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Plug nozzle, a passive altitude adaptive nozzle, for futuristic SSTO applications, exhibits greater efficiency as compared to conventional nozzles over a wide range of altitudes. The plug nozzle comprises of a primary nozzle and a contoured plug; an under–expanded jet exiting the primary nozzle is allowed to further expand over the plug surface for altitude adaptation. At design condition the flow expands correctly to the ambient conditions on the full length plug surface, while at off design conditions the flow adapts to the ambient conditions through wave interactions within the nozzle core jet. Based on thrust to weight considerations, the full length plug is truncated and this results in a base flow rich in flow physics. In addition, the base flow exhibits an interesting transitional behaviour from open wake to a closed wake because of the wave interactions within the nozzle core jet. The plug surface flow can further exhibit flow complexities because of wave interactions resulting from the shear layer emanating from the splitter plates, in case of clustered plug flows. Considering these flow complexities, the design of the plug nozzles and analysing the associated flows can be a challenge to the aerodynamic community. An attempt has been made in understanding this class of flows in this thesis. This objective has been accomplished using both experimental and computational tools. In the present work, both the linear and annular plug nozzle geometries have been analysed for a wide range of pressure ratios spanning from 5to 80. The linear and annular nozzles have been designed for similar flow conditions and their respective design pressure ratios are 60and 66. From the experimental and computational results, it has been shown that the computational solver performs well in predicting the wave interactions on the plug surface. In addition the limitations of the computational solver in predicting the plug base flows in general has been brought out. This limitation in itself need not be considered as a serious handicap in the design and analysis of plug nozzle flows; this is because the plug base contribution to the thrust is very minimal, as has been brought out in this thesis. Apart from this the high quality experimental data generated is also of immense value to the CFD community as this also serves as a valuable data base for CFD code validation. For analysis, the plug flow field has been categorized into three different regimes based on the primary nozzle lip expansion fan extent. The flow field is categorised based on the reflection of the primary nozzle lip expansion fan from plug surface, base region shear layer and symmetry line downstream of the base region recirculation bubble. This flow division is particularly helpful in understanding the base wake characteristics with increasing pressure ratio. The base lip pressure and the base pressure variation have been discussed with respect to the primary nozzle lip expansion fan extent. In the open wake regime (or for low pressure ratios) the wave interactions within the core jet flow impinge on the base region shear layer. Because of these interactions it is difficult to propose an empirical model for open wake base pressure. In the closed wake regime (for higher pressure ratios), the base region recirculation bubble is completely under the shower of primary nozzle lip expansion fan. Hence the base lip pressure and base pressure are frozen with respect to stagnation conditions. Based on these insights it was possible to propose empirical models for linear and annular closed wake base pressure. Along with these, a mathematical model defining a reference pressure ratio PR∗, beyond which the closed wake base pressure is expected to be more than the ambient pressure has also been proposed. This is expected to serve as a good design parameter. In case of linear plug flows, this also serves the purpose of base wake transition, for the cases considered in this thesis. The flow expansion process or the primary nozzle lip expansion fan extent was also useful in understanding the differences between the linear and annular plug nozzle flow fields. In a linear plug nozzle, the flow expands only in the streamwise direction while in an annular plug nozzle the flow expands both along the streamwise and azimuthal directions. The flow expands at a faster rate in case of annular nozzle as against linear nozzle. Hence differences are observed between the linear and annular nozzle on plug and base surfaces. On the annular plug surface more wave interactions are observed because of faster expansion. With regard to base characteristics, faster expansion in annular plug nozzle, with respect to linear nozzle, results in a lower base lip pressure, lower base pressure and higher wake transition pressure ratio. The realistic cluster plug configurations have also been considered for the present studies. The effects of clustering on the plug nozzle flow field have been brought out by considering two different linear cluster nozzles and one annular cluster nozzle. The differences in the flow field of a simple and cluster plug nozzle has been discussed. In case of simple plug nozzle wave interactions are observed only in the stream wise direction, while in case of cluster plug nozzle three dimensional wave interactions are observed because of the splitter plates. Along the splitter plate differential end conditions introduce a curved recompression shock on the plug surface. This recompression shock in turn induces a streamwise vortex and also a secondary shock. It has been observed that differences between the simple and cluster plug surface pressure field are because of three dimensional wave interactions. Regarding the base pressure, differences between the simple and cluster geometries were observed for shorter truncation plug lengths (20% length plug). While for longer plug lengths (more than 34% length) the effects of clustering were reduced on the base pressure. Regarding the transition pressure ratio, differences were observed between simple and clustered plug nozzles for all the plug lengths considered. In addition, the performance of the plug nozzles has been carried out. From the analysis it was found that the primary nozzle and plug surface are major contributors towards thrust. The base surface contributes only about 2– 3% of the thrust at design condition. Hence, from a design point of view, a computational solver can be a useful tool considering its efficacy on the plug surface and in the primary nozzle.

