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  • Managed Pressure Drilling Technology: A Research on the Formation Adaptability
  • Abstract Existing pressure drilling technologies are based on different principles and display distinct characteristics in terms of controlling the pressure and degree of formation adaptability. In the present study, the constant bottom hole pressure (CBHP) and controlled mud level (CML) dual gradient drilling methods are considered. Models for the equivalent circulating density (ECD) are introduced for both drilling methods, taking into account the control pressure parameters (wellhead back pressure, displacement, mud level, etc.) and the relationship between the equivalent circulating density curve in the wellbore and two different types of pressure profiles in deep-water areas. The findings suggest that the main…
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  • Numerical Analysis of a Microjet-Based Method for Active Flow Control in Convergent-Divergent Nozzles with a Sudden Expansion Duct
  • Abstract A method based on microjets is implemented to control the flow properties in a convergent-divergent nozzle undergoing a sudden expansion. Three different variants of this active control technique are explored numerically by means of a finite-volume method for compressible fluid flow: with the first one, the control is implemented at the base, with the second at the wall, while the third one may be regarded as a combination of the other two variants. When the jets are over-expanded, the control is not very effective. However, when a favorable pressure gradient is established at the nozzle, the control becomes effective, leading…
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  • Experimental Study and Numerical Simulation of Polymer Flooding
  • Abstract The numerical simulation of polymer flooding is a complex task as this process involves complex physical and chemical reactions, and multiple sets of characteristic parameters are required to properly set the simulation. At present, such characteristic parameters are mainly obtained by empirical methods, which typically result in relatively large errors. By analyzing experimentally polymer adsorption, permeability decline, inaccessible pore volume, viscosity-concentration relationship, and rheology, in this study, a conversion equation is provided to convert the experimental data into the parameters needed for the numerical simulation. Some examples are provided to demonstrate the reliability of the proposed approach.
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  • Thermographic Observation of High-Frequency Ethanol Droplet Train Impingement on Heated Aluminum and Glass Surfaces
  • Abstract The present study investigates thermal gradients on the heated aluminum and glass surfaces during ethanol droplet train impingement in the surface temperature ranges of 140°C–240°C. The ethanol droplet impingement is applied with an incline of 63 degrees and the droplet diameter is 0.2 mm in both aluminum and glass surface experiments. Thermal gradients are observed with a thermographic camera. Compared to the glass, the aluminum surface has very small liquid accumulations and better evaporation performance thanks to its higher thermal conductivity. Low thermal conductivity of glass results in higher thermal gradients on the surface. The droplet impact area on the…
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  • An Analysis of the Factors Influencing Cavitation in the Cylinder Liner of a Diesel Engine
  • Abstract Avoiding cavitation inside the water jacket is one of the most important issues regarding the proper design of a diesel engine’s cylinder liner. Using CFD simulations conducted in the frame of a mixture multiphase approach, a moving grid technology and near-wall cavitation model, in the present study the factors and fluid-dynamic patterns that influence cavitation are investigated from both macroscopic and mesoscopic perspectives. Several factors are examined, namely: wall vibration, water jacket width, initial cavitation bubble radius, coolant temperature, and number of bubbles. The results show that reducing the cylinder liner vibration intensity can significantly weaken the cavitation. Similarly, increasing…
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  • Group Decision-Making Method with Incomplete Intuitionistic Fuzzy Preference Relations Based on a Generalized Multiplicative Consistent Concept
  • Abstract Based on the analyses of existing preference group decision-making (PGDM) methods with intuitionistic fuzzy preference relations (IFPRs), we present a new PGDM framework with incomplete IFPRs. A generalized multiplicative consistent for IFPRs is defined, and a mathematical programming model is constructed to supplement the missing values in incomplete IFPRs. Moreover, in this study, another mathematical programming model is constructed to improve the consistency level of unacceptably multiplicative consistent IFPRs. For group decisionmaking (GDM) with incomplete IFPRs, three reliable sources inuencing the weights of experts are identified. Subsequently, a method for determining the weights of experts is developed by simultaneously considering…
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  • Numerical Simulation Research on Static Aeroelastic Effect of the Transonic Aileron of a High Aspect Ratio Aircraf
  • Abstract The static aeroelastic effect of aircraft ailerons with high aspect ratio at transonic velocity is investigated in this paper by the CFD/CSD fluid-structure coupling numerical simulation. The influences of wing static aeroelasticity and the ‘scissor opening’ gap width between aileron control surface and the main wing surface on aileron efficiency are mainly explored. The main purpose of this paper is to provide technical support for the wind tunnel experimental model of aileron static aeroelasticity. The results indicate that the flight dynamic pressure has a great influence on the static aeroelastic effect of ailerons, and the greater the dynamic pressure, the…
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  • gscaLCA in R: Fitting Fuzzy Clustering Analysis Incorporated with Generalized Structured Component Analysis
  • Abstract Clustering analysis identifying unknown heterogenous subgroups of a population (or a sample) has become increasingly popular along with the popularity of machine learning techniques. Although there are many software packages running clustering analysis, there is a lack of packages conducting clustering analysis within a structural equation modeling framework. The package, gscaLCA which is implemented in the R statistical computing environment, was developed for conducting clustering analysis and has been extended to a latent variable modeling. More specifically, by applying both fuzzy clustering (FC) algorithm and generalized structured component analysis (GSCA), the package gscaLCA computes membership prevalence and item response probabilities…
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  • Modeling and Prediction of Inter-System Bias for GPS/BDS-2/BDS-3 Combined Precision Point Positioning
  • Abstract The combination of Precision Point Positioning (PPP) with Multi-Global Navigation Satellite System (MultiGNSS), called MGPPP, can improve the positioning precision and shorten the convergence time more effectively than the combination of PPP with only the BeiDou Navigation Satellite System (BDS). However, the Inter-System Bias (ISB) measurement of Multi-GNSS, including the time system offset, the coordinate system difference, and the inter-system hardware delay bias, must be considered for Multi-GNSS data fusion processing. The detected ISB can be well modeled and predicted by using a quadratic model (QM), an autoregressive integrated moving average model (ARIMA), as well as the sliding window strategy…
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