Effektuttaget ur en elmotor grundar sig i hur mycket ström som kan överföras i elmotorns lindning, vilken i sin tur oftast begränsas av hur varm den blir genom resistiv uppvärmning. Målet med arbetet var att ta reda på vilket värme som uppstår i ledaren, vilken kyleffekt ett vätskeflöde genom ledaren har samt vilket vätsketryck som krävs för att temperaturen på kylvätskan inte ska överstiga 95℃. Genom att ställa upp en analytisk modell kring en ledare och ett vätskeflöde genom denna, vilket i sin tur betyder att hitta kopplingar mellan strömningsmekanikens teori och värmeöverföringsteorin sa erhölls ett resultat. Sedan gjordes både simuleringar och experiment med samma förutsättningar för att kunna validera den analytiska modellen. Den analytiska modellen visade sig stämma väl överens med verkligheten och det skulle visa sig att för en elmotor med 48 ledare med en strömflödestäthet på 50 𝐴/𝑚𝑚2, med en inkommande kylvätsketemperatur på 60℃ och där kylvätskan inte får överstiga 95℃ sa kommer det krävas en pump som kan ge ett flöde av 15 𝑙/𝑚𝑖𝑛 vid ett tryckfall på 1 𝑏𝑎𝑟.

<p>The fluid simulation in computer generates realistic animations of fluids by solving Navier-Stokes equation. The methods of simulation are divided into two types. The grid-based methods and particle-based methods. The former one is wildly used for scientific computation because of its precision of simulation while the latter one is used in visual effects, games and other areas requiring real-time simulation because of the less computation time it has. </p> <p> </p><p>The indoor airflow simulations with HVAC system in construction design is one specific application in scientific computation and uses grid-based simulation as the general-purpose simulation does. This study addresses the problem that this kind of airflow simulations in construction design using grid-based methods are very time consuming and always need designers to do pretreatment of the building model, which takes time, money, and effort. On the other hand, the particle-based methods would have less computation time with an acceptable accuracy in indoor airflow simulations because this kind of simulation does not require very high precision.</p> <p><br></p><p>Then this study conducts a detailed and practical comparison of different fluid simulation algorithms in both grid-based methods and particle-based ones. This study's deliverable is a comparison between particle-based and grid-based methods in indoor airflow simulations with HVAC system.</p> <p><br></p><p>The overall methodology used to arrive at the deliverables of this study will need two parts of work. The benchmark data is gathered from a CFD software simulation using FVM with a decent grid resolution. The particle-based data will be generated by simulation algorithms over the same set of room and furniture models implemented by OpenGL and CUDA. After the benchmark FVM simulation being conducted in a CFD software, the temperature field of airflow will be measured. After simulation, the temperature field are gained on each one of 4 particle-based simulation. A comparison standard is set and data will be analyzed to get the conclusion. The result shows that in a short simulation time period, after finding a proper number of particles, the particle-based method will achieve acceptable accuracy of temperature and velocity field while using much less time.</p><p></p>

The aim of the PhD thesis is to design a methodology for generating a material flow using a simulation meta-model of a mass production process. This methodology is in principle based on the relationship between selected material flow characteristics. Simulation of production and logistics processes has been increasingly used in planning, commissioning and subsequent operational management and optimization of the respective technological operations, in particular in mass production. The first part of the PhD thesis summarizes up-to-date findings in the field of discrete event simulation of material flow, related statistical and mathematical disciplines, but also information technology which enables effective realization of simulation studies. Attention is also paid to significant domestic and international conferences, symposia and interest associations related to simulation of manufacturing processes. The next part of the PhD thesis presents the methodology of reconstruction and generation of material flow using simulation meta-models developed for this purpose. Principles of algorithms used by these meta-models and their possible range of use are demonstrated by simulation experiments carried out. Their description and results are also commented. Special focus is put on the selection of significant material flow characteristics and their mutual relationship. For its evaluation a series of simulation experiments was conducted using a simulation model of a closed queuing system with variable parameters. Revealed interdependence between the selected material flow characteristics is experimentally verified using a detailed simulation model of particular selected mass production system. The conclusion of the PhD thesis summarizes provided findings and, with regard to the designed methodology of reconstruction and generating of material flow, it outlines possible further steps both in research and their practical application.

