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In the early 90’ the research institute Deltares began the development of a non-hydrostatic extension for the existing three-dimensional shallow-water simulation software Delft3D-FLOW a modeling package which was originally intended for hydrostatic shallow-water flow. The original non-hydrostatic flow model is based on a non-conservative finite-difference discretization of the momentum equations. A model study demonstrated improved performance of conservative discretization schemes over non-conservative scheme for strongly varying and convection-dominated flow. For non-hydrostatic flow a momentum conservative finite-volume discretization is more appropriate. A three-dimensional finite-volume scheme on staggered z-layer grids is presented with improved momentum conservation properties. For simulations of dynamic flow the conservation properties in time of the numerical scheme become more important. Since many typical non-hydrostatic flow situations do not concern steady state calculations, also attention is paid to the momentum conservation properties of the model in time. For strongly non-hydrostatic flow simulations the treatment of the bottom and free-surface becomes of large importance. The design of the finite-volume discretization gave the opportunity to have a renewed look on of the existing Delft3D z-layer model. Simulations have been carried out of short waves in a basin. The results showed an improvement compared with the existing finite-difference method and brought to the attention other aspects of the existing discretization that demand improvement in order to make the model suitable for strongly non-hydrostatic, convection-dominated flow.

In Aerospace Engineering the field of Computational Flow Dynamics (CFD) studies the aerodynamic behaviour of aircrafts. What is currently being used to perform CFD simulations are Computer Aided Design (CAD) models of the airplanes, which are usually low-detail industrial design models. Research of new methods for improving the results of the simulating process is of great importance. One method that can be tested in this direction is the creation of more detailed models of the actual airplanes via reverse engineering techniques. Laser scanning is one of these techniques. Here, a laser scanner is used to measure TU Delft’s Cessna Citation. Afterwards, parts of the airplane are modelled by using suitable methods to process the obtained laser points.

The goal of this thesis is to contribute to the understanding of the method CFD by engineers in determining wind loads on structures and ideally contribute to the development of a future design tool. The field of wind engineering is explored and wind tunnel and CFD modelling is discussed. Results determined with wind tunnel tests and CFD simulations are compared and verified. This is the focus of this thesis. Recommended actions for a guideline on post-processing steps are presented. Conclusions that are drawn concern the wall-adjacent cell height, the use of turbulence models and simulation methods.

