With the increased frequency of accidental and deliberate explosions, the response of civil infrastructure systems to blast loading has become a research topic of great interest. However, with the high cost and complex safety and logistical issues associated with live explosives testing, North American blast resistant construction standards (e.g. ASCE 59-11 & CSA S850-12) recommend the use of shock tubes to simulate blast loads and evaluate relevant structural response. This study aims first at developing a 2D axisymmetric shock tube model, implemented in ANSYS Fluent, a computational fluid dynamics (CFD) software, and then validating the model using the classical Sod’s shock tube problem solution, as well as available shock tube experimental test results. Subsequently, the developed model is compared to a more complex 3D model in terms of the pressure, velocity and gas density. The analysis results show that there is negligible difference between the two models for axisymmetric shock tube performance simulation. However, the 3D model is necessary to simulate non-axisymmetric shock tubes. The design of a shock tube depends on the intended application. As such, extensive analyses are performed in this study, using the developed 2D axisymmetric model, to evaluate the relationships between the blast wave characteristics and the shock tube design parameters. More specifically, the blast wave characteristics (e.g. peak reflected pressure, positive phase duration and the reflected impulse), were compared to the shock tube design parameters (e.g. the driver section pressure and length, the driven v section length, and perforation diameter and their locations). The results show that the peak reflected pressure increases as the driver pressure increases, while a decrease of the driven length increases the peak reflected pressure. In addition, the positive phase duration increases as both the driver length and driven length are increased. Finally, although shock tubes generally generate long positive phase durations, perforations located along the expansion section showed promising results in this study to generate short positive durations. Finally, the developed 2D axisymmetric model is used to optimize the dimensions of a proposed large-scale conical shock tube system developed for civil infrastructure blast response evaluation applications. The capabilities of this proposed shock tube system are further investigated by correlating its design parameters to a range of explosion threats identified by different hemispherical TNT charge weight and distance scenarios. / Thesis / Master of Applied Science (MASc)

A study of the use of solution adaptive grid (SAG) method for simulations of incompressible flows is carried out in this work. Both laminar and turbulent types of flows are chosen. Investigation on laminar flow simulation starts with mesh adaptation criteria that are based on strong changes of some selected flow parameters; pressure and velocity components. Three most common laminar types of flows are studied; flow in a circular pipe, flow in a channel with sudden expansion and flow in a cavity with a moving lid. It is found that with the use of SAG, a reduction in both computational grid nodes and CPU time can be obtained when compared to those of fixed grid while satisfactory solutions are also achievable. Nevertheless, the refinement criteria setup procedure reveals inconveniences and requirement for several judgments that have to be defined ‘ad hoc’. This hence, makes the refinement criteria dubious for real engineering applications. For the study of turbulent flows with large eddy simulation (LES) and implicit filtering, examination of literature reveals that the lack of connections between the filter width and a physical scale has made LES somewhat unclosed, i.e. in a physical sense. In addition, it is known that numerical and modelling errors are always combined and it is difficult to study each of them separately making the total error magnitude difficult to control. Since both error types are characterised by the grid size, LES users very often find cases where a finer mesh no longer provides better accuracy. An attempt to address this ‘physical’ enclosure property of LES and its complication to implement/setup in FLUENT begins with the construction of a new refinement variable as a function of the Taylor scale. Then a new SAG algorithm is formed. The requirement to satisfy a condition of the selected subgrid scale (SAG) model, the Smagorinsky model, is taken into consideration to minimize the modeling error. The construction of a new refinement algorithm is also aimed to be the key to studying the interaction between the two types of error and could lead to the means of controlling their total magnitude. The validation in terms of its effectiveness, efficiency and reliability of the algorithm are made based on several criteria corresponding to suitability for practical applications. This includes the simplicity to setup/employ, computational affordability, and the accuracy level. For this, two different turbulent flow types that represent different commonly found turbulent phenomena are chosen; plane free jet and the flow over a circular cylinder. The simulations of the two cases were carried out in two dimensions. It is found that there are two key factors that strongly determine the success of the algorithm. The first factor is the Taylor scale definition, with literature only available for the turbulent plane jet study, for which good level of accuracy is expected. Unfortunately, this is not true for the flow over a circular cylinder, indicating a need for further analytical work. The second encountered difficulty results from limited access to software codes, which makes it impossible to implement the proposed scheme. As a result, the algorithm formulation needs be modified with carful judgment. Nevertheless, overall results are in reasonably good agreement with their corresponding experimental data.

