The primary object of the investigation reported in this paper was to obtain information that would aid in the design of a more efficient diffuser for FTU's tunnel, and thus increase the run time. Presently FTU's four inch supersonic wind tunnel uses a constant area, normal shock, diffuser to recover the fluid pressure after the test section. Also, FTU's tunnel is of the intermittent blowdown type, which provides only a relatively short test time before the storage pressure decreases to a limiting value at which flow in the test section ceases to be supersonic. The use of a constant area diffuser and normal shock pressure recovery has the disadvantage of always entailing a large loss in stagnation pressure. These losses increase as the test section Mach number increases. Since a diffuser employing a system of oblique shocks should have a better pressure recovery than one with a single normal shock, efforts were made to improve FTU's wind tunnel along these lines. Variable area diffusers whose throats can be closed after flow has been established were of interest in this report because of their higher pressure recovery. The maximum run time of FTU's wind tunnel is limited by the overall operating pressure ratio required to maintain supersonic flow in the test section area. If one can reduce the losses in the tunnel, the operating pressure ratio can be reduced. The reduction in operation pressure can result in an increase in run time. In FTU's tunnel, the majority of losses occurs in the second throat area or the supersonic diffuser. Tunnel run time improvement may be required to conduct heat transfer studies or to conduct force, moment and pressure tests. The results of the one-dimensional analyses of a variable geometry supersonic diffuser are very promising in that they show a longer run time can be obtained for FTU's tunnel. By using a variable geometry diffuser, an intermittent blowdown wind tunnel run time can be increased two to three times that of a constant are diffuser at high Mach numbers. At the design Mach number of 4.0, the theoretical run time can be increased 321 percent over the run time of a constant area diffuser. The references cited made it possible to geometrically design a relatively simple, yet efficient contractible wall (convergent-constant area-divergent) type diffuser. Three flagellates were chosen to form the side walls of the adjustable diffuser. The length of the plates were a compromise between mechanical construction requirements and the need to keep the wall convergent angle relatively small for the Mach number range of FTU's tunnel and to minimize energy losses. The first adjustable diffuser plate has an overall length of 14.5 inches. The angle of convergent for design was chosen to be 7 degrees at the design Mach number of 4.0. The second diffuser plate that forms the constant area passage has an overall length of 12 inches. The third diffuser plate that forms the divergent section has an overall length of 13.5 inches.

No description available.

Aerodynamics has always been a driving force in motorsport and road vehicle design and development, and continues to play an important role. A significant advancement in race car aerodynamics was the development of the vehicle underbody to produce downforce, in particular the implementation of the diffuser. This thesis concentrates on the performance flow mechanisms found in simple rear diffusers commonly seen in motorsport applications. There is little published work on these mechanisms, especially the influence of the more commonly used multiple-channel diffusers.

More efficient methods are needed for the in-situ evaluation of mass transfer parameters which describe the movement of solutes through aquifer material. The objective of this study was to develop a method for estimating diffusion rate and capacity coefficients using a single-well, "push-pull" tracer test. The method consists of the pulse-type injection of a test solution into the saturated zone of an aquifer through the screen of an existing monitoring well. This is followed by a resting (diffusion) period, after which the test solution is extracted from the same well. During the extraction phase a concentration breakthrough curve is obtained. The method uses numerical simulations of the extraction phase breakthrough curve to estimate mass transfer parameters. The methodology was evaluated using a series of laboratory-scale experiments which were performed in a Physical Aquifer Model (PAM). The sediment pack contained in the PAM was modified to create an immobile region governed by diffusive processes. Results from four laboratory-scale experiments are inconclusive in determining the ability of the method to determine mass transfer parameters. Experimental difficulties contributed a significant source of error during the method evaluation. The resting period between the injection and extraction phase was to allow diffusion into the initially solute-free immobile region. Evidence suggests solute was introduced into the immobile region by advective processes during the injection phase of the experiments. Additional experimental work is required to evaluate the methodology. This may include either laboratory or field-scale evaluation of the test method. / Graduation date: 1999

Responses of biological indicators of soil quality to winter cover cropping were measured on soil samples collected from 6 commercial growers' fields and two experiment research stations in the Willamette Valley of Oregon. The research stations were the North Willamette Research and Extension Center (Aurora, OR), and the Oregon State University Vegetable Farm (Corvallis, OR). The research stations and five on-farm sites compared winter cover crops or winter fallow in rotation with a summer vegetable crop. In one on-farm site, minimum tillage or conventional till following winter cover crops was compared. The objectives of this study were to: 1) monitor changes in soil biological properties under field managed with cover crops; 2) test potential of buried cotton strip as indicator of soil biological activity and as a soil quality index; and 3) assess the degree of correlation between tensile strength and cotton strip weight loss. The major findings were: 1) microbial biomass carbon and ��-glucosidase activity were the most sensitive to cover crop management; 2) cotton strip decomposition was correlated to soil biological properties but was not very sensitive to management changes; and 3) that measuring weight loss was nearly as effective as tensile strength in assessing cotton strip decomposition in soils. / Graduation date: 1999

