A more robust method for solving the governing equations of a one-dimensional stage-by-stage dynamic compression system model was developed and validated. The improved method was then applied to two-dimensional post-stall models. The improvement in robustness was achieved by modeling the governing equations with upwind differencing and use of implicit time integration. A special form of upwind flux, flux difference splitting with source term treatment, FDSS, was developed for the model. A two-dimensional axisymmetric model was developed to allow post-stall modeling of split flowpath systems such as turbofans. This model was an entirely new concept. Additionally, a two-dimensional axial-circumferential model of rotating stall cell development and propagation was developed based on previous work. All of the models developed applied upwind differencing techniques to improve upon central-difference methods. / Ph. D.

An experimental investigation into the effects of inlet temperature transients on the stall and stall recovery aerodynamics of a low speed multi-stage axial flow compressor has been presented. Experiments were conducted on a low speed multi-stage axial flow compression system to demonstrate how a compressor dynamically stalls or recovers from a rotating stall operating condition during an inlet temperature transient. The specific effects of the inlet temperature transients on the compressor rotor blade flow physics during the dynamic stall or rotating stall recovery events of the axial flow compression system have been presented. In one experiment, a full recovery from a rotating stall operating condition was successfully accomplished on the low speed multistage axial flow compressor. Explanations for the axial flow compression system dynamic stall and rotating stall recovery processes during inlet temperature transients have been presented. The method utilized for inducing the rotating stall recovery on the compression system has been proposed as a possible new technique for active recovery from rotating stall for single and multi-stage axial flow compression systems. / Ph. D.

A new method and mechanism for generating non-uniform, or distorted, aircraft engine inlet flow is being developed in order to account for dynamic changes during the creation and propagation of the distortion. Total pressure distortions occur in gas turbine engines when the incoming flow is disturbed. Dynamic total pressure changes may happen slowly, or may occur very rapidly. The disturbance of the incoming flow can change engine operating characteristics, including lowering the surge limit and creating High Cycle Fatigue incidents. In order to create a distorted flow with dynamic characteristics, a mechanism must be developed that when actuated, can change the distortion pattern and intensity with respect to time. This work covers the initial design of both the distorting and actuating device. The design chosen is a low force design that is practically independent of flow forces. This allows the system to be easily sized for all flow conditions. The study also includes developing the working design into an overall prototype. Testing is also performed to validate the design as the most advantageous choice. / Master of Science

O estudo teve como objetivo avaliar as respostas hormonais, fisiológicas e comportamentais de vacas Holandesas frente a situações de conforto ou estresse térmico ambiental. O experimento desenvolvido entre os verões de 2007 e 2008 no Campus Administrativo da Universidade de São Paulo (USP), Pirassununga, SP, utilizou 28 fêmeas de 1ª a 3ª lactações com produção média de 20 kg/dia divididas em dois grupos experimentais após a parição, com e sem disponibilidade de climatização em galpão do tipo free-stall. Os parâmetros ambientais foram avaliados através do cálculo do índice de temperatura e umidade (ITU). As colheitas de dados fisiológicos (temperatura retal, temperatura de superfície corporal do dorso e base da cauda, frequência respiratória), hormonais (cortisol e IGF-I), comportamentais e de produção e qualidade do leite foram realizadas em cinco condições climáticas no ano (outono, inverno, primavera, verão seco e verão chuvoso) caracterizadas pela temperatura, umidade relativa e radiação solar. No verão os animais foram submetidos ao Teste de Capacidade Termolítica (CT) e a um estudo comparativo de um período de sete dias sob estresse calórico em câmara climática e desafio com aplicação de ACTH. No experimento 1 o teste de capacidade termolítica foi validado. A CT foi igual para animais em lactação ou secos (P>0,05), e maior para vacas mantidas sob sistema de climatização ao longo do ano (P<0,01). Houve influência da