Aerodynamic Shape Multi-Objective Optimization for SAE Aero Design Competition Aircraft

The SAE Regular Class Aero Design Competition requires students to design a radio-controlled aircraft with limits to the aircraft power consumption, take-off distance, and wingspan, while maximizing the amount of payload it can carry. As a result, the aircraft should be designed subject to these simultaneous and contradicting objectives: 1) minimize the aerodynamic drag force, 2) minimize the aerodynamic pitching moment, and 3) maximize the aerodynamic lift force. In this study, we optimized the geometric design variables of a biplane configuration using 3D aerodynamic analysis using the ANSYS Fluent. Coefficients of lift, drag, and pitching moment were determined from the completed 3D CFD simulations. Extracted coefficients were used in modeFRONTIER multi-objective optimization software to find a set of non-dominated (Pareto-optimal or best trade-off) optimized 3D aircraft shapes from which the winner was selected based to the desired plane performance

Wave Height Changes and Mass Transport on Tague Reef, a Caribbean Reef, North Coast of St. Croix, U.S. Virgin Islands.

This study of wave and current transformations across a modern coral reef was conducted on Tague Reef, St. Croix (U.S.V.I.), during late March and early April 1987. The project objective was to improve our understanding of the magnitudes, frequencies, and spatial and temporal variations of waves and currents as they interact with a modern reef. Data were collected in 4 experiments over a 2-week period. During the experiments, atmospheric and sea state conditions were typical of Caribbean-Atlantic trade wind dominated areas. Results verify that infragravity waves of 27.7 min period and diurnal tides modulated high frequency wave and current processes. Phase lags associated with these long-term motions cause sea level differences across the reef crest that influence transport of water and suspended sediment. Spectral analyses of wave data indicate that spectra shape was conserved between the forereef and reef crest, and spectral broadening at the crest was induced by energy redistribution and dissipation (average of 65%). Wave propagation into the backreef caused further spectral broadening and increased energy dissipation (average of 78%). Water depth reduction during falling tides increased wave energy dissipation by 15% and 20% from forereef to crest and from forereef to backreef, respectively. A steady wave energy model, including frictional and turbulent dissipation, gives reasonable estimates of wave heights across the reef. This model reveals that, in contrast to sandy beaches, bottom friction on coral reefs is comparable to turbulent energy dissipation. Reef crest currents occur on three important time scales: (a) short period (seconds), associated with wave activity, (b) infragravity fluctuations, and (c) diurnal variations, of uncertain, but probably tidal, origin. Vertical shear of these currents was found to be negligible. The reef crest mean and instantaneous flow fields suggest that seawater, and perhaps sediments and nutrients, are continuously transported lagoonwards. In contrast, wave related instantaneous currents over the forereef indicate off-reef transport. An unsteady, vertically integrated circulation model with bottom friction explains the observed current patterns. Under low trade wind wave conditions the volume flux at the reef crest is 0.024 m\sp3s\sp{-1}, which can flush the lagoon in 37 hours

Multi-Disciplinary Analysis and Design Optimization of a 3D Model Airplane

The SAE Regular Class Aero Design Competition requires students to design a model scale aircraft with limits to the power consumption, take-off distance, and wingspan, while maximizing the amount of payload it can carry. As a result, the aircraft should be designed subject to these simultaneous and contradicting objectives: 1) minimize the drag, 2) minimize the pitching moment, and 3) maximize the lift. This study aims to determine five optimized geometric design variables: 1) incidence angle of the wing, 2) incidence angle of the horizontal tail, 3) distance between the wing and the tail, 4) sweep angle of the winglets, and 5) height of the winglets. To determine the incidence angles, an airplane was initially designed using the highly cambered S1223 airfoil for the wing and the inverted NACA2409 airfoil for the tail. The same fuselage shape was used for all configurations where the only changes were the incidence angles and the distance between the wing and tail. Wing incidence angle was varied in the range 0° to 10°. Tail incidence angle was varied in the range -5° to 0°. Horizontal distance between the wing and the horizontal tail was varied in the range 4L to 10L, where L is the wing chord length. Each random combination of the design variables defined its own 3D aircraft configuration. Aerodynamics of each of these 3D aircraft shapes including their coefficients of lift, drag, and pitching moment were calculated using ANSYS Fluent software. Fourty such aircraft configurations were analyzed before the results were inputted into modeFrontier software to perform the multi-objective optimization study resulting in a Pareto-optimized set of the best trade-off 3D airplane geometries having the best combination of incidence angles and the wing-tail distance to achieve the three stated goals. Structural 3D analysis and static and dynamic stability analyses were also performed

Thermophysical properties of functionalized graphene nanoplatelet dispersions for improving efficiency in a wind turbine cooling system