Summary Of the thesis :’ Mixing and In-situ product removal in micro bioreactors’ by Xiaonan Li The work presented in this thesis is a part of a large cluster project, which was formed between DSM, Organon, Applikon and two university groups (TU Delft and University of Twente), under the ACTS and IBOS program. The aim of this cluster project was to develop a system consisting of parallel bioreactors of 30 to 200 microliter working volume for the cultivation of micro-organisms under well controlled industrially relevant condition (T, pH, DO etc.), and operated as fed-batch reactor in long term (>200h). This platform has the potential to be used for high throughput screening applications for gene identification or the related small scale protein fermentation to increase the protein production process development rate and to reduce the research cost. The development of the platform starts with the design of a single micro-reactor; the single micro-reactor is the integration of well developed sensing system, control system, mixing system and other accessories, like, pumps, valves, adaptors, vessels etc. However many components are not available or not suitable for our application. In this thesis several novel mixing methods, which can provide sufficient mixing in a micro-reactor to satisfy the need of micro-organism fermentation, are developed. Furthermore, microfluidic components are important to facilitate substrate feeding as well as by product removing. An ISPR concept was experimentally demonstrated in this thesis to distinguish a wider scope of micro-reactor applications. One of the main reasons to apply micro systems technology is that compared with traditional reaction (fermentation) technologies, a superior, rapid and sufficient mixing can easily be achieved using micro technologies, especially for those microfluidic devices, which integrated with passive micro structures, with working volume tens of nanoliters. However, the mixing in the microreactor, which with working volme around hundreds microliter, is still be considered as a bottleneck for the high biomass concentration fermentation. In chapter 2, recycle flow mixing (RFM) method was presented. By continuously moving liquid solution from high oxygen concentration area to low oxygen concentration area via multiple fluxes, the system obtains maximum oxygen transfer, which is considered as the bottleneck for high cell density fermentation. Meanwhile, the recycled flows create vigorous convectionin the micro-reactor and obtain good mixing. The mixing performance was experimentally verified with a prototype reactor (with working volume 30 microliter). Under a small recycle flow rate (20 microliter/min), the measured well mixing time was around 800s. However, after taken into account the influence of the recycle tubes (50 microliter), the mixing in the microreactor was considered as comparable as an ideal mixed reactor. The impact of various oxygen transfer abilities on high cell density fermentation was estimated by 2D / 3D CFD simulations. With recycle flow rate 0.001 m/s, the kla value of the microreactor was around 0.023 s-1, which was in the same order of magnitude as a regular stirred tank. This oxygen transfer was sufficient for a high biomass concentration fermentation (Max. biomass concentration > 20 g/l). The mixing performance of RFM method is dependent on the value of the recycle fluxes, therefore, a strong internal micro-pump plays an essential role in the system. To avoid the dependence on the micro-pump development, an alternative micro-mixing method was presented in chapter 3. Oscillation flows, which are created by a central actuator, induce vigorous convection in the micro-reactor(s) to obtain good mixing. The mixing performance within a single reactor was estimated by CFD calculations, a simplified micro-mixing correlation and validated experimentally. With an oscillation frequency (f) of 8.33 Hz, oscillation flow rate (fv) 1000 microliter/min, the experimental well mixing time was 45s; the CFD simulated well mixing time was 37 s; the model calculated well mixing time was 35s. With a stronger oscillation (f=8.33Hz, fv=3000 microliter/min) the well mixing time dropped to 4s.(CFD simulated result & model correlative result) The oscillation mixing method has the potential to be easily integrated with parallel reactorsrrelative This concept has been proven experimentally using a 96-wells micro titer plate and one oscillation pump (f=2.22 Hz, fv=2000 microliter/min). Three parallel reactors followed the same trend and reached to well mixing time at 120s, 122s and 128s, respectively. The comparison of dye distribution results between various tubes indicated a similar mixing behavior in different reactors. Hence, the result show the possibility of using one central actuator to create oscillation fluids to achieve mixing on multi-reactors. Additional experiments have been done with oscillation mixing method to test the influence of the mixing methods on cells viability and influence of the oscillation mixing method on cells suspension. The experiment clearly indicated that compared to the magnetic stirrer mixing method, oscillation mixing method showed less damage on the cells during cell viability test. Homogeneous cell suspension was maintained in the micro bioreactor during overnight oscillation mixing. The characteristics of microfluidic channels for mass transfer were explored in chapter 4. When two liquid streams join into one microchannel with diameter around 150 mm, both streams will behave as laminar flows and run parallel to each other with a stable interface in between. If for certain components there are concentration differences between two streams, over the interface, components can transfer from one stream to another via diffusion. In this chapter the quantitative transfer of glucose between two cocurrent streams was estimated by CFD and experimentally verified. A microchannel has a large surface to volume ratio; therefore, within a short time significant amount of glucose can be transferred from one stream to another. The transfer rate of glucose was measured to be 2.4 - 11.9 nmol /min at a residence time of 54 - 857ms and glucose concentration in the feed stream of a modest 10.4mM. If this transfer would be applied for a fed-batch cultivations in a 100ml microbioreactor, glucose feed rates ranging from 0.26 to 1.3 g/Lreactor/h could be achieved, which is sufficient to perform industrial fermentation processes of fed-batch cultivations at high biomass concentrations. This microfluidic channel also could be used for by-product removal application. The reason by-product needs to be removed is because of the potential risk of the product inhibition, which may cause a decrease in microorganism activity. An implementaed In Situ Product Removal (ISPR) method can circumvent this risk by keeping the dissolved product concentration low in the reactor. Chapter 5 focuses on demonstrating the feasibility of applying a suitable ISPR method on micro-scale bioreactor. Lactic acid was selected as the target chemical. Extraction was selected as the separation method. By pushing a selected extractant (trioctylamine / decanol / dodecane) through a hydrophobic micro hollow fiber, lactic acid is extracted from the aqueous phase into organic phase, and then removed from the microreactor. The micro hollow fiber has the sole task to be the barrier to isolate microorganism from organic phase. The extraction ability was estimated by a model and then validated experimentally. The high specific interfacial area in the micro ISPR system (13.3E+3 m2/m3) shows the advantage of the microextraction for ISPR processes. High ISPR removal rate (1.92e-6 mol/l/s) was obtained experimentally. This removal rate was in the same order of magnitude as the reported lactic acid production rates in mammalian cell cultures (7.09e-7 to 3.7 e-5 mol/l/s). In conclusion, this thesis presents the development of novel micro-mixing methods and the preliminary application of possible In Situ Production Removal (ISPR) methods, leading to the increased applicability of (fed-) batch micro bioreactor for long-term high-biomass concentration fermentation. However, a combined microbioreactor (including sensor, ISPR design and novel mixing design) has yet not been tested experimentally. A number of present challenges is discussed in Chapter 6.