Plug nozzle, a passive altitude adaptive nozzle, for futuristic SSTO applications, exhibits greater efficiency as compared to conventional nozzles over a wide range of altitudes. The plug nozzle comprises of a primary nozzle and a contoured plug; an under–expanded jet exiting the primary nozzle is allowed to further expand over the plug surface for altitude adaptation. At design condition the flow expands correctly to the ambient conditions on the full length plug surface, while at off design conditions the flow adapts to the ambient conditions through wave interactions within the nozzle core jet. Based on thrust to weight considerations, the full length plug is truncated and this results in a base flow rich in flow physics. In addition, the base flow exhibits an interesting transitional behaviour from open wake to a closed wake because of the wave interactions within the nozzle core jet. The plug surface flow can further exhibit flow complexities because of wave interactions resulting from the shear layer emanating from the splitter plates, in case of clustered plug flows. Considering these flow complexities, the design of the plug nozzles and analysing the associated flows can be a challenge to the aerodynamic community. An attempt has been made in understanding this class of flows in this thesis. This objective has been accomplished using both experimental and computational tools. In the present work, both the linear and annular plug nozzle geometries have been analysed for a wide range of pressure ratios spanning from 5to 80. The linear and annular nozzles have been designed for similar flow conditions and their respective design pressure ratios are 60and 66. From the experimental and computational results, it has been shown that the computational solver performs well in predicting the wave interactions on the plug surface. In addition the limitations of the computational solver in predicting the plug base flows in general has been brought out. This limitation in itself need not be considered as a serious handicap in the design and analysis of plug nozzle flows; this is because the plug base contribution to the thrust is very minimal, as has been brought out in this thesis. Apart from this the high quality experimental data generated is also of immense value to the CFD community as this also serves as a valuable data base for CFD code validation. For analysis, the plug flow field has been categorized into three different regimes based on the primary nozzle lip expansion fan extent. The flow field is categorised based on the reflection of the primary nozzle lip expansion fan from plug surface, base region shear layer and symmetry line downstream of the base region recirculation bubble. This flow division is particularly helpful in understanding the base wake characteristics with increasing pressure ratio. The base lip pressure and the base pressure variation have been discussed with respect to the primary nozzle lip expansion fan extent. In the open wake regime (or for low pressure ratios) the wave interactions within the core jet flow impinge on the base region shear layer. Because of these interactions it is difficult to propose an empirical model for open wake base pressure. In the closed wake regime (for higher pressure ratios), the base region recirculation bubble is completely under the shower of primary nozzle lip expansion fan. Hence the base lip pressure and base pressure are frozen with respect to stagnation conditions. Based on these insights it was possible to propose empirical models for linear and annular closed wake base pressure. Along with these, a mathematical model defining a reference pressure ratio PR∗, beyond which the closed wake base pressure is expected to be more than the ambient pressure has also been proposed. This is expected to serve as a good design parameter. In case of linear plug flows, this also serves the purpose of base wake transition, for the cases considered in this thesis. The flow expansion process or the primary nozzle lip expansion fan extent was also useful in understanding the differences between the linear and annular plug nozzle flow fields. In a linear plug nozzle, the flow expands only in the streamwise direction while in an annular plug nozzle the flow expands both along the streamwise and azimuthal directions. The flow expands at a faster rate in case of annular nozzle as against linear nozzle. Hence differences are observed between the linear and annular nozzle on plug and base surfaces. On the annular plug surface more wave interactions are observed because of faster expansion. With regard to base characteristics, faster expansion in annular plug nozzle, with respect to linear nozzle, results in a lower base lip pressure, lower base pressure and higher wake transition pressure ratio. The realistic cluster plug configurations have also been considered for the present studies. The effects of clustering on the plug nozzle flow field have been brought out by considering two different linear cluster nozzles and one annular cluster nozzle. The differences in the flow field of a simple and cluster plug nozzle has been discussed. In case of simple plug nozzle wave interactions are observed only in the stream wise direction, while in case of cluster plug nozzle three dimensional wave interactions are observed because of the splitter plates. Along the splitter plate differential end conditions introduce a curved recompression shock on the plug surface. This recompression shock in turn induces a streamwise vortex and also a secondary shock. It has been observed that differences between the simple and cluster plug surface pressure field are because of three dimensional wave interactions. Regarding the base pressure, differences between the simple and cluster geometries were observed for shorter truncation plug lengths (20% length plug). While for longer plug lengths (more than 34% length) the effects of clustering were reduced on the base pressure. Regarding the transition pressure ratio, differences were observed between simple and clustered plug nozzles for all the plug lengths considered. In addition, the performance of the plug nozzles has been carried out. From the analysis it was found that the primary nozzle and plug surface are major contributors towards thrust. The base surface contributes only about 2– 3% of the thrust at design condition. Hence, from a design point of view, a computational solver can be a useful tool considering its efficacy on the plug surface and in the primary nozzle.

