The submitted diploma thesis deals with wind machines in densely populated areas. The aim of the work is to design a appropriate wind machine for use on the roofs of buildings, including all the specifics that the air flow in the city may contain. At the beginning, the work focuses on the production of electricity in cities in general, which results in an ideal system of obtaining energy for households. Furthermore, the work deals with the wind in general, where all its specifics are taken over. A very important part of the work is the study of the specifics of air flow in the urban environment together with the numerical simulation of this flow, which results in certain regularities of the location of wind machines on the roofs of buildings. The work then passes to a search of used wind machines, from which the most suitable candidate for use in cities is subsequently selected. The last part of the work is the design of the machine itself for a specific location. In this chapter, the design wind speed is determined from the measured data, which is later followed by the calculation of the geometry of the blades, and finally its benefits and advantages are determined from the properties of the wind machine

<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>

No description available.

No description available.

Investigations of the three-dimensional flow around a 6:1 prolate spheroid model 1.37 m long were conducted in the separation and near wake regions along the leeward side. Mean velocity flow field measurements, at α = 10∘ and 15∘ , and at Re = 1.3 x 10⁶ (U_re= 15.2 mls) and 4.0x 10⁶ (Ure=45.7 m/s), were obtained at four axial locations along the afterbody. Boundary layer profiles and Reynolds shear stress measurements were obtained at two axial locations, with a = 100 and Re=4.0 X 10⁶. Results of the flow field measurements indicate vortical flow along the surface of the body, growing in strength with increasing Reynolds number and increasing angle of attack. Skewing of the three-dimensional boundary layer is seen in the boundary layer profiles, with the surface shear stress direction lagging the local free-stream velocity direction. Growth of the boundary layer is evident circumferentially and axially along the body. Results of the turbulence measurements show that the distribution of Reynolds stress quantities is different from that of a two-dimensional flow over a flat plate, due to the three-dimensional flow and separation that is present. Estimates of x and z eddy viscosities show that the eddy viscosity is not isotropic. Estimates of the mixing length compared to values for a two-dimensional flow model indicate that the model predicts high values for the mixing length. Comparisons made with results obtained at DFVLR in West Germany show good agreement for the mean velocity and Reynolds normal stress values; however, the agreement of the Reynolds shear stresses is not as good. / Master of Science

No description available.

M.S.

M.S.

This investigation studies the mixing in a shear layer developed from helium slot injection into a parallel supersonic airstream and compares the results to those of previous slot-injection tests. The objectives of this study include documenting the helium slot-injection flowfield; providing a baseline for use as a reference for future work; contributing representative and consistent data to the general database; and increasing understanding of shear layer dynamics, especially as a result of foreign-gas injection. The helium injectant exits the slot at y = 1.67, M₋₁ = 1.78, P_u = 0.892 atm, and T_u = 287° K tangentially to an airstream at y = 1.4, M_∞= 3, P_t∞= 6.5 atm, and T_t∞= 282° K. The freestream has Re/cm = 5.4x10⁵ and a boundary-layer thickness of (δ_au/H) = 0.58. The pertinent ratios are (P₁/P_∞) = 0.838, (U₁/U_∞) = 2, and (P₁/P_∞) = 0.1. The slot height H is 1.21 cm. Along with short-duration Schlieren and Shadowgraph photography, concentration, Pitot, cone-static, and stagnation-temperature measurements are taken at each of four streamwise stations (x H = 0.3, 4.2, 10.5, 21.1) to document the development of the mixing layer. ln light of the binary-gas mixture, local concentration information is required to reduce the data to pertinent mean-flow variables (M, p, U, pU, P, and T). As expected, slot injection in general shows poor initial penetration of the injectant into the freestream, and, thus, poor initial mixing. Nevertheless, the helium case shows better mixing than a similar air injection case of a previous experiment, as the mixing shear layer grows 25 percent larger than that in the air case by the last station. Also, about 30 percent more freestream air is entrained into the shear layer in the helium case and is confined mainly to the top third of the mixing layer. The higher mixing rate stems from larger gradients in velocity and density and lower pU values which result in more active transport mechanisms in the helium injection test / Master of Science

