fluid from the near-wall
boundary
layer of the incoming pipe flow to the back side of the jet. There, the
hanging vortex
encounters an adverse pressure gradient and breaks down. As this breakdown
occurs,
the vortex diameter expands dramatically, and a weak counter-rotating vortex
pair is
formed that is aligned with the jet trajectory.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.