The performance benefits of boundary layer ingestion in aircraft with distributed propulsion have been extensively studied in the past. These studies have indicated that propulsion system integration issues such as distortion and intake pressure losses could mitigate the expected benefits. This paper introduces and develops a methodology that enables the assessment of different propulsion system designs, which are optimized to be less sensitive to the effects of the aforementioned issues. The study models the propulsor array and main engine performance at design point using a parametric approach, and further at component level, the study focuses on identifying optimum propulsor configurations, in terms of propulsor pressure ratio and BL capture sheet height. At a system level, the study assesses the effects of splitting the thrust between the propulsor array and main engines. The figure of merit used in the optimization is the TSFC. The suitability of the concepts is further assessed using performance predictions for HTS electrical motors. For the purpose of this study, the NASA N3-X aircraft concept is selected as baseline configuration, where the different propulsion designs are tested. As the study focuses on performance assessment of the propulsion system, sizing implication issues and aircraft performance installations effects have not been included in the analysis. The results from the parametric analysis corroborated previous studies regarding the high sensitivity of the propulsion system performance to intake losses and BL inlet conditions. As the study found low-power consumption configurations at these operating conditions, this may be considered as a major issue. The system analysis from the study indicated that splitting the thrust between propulsors and main engines results in improved system efficiency with beneficial effects in fuel savings. When a 2% increase in intake pressure losses and a similar reduction in fan efficiency were assumed due to boundary layer ingestion, the study found an optimum configuration with 65% of thrust delivered by the propulsor array. To summarize, the present work built on past research further contributes to the field through the inclusion of the thrust split as a key variable in the propulsion system design. The thrust split, when introduced, enabled reduction of the detrimental effects of intake losses on the overall system performance. Additionally, as it reduces the power required for the propulsor array, it is expected to reduce the operating power of HTS and cooling systems and therefore improve the effectiveness of the concept.

The present paper focuses on the numerical simulation of unsteady cavitation around a NACA66 hydrofoil to improve the understanding of the cavitation effects on hydraulic machinery. For this aim, the Zwart–Gerber–Belamri cavitation model was updated and uploaded as a library file for OpenFOAM’s solvers using C++ language. Furthermore, the hybrid Reynold average Navier–Stokes (RANS)–large eddy simulation (LES) model k - ω SST scale adaptive simulation (SAS) was implemented as a turbulence model for the present study of scale adaptive simulation. For validation, numerical results were compared with experimental results obtained by Leroux at the Naval Academy Research Institute in France. In order to highlight the benefits in terms of computational consumption and reproduction of the phenomenon the k - ω SST SAS model was compared against implicit large eddy simulation (ILES). Results show that the cavitation evolution including the maximum vapor length, the detachment and the oscillation frequency were reproduced satisfactorily using k - ω SST SAS. Moreover, k - ω SST SAS results predicted a lower total vapor volume on time than ILES, which is related to observed pulses of pressure coefficient, C p , and those match fairly well with the experimental results. To summarize, the k - ω SST SAS model predicts with good accuracy unsteady cavitation behavior around hydrofoils and shows improved versatility over the ILES approach.

The Bitcoin (BTC) market presents itself as a new unique medium currency, and it is often hailed as the “currency of the future”. Simulating the BTC market in the price discovery process presents a unique set of market mechanics. The supply of BTC is determined by the number of miners and available BTC and by scripting algorithms for blockchain hashing, while both speculators and investors determine demand. One major question then is to understand how BTC is valued and how different factors influence it. In this paper, the BTC market mechanics are broken down using vector autoregression (VAR) and Bayesian vector autoregression (BVAR) prediction models. The models proved to be very useful in simulating past BTC prices using a feature set of exogenous variables. The VAR model allows the analysis of individual factors of influence. This analysis contributes to an in-depth understanding of what drives BTC, and it can be useful to numerous stakeholders. This paper’s primary motivation is to capitalize on market movement and identify the significant price drivers, including stakeholders impacted, effects of time, as well as supply, demand, and other characteristics. The two VAR and BVAR models are compared with some state-of-the-art forecasting models over two time periods. Experimental results show that the vector-autoregression-based models achieved better performance compared to the traditional autoregression models and the Bayesian regression models.