The keel of a sailing yacht has been shown to constitute a significant part of the overall resistance. Where the details of this effect are not yet fully understood, Computational Fluid Dynamics (CFD) analysis might reveal mechanisms unseen to the experimental eye. An important step in CFD application is the simulation of a number of validation cases. In the present study I simulate three different validation cases in the commercial CFD solver FLUENT, applying a Reynold's Averaged Navier-Stokes (RANS) method with a realizable k-epsilon turbulence model and a Volume of Fluid (VOF) free-surface approach. From these three validation cases I obtain five drag coefficients, four of which are within an acceptable range of error of the experimental values. After this validation, I consider several mechanisms related to keel resistance. Simulations indicate that the keel rudder interaction is Froude scaled and that the keel resistance can be scaled by a form factor method, presumably by means of a flat plate skin friction line.

The main aim of the research is to passively use the on-site energy to create passive climate comfort. Usually this these passive strategies are not integrated into the design process but added to the building design later on when the building design is already finalized. The main topic of this building technology research is to integrate sustainability concepts into the decisions making process of the building design. Out of all passive ways to us on-site energy, wind and daylight are chosen as the sub topics for this research in order to improve the architectural design. The envelope of the building filters/uses the wind and daylight energy to climatise the building in a passive way. The wind research will transform the building envelope on a large scale while the daylight research will transform the building envelope on a small/component scale. Both of them will work together in improving the architectural design and the energy performance of the building.

We study flow and heat transfer to a cylinder in cross flow at Re = 3,900–80,000 by means of three-dimensional transient RANS (T-RANS) simulations, employing an RNG k − ε turbulence model. Both the case of a bare solid cylinder and that of a solid cylinder surrounded at some fixed distance by a thin porous layer have been studied. The latter configuration is a standard test geometry for measuring the insulating and protective performance of garments. In this geometry, the flow in the space between the solid cylinder and the porous layer is laminar but periodic, whereas the outer flow is transitional and characterized by vortex shedding in the wake of the cylinder. The results from the T-RANS simulations are validated against data from Direct Numerical Simulations and experiments. It is found that T-RANS is very well suited for simulating this type of flow. The transient nature of the flow underneath the porous layer is well reproduced, as well as the influence of vortex shedding on the heat transfer in the downstream stagnation zone. T-RANS results are found to be in much better agreement with DNS and experimental data than results from steady-state RANS.

Renewed interest in propeller propulsion on aircraft configurations combined with higher propeller loads lead to the question how the effects of the propulsion on model support disturbances should be accounted for. In this paper, the determination of engine power effects on support interference of sting-mounted models is demonstrated by a measurement on a four-engine turboprop aircraft. CFD results on a more generic model are presented in order to clarify the possible mechanism behind engine power effects on support interference. The engine slipstream induces a local change in angle of sideslip at the model sting thereby influencing the sting near-field and far-field effects. Whether or not the net result of these changes in the disturbance pattern leads to a significant engine power effect depends on the configuration of the wind tunnel model and the test setup.