Approved for public release, distribution is unlimited / Resonant excitation tests of rotor blades in vacuum spin pits using discrete oil jets showed that impact erosion of the blades could limit test times, but lower excitation amplitudes were produced using mist nozzles. Smaller diameter discrete jets might extend test times, but to fully prevent erosion, oil mist droplet size needed to be 30 microns or less. The present study examined both approaches. Prototype nozzles were developed to create 0.005 inch diameter multiple discrete jets using first alumina, then stainless steel tubing, laser and micro-machine drilling. The latter technique was selected and 50 were manufactured for evaluation in HCF spin tests. A vacuum test chamber was built to observe and photograph spray patterns from the prototype nozzles and from commercially available mist nozzles. An LDV system was used successfully to determine the velocity of the oil droplets within the mist. A complete mapping of mist nozzle sprays is required to allow routine design of blade excitation systems. / Lieutenant, United States Navy

Une part importante du bruit généré par les moteurs d'avion est liée à la combustion. Afin de réduire cette source de bruit, une compréhension fine des phénomènes associés est nécessaire. Deux mécanismes générateurs de bruit, et ayant pour origine la combustion, ont été identifié dans les moteurs d'avions dans les années 1970: un premier mécanisme dit direct, qui est lié directement à un dégagement de chaleur instationnaire, et l'autre dit indirect qui est lié aux interactions entre les étages de turbine et les fluctuations de température en sortie de chambre, également produites par la combustion. Des méthodes analytiques et des simulations numériques sont utilisées ici à la fois pour montrer l'importance du bruit de combustion indirect par rapport au bruit direct, et pour donner des limites de validité des approches analytiques qui sont basées sur l'hypothèse de tuyère compacte. Trois configurations différentes sont étudiées dans un premier temps: une tuyère quasi-1-D, une tuyère axi-symétrique 2-D, ainsi qu'une aube de turbine 2-D. Finalement, un secteur de chambre de combustion 3-D réelle (SNECMA) est calculé à l'aide de la Simulation aux Grandes Echelles. Les fluctuations en sortie du brûleur sont utilisées pour évaluer le bruit total généré par la combustion (direct et indirect) à l'aide des approches analytiques précédemment étudiées. / An important part of the noise generated by aero-engines is caused by the combustion. To decrease this source of noise, a precise comprehension of the underlying phenomenon is required. Two different mechanisms generating noise in aero-engines because of the combustion have been identified in the 1970’s: the direct mechanism that is directly related to the unsteady heat release, and the indirect one that is caused by the interactions between the turbine stages and the temperature fluctuations also produced by the combustion. Analytical methods and numerical simulations are used here both to show the importance of the indirect combustion noise compared with the direct one, and to provide some validity limits of compact nozzles analytical approaches. Three different configurations dealing with indirect noise are investigated: quasi-1- D nozzle, axisymmetric 2-D nozzle and 2-D turbine blade. Finally, an actual 3-D combustion chamber sector (SNECMA) is addressed with Large-Eddy Simulation. Fluctuations at the outlet of the combustor are used to compute the overall noise caused by the combustion (direct and indirect), by means of the investigated analytical models.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The performance of wet cooling towers can be improved by installing spray nozzles that distribute the cooling water uniformly onto the fill whilst operating at a low pressure head. In this thesis, three commercial spray nozzles are experimentally evaluated in terms of flow and pressure loss characteristics as well as water distribution patterns. The results of the evaluation process highlight the need for spray nozzles with enhanced performance characteristics. The theory required to implement the results of the evaluation process in the design of a cooling tower is presented and discussed. A systematic approach to enhance the performance of a spray nozzle through minor alterations is applied to one of the commercial spray nozzles that was evaluated. The fluid dynamics of an orifice nozzle, such as the effect of a change in pressure head, spray angle, spray height, orifice diameter and wall thickness on drop diameter and spray distance, is experimentally investigated