The Direct Simulation Monte Carlo algorithm as coded in FENIX is used to model the transport of trace ions in the first vacuum stage of the inductively coupled plasma mass spectrometer. Haibin Ma of the Farnsworth group at Brigham Young University measured two radial trace density profiles: one 0.7 mm upstream of the sampling cone and the other 10 mm downstream. We compare simulation results from FENIX with the experimental results. We find that gas dynamic convection and diffusion are unable to account for the experimentally-measured profile changes from upstream to downstream. Including discharge quenching and ambipolar electric fields, however, makes it possible to account for the way the profiles change.

abstract Recognizing the importance of the Food, Energy and Water -nexus sustainable approaches and develop according to their framework, would help to achieve global goals such as water security, energy security and food security. And because of the increasing number of human beings, energy demand, food demand, massive amount of land must be used in order to meet these demands. Agrivoltaic system shows promising potential in helping these areas to thrive, the system combines farm activities with PV energy system on the same piece of land, thus, its fits the requirements of Food, Energy and Water -nexus as a valid solution in optimizing the usage in land along with irrigation. However, understanding of the microclimatic conditions in an Agrivoltaic system is essential for adequate crop management because it represents the physical conditions experienced by organisms, in turn these conditions constrain the crop yield. The issue is that this topic is not fully understood, hence, this research studies the important factors affecting microclimatic conditions. After surveying relative literature review regarding Agrivoltaic system and the surrounding microclimate, a model of the reference plant at KärrboPrästgård in Sweden was developed in the simulation software ‘’Solidworks’’. This was done in order to properly analyze the influence between microclimate versus PV system. The model was then validated with measurements taken from the reference plant such as, temperature and solar intensity absorbed by the panels. And had relatively similar trendlines, which confirmed that the model was in order however, there was a slight difference in both of temperature and solar intensity diagrams. Regarding the result obtained from the CFD simulation showed that the implantation of PV panels could potentially conduct unwanted heat if the air could not travel always to the source of heat and exchange with cooler air. The result also showed the direction of the air showed important value, because when the direction of the air was heading against the front side of the panels, less velocity in air reached the next rows of panels.     Preface This degree project was carried out in the School of Business, Society and Engineering (EST) at Mälardalen University within the framework of Future Energy Center. It aims to develop a detailed CFD model of a vertically mounted agrivoltaic system within the Swedish Energy Agency project “Evaluation of the first agrivoltaic system in Sweden”. We want to thank Pietro Campana for arranging the project along with our main supervisor, Sebastian Zainali, who has guided and assisted us throughout the project.

Control of vortex-driven instabilities was demonstrated via a scaled-down, cold-flow simulation that modeled closed-end acoustics. When vortex shedding frequencies couple with the natural acoustic modes of a choked chamber, potentially damaging low-frequency instabilities may arise. Although passive solutions can be effective, an active control solution is preferable. An experiment was performed to demonstrate an active control scheme for the reduction of vortex-driven oscillations. A non-reacting experiment using a primary flow of air, where both the duct exit and inlet are choked, simulated the closed-end acoustics. Two plates, separated by 1.27 cm, produced the vortex shedding phenomenon at the chamber's first longitudinal mode. Two active control schemes, closed-loop and open-loop, were studied via a cold-flow simulation for validating the effects of reducing vortex shedding instabilities in the system. Actuation for both control schemes was produced by using a secondary injection method. The actuation system consisted of pulsing compressed air from a modifed, 2-stroke model airplane engine, controlled and powered by a DC motor. The use of open-loop only active control was not highly effective in reducing the amplitude of the first longitudinal acoustic mode, near 93 Hz, when the secondary injection was pulsed at the same modal frequency. This was due to the uncontrolled phasing of the secondary injection system. A Pulse Width Modulated (PWM) signal was added to the open-loop control scheme to correct for improper phasing of the secondary injection flow relative to the primary flow. This addition allowed the motor speed to be intermittently increased to a higher RPM before returning to the desired open-loop control state. This proved to be effective in reducing the pressure disturbance by approximately 46%. A closed-loop control scheme was then test for its effectiveness in controlling the phase of the secondary injection. Feedback of the system's state was determined by placing a dynamic pressure transducer near the chamber exit. Closed-loop active control, using the designed secondary injection system, was proven as an effective means of reducing the problematic instabilities. A 50% reduction in the FFT RMS amplitude was realized by utilizing a Proportional-Derivative controller to modify the phase of the secondary injection.

