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The incompressible temporally developing turbulent boundary layer (TBL) and spatially developing turbulent boundary layer (SBL) with and without blowing is analyzed using the map-based stochastic one-dimensional turbulence (ODT) model. An understanding of these idealized flows is of fundamental relevance for boundary layer-type problems, which are frequently encountered in several applications, from atmospheric sciences to engineering. In the ODT model, the flow variables are resolved on all scales along a wall-normal, 1-D domain. These variables are evolved by a deterministic process representing molecular diffusion and by a stochastic process modeling the effect of turbulent advection and pressure fluctuations. Due to the reduction in dimensionality, the model is particularly appropriate for high Reynolds number flow. It is shown that the ODT model is able to capture salient features of the turbulent boundary layer-type flows by comparing the results with various available reference direct numerical simulation (DNS), large eddy simulation (LES) and experimental results. The comparison is presented for the mean velocity profiles, turbulent velocity fluctuation profiles (up to fourth order), the skin friction coefficient and shape factor for different bulk (Reb) and momentum Reynolds numbers (Reθ) using fixed model parameters. The influence of the model parameters is also discussed for various momentum Reynolds numbers for each investigated flow configuration. The results discussed in this thesis suggest that the ODT model is an economical and reasonably accurate approach for the simulation of turbulent boundary layer flows.
Background: Food sustainability is becoming increasingly important for the achievement of sustainable development goals, especially in light of recent global challenges of climate change, geopolitical conflict and the increasing vulnerability of food systems. The world is emphasising the importance of holistic approaches to agriculture and food systems to tackle these challenges. Germany’s Sustainable Development Strategy for 2030 associates SDGs 2, 3 12 and 15 with sustainable agriculture and food systems as crucial elements to achieve these goals. However, with the lack of knowledge in this area, and the scarcity of tools to monitor and assess food sustainability, it has become crucial to investigate potential holistic approaches and frameworks to assess the sustainability of food systems.
Purpose: This study uses the national framework of Sustainable Development Goals (SDGs), as the only available valid holistic framework, to explore the sustainability of the bread system in Germany. It operationalises the SDGs to bakery level to identify significant indicators that could, potentially, be used to assess the sustainability of artisan bakeries, and identify to which SDGs the bakeries contribute.
Methods: This study utilises a mixed-methods research design to address the multi-disciplinary nature of the food sustainability concept. It critically evaluates the SDG framework and identifies a set of indicators, which are expanded with further indicators to address the cultural dimension of bread as a cultural heritage. To collect data, a 26-item questionnaire was issued to 586 artisan bakeries with a response rate of 8.8% (n = 52); the 52 bakeries own 562 branches. This was followed by interviews with an acceptance rate of 19% (n = 10). Descriptive and inferential statistics were used to analyse the quantitative data, while the interviews were transcribed from German to English and coded using NVivo 11.
Results: Sustainable bread is redefined from a holistic perspective encompassing theory, policies and artisan bakeries. The results confirm that bakeries positively contribute to bread sustainability in Germany, as well as towards achieving the national SDGs. Progress areas include energy efficiency, sustainable packaging, local procurement, heritage promotion, waste reduction and ecolabels. Interestingly, individual bakeries appear to be slightly more sustainable than chains due to their flexibility in adapting to new practices and their use of organic products; however, chain bakeries are slightly less sustainable, but are proven to be more efficient in terms of productivity and market reach.