exposição ao sol sobre todas as variáveis fisiológicas (P<0,01). Os níveis plasmáticos de cortisol foram maiores antes da exposição ao sol e depois do repouso por 1 hora à sombra para vacas em lactação (P=0,03) e para as sem disponibilidade de climatização (P=0,03). O IGF-I foi maior nas vacas secas em final de gestação (P<0,01). No experimento 2 a temperatura retal não teve influência da climatização, com os dois grupos apresentando valores abaixo de 38,56 ºC ao longo do ano (P=0,11). Observou-se uma tendência de alta (P<0,01) nas concentrações plasmáticas de cortisol entre outono e inverno, começando o decréscimo até o início do verão seco e um novo aumento durante o verão chuvoso, e um comportamento inverso para o IGF-I. Temperatura retal mostrou uma correlação moderada e positiva (P<0,01) com a temperatura superficial (0,46) e frequência respiratória (0,35). A temperatura do ar e ITU apresentaram correlações positivas de moderada à alta com as temperaturas retal, da base da cauda e superficial, e também com a frequência respiratória (P<0,01). No experimento 3 as vacas passaram a maior parte do dia na sombra em pé (84,2 %) independente da estação do ano. O ambiente climatizado proporcionou maior frequência de alimentação e produção de leite durante o verão (P<0,05), assim como teor de gordura 17,9 % maior (P<0,01). No experimento 4 os animais foram submetidos ao estresse pontual causado pelo uso do ACTH e ao estresse calórico prolongado em câmara climática. Tanto a administração de ACTH quanto a exposição ao calor prolongado em câmara climática aumentaram os níveis de cortisol plasmático. Durante o estresse calórico houve diminuição do IGF-I e produção leiteira e aumento das variáveis fisiológicas ligadas a termorregulação. / The study aimed to evaluate the hormonal, physiological and behavioral responses of Holstein cows in situations of a comfort or heat environment. The experiment was conducted between the summers of 2007 and 2008 in the University of São Paulo (USP), Pirassununga, SP, and used 28 females from 1st to 3rd lactations with average production of 20 kg/day divided into two experimental groups after birth, with and without an evaporative cooling system in a free-stall. Environmental parameters were evaluated by temperature and humidity index (THI). Collection of physiological data (rectal temperature, body surface, internal base of tail, respiratory rate), hormonal (cortisol and IGF-I), behavioral and production and milk quality were conducted in five climatic conditions (autumn, winter, spring, dry summer and rainy summer) characterized by air temperature, relative humidity and solar radiation. In summer the animals were subjected to Thermolysis Capacity Test (CT) and a comparative study of a period of seven days under heat stress in climatic chamber and challenged with ACTH administration. In experiment 1 the Thermolysis Capacity Test was validated. The CT was the same for dry or lactating animals (P>0.05) and higher for cows kept in evaporative cooling system throughout the year (P<0.01). The results showed influence of sun exposure on all physiological variables (P<0.01). Plasma levels of cortisol were higher before sun exposure and after the one hour rest under shade for lactating cows (P=0.03) and for no cooled animals (P=0.03). IGF-I was higher in dry cows in late gestation (P<0.01). In experiment 2 the evaporative cooling system did not show influence on rectal temperature, with both groups having values below 38.56 ºC throughout the year (P=0.11). It was observed an upward trend (P<0.01) in plasma cortisol concentrations between autumn and winter, starting the decline until the beginning of dry summer and a further increase during rainy summer, and an opposite pattern for IGF- I. Rectal temperature showed a moderate and positive correlation (P<0.01) with the body surface temperature (0.46) and respiratory rate (0.35). The air temperature and THI showed moderate to high positive correlations with rectal temperatures, and the internal base of tail, and also with the respiratory rate (P<0.01). In experiment 3 cows spent most of the day standing in the shade (84.2%) regardless of season. Cooled cows had a higher feeding frequency and milk production during summer (P<0.05) and fat content 17.9% higher (P<0.01). In experiment 4, cows were subjected to the short stress caused by the ACTH administration and prolonged heat stress in climatic chamber. Both the administration of ACTH as prolonged exposure to heat in climatic chamber increased the levels of plasma cortisol. During heat stress a decrease in plasma IGF-I and milk production was observed, and an increase in physiological variables related to thermoregulation.