In this thesis three different combustion systems, equipped with either a single or multiple flameless combustion burner(s), are discussed. All these setups were investigated both experimentally and numerically, i.e., using Computational Fluid Dynamics (CFD) simulations. Flameless combustion is a combustion technology capable of accomplishing the combination of high energy efficiency (by preheating of the combustion air) and low emissions, especially nitrogen oxides (NOx ). These high combustion air preheat temperatures normally account for increased thermal formation of NOx , however, in flameless combustion, by delayed mixing of the fuel and oxidizer and high internal flue gas recirculation, the rates of these reactions are decreased. Nitrogen oxide plays a key role in acid rain formation and the generation of photochemical smog. The first setup that has been investigated is a furnace equipped with two regenerative flameless combustion burner pairs, with a thermal power of 100 kWth each, located at the laboratories of Kungliga Tekniska H¨ gskolan (KTH) in Stockholm, Sweden (Chapter 4). The objective of this study is to investigate the performance of the furnace operating in two different firing modes, parallel and staggered. The furnace performance is defined as the energy efficiency and the NO emissions. Experimental results show that for parallel firing mode both the efficiency was higher and the NO emissions were lower compared to staggered firing mode. With the use of the CFD simulations, it was shown that in parallel mode the radiative heat transfer was higher due to formation of a larger zone with gases with improved radiative properties and that higher velocities along the cooling tubes, due to lower momentum destruction, led to higher convective heat transfer. Both of these heat transfer methods contributed to the higher energy efficiency in parallel firing mode. Additionally, the lower formation of NO emissions in parallel firing mode was due to the fact that the low-momentum fuel jets merged slower with the high-momentum combustion air jets, resulting in more internal flue gas recirculation and a less intense combustion zone. Moreover, it was found that NOx was formed via the thermal and N2O intermediate pathways. No prompt NO was formed, while the reburning pathway resulted in a reduction of the total NO emissions. The second setup is a 300 kWth furnace equipped with three pairs of regenerative flameless combustion burners, located at Delft University of Technology (DUT) in the Netherlands (Chapter 5). An experimental parametric study was performed, varying the positions of the burners in the furnace (the burner configuration), the firing mode (parallel and staggered), the excess air ratio and the cycle time, with the objective to optimize the furnace performance. Since similar trends in the furnace performance, as for the furnace at KTH, comparing parallel and staggered firing mode, were observed, staggered mode was exempted from further analysis. Additionally, one of the five investigated burner configurations has also been exempted due to a significant lower energy efficiency compared to the other configurations. The experimental results show that the burner positioning and the cycle time had a significant influence on the temperature inside the regenerators, and thus on the preheat temperature of the combustion air. This temperature turned out to be important regarding the CO emissions. Furthermore, it was found that comparing different cases firing in flameless mode, an improved temperature uniformity in the furnace was not reflected by a higher energy efficiency. Finally, a horizontal setup of the firing burners (the three firing burners positioned in a horizontal row) improved the energy efficiency at similar temperature uniformities. Steady CFD simulations have been performed for this furnace for four different burner configurations firing in parallel mode (Chapter 6). During the careful selection of the set of physical models to be used, it was found that, due to relatively low Reynolds numbers in the cooling air flow in the annulus of the cooling tubes, predictions of the heat extraction rates of these cooling tubes were improved by treating the flow in the cooling tubes as laminar. Furthermore, the applied error tolerance of the ISAT procedure was insufficient for accurate species concentration predictions, however, based on analysis of the main species concentrations in the flue gas, this inaccuracy did not influence the overall predictions. It was possible to explain the most important results of the experimental study using the CFD simulations. In the first place, it was found that a recirculation zone between the upper firing burners and the stack in two configurations resulted in a smaller fraction of the flue gases leaving the furnace via the stack compared to the other two configurations. Thus, a larger fraction of the flue gas left the furnace via the regenerating burners, which resulted in higher preheat temperatures of the combustion air. Secondly, the experimentally observed differences in the temperature uniformity between the four configurations could be explained by the presence of less or more pronounced recirculation zones, the latter leading to higher temperature uniformities in the furnace. Finally, it was confirmed that the jets of the burners showed similar merging behaviour for different burner configurations, leading to similar NO emissions, a trend that was also observed in the experiments. The third setup is a prototype flameless combustion gas turbine combustor (Chapter 7). The combustor was fired with various Low Calorific Value (LCV) gases. The influence of several parameters (the fuel composition, the outlet temperature and the inlet nozzle diameter) on the CO and NO emissions has been investigated. In the first place, it was shown that this prototype flameless combustion gas turbine combustor could be operated in flameless mode firing the LCV gases. Moreover, for both pollutants ultra-low emissions (single-digit) have been achieved. In the CFD simulations, different turbulence models and chemistry mechanisms have been compared, leading to a set with models which gave the best results. Comparing the measured and predicted axial temperature profiles in the combustor, it was concluded that the observed discrepancies were within the range of uncertainty in what are optimal values of the model constants. From NO calculations, ultra-low emission combustion was confirmed. Also, it was found that 90% of the NO was formed via the N2 O path, and the remaining 10% via the thermal pathway. No prompt NO was formed, a trend also observed for the KTH furnace. In conclusion, important knowledge on the behaviour of furnaces equipped with multiple flameless combustion burners has been attained. Especially, the influence on the furnace performance of the firing configuration of the burners and the burner positioning in the furnace will contribute to more successful (industrial) application of this combustion technology in the future. Recommendations for the installation of flameless combustion burners in large industrial-scale furnaces have been proposed. Finally, the shown possibility of firing a (prototype) gas turbine combustor with low calorific value gases in flameless mode, enables the utilization of biomass derived gaseous fuels in existing equipment.