A new generation of heat transfer fluids, nanofluids, can play a major role in the development of today’s renewable energies. In the particular case of wind turbines, an undesirable overheating of electrical and mechanical components can provoke a noticeable reduction of overall efficiency due to the temperature is a limiting factor to the electricity generation or even very expensive repair cost because of an unexpected crash of generators, or others turbine components. Dispersions of multiple-layer graphene nanostructures with high thermal conductivity in conventional working fluids are a promising type of new heat transfer fluids due to the excellent performance of nanoadditives in heat transference. Hence, determining the thermophysical properties of these nanomaterials under different conditions is the first step and key issue for analysing and optimizing the dispersions. Although water-based graphene nanoplatelet nanofluids have been investigated and some correlations can be found in the literature, scarce studies were conducted using other industrial working fluids as base fluids. The purpose of this study is to carry out a thorough thermophysical characterization of different loaded samples of functionalized graphene nanoplatelet dispersions in an industrial heat transfer fluid, Havoline XLC Pre-mixed 50/50. Four different nanofluids at mass concentrations (0.25, 0.50, 0.75 and 1.0) wt.% of functionalized graphene nanoplatelets powder were produced. In order to obtain improved long-term stabilities, sodium dodecyl benzene sulphonate was added to the samples at a mass concentration of 0.125 % in relation to the base fluid without appreciable variations in the pH value. Stability was assessed through zeta potential and dynamic light scattering measurements. Tests for determining thermal conductivity were conducted with a transient hot wire technique in a wide temperature range. In addition, densities, dynamic viscosities and specific heat capacities of the samples were experimentally determined at different temperatures in order to carry out further studies such as experimental convective heat transfer coefficients and pressure drops. Increases in thermal conductivity up to 7.3 % were found with not very high viscosity rises.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Flow behaviour of glycolated water suspensions of functionalized graphene nanoplatelets

The heat transfer performance of the conventional fluids used in heat exchange processes improves by dispersing nanoparticles with high thermal conductivity, as many researches have shown in the last decades. The heat transfer capability of a fluid depends on several physical properties among which the rheological behavior is very relevant, as we have previously pointed out. In this study, different samples of nanofluids have been analyzed by using a DHR-2 rotational rheometer of TA Instruments with concentric cylinder geometry in the temperature range from (278.15 to 323.15) K. The used base fluids were two different binary mixtures of propylene glycol and water at (10:90)% and (30:70)% mass ratios. Two different mass concentrations (viz. 0.25 and 0.5 wt.%) of graphene nanoplatelets functionalized with sulfonic acid (graphenit- HW6) were dispersed in these two base fluids. Firstly, with the goal of checking and calibrating the operation of the rheometer, the viscosity-shear stress curves for pure propylene glycol, Krytox GPL102 oil, and the two base fluids were experimentally determined. A detailed comparative study with those well-known data over the entire range of temperature was stabilized obtaining deviations in viscosity less than 3.5%. Then, the flow curves of the different nanofluid samples were studied at different temperatures to characterize their flow behavior.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

Place of Preoperative Treatment of Acromegaly with Somatostatin Analog on Surgical Outcome: A Systematic Review and Meta-Analysis

Context: Transsphenoidal neurosurgery is the accepted first-line treatment of acromegaly in the majority of patients. Previous studies addressing preoperative somatostatin analog (SSA) treatment and subsequent surgical cure rates are conflicting, reporting either benefits or no significant differences. Objective: The aim of this study, based on a meta-analysis of all published reports, was to investigate whether treatment with SSA before surgery improves the surgical outcome of acromegaly. Data sources: All studies of preoperative treatment of acromegaly with SSA were systematically reviewed up to December 2011. We searched the Medline, Embase, Cochrane and Google Scholar electronic databases. Study selection: The primary endpoint was the biochemical postoperative cure rate. We identified 286 studies, out of which 10 studies (3.49%) fulfilling the eligibility criteria were selected for analysis; five retrospective studies with a control group, two prospective non-randomized trials, and three prospective controlled trials. The meta-analysis was conducted using the random-effects model. Data extraction: Data were extracted from published reports by two independent observers. Data synthesis: A borderline effect was detected in the analysis of all of the trials with control groups, with a pooled odds ratio (OR) for biochemical cure with SSA treatment of 1.62 (95% CI, 0.93-2.82). In the analysis of the three prospective controlled trials, a statistically significant effect was identified OR: 3.62 (95% CI, 1.88-6.96). Conclusions: Preoperative treatment with SSA og GH-secreting pituitary adenomas shows a significant improvement on surgical results. This meta-analysis suggests that in centers without optimal results all patients with a GH-secreting pituitary macroadenoma should be treated with a long-acting SSA prior to surgical treatment

Region-wide temporal and spatial variation in Caribbean reef architecture: is coral cover the whole story?

The architectural complexity of coral reefs is largely generated by reef-building corals, yet the effects of current regional-scale declines in coral cover on reef complexity are poorly understood. In particular, both the extent to which declines in coral cover lead to declines in complexity and the length of time it takes for reefs to collapse following coral mortality are unknown. Here we assess the extent of temporal and spatial covariation between coral cover and reef architectural complexity using a Caribbean-wide dataset of temporally replicated estimates spanning four decades. Both coral cover and architectural complexity have declined rapidly over time, with little evidence of a time-lag. However, annual rates of change in coral cover and complexity do not covary, and levels of complexity vary greatly among reefs with similar coral cover. These findings suggest that the stressors influencing Caribbean reefs are sufficiently severe and widespread to produce similar regional-scale declines in coral cover and reef complexity, even though reef architectural complexity is not a direct function of coral cover at local scales. Given that architectural complexity is not a simple function of coral cover, it is important that conservation monitoring and restoration give due consideration to both architecture and coral cover. This will help ensure that the ecosystem services supported by architectural complexity, such as nutrient recycling, dissipation of wave energy, fish production and diversity, are maintained and enhanced