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We consider the optimal shape design of polymer distributors for the industrial spinning process, where long residence times are known to have a negative impact on the quality of the fibers. To this end we introduce a cost function based on the material age and the pressure energy required for the fluid transport. We obtain the shape derivative of the cost function without using the material derivative of the state based on a recent differentiability result for the Lagrangian formulation of shape optimization problems. Numerical experiments for a three-dimensional distributor verify the feasibility of our approach. [ABSTRACT FROM AUTHOR]

In this paper, we consider the topology optimization for a bipolar plate of a hydrogen electrolysis cell. We present a model for the bipolar plate using the Stokes equation with an additional drag term, which models the influence of fluid and solid regions. Furthermore, we derive a criterion for a uniform flow distribution in the bipolar plate. To obtain shapes that are well‐manufacturable, we introduce a novel smoothing technique for the fluid velocity. Finally, we present some numerical results and investigate the influence of the smoothing on the obtained shapes. [ABSTRACT FROM AUTHOR]

We analyze the theoretical framework of a shape optimization problem for a microchannel cooling system. To this end, a cost functional based on the tracking of absorbed energy by the cooler as well as some desired flow on a subdomain of the cooling system is introduced. The flow and temperature of the coolant are modeled by a Stokes system coupled to a convection diffusion equation. We prove the well-posedness of this model on a domain transformed by the speed method. Further, we rigorously prove that the cost functional of our optimization problem is shape differentiable and calculate its shape derivative by means of a recent material derivative free adjoint approach. [ABSTRACT FROM AUTHOR]

We consider the optimal shape design of polymer distributors used for industrial fiber spinning. In this laminar flow problem the residence time, the volume‐averaged age distribution of the fluid particles, has to be controlled to avoid material degradation. The residence time is modelled by an advection‐diffusion‐reaction equation with the fluid velocity being the transport field. This approach is more suitable for PDE‐constrained shape optimization than the Lagrangian particle‐tracking approach, where the observable is a finite set of trajectories. In order to develop an efficient shape optimization algorithm we derive the shape gradient of a tracking‐type cost functional by introducing the adjoint state. [ABSTRACT FROM AUTHOR]

Objectives: We want to investigate whether temperature measurements obtained from MR thermometry are accurate and reliable enough to aid the development and validation of simulation models for Laser-induced interstitial thermotherapy (LITT). Methods: Laser-induced interstitial thermotherapy (LITT) is applied to ex-vivo porcine livers. An artificial blood vessel is used to study the cooling effect of large blood vessels in proximity to the ablation zone. The experimental setting is simulated using a model based on partial differential equations (PDEs) for temperature, radiation, and tissue damage. The simulated temperature distributions are compared to temperature data obtained from MR thermometry. Results: The overall agreement between measurement and simulation is good for two of our four test cases, while for the remaining cases drift problems with the thermometry data have been an issue. At higher temperatures local deviations between simulation and measurement occur in close proximity to the laser applicator and the vessel. This suggests that certain aspects of the model may need some refinement. Conclusion: Thermometry data is well-suited for aiding the development of simulations models since it shows where refinements are necessary and enables the validation of such models. [ABSTRACT FROM AUTHOR]

The transport of gas‐solid suspensions in bended pipes can lead to erosion of the walls due to particle impact. In this context the numerical prediction of the erosion rate is usually based on an Eulerian flow description in combination with Lagrangian particle tracking, which however does not lend itself straightforwardly to the continuous adjoint approach of shape optimization. In order to find a pipe design, which is less prone to erosion, we therefore use a one‐way coupled Eulerian particle model. Upon formally computing the shape derivative of the resulting PDE‐constrained shape optimization problem, we minimize the erosion rate for a three‐dimensional tube bend under laminar flow conditions using a gradient descent method. [ABSTRACT FROM AUTHOR]

