TY  - RPRT
A1  - Drescher, Hans Paul
T1  - The irreversible thermodynamic’s theorem of minimum entropy production applied to the laminar and the turbulent Couette flow
N2  - Analyzing thermodynamic non-equilibrium processes, like the laminar and turbulent fluid flow, the dissipation is a key parameter with a characteristic minimum condition. That is applied to characterize laminar and turbulent behaviour of the Couette flow, including its transition in both directions. The Couette flow is chosen as the only flow form with constant shear stress over the flow profile, being laminar, turbulent or both. The local dissipation defines quantitative and stable criteria for the transition and the existence of turbulence. There are basic results: The Navier Stokes equations cannot describe the experimental flow profiles of the turbulent Couette flow. But they are used to quantify the dissipation of turbulent fluctuation. The dissipation minimum requires turbulent structures reaching maximum macroscopic dimensions, describing turbulence as a “non-local” phenomenon. At the transition the Couette flow profiles and the shear stress change by a factor ≅ 5 due to a change of the “apparent” turbulent viscosity by a calculated factor ≅ 27. The resulting difference of the laminar and the turbulent profiles results in two different Reynolds numbers and different loci of transition, which are identified by calculation.
KW  - Turbulence
KW  - Transition
KW  - Minimum dissipation
Y1  - 2018
ER  - 
TY  - CHAP
A1  - Barnat, Miriam
A1  - Bosse, Elke
A1  - Tight, Malcolm
T1  - The Guiding Role of Theory in Mixed-Methods Research: Combining Individual and Institutional Perspectives on the Transition to Higher Education
T2  - Theory and Method in Higher Education Research. Vol 3
N2  - The methodological discourse of mixed-methods research offers general procedures to combine quantitative and qualitative methods for investigating complex fields of research such as higher education. However, integrating different methods still poses considerable challenges. To move beyond general recommendations for mixed-methods research, this chapter proposes to discuss methodological issues with respect to a particular research domain. Taking current studies on the transition to higher education as an example, the authors first provide an overview of the potentials and limitations of quantitative and qualitative methods in the research domain. Second, they show the need for a conceptual framework grounded in the theory of the research object to guide the integration of different methods and findings. Finally, an example study that investigates transition with regard to the interplay of the individual student and the institutional context serves to illustrate the guiding role of theory. The framework integrates different theoretical perspectives on transition, informs the selection of the research methods, and defines the nexus of the two strands that constitute the mixed-methods design. As the interplay of individual and context is of concern for teaching and learning in general, the example presented may be fruitful for the wider field of higher education research.
KW  - Quantitative research
KW  - Mixed-Methods Research
KW  - Transition
KW  - Students
KW  - Higher education
Y1  - 2017
SN  - 978-1-78743-222-2
U6  - http://dx.doi.org/10.1108/S2056-375220170000003001
SP  - 1
EP  - 19
PB  - Emerald Publishing Limited
ER  -