A finite element method is employed for solving two- and three-dimensional incompressible flows. The formulation is based on a segregated solution method. In this segregated formulation, the velocities and pressures are uncoupled and the equations for each are solved one after the other. This segregated solution method is numerically compared to the penalty method and to previous reported data to determine its validity. Next an iterative solution method which employs an element by - element data structure of the finite element method is developed. Two types of iterative methods are used. For a symmetric stiffness matrix, the conjugate gradient method is used. For an unsymmetric stiffness matrix, the bi-conjugate gradient method is used. Both iterative solution methods make use of a diagonal preconditioning method (Jacobi preconditioning). Several problems are solved using this segregated method. In two-dimensions, flow over a backward facing step and flow in a cavity are investigated. In three-dimensions, the problems include flow in a cavity at Reynolds number 100 and 1000, and flow in a curved duct. The simulation compares very well with previously reported data, where available. / Ph. D.

An effective medium approximation and a refined Monte Carlo simulation procedure for solving the stochastic groundwater flow problem are presented. The effective medium approximation permits one to solve the stochastic groundwater flow problem in a single run to generate the expected pressure head field. The proposed effective hydraulic conductivity expression for the effective medium is of the same form as the local Gardner’s equation and is easy to use. The refined Monte Carlo simulation procedure uses analytical means to estimate the sample size by controlling the error incurred in using the sample average in place of its population mean at a chosen confidence level. This estimator consistently performs well. Also, a variance reducing estimator which is different from the simple average for pressure head is developed. This estimator takes advantage of the correlation between the saturated conductivity and the pressure head distribution to reduce the output variance and is unbiased. This reduced variance results in a smaller width of uncertainty about the predicted pressure head. Both the effective medium approximation and the Monte Carlo approaches perform well when applied to several problems. / Ph. D.

Composite flow simulation tools for LCM processing can be expensive and time-consuming but necessary to design a mold system with proper placement of resin inlets and vacuum outlets. Composites manufacturing engineers would benefit from data regarding the impact of mold curvature radius on resin flow. This could help determine whether or not a particular part and mold would require expensive simulation software designed to handle complex flow paths through curved fabric architectures exhibiting variable permeability over the curvature, or if simple flow modeling would provide accurate enough simulations for sound tooling setup decision making. Four molds, with double curvature having equal radii, were fabricated with radii ranging from 3.2 to 25.4 mm to characterize the permeability of two different fiber reinforcements 1) a carbon biaxial NCF and 2) a fiberglass CSM over the mold curvatures. Three infusions of each material type were conducted on each of the 4 molds for a total of 24 test infusions. Flow front position vs. time data was captured during each experimental infusion. The permeability in the bend regions, KB, was first estimated by the integrated form of Darcy's Law to evaluate the permeability for average flow across the entire bend region. This was done for both the convex and concave regions using a geometric estimate for the increased compaction in the bend regions. The permeability increases as the tool radius increases, and the rate of increase diminishes as the tool radius increases and the permeability approaches the flat region permeability. An estimate of KB for VI was then made by applying a ratio calculated from the resulting permeability from the rigid- and VI-based models in the flat regions. Generic power law fits are reported that could be used in LCM process simulation, to give a model to estimate the permeability for any bend in the reinforcement part geometry. The results suggest that any curve with a radius higher than 25 mm requires no adjustment to the flat permeability.

Simulations were performed to investigate flow separation of an asymmetricdiffuser - like geometry. The geometry used for the simulations was modeledafter an experimental setup with recorded flow data, which was compared tothe simulated data. For all simulations, steady state flow at the inlet was usedwith the assumption of a 2D flow.A grid convergence study consisting of three different grids was performed.From this study no apparent change in simulation results were observed forfiner grids. This is caused by the fact that the coarse grid had a high enoughresolution to fully capture the flow, meaning that the higher resolution gridsyielded small improvements.Additionally, two different turbulence models RN G k − ε and SST k − ωwere used for evaluating which model was best suited to model flow separation.The simulations showed that the RN G k − ε model could not capture the flowseparation and had a poor accuracy when predicting the turbulent kinetic energy(TKE). Simulation results from SST k − ω gave good results in capturing flowseparation and predicting both the velocity and TKE when compared to theexperimental data.Finally, a turbulence intensity study was made for the mid grid with theSST k − ω model. The turbulent intensity was set to 5%, 10%, 15% and 20%at the inlet. This resulted in the point of separation moving further down thegeometry to x/H ≈ [17.68, 18.71, 19.58, 20.72] for respective intensity. The pointof reattachment also moves to x/H ≈ [44.85, 43.60, 42.67, 41.67] for respectiveintensity.In summary for simulating flow separation in turbulent flows the SST k − ωmodel is optimal and an increase in turbulent intensity reduces the recirculationzone.