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Wetlands in the Andean region have been altered and have been lost as a result of the agricultural frontier expansion and human activities. The disturbance of the paramo ecosystem by the destruction or alteration of the wetlands modifies the load and endowment of water to the hydrological systems, which provide water to main cities in the highlands. Therefore, the present work focuses on setting up the framework for wetland monitoring in the Andean paramo region using Unmanned Aerial Vehicles (UAVs). For this aim, the study was based on a mission profile using a fixed wing UAV incorporated with a RGB camera in one of the most documented wetlands in the Ecuadorian paramo region, Pugllohuma wetland. Furthermore, to assess the saturation of the wetland, field testing data has been collected to set the range values of saturation for the monitoring system. In the same way, a review regarding multispectral imagery for the assessment of water and vegetation indices is explored and highlighted for future work. This work is a first stage in the monitoring process and hence it aims to set a baseline study for the implementation of a more detailed methodology.

A clear requirement for the textile industry is to adapt to low-production quantities because of ever-changing fashion trends. This leads to frequent changes in textile processes and materials. Flexibility in the textile industry seems to be the key to success. Nevertheless quality and reliability must be maintained while at the same time maintaining or reducing production costs. The textile industry must also be environmentally sensitive.This current trend affects, in particular, spinning processes because they require high investment due to the complexity and dimensions of the facilities.Since the requirements listed above cannot be accomplished with current technology, it is necessary to develop more advanced yarn production technologies. 1 The conventional spinning system, which is currently responsible for 98% of the world's yarn production for a yarn count below 20 tex, is no longer able to achieve the productivity standards required. The main problem with the conventional system is its production rate limit of 15-25 m/min.Other systems, such as the OE rotor, have a much higher productivity rate, but due to the main features of the process it is not economically viable to produce yarn Abstract Traditional spinning systems are reaching profitability limits due to high production costs and low productivity. Pneumatic spinning is seen as a developing system; its productivity is much higher than that achieved by conventional systems. This paper evaluates one of the main factors that prevents an increase of productivity in pneumatic spinning. This is the air currents generated at the drafting cylinder entrance, which interact with the incoming fibers, diverting them from their expected path. Using laser anemometry, the airflow velocity distribution around drafting cylinders has been measured and it has been found that vorticity is created at the cylinder entrance. Extensive CFD simulation on the airflow drag by the cylinders has given a clear insight into the vortex created, producing valuable information on how cylinder design affects the vorticity created. It has been found experimentally that the use of a drafting cylinder with holes in it produced good results, reducing the air currents and allowing a sharp increase in yarn quality, as well as an increase in productivity. A study of vortex kinematics has been undertaken, bringing a better understanding of vortex creation, development, and breakdown.

Current environmental policies for the aviation sector motivate the use of cleaner propulsion alternatives in order to reduce their CO2 footprint and noise pollution in the coming years. In this context, hybrid propulsion systems have emerged as a potential solution, as they have demonstrated a good trade-off between performance and low pollutant emissions. The present work carries out a comparison between parallel and series hybrid propulsion systems using heterogeneous and homogeneous distributed propulsion architectures. In order to highlight the opportunities of distributed propulsion systems and validate the methodology developed, a single propulsion hybrid configuration is used as baseline case for this study. For the propulsion system sizing, this work uses a parametric modelling tool, which includes a constraint analysis coupled with a weight estimation module to determine suitable configurations for a environmental monitoring mission. The latter module includes semi-empirical correlations to size the electric and mechanical components for each propulsion setup. From the results, it has been found that for the representative case of monitoring in the Galapagos Islands, which requires an endurance of approximate 7 h, the parallel hybrid system using three distributed propulsors presents the best performance features in terms of fuel savings, showing a 34% reduction compared with the baseline case. To summarize, the main contribution of this study lies on the development of a methodology to set potential hybrid distributed propulsion configurations for UAVs aimed for determined monitoring missions.

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