and a model with which a spray nozzle can be designed is finally presented. Two prototype spray nozzles show that it is possible to enhance the performance of spray nozzles and thus wet cooling towers by means of the methods presented. / AFRIKAANSE OPSOMMING: Die werkverrigting van natkoeltorings kan verbeter word deur sproeiers te installeer wat die verkoelingswater uniform versprei op die pakking teen 'n lae pomp drukhoogte. In hierdie tesis word drie kommersiële sproeiers eksperimenteel geëvalueer in terme van vloei en drukverlies eienskappe sowel as water verdelings patrone. Die resultate van die evaluasie proses beklemtoon die behoefte aan sproeiers met verbeterde werkverrigtingseienskappe. Die teorie wat benodig word om die resultate van die evaluasie proses te implementeer in die ontwerp van 'n natkoeltoring word bespreek. 'n Stelselmatige benadering om die werkverrigtings van 'n sproeier te verhoog deur klein veranderinge aan die ontwerp aan te bring, word toegepas op een van die sproeiers wat getoets is. Die vloeidinamika van 'n plaatmondstuk, soos die effek van 'n verandering in drukhoogte, sproeihoek, sproeihoogte, gatdiameter en wanddikte op druppel diameter en sproeiafstand, is eksperimenteel ondersoek en 'n model word aangebied waarmee 'n sproeier ontwerp kan word. Twee prototipe sproeiers wys dat dit moontlik is om die werkverrigting van sproeiers, en dus ook natkoeltorings, te verbeter deur die metodes wat in die tesis aangebied word, toe te pas.

The impingement of supersonic jets on surfaces is of interest because of its important application to jet blast deflectors (JBD), and short takeoff and vertical landing aircraft (STOVL) during hover. Typically, on an aircraft carrier deck, the impingement of the jet blast on the deflector generates impingement tones, and structural vibrations, not only on the JBD but also on the ship deck. Therefore, apart from direct transmission of jet noise to the gallery level, there is a component of noise transmitted due to the impingement of the jet on the JBD. The objectives of this work are to study the pressure spectra (i) on a flat plate, and separately on a cone due to axisymmetric impingement of a supersonic underexpanded cold jet issuing from a convergent-divergent nozzle and (ii) on a plane jet impinging on a finite plate and an adjoining ground plane due to the impingement of a planar jet on the plate. The characteristics of the surface pressure fluctuations are numerically investiga ted using WIND-US 2.0. The time-dependent, compressible Euler equations for perfect gas are employed for the present computations. The impingement distance between the jet nozzle and the deflector plate, and the plate inclination with respect to the incident jet are varied. The impingement zone stagnation bubble and a high-speed radial jet with several embedded structures (shocklets) were identified on the perpendicular plate. Flows involving cones reveal the presence of detached cone shocks, enclosing a recirculation zone. The location and magnitude of the peak pressure on the cone surface are a strong function of the cone apex angle. For the two-dimensional jet impingement on angled plate the peak value of pressure occurs at normal jet impingement. The pressure at the intersection point of the plate and the ground plane is sometimes higher than the peak pressure on the plate. Beyond this point there is a sharp decrease in pressure. As the flow accelerates, an oblique shock is / Beyond this point there is a sharp decrease in pressure. As the flow accelerates, an oblique shock is sometimes formed in this grazing flow region. A recirculation region at the lower lip of the nozzle was observed for all the separation distances and plate inclinations. / by Binu Pundir. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

O presente trabalho teve por objetivo avaliar e comparar dois sistemas de aplicação de agrotóxicos em citros visando à redução do volume de aplicação com base no estudo da quantidade de produto que permanece no alvo (deposição) e análise das gotas. Na citricultura utilizam-se altos volumes de aplicação (de 2000 a 5000 L.ha-1) para o controle de pragas e doenças incrementando os custos operacionais, por esse motivo, atualmente vem-se desenvolvendo diversos sistemas de aplicação com tecnologia sofisticada visando diminuir esses volumes para 200 ou 500 L.ha-1 mas permitindo que a quantidade de produto depositado no alvo seja eficaz no controle de pragas e doenças. Procuramos avaliar dois sistemas de aplicação de agrotóxicos com um pulverizador de jato transportado. Os sistemas de aplicação utilizaram os atomizadores rotativos de discos e os