Characterisation of Turbulent Duct Flows
Characterisation of Turbulent Duct Flows

Author: Bayode Owolabi

Publisher: Springer

Published: 2019-05-31

Total Pages: 165

ISBN-13: 303019745X

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This book presents several new findings in the field of turbulent duct flows, which are important for a range of industrial applications. It presents both high-quality experiments and cutting-edge numerical simulations, providing a level of insight and rigour rarely found in PhD theses. The scientific advancements concern the effect of the Earth’s rotation on large duct flows, the experimental confirmation of marginal turbulence in a pressure-driven square duct flow (previously only predicted in simulations), the identification of similar marginal turbulence in wall-driven flows using simulations (for the first time by any means) and, on a separate but related topic, a comprehensive experimental study on the phenomenon of drag reduction via polymer additives in turbulent duct flows. In turn, the work on drag reduction resulted in a correlation that provides a quantitative prediction of drag reduction based on a single, measurable material property of the polymer solution, regardless of the flow geometry or concentration. The first correlation of its kind, it represents an important advancement from both a scientific and practical perspective.

Angular momentum transport and pattern formation in medium- and wide-gap turbulent Taylor-Couette flow
Angular momentum transport and pattern formation in medium- and wide-gap turbulent Taylor-Couette flow

Author: Andreas Froitzheim

Publisher: Cuvillier Verlag

Published: 2019-08-26

Total Pages: 172

ISBN-13: 3736960735

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Turbulent Taylor-Couette flow, where the fluid is confined by two coaxial and independently rotating cylinders, is experimentally investigated within this thesis for medium and wide gaps. To reveal the influence of flow patterns on the angular momentum transport, direct torque measurements, flow visualizations and particle image velocimetry are performed in two different facilities. For the largely unexplored radius ratio regime of η = 0.357, the directly measured torque features a transition as a function of shear, which is connected to the capacity of the outer cylinder to emit small-scale plumes. When the cylinders rotate slightly in counter-direction, a maximum in torque occurs at μmax = -0.123, which is induced by the formation of large-scale Taylor vortices. The contribution of these vortices to the overall momentum transport clearly exceeds the contribution of the turbulent fluctuations for η = 0.5. Furthermore, the large-scale Taylor rolls are driven by small-scale plumes and feature azimuthally traveling waves for η = 0.714. Accordingly, the angular momentum transport in medium and wide-gap turbulent Taylor-Couette flow is determined by the interaction of turbulence and flow patterns of different scales.

IUTAM Symposium on Laminar-Turbulent Transition and Finite Amplitude Solutions
IUTAM Symposium on Laminar-Turbulent Transition and Finite Amplitude Solutions

Author: Tom Mullin

Publisher: Springer Science & Business Media

Published: 2005-12-28

Total Pages: 335

ISBN-13: 1402040490

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An exciting new direction in hydrodynamic stability theory and the transition to turbulence is concerned with the role of disconnected states or finite amplitude solutions in the evolution of disorder in fluid flows. This volume contains refereed papers presented at the IUTAM/LMS sponsored symposium on "Non-Uniqueness of Solutions to the Navier-Stokes equations and their Connection with Laminar-Turbulent Transition" held in Bristol 2004. Theoreticians and experimentalists gathered to discuss developments in understanding both the onset and collapse of disordered motion in shear flows such as those found in pipes and channels. The central objective of the symposium was to discuss the increasing amount of experimental and numerical evidence for finite amplitude solutions to the Navier-Stokes equations and to set the work into a modern theoretical context. The participants included many of the leading authorities in the subject and this volume captures much of the flavour of the resulting stimulating and lively discussions.