O estudo teve como objetivo avaliar as respostas hormonais, fisiológicas e comportamentais de vacas Holandesas frente a situações de conforto ou estresse térmico ambiental. O experimento desenvolvido entre os verões de 2007 e 2008 no Campus Administrativo da Universidade de São Paulo (USP), Pirassununga, SP, utilizou 28 fêmeas de 1ª a 3ª lactações com produção média de 20 kg/dia divididas em dois grupos experimentais após a parição, com e sem disponibilidade de climatização em galpão do tipo free-stall. Os parâmetros ambientais foram avaliados através do cálculo do índice de temperatura e umidade (ITU). As colheitas de dados fisiológicos (temperatura retal, temperatura de superfície corporal do dorso e base da cauda, frequência respiratória), hormonais (cortisol e IGF-I), comportamentais e de produção e qualidade do leite foram realizadas em cinco condições climáticas no ano (outono, inverno, primavera, verão seco e verão chuvoso) caracterizadas pela temperatura, umidade relativa e radiação solar. No verão os animais foram submetidos ao Teste de Capacidade Termolítica (CT) e a um estudo comparativo de um período de sete dias sob estresse calórico em câmara climática e desafio com aplicação de ACTH. No experimento 1 o teste de capacidade termolítica foi validado. A CT foi igual para animais em lactação ou secos (P>0,05), e maior para vacas mantidas sob sistema de climatização ao longo do ano (P<0,01). Houve influência da exposição ao sol sobre todas as variáveis fisiológicas (P<0,01). Os níveis plasmáticos de cortisol foram maiores antes da exposição ao sol e depois do repouso por 1 hora à sombra para vacas em lactação (P=0,03) e para as sem disponibilidade de climatização (P=0,03). O IGF-I foi maior nas vacas secas em final de gestação (P<0,01). No experimento 2 a temperatura retal não teve influência da climatização, com os dois grupos apresentando valores abaixo de 38,56 ºC ao longo do ano (P=0,11). Observou-se uma tendência de alta (P<0,01) nas concentrações plasmáticas de cortisol entre outono e inverno, começando o decréscimo até o início do verão seco e um novo aumento durante o verão chuvoso, e um comportamento inverso para o IGF-I. Temperatura retal mostrou uma correlação moderada e positiva (P<0,01) com a temperatura superficial (0,46) e frequência respiratória (0,35). A temperatura do ar e ITU apresentaram correlações positivas de moderada à alta com as temperaturas retal, da base da cauda e superficial, e também com a frequência respiratória (P<0,01). No experimento 3 as vacas passaram a maior parte do dia na sombra em pé (84,2 %) independente da estação do ano. O ambiente climatizado proporcionou maior frequência de alimentação e produção de leite durante o verão (P<0,05), assim como teor de gordura 17,9 % maior (P<0,01). No experimento 4 os animais foram submetidos ao estresse pontual causado pelo uso do ACTH e ao estresse calórico prolongado em câmara climática. Tanto a administração de ACTH quanto a exposição ao calor prolongado em câmara climática aumentaram os níveis de cortisol plasmático. Durante o estresse calórico houve diminuição do IGF-I e produção leiteira e aumento das variáveis fisiológicas ligadas a termorregulação. / The study aimed to evaluate the hormonal, physiological and behavioral responses of Holstein cows in situations of a comfort or heat environment. The experiment was conducted between the summers of 2007 and 2008 in the University of São Paulo (USP), Pirassununga, SP, and used 28 females from 1st to 3rd lactations with average production of 20 kg/day divided into two experimental groups after birth, with and without an evaporative cooling system in a free-stall. Environmental parameters were evaluated by temperature and humidity index (THI). Collection of physiological data (rectal temperature, body surface, internal base of tail, respiratory rate), hormonal (cortisol and IGF-I), behavioral and production and milk quality were conducted in five climatic conditions (autumn, winter, spring, dry summer and rainy summer) characterized by air temperature, relative humidity and solar radiation. In summer the animals were subjected to Thermolysis Capacity Test (CT) and a comparative study of a period of seven days under heat stress in climatic chamber and challenged with ACTH administration. In experiment 1 the Thermolysis Capacity Test was validated. The CT was the same for dry or lactating animals (P>0.05) and higher for cows kept in evaporative cooling system throughout the year (P<0.01). The results showed influence of sun exposure on all physiological variables (P<0.01). Plasma levels of cortisol were higher before sun exposure and after the one hour rest under shade for lactating cows (P=0.03) and for no cooled animals (P=0.03). IGF-I was higher in dry cows in late gestation (P<0.01). In experiment 2 the evaporative cooling system did not show influence on rectal temperature, with both groups having values below 38.56 ºC throughout the year (P=0.11). It was observed an upward trend (P<0.01) in plasma cortisol concentrations between autumn and winter, starting the decline until the beginning of dry summer and a further increase during rainy summer, and an opposite pattern for IGF- I. Rectal temperature showed a moderate and positive correlation (P<0.01) with the body surface temperature (0.46) and respiratory rate (0.35). The air temperature and THI showed moderate to high positive correlations with rectal temperatures, and the internal base of tail, and also with the respiratory rate (P<0.01). In experiment 3 cows spent most of the day standing in the shade (84.2%) regardless of season. Cooled cows had a higher feeding frequency and milk production during summer (P<0.05) and fat content 17.9% higher (P<0.01). In experiment 4, cows were subjected to the short stress caused by the ACTH administration and prolonged heat stress in climatic chamber. Both the administration of ACTH as prolonged exposure to heat in climatic chamber increased the levels of plasma cortisol. During heat stress a decrease in plasma IGF-I and milk production was observed, and an increase in physiological variables related to thermoregulation.

Highly-loaded turbomachine blades can stall under off-design conditions. In this regime, the flow can separate close to the leading edge of the blade in a periodic manner that can lead to blade vibrations, commonly referred to as stall flutter. Prior experimental studies on stall flutter have been at large Re (Re ~ 106). In the present work, motivated by applications in Unmanned Air Vehicles (UAV) and Micro Air Vehicles (MAV), we study experimentally the forces and flow fields around an oscillating blade at low Re (Re ~ 3 x 104). At these low Re, the flow even over the stationary blade can be quite different. We experimentally study the propensity of an isolated symmetric and cambered blade (with chord c) to undergo self-excited oscillations at high angles of attack and at low Reynolds numbers (Re ~ 30, 000). We force the blade, placed at large mean angle of attack, to undergo small amplitude pitch oscillations and measure the unsteady loads on the blade. From the measured loads, the direction and magnitude of energy transfer to/from the blade is calculated. Systematic measurements have been made for varying mean blade incidence angles and for different excitation amplitudes and frequencies (f). These measurements indicate that post stall there is a possibility of excitation of the blade over a range of Strouhal Numbers (St = fc/U) with the magnitude of the exciting energy varying with amplitude, frequency and mean incidence angles. In particular, the curves for the magnitude of the exciting energy against Strouhal number (St) are found to shift to higher St values as the mean angle of attack is increased. We perform the same set of experiments on two different blade shapes, namely NACA 0012 and a compressor blade profile, SC10. Both blade profiles show qualitatively similar phenomena. The flow around both the stationary and oscillating blades is studied through Particle Image Velocimetry (PIV). PIV measurements on the stationary blade show the gradual shift of the flow separation point towards the leading edge with increasing angle of attack, which occurs at these low Re. From PIV measurements on an oscillating blade near stall, we present the flow field around the blade at different phases of the blade oscillation. These show that the boundary layer separates from the leading edge forming a shear layer, which flaps with respect to the blade. As the Strouhal number is varied, the phase between the flapping shear layer and the blade appears to change. This is likely to be the reason for the observed change in the sign of the energy transfer between the flow and the blade that is responsible for stall flutter.