The office environment is an important part of the workers’ performance and need therefore to be designed in a pleasant and functional way. The problem is not that today’s offices do not function but rather that these need to be improved to achieve better work results. Lighting and ventilation are big parts of the office environment. In this project will three offices be examined, and these are Archus, WSP and Sweco. Purpose: This study is done to find improvement measures for these three offices based on the examination of the light and ventilation conditions. The improvements that will be suggested are mainly based on a survey but also a study on how these two factors affect the employees’ performances. Method: To perform this project was a literature study, a case study and measurement of illuminance used. A survey om how the employees experience the office environment were also conducted. Drawings provided by the office managers were used to perform calculations of the airflow. Results: The survey shows that 73.5 percent of the 68 people who answered the survey feel comfortable in the current design of the offices. The rest feel that they lack privacy and a quiet environment. In addition, 82.4 percent are happy with the lighting situation and 69.1 percent with the air quality. Archus, WSP and Sweco all meet the required guidelines set for illuminance in an office with certain deficiency. For ventilation do Archus and Sweco meet the minimum requirements for airflow, but there are small differences between the dimensioned airflow and the minimum requirement for WSP. Conclusions: The conclusion of this study is that the three studied offices lack seclusion which affects the office workers’ ability to work. The current lighting, and the ventilation in smaller rooms also contribute worsened working conditions. Good lighting conditions is required to achieve good work results. The same applies to ventilation where the air flow is deficient in certain rooms and should be regulated. / Kontorsmiljön är en viktig del i arbetarnas prestation och ska därför utformas på ett trivsamt och funktionellt sätt. Problematiken är inte att dagens kontor inte fungerar utan att dessa kan förbättras för att uppnå goda arbetsresultat. Belysning och ventilation är stora delar inom ämnet och kontoren som undersöks i detta arbete är Archus, WSP och Sweco.  Syftet med studien är att ta fram förbättringsåtgärder för tre kontorslokaler utifrån en undersökning avseende belysnings- och ventilationsförhållanden. Förbättringsförslaget bygger främst på en enkät men även en studie om hur de två faktorer spelar in i medarbetarnas presterande.  För att utföra studien tillämpades ett antal olika metoder däribland en litteraturstudie för att sätta grund till arbetet, en fallstudie där ett studiebesök till de undersökta kontoren och mätningar utfördes. Även en enkät om hur medarbetarna upplever sina kontorsmiljöer gjordes. Ritningar som tillhandahölls av ansvariga på kontoren tillämpades för att utföra beräkningar av luftflödet.  I resultat visar enkäten att 73,5% av de 68 personer som besvarade enkäten känner sig bekväma i den nuvarande utformningen men att resterande att de saknar avskildhet och tystare miljö. Utöver det trivs 82,4% med belysningen och 69,1% med luftkvalitén i dagsläget.  Archus, WSP och Sweco uppfyller de riktvärden som ställs för belysningsstyrka i kontorslokaler med vissa avvikelser. För ventilation uppfyller Archus och Sweco minimikraven för luftflödet men för WSP förekommer det skillnader mellan minimikravet och det dimensionerade luftflödet.  Diskussionen visar att vid utförandet av mätningar var det svårt att anpassa omgivningen efter önskemål vilket medförde att vissa mätvärden avviker från verkligheten. Även för beräkning av ventilation uppstod oförväntade svårigheter som att tillgång till egna instrument för luftflödesmätning saknades samt brister i ritningar.  Slutsatserna som dras för arbetet är att de tre kontoren saknar avskildhet vilket påverkar kontorsarbetarnas arbetsförmåga. Även den nuvarande belysningen samt ventilationen i mindre rum bidrar med försämrade arbetsförhållanden. För att uppnå ett gott arbetsresultat krävs god belysning i verksamheten. Samma gäller för ventilation där luftflödet brister i vissa rum och bör regleras.