The purpose of the study is to find a suitable method for removal of iron and manganese considering local economic and environmental aspects. El Salvador is situated in Central America with a coast line towards the Pacific Ocean. The country borders Guatemala and Honduras. Aguilares is a town situated in the department of San Salvador, with a population of approximately 33,000 people. Currently, the population is provided with water for about two hours per day, since it is the highest capacity of the existing wells. During these two hours many households fill a small tank with water to use for the remainder of the day. The water is not safe to use for oral consumption because of the levels of bacteria and other contamination. One of the wells, situated in the community of Florída is not in use at this date because of the high levels of Iron and Manganese in the ground water which cannot be removed with the present technique.Ground water is naturally pure from bacteria at a depth of 30 m or more, however solved metals may occur and if the levels are too high the water is unsuitable to drink. The recommended maximum levels by WHO (2008) [1] for Iron and Manganese are 2 mg/l and 0.5 mg/l respectively.Literature and field studies led to the following results; Iron and manganese can be removed by precipitation followed by separation. Precipitation is achieved by aeration, oxygenation or chemical oxidation and separation is achieved by filtration or sedimentation.The different methods all have advantages and disadvantages. However the conclusion reached in this report is that aeration and filtration should be used in the case of Florída. What equipment and construction that should be used depends on economic and resource factors as well as water requirements, which is up to the council of Aguilares to deliberate.

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

Master of Science

<p>One of the most fundamental human needs is fresh air. It has been estimated that people spend comparatively much time in indoor premises. That creates an elevated need for high-quality ventilation systems in buildings. The ventilation airflow rate is recognised as the main parameter for measuring the indoor air quality. It has been shown that the ventilation airflow rates have effects on respiratory diseases, on “sick building syndrome” symptoms, on productivity and perceived air quality. Ventilation is necessary to remove indoor-generated pollutants by diluting these to an acceptable level. The choice of ventilation airflow rate is often based on norms or standards in which the airflow rate is determined based on epidemiological research and field or laboratory measurements. However, the determination of ventilation flow rate is far more complex. Indoor air quality in the occupied zone can be dependent of many factors such as outdoor air quality, airflow rate, indoor generation of pollutants, moisture content, thermal environment and how the air is supplied into the human occupied zone. One needs to acknowledge the importance of air distribution which clearly affects the comfort of occupants. To design a ventilation system which considers all aspects of room ventilation can only be achieved by computer modelling. The objective of this thesis is to investigate air diffusion, indoor air quality and comfort issues by CFD (computational fluid dynamics) modelling. The crucial part of the CFD modelling is to adopt BCs (boundary conditions) for a successful and accurate modelling procedure. Assessing the CFD simulations by validated BCs enabled constructing the ventilation system virtually and various system layouts were tested to meet given design criteria. In parallel, full-scale measurements were conducted to validate the diffuser models and the implemented simplified particle-settling model. Both the simulations and the measurements reveal the full complexity of air diffusion coupled with solid contaminants. The air supply method is an important factor for distribution of heat, air velocity and solid contaminants. The influence of air supply diffuser location, contaminant source location and air supply method was tested both numerically and by measurements to investigate the influence of different parameters on the efficiency of room ventilation. As example of this, the well-known displacement ventilation is not fully able to evacuate large 10 μm airborne particles from a room. Ventilation should control the conditions in the human breathing zone and therefore the ventilation efficiency is an important parameter. A properly designed ventilation system could use less fresh air to maintain an acceptable level of contaminant concentration in the human breathing zone. That is why complete mixing of air is not recommended as the ventilation efficiency is low and the necessary airflow rate is relatively high compared to other ventilation strategies. Especially buoyancy-driven airflows from heat sources are an important part of ventilation and should not be hampered by supply airflow from the diffusers. All the results revealed that CFD presently is the only reliable method for optimising a ventilation system considering the air diffusion and contaminant level in all locations of any kind of room. The last part of the thesis addresses the possibility to integrate the CFD modelling into a building design process where architectural space geometry, thermal simulations and diffuser BCs could be embedded into a normal building design project.</p>

A sudden expansion combustor (SUE) is analyzed using computation fluid dynamics (CFD). CO emissions and NOx emissions are computed for various operating conditions of the SUE combustor using a can type and an annular type geometrical configurations. The goal of this thesis is to see if the SUE combustor is a viable alternative to conventional combustors which utilize swirlers. It is found that for the can type combustor the NOx emissions were quite low compared to other combustor types but the CO emissions were fairly high. The annular combustor shows better CO emissions compared to the can type, but the CO emissions are still high compared to other combustors. Emissions can be improved by providing better mixing in the primary combustion zone. The SUE combustor design needs to be further refined in order for it to be a viable alternative to conventional combustors with swirlers. / by Daniel Rodriguez. / Thesis (M.S.C.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.