As relações entre os fatores climáticos e as respostas fisiológicas de vacas lactantes são bastante conhecidas, porém sob condições de ambiente controlado. Este estudo teve como objetivo monitorar as respostas dos animais em instalações típicas para vacas leiteiras, para identificar o real impacto do ambiente climático sobre o animal. Foi proposto um método para avaliar o nível de estresse de vacas, que poderá servir como uma ferramenta simples, que traduza as sensações de conforto térmico dos animais. O experimento foi realizado em três fases, a saber: primavera (28 dias), verão (31 dias) e inverno (31 dias). Foram utilizados animais da raça Holandesa com produção média entre 20 a 25 kg leite/dia. Os animais foram alojados em instalação tipo free-stall com acesso livre a um piquete adjacente. Foram avaliadas a freqüência respiratória (FR), a temperatura retal (TR), a temperatura do pelame (TPE), a temperatura auricular (TAU), a temperatura da base da cauda (TCAU), a temperatura da vulva (TVU) e a produção de leite (PL). O ambiente foi monitorado 24 horas por dia, todos os dias, com registros da temperatura de bulbo seco (TBS), da umidade relativa (UR), da temperatura de ponto de orvalho e da temperatura de globo negro (TG). Posteriormente foram calculados os índices de temperatura e umidade (ITU) e o de temperatura de globo e umidade (ITGU). Todas as variáveis fisiológicas apresentaram padrão sazonal bem claro, com maiores valores durante as estações mais quentes (primavera e verão) e menores valores no inverno. A TAU, a TVU e a TCAU apresentaram correlações positivas com a TR, a FR e a TPE, o que indica uma associação entre estas variáveis. Porém estudos adicionais devem ser conduzidos para validar a aplicabilidade destas variáveis (TAU, TVU e TCAU) na caracterização do estresse térmico dos animais. A TPE e a FR foram as variáveis mais influenciadas pelo ambiente climático em todas as estações do ano. O ambiente noturno foi associado às variações da TR, da FR e da TPE, enquanto o ambiente do dia anterior não explicou a variação das respostas fisiológicas. Não houve evidência de efeitos de uma variável ambiental isolada sobre as variáveis fisiológicas, o que indicou a complexidade das relações entre o animal e o ambiente climático. Mesmo com ITU acima de 79, considerado estressante pela literatura estrangeira para vacas lactantes, não foram evidenciados valores estressantes para TR e FR e reduções na produção de leite. O modelo proposto neste trabalho para estimar presença ou ausência de estresse em vacas alojadas em free-stall, apresentou boa aderência ao conjunto de dados, com R&sup2; de 0,43. Dessa forma, disponibiliza uma ferramenta simples e rápida para produtores e técnicos, pela associação de duas medidas fisiológicas (FR e TPE) de fácil mensuração, ou então pela associação de duas variáveis ambientais (TBS e UR). Tal ferramenta diz respeito a uma amostra da população de vacas Holandesas alojadas em determinada instalação e região, o que condiciona o modelo proposto a outros estudos para sua validação em outros rebanhos e regiões. / It has been well known the relation between the environment and physiological answers of lactating dairy cows under controlled environmental conditions. The present study aimed to monitor the animal answers allocated at typical housing system to identify the real environmental impact over it. A method was proposed to evaluate the stress level of the animal, to be used as a tool to identify the sensations of thermal comfort. The experiment was conducted in three phases, in spring (28 days), summer (31 days) and winter (31 days) periods. Holstein dairy cows were used averaging milk yield around 20 to 25 kg/day. The animals were housed in a free stall shed with an open area. Respiratory rate (FR), rectal temperature (TR), surface skin temperature (TPE), internal ear temperature (TAU), tail temperature (TCAU), vulva temperature (TVU) and milk yield (PL) were evaluated. The environmental conditions were monitored during 24 hours every