Power producing companies have faced a new situation following the development of unregulated electricity markets. Strong competition forces them to take power production costs into account more carefully in order to maintain or increase profits. Additionally, to promote the efforts to reduce CO2 emissions,legislation and taxation drives operators to increase the use of coal and renewable energy sources more efficiently and over a wider range. This results in an increasing interest in the use of solid-biomass-based fuels in pulverized coal fired power plants. Therefore, fuel flexibility due to the combustion of varying relative shares of coal and biomass poses new challenges for plant operators. The understanding of deposition formation and its behavior and consequences has become a key issue in optimizing plant operation and in securing plant performance and availability. The investigation presented in this dissertation was carried out as part of the EU-ADMONI project. The overall objective of the work presented here is the development of advanced monitoring models for solid fuel fired steam power plants. To obtain such advanced monitoring methods, three kinds of models are to be coupled with each other. They are: Process Monitoring Models, Dynamic Process Models and 3D Boiler Models. This coupling consists of the exchange of different boundary conditions (BCs) with each other. Although the development of an overall monitoring methodology has been outside the scope of this work, this dissertation contains descriptions and examples of the three separate modelling techniques needed to obtain the overall monitoring methodology which can be used for improving the operation of steam power plants. Process monitoring models have been developed to predict or monitor either heat transfer resistances of the heat exchanging equipment of the steam cycle (this is an indicator of the amount of deposit formation) or the overall steam cycle efficiency of the power plant at hand, using the process data provided by the Data Acquisition System (DAS) of the plant. The novelty of the models presented in this work is the investigation of the possible use of exergy analysis within the existing monitoring models to detect a possible decay of plant performance due to arising operational problems. Dynamic process models of the steam cycle have been developed to provide insight in the physics and plant behavior when (co)-firing varying biomass and coal blends. The results of these models can be very important for the design of the control system of plants which are co-firing these kinds of mixtures. Physically based models have been formulated, since no historical data is available in the design phase, and thus black box models were not an option. A methodology for the dynamic modelling of energy conversion systems has been proposed, and the modelling of a simple single pressure, small, steam power cycle, has been done as a "proof-of-concept". An accurate methodology for the simulation of 3D pf combustion has been developed to accurately predict the flow and temperature fields inside the boiler. To be able to accurately predict these phenomena, detailed combustion models are necessary. Various combustion models for solid fuel combustion have been proposed in literature, but an extensive validation of these models is hardly given. Therefore, several combustion models have been validated against experimental data and the most accurate model has been used for full scale 3D boiler

Two transported PDF strategies, joint velocity-scalar PDF (JVSPDF) and joint scalar PDF (JSPDF), are investigated for bluff-body stabilized jet-type turbulent diffusion flames with a variable degree of turbulence–chemistry interaction. Chemistry is modeled by means of the novel reaction-diffusion manifold (REDIM) technique. A detailed chemistry mechanism is reduced, including diffusion effects, with N 2 and CO 2 mass fractions as reduced coordinates. The second-moment closure RANS turbulence model and the modified Curl’s micro-mixing model are not varied. Radiative heat loss effects are ignored. The results for mean velocity and velocity fluctuations in physical space are very similar for both PDF methods. They agree well with experimental data up to the neck zone. Each of the two PDF approaches implies a different closure for the velocity-scalar correlation. This leads to differences in the radial profiles in physical space of mean scalars and mixture fraction variance, due to different scalar flux modeling. Differences are visible in mean mixture fraction and mean temperature, as well as in mixture fraction variance. In principle, the JVSPDF simulations can be closer to physical reality, as a differential model is implied for the scalar fluxes, whereas the gradient diffusion hypothesis is implied in JSPDF simulations. Yet, in JSPDF simulations, turbulent diffusion can be tuned by means of the turbulent Schmidt number. In the neck zone, where the turbulent flow field results deteriorate, the joint scalar PDF results are in somewhat better agreement with experimental data, for the test cases considered. In composition space, where results are reported as scatter plots, differences between the two PDF strategies are small in the calculations at hand, with a little more local extinction in the joint scalar PDF results.

