University of Jyväskylä

Dissertation: A study into paper production in mathematical terms (Jeronen)

Start date: Dec 16, 2011 12:00 PM

End date: Dec 16, 2011 03:00 PM

Location: Mattilanniemi, Agora, AgC 231

Juha JeronenM.Sc. Juha Jeronen defends his doctoral dissertation titled “On the mechanical stability and out-of-plane dynamics of a travelling panel submerged in axially flowing ideal fluid: a study into paper production in mathematical terms”.  Opponent Professor Reijo Kouhia (Tampere University of Technology) and custos Professor Pekka Neittaanmäki (University of Jyväskylä).

Abstract

In this study, we consider the dynamical behaviour and stability of a moving panel submerged in two-dimensional potential flow in a papermaking context. The steady-state critical velocity of the system is determined in terms of problem parameters.

Dynamical response is predicted via direct temporal simulations, and the eigenfrequency spectrum is analyzed, obtaining both the
subcritical free vibration behaviour and the initial postbuckling response.

By using an analytical functional solution for the reaction force of the surrounding air, the fluid-structure interaction model is reduced to one integro-differential equation. This makes it possible to work with this fluid-structure interaction problem efficiently with modest computational resources, while improving on the accuracy when compared to the classical technique of added-mass approximation.

Discretization is performed by the Fourier--Galerkin method, and results from the numerical computations are visualized. The predictions of the model are successfully validated against existing results. It is found that the model works especially well for long, narrow web spans.

To accomodate readers from various technical backgrounds, the topics are reported in a detailed, ground-up manner. After a general introduction, the elastic stability properties of the classical moving string and those of the damped moving string are analyzed in detail as an introduction to this class of problems.

Finally, to facilitate eigenfrequency spectrum analysis for the main problem, techniques are developed for overcoming the two main practical challenges: producing continuous curves out of randomly ordered eigenvalue data, and classifying physically meaningful solutions versus numerical artifacts.

Further information:

Juha Jeronen, tel. 040 7607 328, juha.jeronen@jyu.fi

The dissertation is published in the series Jyväskylä Studies in Computing no 148, Jyväskylä: University of Jyväskylä, 2011, 243 p., ISSN 1456-5390; 148, ISBN 978-951-39-4595-4, ISBN 978-951-39-4596-1 (PDF). Inquiries: University Library, Publishing Unit, tel. 040 805 3825, myynti@jyu.fi.


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