day, by recording the dry bulb temperature (TBS), relative humidity (UR), dew point temperature (Tpo) and black globe temperature (Tg). The calculation of temperature humidity index (ITU) and the black globe humidity index (ITGU) was based on these environmental variables. The physiological variables had a seasonal standard with higher values during hot periods (spring and summer) and lower values during the winter. The IET, VT and TT demonstrated positive correlations with RT, RR and SKT showing association between them. More studies are necessary to validate the applicability of these variables (IET, VT and TT) and to characterize heat stress in dairy cows. SKT and RR were the most influenced by the environment in all seasons. The night environment was associated to the RT, RR and SKT, while the day before environment did not explained the physiological variations. There was no evidence of isolated environmental variables over the physiological ones, showing the complexity between the animal and the environment. Even with the THI values above 79, what is considered stressful to dairy cows, there was no evidence of stressful values for RT and RR and of MY losses. The model proposed in this study to estimate presence or absence of heat stress in dairy cows avails a simple and fast tool to milk producers and technicians, where it could be associated two physiological variables (RR and SKT) of easy measurement or other two environment variables (DBT and RH). However, this result is related to the studied population at a specific housing system and situated at a specific region. Addiitonal studies must be conducted to validate the proposed model to others dairy herds and locations.

Wind turbines installed in the open atmosphere experience much more complex and highly-varying flow than their counterparts in wind tunnels or numerical simulations. In particular, aerodynamic stall—which occurs often on stall-regulated wind turbines in such variable flow conditions—can affect both wind turbine blade lifespan and noise generation. A field test site was therefore installed at the outer limits of the city of Waterloo, Ontario to study a small-scale 30 kW stall-regulated wind turbine. Experimental equipment was installed to monitor parameters such as wind speed and direction, electrical power output, blade pitch angle, rotor rotational speed, and wind turbine yaw orientation. Extensive hardware and software was developed and installed to wirelessly collect data from all instrumentation. Tufts and a remote-operated camera were also installed on one of the two blades of the 10 m diameter horizontal-axis turbine. In a variation on the tuft flow visualisation technique, video files were analysed using a novel digital image processing code. The code was developed in MATLAB to calculate the fraction of the blade which was stalled by determining the position and angle of each tuft in every video frame. The algorithm was able to locate on average 85% of the visible tufts and correctly tagged those which were stalled with a bias of only −5% compared to the typical manual method. When the algorithm was applied to 7 h of tuft video at the outboard 40% of the blade, the total average fraction of stalled tufts varied from 5% at 5 m/s to 40% at 21 m/s. This trend was expected for the stall-regulated design since, as the wind speed is increased, the stall progresses from inboard to outboard regions and from trailing edge to leading edge. The 7 h time period represents at least a two order-of-magnitude increase compared with time periods analysed using previous manual methods. This work has demonstrated a digital implementation of tuft flow visualisation which lends statistical validity (through long-time-period averaging) to a common tool for researching wind turbine stall. The speed and ease with which the tuft method can be implemented, combined with the high cost per energy of small-scale wind turbines, suggest that this digital algorithm is a highly beneficial tool for future studies.

