In the present work, we experimentally study thrust generation from sinusoidally pitched rigid and flexible foils immersed in a uniform flow. The flexible foils are made by attaching a flexible flap of known flexural rigidity and flap length to the trailing edge of a rigid foil. For such thrust generating systems, a propulsive efficiency (η) may be defined as the ratio of the useful work done to the input energy requirement. In the present experiments, the propulsive efficiency (η) of the flapping foil can be determined from direct measurement of the unsteady forces and torque on the foil. The effects of systematic variation of the flexural rigidity of the foil, from highly flexible to rigid, on the thrust and efficiency characteristics of the foil are investigated. Studying such oscillating foils helps one to understand and mimic the efficient thrust generating mechanism in fishes and other creatures that use flapping to locomote themselves. A strain guage based loadcell is used to measure the forces normal to the foil (N) and forces along the chord of the foil (A). With a potentiometer, the instantaneous angular position (θ) is also measured, so that instantaneous lift (L) and thrust (T ) can be calculated. The measured moment (M) is used to calculate the instantaneous power input (P = Mθ˙). The foil is immersed in a uniform flow (u) set in a water tunnel, and the sinusoidal pitching (θ = θmaxsinωt) is provided by a servo motor. The Reynolds number (Re = uc/ν) in the present study is in the range of 103 to 104 . For the case of the rigid foil, the thrust and efficiency characteristics are presented for variation of the non-dimensional flapping frequency called the ‘reduced frequency’ (k = πfc/u), which is varied in the range of 1 to 10. At small reduced frequency (k < 3), the foil experiences a mean drag, while at k > 3, the foil experiences a mean thrust that grows rapidly as the reduced frequency (k) is increased. The thrust characteristics of the rigid foil are decided mainly by the normal force’s phase with respect to θ (φCN ) and its magnitude ([CN ]), as the chord-wise force is very small compared to the normal force (A << N). The measurements show that the non-dimensional mean thrust coefficient (CT ) scales as k2 and non-dimensional mean power (CP ) scales as k3 for k Ҳ 4. The maximum efficiency for rigid foils is found to be 8 % and it occurs at k 6. For the flexible foil case, the effect of making a portion of the total foil flexible by means of attaching a flexible flap of known flexural rigidity (EI) and flap length (cF ) to a rigid foil of length (cR) is studied. Unlike the rigid foils, the chordwise force (A) becomes an important factor in determining the thrust and efficiency characteristics of the flexible foils, due to the bending of the flap. We present results for a broad range of flexural rigidities from highly flexible flaps to stiff flaps, with the extent of flexibility fixed at cF /cR =0.8. We find that there is an optimal flexural rigidity for which the efficiency (η) reaches a maximum of 28 %. This represents a 250 % improvement compared to the rigid foil. The flexible foils with stiff flaps show a strange behavior with all the mean thrust coming from chordwise forces (A), unlike other flexible foils where the contribution to mean thrust come from both normal and chordwise forces. The effect of varying the extent of flexibility (cF/cR) with fixed flexural rigidity has also been studied. We define a non-dimensional flexibility parameter, R∗ = EI/(0.5ρu2sc3F ), which can combine the effect of variations in EI and cF /cR. Using this non-dimensional flexibility parameter (R∗), we find out that mean thrust and efficiency data for both the EI and cF/cR variation study collapse onto a single curve, indicating that R∗ can indeed be a single parameter characterizing flexibility. The present work shows that flexible foils can improve efficiency over rigid foils. Efficiency improvements can come in two ways depending on the R∗ of the flexible foil. Flexible foils with R∗ in the range of 10−2 to 100 show nearly 250% improvement in efficiency, accompanied by nearly 70 % loss in thrust compared to an entirely rigid foil of the same total chord. Flexible foils with R∗ in the range of 100 to 101 show nearly 50 % improvement in efficiency accompanied by nearly 100% increase in thrust.

No description available.

Thesis (M.S.)--Ohio University, November, 1997. / Title from PDF t.p.

Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on July 10, 2009. Major professor: Dr. Eric Mehiel. "Presented to the faculty of California Polytechnic State University at San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Aerospace Engineering with specialization in Space Systems Engineering." "April 2009." Includes bibliographical references (p. 48).