Advanced Oxidation Processes (AOPs) are innovative, cost-effective, catalyzed chemical oxidation processes for treating pollutants in low or high concentration from contaminated soil, sludge and water. The common used AOPs in drinking water treatment include UV/H2O2 process, UV/Ozone Process, UV/Titanium Dioxide and Fenton’s Reagent. AOPs are ultraviolet driven, which share predominance from photochemical technology, and often, give the clients dual benefit of both environmental contaminant treatment and disinfection. Endocrine Disrupting Chemicals (EDCs) are very disturbing contaminants measured in natural waters. Phenols and their tert-butyl derivatives are important contaminants belonging to EDCs. After a successful workshop for developing alternative drinking water treatments at Shanghai, AOPs with UV/H2O2 technology are chosen to remove 4-tert-butylphenol (4TBP) from Shanghai water. The kinetics of reaction was studied in the first part of this thesis. The results show that UV/H2O2 process can effectively decrease 4TBP concentration than hydrogen peroxide alone. Good free oxidation radical production can be achieved within UV dose range from 0 to 200mJ/cm2 by a low pressure mercury lamp. The 4TBP degradation process fits with pseudo first order equation for UV-dose and H2O2-dose. However, at very high H2O2-doses, the scavenging of hydroxyl-radicals needs to be taken into account. Computational Fluid Dynamics (CFD) modeling of UV reactor and validation of CFD model were studied in the second part of this thesis work in order to provide an applicable UV reactor design for the 4TBP treatment and also give possible reactor improvement suggestions. The CFD model used in this study is a 2-D model developed using software Comsol, V3.3a, based on a current UV reactor design at Kiwa Water Research, the Netherlands. The developed UV dose model includes three parts, a k-ε flow model, a UV intensity model and a random walk model. Different feed flow rates and different lamp configurations were studied by the model. The calculation results show that a higher feed flow rate contributes to a relative narrow UV dose distribution than the lower flow rate. With three lamp configurations, position 0 is the best among the three with the highest average UV dose as well as the narrowest dose distribution pattern. Model also predicted low pressure lamps have about 8% higher power output to UV dose efficiency than medium pressure lamps. Validation of the flow model was helped by flow measurements at Delft University of Technology. Experimental studies of velocity measurements by Laser Doppler Velocity Meter were conducted together with salt and dye dose experiments. After comparisons of model predictions and experimental measurements, it was found that the k-ε CFD flow model demonstrated generally good qualitative prediction of flow inside the reactor but failed to give correct prediction of recirculation zones behind the quartz tubes. There are dead zones of water at the top and bottom near the inlet of the reactor. Bigger areas exist behind the quartz tubes that have water recirculation than the model predicted, which may result 25% of more UV dose prediction by the model. And differences caused by 2-D model and 3-D measurements may result about 20% less UV dose model prediction. Current UV reactor design at Kiwa Water Research, position 0 and low pressure mercury lamps applied at a feed flow rate of 4.1m3/h appears to be an applicable design for advanced oxidation treatment of 4TBP by UV/H2O2 in Shanghai. High roughness quartz tubes walls and relative smaller ratio of reactor to feed pipe diameters are recommended to improve reactor performance in the recirculation and dead zones with current design. Further investigations of the dose model and UV-sensitive dyed microspheres particle tracking experiments are recommended.

As one of the most fast growing species on earth, microalgae provides great potential to satisfy the ever increasing demand in food, energy and material in a sustainable way. The focus for this thesis work is on one of the most important bottle neck of microalgae harvest process: microalgae dewatering, by CFD modeling of the flow and sedimentation separation in Evodos SPT centrifuge. Various microalgae dewatering technologies have been reviewed and evaluated. Compare to traditional conical disk centrifuge Evodos SPT centrifuge provides 10% to 20% energy consumption, removing up to 95% extracellular water and other benefits i.e. mechanical simplicity and process flexibility etc. In the model, the fluid dynamic behaviors of multiphase flow has been considered. In this research a complete 3D CFD model of the Evodos centrifuge consisting of five sub components have been built. The particle behavior for the centrifugation separation is based on DPM (Discrete Phase Model) in Fluent. The result of the 3D CFD model gives a clear overview of the pathline, flow pattern and pressure profile inside the centrifuge as well as separation efficiency on particle sizes. The model has been validated through visual result from algae separation test runs, theoretical equations and starch test run measurements. A test and sample taking with starch solution has also been carried out on Evodos site in Breda. This thesis work laid a good foundation for future studies in the CFD modeling of Evodos SPT centrifuge and similar machines. The future focus should be on optimizing the geometry of the parallel plates, impeller chamber for separation efficiency; understanding the effects and impacts of operation conditions and further develop the multiphase model.