As relações entre os fatores climáticos e as respostas fisiológicas de vacas lactantes são bastante conhecidas, porém sob condições de ambiente controlado. Este estudo teve como objetivo monitorar as respostas dos animais em instalações típicas para vacas leiteiras, para identificar o real impacto do ambiente climático sobre o animal. Foi proposto um método para avaliar o nível de estresse de vacas, que poderá servir como uma ferramenta simples, que traduza as sensações de conforto térmico dos animais. O experimento foi realizado em três fases, a saber: primavera (28 dias), verão (31 dias) e inverno (31 dias). Foram utilizados animais da raça Holandesa com produção média entre 20 a 25 kg leite/dia. Os animais foram alojados em instalação tipo free-stall com acesso livre a um piquete adjacente. Foram avaliadas a freqüência respiratória (FR), a temperatura retal (TR), a temperatura do pelame (TPE), a temperatura auricular (TAU), a temperatura da base da cauda (TCAU), a temperatura da vulva (TVU) e a produção de leite (PL). O ambiente foi monitorado 24 horas por dia, todos os dias, com registros da temperatura de bulbo seco (TBS), da umidade relativa (UR), da temperatura de ponto de orvalho e da temperatura de globo negro (TG). Posteriormente foram calculados os índices de temperatura e umidade (ITU) e o de temperatura de globo e umidade (ITGU). Todas as variáveis fisiológicas apresentaram padrão sazonal bem claro, com maiores valores durante as estações mais quentes (primavera e verão) e menores valores no inverno. A TAU, a TVU e a TCAU apresentaram correlações positivas com a TR, a FR e a TPE, o que indica uma associação entre estas variáveis. Porém estudos adicionais devem ser conduzidos para validar a aplicabilidade destas variáveis (TAU, TVU e TCAU) na caracterização do estresse térmico dos animais. A TPE e a FR foram as variáveis mais influenciadas pelo ambiente climático em todas as estações do ano. O ambiente noturno foi associado às variações da TR, da FR e da TPE, enquanto o ambiente do dia anterior não explicou a variação das respostas fisiológicas. Não houve evidência de efeitos de uma variável ambiental isolada sobre as variáveis fisiológicas, o que indicou a complexidade das relações entre o animal e o ambiente climático. Mesmo com ITU acima de 79, considerado estressante pela literatura estrangeira para vacas lactantes, não foram evidenciados valores estressantes para TR e FR e reduções na produção de leite. O modelo proposto neste trabalho para estimar presença ou ausência de estresse em vacas alojadas em free-stall, apresentou boa aderência ao conjunto de dados, com R&sup2; de 0,43. Dessa forma, disponibiliza uma ferramenta simples e rápida para produtores e técnicos, pela associação de duas medidas fisiológicas (FR e TPE) de fácil mensuração, ou então pela associação de duas variáveis ambientais (TBS e UR). Tal ferramenta diz respeito a uma amostra da população de vacas Holandesas alojadas em determinada instalação e região, o que condiciona o modelo proposto a outros estudos para sua validação em outros rebanhos e regiões. / It has been well known the relation between the environment and physiological answers of lactating dairy cows under controlled environmental conditions. The present study aimed to monitor the animal answers allocated at typical housing system to identify the real environmental impact over it. A method was proposed to evaluate the stress level of the animal, to be used as a tool to identify the sensations of thermal comfort. The experiment was conducted in three phases, in spring (28 days), summer (31 days) and winter (31 days) periods. Holstein dairy cows were used averaging milk yield around 20 to 25 kg/day. The animals were housed in a free stall shed with an open area. Respiratory rate (FR), rectal temperature (TR), surface skin temperature (TPE), internal ear temperature (TAU), tail temperature (TCAU), vulva temperature (TVU) and milk yield (PL) were evaluated. The environmental conditions were monitored during 24 hours every day, by recording the dry bulb temperature (TBS), relative humidity (UR), dew point temperature (Tpo) and black globe temperature (Tg). The calculation of temperature humidity index (ITU) and the black globe humidity index (ITGU) was based on these environmental variables. The physiological variables had a seasonal standard with higher values during hot periods (spring and summer) and lower values during the winter. The IET, VT and TT demonstrated