A Terapia por Captura de Nêutrons pelo Boro (BNCT) é uma técnica radioterapêutica, que visa o tratamento de alguns tipos de câncer, em que sua energia útil é proveniente da reação nuclear promovida pela incidência de nêutrons térmicos no isótopo de 10B. No Brasil existe uma instalação, localizada junto ao canal de irradiação número 3 do Reator de Pesquisas IEA-R1 do IPEN, que foi projetada para o desenvolvimento de pesquisas em BNCT. Para uma aplicação adequada da técnica é necessário que o feixe de irradiação na posição de amostra, seja composto predominantemente por nêutrons térmicos com reduzida contaminação dos componentes do feixe, correspondente aos nêutrons epitérmicos e rápidos e à radiação gama. Este trabalho tem como objetivo monitorar e avaliar o feixe de irradiação na posição de irradiação de amostras, através do uso de detectores de ativação (folhas de ativação), e a partir de simulações utilizando o código de transporte de radiação, MCNP, avaliar mudanças na instalação, mais especificamente no conjunto de filtros e moderadores, para que se aprimore as condições de irradiação na instalação. O trabalho propos uma nova metodologia de cálculo para estudos de otimização do feixe a partir do recurso de redução de variância presente no MCNP, o wwg (weight window generation). Com os resultados obtidos através da adoção de um conjunto maior de folhas de ativação, foi possível a discriminação experimental do feixe de nêutrons em 5 faixas de energia e concluir que a instalação para estudos em BNCT do IPEN possui fluxo de nêutrons térmicos de 108 n/cm2.s, intensidade suficiente para que os estudos na área possam ser realizados com grande potencial de alteração de suas componentes conforme demanda experimental. / Boron Neutron Capture Therapy (BNCT) is a radiotherapeutic technique for the treatement of some types of cancer whose useful energy comes from a nuclear reaction that occurs when thermal neutron impinges upon a Boron-10 atom. In Brazil there is a research facility built along the beam hole number 3 of the IEA-R1 research reactor at IPEN, which was designed to perform BNCT research experiments. For a good performance of the technique, the irradiation beam should be mostly composed of thermal neutrons with a minimum as possible gamma and above thermal neutron components. This work aims to monitor and evaluate the irradiation beam on the sample irradiation position through the use of activation detectors (activation foils) and also to propose, through simulation using the radiation transport code, MCNP, new sets of moderators and filters which shall deliver better irradiation fields at the irradiation sample position In this work, a simulation methodology, based on a MCNP card, known as wwg (weight window generation) was studied, and the neutron energy spectrum has been experimentally discrimanted at 5 energy ranges by using a new set o activation foils. It also has been concluded that the BNCT research facility has the required thermal neutron flux to performe studies in the area and it has a great potencial for improvement for tailoring the irradiation field.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Robert L. Opila, Dept. of Materials Science & Engineering. Includes bibliographical references.

A Terapia por Captura de Nêutrons pelo Boro (BNCT) é uma técnica radioterapêutica, que visa o tratamento de alguns tipos de câncer, em que sua energia útil é proveniente da reação nuclear promovida pela incidência de nêutrons térmicos no isótopo de 10B. No Brasil existe uma instalação, localizada junto ao canal de irradiação número 3 do Reator de Pesquisas IEA-R1 do IPEN, que foi projetada para o desenvolvimento de pesquisas em BNCT. Para uma aplicação adequada da técnica é necessário que o feixe de irradiação na posição de amostra, seja composto predominantemente por nêutrons térmicos com reduzida contaminação dos componentes do feixe, correspondente aos nêutrons epitérmicos e rápidos e à radiação gama. Este trabalho tem como objetivo monitorar e avaliar o feixe de irradiação na posição de irradiação de amostras, através do uso de detectores de ativação (folhas de ativação), e a partir de simulações utilizando o código de transporte de radiação, MCNP, avaliar mudanças na instalação, mais especificamente no conjunto de filtros e moderadores, para que se aprimore as condições de irradiação na instalação. O trabalho propos uma nova metodologia de cálculo para estudos de otimização do feixe a partir do recurso de redução de variância presente no MCNP, o wwg (weight window generation). Com os resultados obtidos através da adoção de um conjunto maior de folhas de ativação, foi possível a discriminação experimental do feixe de nêutrons em 5 faixas de energia e concluir que a instalação para estudos em BNCT do IPEN possui fluxo de nêutrons térmicos de 108 n/cm2.s, intensidade suficiente para que os estudos na área possam ser realizados com grande potencial de alteração de suas componentes conforme demanda experimental. / Boron Neutron Capture Therapy (BNCT) is a radiotherapeutic technique for the treatement of some types of cancer whose useful energy comes from a nuclear reaction that occurs when thermal neutron impinges upon a Boron-10 atom. In Brazil there is a research facility built along the beam hole number 3 of the IEA-R1 research reactor at IPEN, which was designed to perform BNCT research experiments. For a good performance of the technique, the irradiation beam should be mostly composed of thermal neutrons with a minimum as possible gamma and above thermal neutron components. This work aims to monitor and evaluate the irradiation beam on the sample irradiation position through the use of activation detectors (activation foils) and also to propose, through simulation using the radiation transport code, MCNP, new sets of moderators and filters which shall deliver better irradiation fields at the irradiation sample position In this work, a simulation methodology, based on a MCNP card, known as wwg (weight window generation) was studied, and the neutron energy spectrum has been experimentally discrimanted at 5 energy ranges by using a new set o activation foils. It also has been concluded that the BNCT research facility has the required thermal neutron flux to performe studies in the area and it has a great potencial for improvement for tailoring the irradiation field.