Industrial buildings, used as warehouses or distribution centres, are characterized by large doors which are opened temporarily or for longer periods. A new technique - called Ambergy - is investigated which prevents unnecessary energy loss through open overhead doors in heated industrial halls. This technique consists of a smart coupling between the heating system and the overhead doors. By temporarily switching off gas-fired heaters near open doors, the heat loss through the door should be minimized. It is expected that the Ambergy system can contribute to energy savings, also when the indoor thermal comfort is taken into account. However, at the start of the research, the amount of energy which can be saved and the effect of the Ambergy system on the thermal comfort, was not known yet. If energy can be saved by using the Ambergy system, and the current thermal comfort level can be retained, many industrial buildings can benefit from this. This thesis aimed to get an insight in the energy saving effects of the Ambergy system and to determine its potential - technical - feasibility. To fulfil this aim, a literature study is performed to predict important physical aspects affecting the heat balance, to gain insight in air transport phenomena and to derive criteria to compare thermal comfort levels. By using the software packages Matlab and Simulink, these physical aspects and air flow phenomena are implemented in a thermal building-dynamics simulation. This simulation predicts effect of the Ambergy system on the air temperature across the hall and the fuel savings for different circumstances during a whole winter season. Assumptions made in the thermal building-dynamics simulation - regarding the air flow direction - are verified with a computational fluid dynamics (CFD) model. Furthermore, measurements are performed in one representative industrial hall (Alphatron, Rotterdam), to gain input data for both models and to validate the outcome. To make the system as optimal as possible and accepted by the employees, also the effect on the indoor thermal comfort is taken into account. A comparison between the current thermal comfort level and the expected thermal comfort level, when applying Ambergy, is performed by calculating the required insulation value of the clothing of the employees (IREQ-value). As part of this thesis, also requirements for pilot projects at business facilities of DHL and Alphatron - in ’s Hertogenbosch and Rotterdam respectively - are defined and these pilot projects were carried out during this thesis. Due to the confidential nature of this research and the embargo set by the TU Delft and BreedofBuilds B.V., no information can publicly be given regarding the results, conclusions and recommendations done in this research until August 2017.

At present it is widely accepted that there is no universal turbulence model, i.e. no turbulence model can give acceptably good predictions for all turbulent flows that are found in nature or engineering. Every turbulence model is based on certain assumptions, and hence it is aimed at certain type of flows for which it recovers the effects that are occurring in that flow. The work presented in this thesis aims at improving the turbulence modelling applicable to the complex wall-bounded engineering flows and heat transfer. However, the basic requirement for the development of a new turbulence model is the understanding of the fundamental fluid flow principles. Therefore this work also presents a detailed analysis of a complex wall-bounded flow and heat transfer with multiple flow phenomena. The proposed turbulence model is a robust and reliable modification of the elliptic relaxation eddy-viscosity model, which gives accurate flow and heat transfer predictions in complex wall-bounded flows. In order make this model suitable for engineering computations, the compound near-wall treatment is presented, which makes flow predictions insensitive to the quality and resolution of the computational mesh used in the near-wall region. Both turbulence model and near-wall treatment are tested on several generic non-equilibrium test flows. Originating from the electronics industry applications, this thesis also gives LES study of the vortical structures and heat transfer in the case of the cooling of one in a series of wall-mounted cubes placed in an array on the wall of a channel flow by a round impinging jet. The geometry in this numerical analysis is defined by an in-line array of five cubes mounted on the wall of a plane channel. The central cube consists of the copper core and a layer of epoxy around the core, and only this cube is heated by specifying the constant temperature of the copper core. This cube is cooled by two mutually perpendicular streams: a channel flow parallel to the mounting wall, and a round impinging jet issued from the orifice which connects the channel with cubes and the chamber placed above it. There are several flow structures occurring in this flow, such as roll-up vortex rings, impingement, separation and reattachment, which dictated the conjugate heat transfer from the central heated cube.

Hydrodynamic processes largely determine the efficacy of drinking water treatment systems, in particular disinfection systems. A lack of understanding of the hydrodynamics has resulted in suboptimal designs of these systems. The formation of unwanted disinfection-by-products and the energy consumption or use of chemicals is therefore higher than necessary. In drinking water engineering, computational fluid dynamics (CFD) is therefore increasingly applied to predict the performance of treatment installations and to optimise these installations. CFD uses advanced numerical models to predict flow, mixing and (bio)-chemical reactions. In this thesis, the hydrodynamics and (bio)-chemistry in ozone and UV systems are studied by means of CFD models combined with experimental techniques. This combination leads to further development of CFD modelling as a tool to evaluate the performance of drinking water treatment installations. If the CFD model is applied properly, accounting for the complex turbulent motions and validated by experiments, this tool leads to a better design of UV reactors, ozone systems and other systems dictated by hydrodynamics. This work resulted in new insights in the applicability of models in ozone and UV installations, and new insights in design aspects of these installations.