positive correlations with RT, RR and SKT showing association between them. More studies are necessary to validate the applicability of these variables (IET, VT and TT) and to characterize heat stress in dairy cows. SKT and RR were the most influenced by the environment in all seasons. The night environment was associated to the RT, RR and SKT, while the day before environment did not explained the physiological variations. There was no evidence of isolated environmental variables over the physiological ones, showing the complexity between the animal and the environment. Even with the THI values above 79, what is considered stressful to dairy cows, there was no evidence of stressful values for RT and RR and of MY losses. The model proposed in this study to estimate presence or absence of heat stress in dairy cows avails a simple and fast tool to milk producers and technicians, where it could be associated two physiological variables (RR and SKT) of easy measurement or other two environment variables (DBT and RH). However, this result is related to the studied population at a specific housing system and situated at a specific region. Addiitonal studies must be conducted to validate the proposed model to others dairy herds and locations.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this investigation is to determine the performance of an axial ow compressor operating in a closed loop helium cycle under high through- ow conditions. The GTHTR300 four-stage helium test compressor was chosen for this investigation. Limited information on the helium test compressor's blade pro les are available, therefore a mathematical model was developed to calculate the blade geometries based on the theory of Lieblein and Aungier. A locally available three-stage compressor was used to con rm whether the mathematical model calculated the blade pro le geometries correctly. The Stellenbosch University Compressor Code (SUCC), an axisymmetric inviscid through- ow code, was used to compare the performance of the calculated three-stage compressor blade geometries with available experimental data. Excellent correlation was obtained, thus it was concluded that the mathematical model as well as the SUCC could be used to predict the performance of an axial ow compressor. The blade geometries of the helium test compressor were calculated and the pressure ratio and e ciency predictions of the SUCC correlated well with the experimental data. The helium test compressor was simulated to verify the calculated blade geometries further using the Computational Fluid Dynamics (CFD) package NUMECA FINE /Turbo. The FINE /Turbo pressure ratio and e ciency predictions compared adequately with the SUCC and available experimental data, especially in the design region. At high mass ow rates the stator blade row experiences negative incidence stall which results in a large recirculation zone in the stator blade wake. / AFRIKAANSE OPSOMMING: Die doel van hierdie ondersoek is om vas te stel wat die werkverrigting is van 'n aksiale kompressor in 'n geslote lus helium siklus onderhewig aan hoë deurvloei kondisies. Die GTHTR300 vier-stadium helium toets kompressor is gekies vir die ondersoek. Daar is egter beperkte inligting oor die helium kompressor se lem geometrie, dus is 'n wiskundige model ontwikkel om dit te bereken gebaseer op die werk van Lieblein en Aungier. Om te bevestig dat die lem geometrie akkuraat was, was die lem geometrie van die 'n plaaslike beskikbare drie-stadium kompressor bereken. Die Stellenbosch University Compressor Code (SUCC), 'n aksisimmetriese nie-viskeuse deurvloei kode, is gebruik om die prestasie van die berekende lem geometrie met beskikbare eksperimentele data te vergelyk. Uitstekende korrelasie is verkry vir die drukverhouding en benuttingsgraad resultate, dus is die gevolgtrekking gemaak dat die wiskundige model sowel as die SUCC gebruik kon word om die lem geometrie en werkverrigting van aksiale kompressors te bereken en voorspel. Die helium toets kompressor is gesimuleer met behulp van die numeriese vloei-dinamika pakket NUMECA FINE /Turbo om die berkende lem geometrie verder te veri eer. Die FINE /Turbo drukverhouding en benuttingsgraad resultate het goed gekorreleer met beide die SUCC resultate en eksperimentele data, veral in die ontwerpsgebied. Teen hoë massa vloei tempo's vind daar groot wegbreking teen negatiewe invalshoek plaas in die stator lemry en dit veroorsaak 'n hersirkulasie sone in die naloop van die stator lem.