No description available.

A laser-driven flyer impact system was constructed, characterized, and validated for performing uniaxial-strain experiments to investigate the shock equation-of-state (EOS) and processes leading to reaction initiation in thin, fully-dense Ni-Al nanolayered foils. Additionally, various fully-dense Ni-Al mixtures with highly heterogeneous microstructures and widely varying length scales were investigated to understand influence of meso-scale features on the shock compression and reaction response. Ni-Al composites are a class of reactive materials also called Structural Energetic Materials (SEMs), which aim to combine stiffness and strength with the ability to release large amounts of energy through highly exothermic reactions when the constituents are intimately mixed during shock loading. While porous reactive materials have been studied extensively, the processes leading to reaction initiation in fully-dense mixtures consisting of phases with disparate mechanical properties is more ambiguous. A table-top, small-scale laser system was developed for studying shock-induced effects in extremely thin reactive materials. Laser accelerated thin foil impact experiments utilizing time-resolved interferometry allowed for measuring the Hugoniot of the nanolayered Ni-Al foil over a range of particle velocities/pressures. Separate recovery experiments were performed by shock-loading Ni-Al foils slightly below the reaction initiation threshold and performing post-mortem TEM/STEM analysis to identify the constituent mixing processes leading to reaction. Direct-shock experiments were performed on the different fully-dense Ni-Al mixtures and hydrodynamic simulations using real microstructures allowed direct correlations with the experiment results, which yielded an improved understanding of the effect of phase arrangement on the shock propagation and reaction initiation response. The EOS experiments performed at particle velocities > 200 m/s showed a deviation from the predicted inert trend and recovered targets showed complete reaction to the B2-NiAl intermetallic phase. The measured deviation from inert behavior and state of recovered material suggests the occurrence of a shock-induced chemical reaction. The shocked (but unreacted) Ni-Al materials contained distinct constituent mixing features (layer jets and intermixed zones), where significant elemental penetration occurred and are likely sources of reaction initiation. The observed results provide the first clear evidence of shock-induced reactions in fully-dense nanolayered Ni-Al foils.

No / Transient liquid phase (TLP) brazing of Mg–AZ31 alloy and Ti–6Al–4V alloy was performed using double Ni and Cu sandwich foils. Two configurations were tested; first, Mg–AZ31/Cu–Ni/Ti–6Al–4V and second, Mg–AZ31/Ni–Cu/Ti–6Al–4V. The effect of set-up configuration of the foils on microstructural developments, mechanical properties and mechanism of joint formation was examined. The results showed that different reaction layers formed inside the joint region depending on the configuration chosen. The formation of e phase (Mg), r (CuMg2), d (Mg2Ni) and Mg3AlNi2 was observed in both configurations. Maximum shear strength obtained was 57 MPa for Mg–AZ31/Ni–Cu/Ti–6Al–4V configuration and in both configurations, the increase in bonding time resulted in a decrease in joint strength to 13 MPa. The mechanism of joint formation includes three stages; solid state diffusion, dissolution and widening of the joint, and isothermal solidification. / The authors would like to acknowledge The German Jordanian University (GJU), and NSERC Canada for the financial support for this research.