bicos hidráulicos para efeito comparativo do desempenho. Foi realizada uma pulverização em duas passadas para cada sistema sobre uma amostra de quatro árvores. Utilizaram-se papéis hidrosensíveis, folhas e placas de vidro para a coleta dos dados. Para a análise da gota utilizou-se o software de leitura visual e-Sprinkle e a análise de deposição foi realizada com cromatografia gasosa e cromatografia de permeação em gel. Concluiu-se que o sistema de aplicação com atomizadores rotativos mostrou resultados favoráveis de deposição quando comparado com o sistema de aplicação com bicos hidráulicos, uma vez que esses resultados não foram significativamente diferentes. O que resulta bastante importante é que o sistema de aplicação com atomizadores rotativos utilizou um quinto do volume de aplicação quando comparado ao sistema com bicos hidráulicos, pelo que se deve considerar de vital importância o aspecto econômico para trabalhos complementares. / The aim of the work was to evaluate and compare two application spray systems of pesticides in citrus, aiming the reduction of the application volume rate in based in the amount of product that remains in the target (spray deposition) and distribution of the drops. Actually in the citrus orchard high application volumes rates for the pest control are used increasing the operational costs. The application system must be based in sophisticated technology to reduce the application volumes rates and also be efficient in the pest control. For such we evaluated two pesticides application systems with an air carrier sprayer. The application systems used were the rotary discs atomizers and the hydraulic nozzles, to compare the performance based in the applied volume rates, spray deposition and droplets distribution. A spraying run for each system was performed on a random sample of four trees for each system, water-sensitive papers, leaves and glass slides had been used for data collection. The water-sensitive papers were analyzed with visual imaging software (e-Sprinkle) and the spray deposition was analyzed with gas chromatography and gel permeation chromatography. The application system with rotary discs atomizers used reduced application volumes rates and had less deposit than hydraulic nozzles but did not significantly differents. Those results were important because the application system with rotary discs atomizers only used fifth of the application volume rate compared with hydraulic nozzles, must be consider of vital importance the economical aspect to complementary works.

"Spray cooling has been important to control die temperature in forging processes for years. One area that has had little research is how thermal stresses in a metal are related to flow characteristics of the spray. Wyman-Gordon Corporation at its North Grafton MA facility uses spray cooling to cool their die after a forging process. The current system used is found to cause cracking along the surface of the impression in the die. The purpose of this project is to compare the nozzle system used by Wyman-Gordon to selected commercially available spray nozzles, and determine if there is a better spray cooling system than the one currently used. First the flow parameters, of Sauter mean diameter, particle velocity, and volumetric spray flux were experimentally found using a laser PDA system for four water driven nozzles, including the Wyman-Gordon nozzle, and one air-atomizing nozzle. The water atomizing nozzles were tested using pressures from 30 psi to 150 psi. For the air-atomizing nozzle, the water pressure was set at 60 psi and the air pressure was varied from 30 to 150 psi. Three nozzles were chosen, the Wyman-Gordon nozzle, the smaller orifice water atomizing nozzle, the air-atomizing nozzle, and an air stream, to conduct an inverse heat conduction experiment. Using the temperature gradients created by the cooling effects of each nozzle, the heat flux and induced thermal stresses were determined. The results showed the Wyman-Gordon nozzle was causing higher thermal stresses than the air/water and water nozzles. However, the air-atomizing nozzle and air stream, due to the high temperatures that the dies are subjected to, did not cool the die quick enough to be practical. The smaller orifice water atomizing nozzle proved to be the nozzle that would cool the surface of the dies within a practical time, and induce allowable thermal stresses, sufficiently enough below the yield strength of the die material. These results, although collected specifically to study the cooling of dies at Wyman-Gordon, could be generalized to include the cooling of any test piece with a high surface temperature. "