In current production systems, automation and handling of workpieces is often solved by use of vacuum technology. Most production systems use vacuum ejectors which generate vacuum from compressed air by means of the Venturi effect. However, producing vacuum with compressed air is significantly less efficient than using other principles. To minimize the energy costs of pneumatic vacuum generation or to make full use of the energy available, it is important that the inner contour of the nozzle is shaped precisely to suit the specific application - also the system\'s flow conduction needs to be optimal and the flow losses have to be minimized. This paper presents a method for optimally designing pneumatic vacuum generators and producing them economically even at very low lot sizes in order to keep the operation costs low and address other concerns (such as noise emissions) as well.

The depth-averaged Saint-Venant equations, which are used for most computational flow models, are adequate in simulating open channel flows with insignificant curvatures of streamlines. However, these equations are insufficient when applied to flow problems where the effects of non-hydrostatic pressure distribution are predominant. This study provides a comprehensive examination of the feasibility of a simple one-dimensional Boussinesq-type model equation for such types of flow problems. This equation, which allows for curvature of the free surface and a non-hydrostatic pressure distribution, is derived using the momentum principle together with the assumption of a constant centrifugal term at a vertical section. Besides, two Boussinesq-type model equations that incorporate different degrees of corrections for the effects of the curvature of the streamline are investigated in this work. One model, the weakly curved flow equation model, is the simplified version of the flow model based on a constant centrifugal term for flow situations that involve weak streamline curvature and slope, and the other, the Boussinesq-type momentum equation linear model is developed based on the assumption of a linear variation of centrifugal term with depth.

The depth-averaged Saint-Venant equations, which are used for most computational flow models, are adequate in simulating open channel flows with insignificant curvatures of streamlines. However, these equations are insufficient when applied to flow problems where the effects of non-hydrostatic pressure distribution are predominant. This study provides a comprehensive examination of the feasibility of a simple one-dimensional Boussinesq-type model equation for such types of flow problems. This equation, which allows for curvature of the free surface and a non-hydrostatic pressure distribution, is derived using the momentum principle together with the assumption of a constant centrifugal term at a vertical section. Besides, two Boussinesq-type model equations that incorporate different degrees of corrections for the effects of the curvature of the streamline are investigated in this work. One model, the weakly curved flow equation model, is the simplified version of the flow model based on a constant centrifugal term for flow situations that involve weak streamline curvature and slope, and the other, the Boussinesq-type momentum equation linear model is developed based on the assumption of a linear variation of centrifugal term with depth.

<p> </p><p>The cooling system of a DC-motor is examined in this thesis. A change of direction of the cooling air is desired to prevent the generated coal dust from entering into the windings of the machine. Ultimately this will have a negative effect on the cooling in the machine and the loss of cooling needs to be compensated through other ways. The purpose of this thesis is to work for an improved operational safety and performance of the DC-motor and to make it more competitive in the market. By modelling the interior geometry of the machine and defining the boundaries in the software programs Gambit and FLUENT respectively, the motion and the heat transfer of the airflow could be simulated. The simulation results would give us an understanding of the flow pattern which later could be used to develop design modifications on the cooling system of a DC-motor. In this thesis the main focus lies on creating a simulation model with a sufficiently fine mesh size.</p>

The cooling system of a DC-motor is examined in this thesis. A change of direction of the cooling air is desired to prevent the generated coal dust from entering into the windings of the machine. Ultimately this will have a negative effect on the cooling in the machine and the loss of cooling needs to be compensated through other ways. The purpose of this thesis is to work for an improved operational safety and performance of the DC-motor and to make it more competitive in the market. By modelling the interior geometry of the machine and defining the boundaries in the software programs Gambit and FLUENT respectively, the motion and the heat transfer of the airflow could be simulated. The simulation results would give us an understanding of the flow pattern which later could be used to develop design modifications on the cooling system of a DC-motor. In this thesis the main focus lies on creating a simulation model with a sufficiently fine mesh size.