Diazo compounds are gathering interest for their potential in promoting greener synthesis routes. We investigate, at a lab‐scale, the continuous synthesis of diazo acetonitrile (DAN) using a micro‐structured flow reactor and a flow reaction calorimeter. Data concerning DAN formation in the former, and relative to reaction heat and gas flow rate in the latter, are collected. We present a physical and a grey‐box model, both of which are calibrated to our data. Compared to the physical model, the grey‐box approach allows to better incorporate the complex chemical reaction pathways of DAN. [ABSTRACT FROM AUTHOR]

A novel reactor concept for ammonia decomposition utilizing tail gas from a purification unit as heat supply is presented. The designed micro‐structured reactor integrates both endothermic ammonia decomposition and exothermic tail gas combustion. The reactor and corresponding process are simulated using a mathematical multi‐scale model, which combines the results of multiple detailed computational fluid dynamics simulations into a fast surrogate model. The latter is coupled with a process simulation software via a so‐called container to simulate the entire process. The efficiency of the presented reactor concept is determined and benefits over alternative approaches are highlighted. [ABSTRACT FROM AUTHOR]

Shape optimization of flow fields for electrochemical cells is performed. Simulation models of the flow field are introduced with and without the porous transport layer. The latter model is less detailed and used for shape optimization whereas the former one is used to validate the obtained results. Three objective functions are proposed based on the uniformity of the flow and residence time as well as the wall shear stress. After considering the respective optimization problems separately, techniques from multi‐criteria optimization are used to treat the conflicting objective functions systematically. The results highlight the potential of this approach for generating novel flow field designs for electrochemical cells. [ABSTRACT FROM AUTHOR]

A shape optimization approach for the design of cavities with a specified wall shear stress profile is presented. Applications are the design of spin pack geometries with low and uniform residence times and without dead spaces to prevent polymer degradation for sensitive materials. The optimization uses a Surrogate Model based on the Newtonian Stokes equation as a simplification. An indirect objective based on wall shear stress is used to improve the residence time. The results are then validated on a realistic spin pack with the Full Model based on the non-Newtonian Navier-Stokes equation. [ABSTRACT FROM AUTHOR]

Using PDE-constrained optimization we introduce a parameter identification approach which can identify the blood perfusion rate from MR thermometry data obtained during the treatment with laser-induced thermotherapy (LITT). The blood perfusion rate, i.e., the cooling effect induced by blood vessels, can be identified during the first stage of the treatment. This information can then be used by a simulation to monitor and predict the ongoing treatment. The approach is tested with synthetic measurements with and without artificial noise as input data. [ABSTRACT FROM AUTHOR]

Laser-induced thermotherapy (LITT) is a minimally invasive method causing tumor destruction due to heat ablation and coagulative effects. Computer simulations can play an important role to assist physicians with the planning and monitoring of the treatment. Our recent study with ex-vivo porcine livers has shown that the vaporization of the water in the tissue must be taken into account when modeling LITT. We extend the model used for simulating LITT to account for vaporization using two different approaches. Results obtained with these new models are then compared with the measurements from the original study. [ABSTRACT FROM AUTHOR]

We introduce a new approach to solve shape optimization problems with state constraints. The problem is reformulated on a fixed reference domain using conformal pull-back. The shape dependence is then hidden in the conformal parameter. The problem is discretized using FEM and solved as an NLP. Finally the optimal shape can be reconstructed from the optimal conformal parameter. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Free-form shape optimization techniques are investigated to improve the separation efficiency of structured packings in laboratory-scale distillation columns. A simplified simulation model based on computational fluid dynamics (CFD) for the mass transfer in the distillation column is used and a corresponding shape optimization problem is formulated. The goal of the optimization is to increase the mass transfer in the column by changing the packing's shape, which has been previously used as criterion for increasing the separation efficiency of the column. The computational shape optimization yields promising results, with an increased mass transfer of nearly 20%. For validation, the resulting optimized shape is additively manufactured using 3D-printing and investigated experimentally. The experimental results are in good agreement with the performance improvement predicted by the computational model, yielding an increase in separation efficiency of around 20%. [ABSTRACT FROM AUTHOR]