A new satellite philosophy, developed during the last two decades, suggests to make satellites smaller and lighter rather than bigger and heavier. In other words, large (∼m3), single system satellites are being replaced by fleets of small (∼dm3), so-called micro-satellites. Future developmentsmay result in swarms ofmicro satellites flying through space in formation. Together they would perform the same tasks as a single large satellite, but with great savings in costs, increased simplicity, less vulnerability, and better replicability. As part of this new generation of (micro-)satellites, in order to provide highly precise station keeping, altitude control or long duration low thrust acceleration, new propulsion systems with thrusts in the ¹N to mN range need to be developed. One of the simplest forms ofmicro propulsion systems is a cold gas thruster: here, the energy stored in a pressurized gas is converted into kinetic energy through an expansion. The efficiency of such devices is strongly geometry and size dependent. Moreover, due to their small dimensions, combined with the low exhaust pressures in space, these systems behave differently than conventional large scale nozzles. Whereas experimental studies of micro propulsion systems are time consuming, difficult to perform with sufficient accuracy, and require expensive experimental setups, numerical computer simulations can be a powerful tool of investigation. This thesis deals with the use and, where needed, the optimum combination of different numerical simulation models for the computational design of micro-thrusters, aimed at optimizing their performance and understanding the physics of the flow in such systems. In the first phase of this work, we developed and used models for the design and optimization of micro thrusters providing a thrust in the mN range, as being developed for the actual state-of-the-art in micro propulsion system design. It was shown that conventional continuum Computational Fluid Dynamics can be used to study the gas flow and pressure distribution in such these micro-nozzles. Computationally predicted thrusts were in good agreement with experimental data. For mN thruster micro nozzles, in deviation from conventional large (kN-MN) thruster nozzles, viscous effects cannot be neglected due to the largely increased surface-to-volume ratio. As a result, efficiency loss due to developing viscous boundary layers, as well as surface roughness, are two main areas of concern in micro nozzles. Viscous losses were found to lead to an efficiency decrease of about 10%. Wall roughness added an extra 10% in efficiency loss. The increased boundary layer thickness reduced the effective cross sectional area of the divergent part of the nozzle. As a consequence it was found that, for optimum performance, micro nozzles should have a larger divergent angle than common in large scale nozzles. When the dimensions of micro-nozzles are further reduced, towards thrusts in the order of ¹N’s, the gas in the nozzle, particularly in its divergent part, becomes rarefied. Under these conditions continuum based Computational Fluid Dynamics no longer provides an accurate description of flows and pressures, and non-continuum models should be used instead. Direct Simulation Monte Carlo was selected as the simulation method of choice for these conditions, because of its favorable combination of accuracy, flexibility and computational costs compared to other available methods. Nevertheless, DSMC simulations are extremely more expensive than CFD simulations, particularly for weakly rarefied gases. A possible solution lies in the application of a hybrid CFD/DSMC approach, where CFD is applied in those regions where rarefaction is not important, and DSMC is used in those regions where rarefaction needs to be accounted for. One of the main challenges faced in the second phase of this project was therefore in the consistent and efficient coupling of DSMC and CFD, making use of an existing general purpose CFD code and an existing general purpose DSMC code. The general idea was to apply continuum CFD in the upstream, high pressure convergent part of the nozzle, and use the CFD results as boundary condition for DSMC simulations in the downstream, low pressure divergent part of the nozzle. A detailed analysis of the numerical accuracy and computational costs of such a hybrid approach was carried out by comparing the results to those of, extremely costly, full DSMC simulations. Both accuracy and computational costswere found to critically depend on the chosen location of the interface between the CFD and DSMC regions, at which data is transferred from the first to the latter. Rather than locating this interface at the throat, as is common in literature, we provide a simple recipe for the a priori determination of the optimal interface location. In this way, we were able to find an optimum combination between accuracy and costs, leading to results that deviate less than 2% from full DSMC simulations at typically 5-25% of the computational costs of full DSMC. Finally, combining the three computational approachesmentioned above,we were able to produce master curves for the performance of micro nozzles as a function of the gas-wall collision accommodation coefficient, over a wide range of nominal thrusts from O(10N) down to O(0.1¹N). For thrusts larger than 1mN, efficiencies larger than 90% were found, independent of the accommodation coefficient. For smaller thrusts, the efficiency becomes strongly dependent on the accommodation coefficient, i.e. on the nature of gas-wall collisions, and drops to 50% for thrusters in the ¹Nrangewith accommodation coefficients equal to one. By reducing this accommodation coefficient to a value below 0.5, which may be achieved by a proper selection of nozzle wall material and nozzle fabrication technique in combination with the proper choice of gas, this efficiency may be increased up to 70-80%. This thesis has resulted in: (i) design rules for micro thruster nozzles, (ii) computation methods that can be used in their design and evaluation, and (iii) in master efficiency curves that relate their nominal thrust and material properties to their thruster efficiency.