Syftet med arbetet var att undersöka möjligheten för optimering av produktflödet. Företagets produkter transporteras på ett transportband till en gemensam process. Det nuvarande flödet till processen är inte optimerat vilket resulterar i att processen körs ineffektivt. Ackumulering av produkter innan processen ska därför undersökas som en lösning till problemet. Fyra olika ackumuleringsförslag har analyserats och jämförts: hängande bansystem, palleteringssystem, depalleteringssystem och kombination av bansystem och palleteringssystem. Förslagen har blivit bedömda och jämförda utifrån följande parametrar: yta, investeringskostnad, flexibilitet, arbetsbelastning, arbetsmiljö och tid. Hängande bansystem fick det högsta snittvärdet och valdes därför för fortsatt analys med stöd av simulering. Simuleringen gjordes i ExtendSim 7. Två simuleringsmodeller jämfördes, en med ackumulering av produkter i bansystem och en utan. Resultatet var att ackumulering av produkter kan ge en besparing på 16 procent i driftkostnader per år. Simulering av övriga förslag kan göras för att få en tydligare jämförelse mellan förslagen. Rekommendationen till företaget är att ackumulera produkter i ett bansystem. Det baseras på analys av jämförelsen. Analysen och diskussionen visar också att robothantering inte är en passande lösning på problemet, eftersom rörelserna skulle skaka om produkterna för mycket. En vidare undersökning av utformningen av bansystemet bör göras för att få fram den optimala utformningen. / The purpose of the work was to investigate possibilities for optimization of the material flow. The different products of the company are being transported by a conveyor belt to a common process. The current flow to the process is not optimized with the result that the process runs inefficiently. Accumulation of products before the process should therefore be investigated as a solution. Four different accumulating systems have been analyzed and compared: hanging conveyor belts, palletizing, depalletizing and a combination of conveyor belts and palletizing. The systems have been assessed and compared according to six parameters: area, investment cost, flexibility, work load, work environment and time. The hanging conveyor belt yielded the highest average score and was therefore chosen for further analysis with the support of simulation. The simulation was made in ExtendSim 7. Two simulation models were compared, one with accumulation of product in conveyor belts and one without. The result of the simulation part was that accumulation of product results in savings of running costs with 16 percent per year. To get a better comparison between the accumulation systems simulations of all systems can be done. The recommendation to the company is to accumulate products in a conveyor system. This is based on the analysis of the comparison. The analysis and discussion also shows that robot handling is not an appropriate solution to the problem, because the movements would shake the products too much. A further investigation of the layout should be done in order to find the optimal layout.

A method has been developed, Physical Hybrid Model, to investigate the physical large scale electrical effects of a Battery Energy Storage System (BESS) on a distribution grid by scaling the response from a small size Research Development and Demonstration (RD&amp;D) platform. In order to realize the model the control system of an existing RD&amp;D platform was refurbished and stability of components ensured. The Physical Hybrid Model proceeds as follows: Data from a distribution grid are collected. A BESS cycle curve is produced based on analyzed measurements. Required BESS power and capacity in investigated grid is scaled down by factor k to that of the physical test installation of the RD&amp;D platform. The scaled BESS cycle is sent as input to control of the battery cycling of the RD&amp;D platform. The response from the RD&amp;D platform is scaled – up, and used in simulation of the distribution grid to find the impact of a BESS. The model was successfully implemented on a regional distribution grid in southern Sweden.

Atherosclerosis is a disease of the cardiovascular system where a stenosis may develop in an artery which is an abnormal narrowing in the blood vessel that adversely affects the blood flow. Due to the constriction of the blood vessel, the flow is disturbed, forming a jet and recirculation downstream of the stenosis. Dynamic pressure fluctuations on the inner wall of the blood vessel leads to the vibration of the vessel structure and acoustic energy is propagated through the surrounding tissue that can be detected on the skin surface. Acoustic energy radiating from the interaction of blood flow and stenotic blood vessel carries valuable information from a diagnostic perspective. In this study, a constricted blood flow is modeled by using ADINA finite element analysis software together with the blood vessel in the form of a thin cylindrical shell with an idealized blunt constriction. The flow is considered as incompressible and Newtonian. Water properties at indoor temperature are used for the fluid model. The diameter of the modeled vessel is 6.4 mm with 87% area reduction at the throat of the stenosis. The flow is investigated for Reynolds numbers 1000 and 2000. The problem is handled in three parts which are rigid wall Computational Fluid Dynamics (CFD) solution, structural analysis of fluid filled cylindrical shell, and Fluid Structure Interaction (FSI) solutions of fluid flow and vessel structure. The pressure fluctuations and consequential vessel wall vibrations display broadband spectral content over a range of several hundred Hz with strong fluid-structural coupling. Maximum dynamic pressure and vibration amplitudes are observed around the reattachment point of the flow near the exit of the stenosis and this effect gradually decreases along downstream of flow. Results obtained by the numerical simulations are compared with relevant studies in the literature and it is concluded that ADINA can be used to investigate these types of problems involving high frequency pressure fluctuations of the fluid and the resulting vibratory motion of the surrounding blood vessel structure.