bluuebunny/crossref_metadata_2025_split huggingface dataset:
How Turbulence Models Perform in Simulating Pipeflow Response to Targeted Wall-Shapes?
Authors: Masoumifar Mehran , Verma Suyash , Hemmati Arman 
Published: October 2021

Abstract
This study evaluates how Reynolds-averaged Navier–Stokes (RANS) models perform in simulating the characteristics of mean three-dimensional perturbed flows in pipes with targeted wall-shapes. The principal objective of this investigation is to evaluate which of the well-established RANS models can best predict the flow response and recovery characteristics in perturbed pipes at moderate and high Reynolds numbers (1×104−1.58×105). First, the flow profiles at various axial locations are compared between simulations and experiments. This is followed by assessing the well-known mean pipeflow scaling relation in the far downstream region, where the flow obtains a fully-developed state. The consistency of computationally predicted results and their similarities with experiments suggested that the Standard k−ε model can accurately capture the pipeflow characteristics in response to introduced perturbation with smooth sinusoidal axial variations.
Impacts of Tandem Configurations on the Aerodynamic Performance of an Axial Supersonic Through-Flow Fan Cascade
Authors: Sun Shijun , Hao Jiaqi , Yang Jutao , Zhou Ling , Ji Lucheng 
Published: October 2021

Abstract
In the current study, the tandem blade technology is applied to an supersonic throughflow fan (STFF) tandem cascade for the first time and a 2D STFF tandem cascade is preliminarily designed. Through the modification design of the tandem airfoils and their configuration (axial overlap (AO) and percent pitch (PP)), the coefficients of total pressure loss and loading are reduced by 4% and 8.58%, respectively. Furthermore, the impact of tandem configurations on the performance is parametrically investigated by numerical simulations. The results indicate that compared with AO, the performance under design incidence is more sensitive to PP except for the cases with PP exceeding a threshold value (1.15). PP dominates the loss and load by controlling the evolution of the FB wake and the shock structure of FB and the rear one of the tandem blade (RB), while AO mainly adjusts the entire shock system structure through the change of virtual shape, resulting in the variation in load distribution between FB and RB. It is worth noting that the overall loading and the total loss remain unchanged with increasing AO except for the tandem configurations (PP = 1.05, AO ≤ −0.01), which make the flow structure in the gap region undergo a fundamental change. With the optimal tandem configuration (PP = 1.05, AO = −0.01) and the modified tandem blades (the ratios of chord length and camber for FB over RB are 0.67 and 0.5, respectively), the total pressure loss coefficient is further reduced by 19.7% in comparison with the preliminary tandem design.
Vortex Tracking of Purge-Mainstream Interactions in a Rotating Turbine Stage
Authors: Mesny Alex W. , Glozier Mark A. , Pountney Oliver J. , Scobie James A. , Li Yan Sheng , Cleaver David J. , Sangan Carl M. 
Published: October 2021

Abstract
The use of purge flow in gas turbines allows for high turbine entry temperatures, which are essential to produce high cycle efficiency. Purge air is bled from the compressor and reintroduced in the turbine to cool vulnerable components. Wheel-spaces are formed between adjacent rotating and stationary discs, with purge air supplied at low radius before exiting into the mainstream gas-path through a rim-seal at the disc periphery. An aerodynamic penalty is incurred as the purge flow egress interacts with the mainstream. This study presents unparalleled three-dimensional velocity data from a single-stage turbine test rig, specifically designed to investigate egress–mainstream interaction using optical measurement techniques. Volumetric velocimetry is applied to the rotating environment with phase-locked measurements used to identify and track the vortical secondary flow features through the blade passage. A baseline case without purge flow is compared to experiments with a 1.7% purge mass fraction; the latter was chosen to ensure a fully sealed wheel-space. A non-localized vortex tracking function is applied to the data to identify the position of the core centroids. The strength of the secondary flow vortices was determined using a circulation criterion on rotated planes aligned to the vortex filaments. The pressure-side leg of the horseshoe vortex and a second vortex associated with the egress flow were identified by the experimental campaign. In the absence of purge flow, the two vortices merged, forming the passage vortex (PV). With the addition of purge flow, the two cores remained independent to 40% of the blade axial chord, while also demonstrating an increased radial migration and intensification of the PV. The egress core was shown to remain closer to the suction-surface with purge flow. Importantly, where the vortex filaments demonstrated strong radial or tangential components of velocity, the circulation level calculated from axial planes underpredicted the true circulation by up to 50%.
Locomotion Identification Method of one-DOF Six-Bar for Jumping Robot
Authors: Shun Gui 
Published: October 2021

Abstract
Exploring the locomotion of creatures is a challenging task in bionic robots, and the existing iterative design methods are mainly based on one or two characteristics to optimize robots. However, it is hard to obtain other features. Here, we introduced the thinking of system identification theory to the bionic robots, averting the exploration of the dynamics and reducing the difficulty of design greatly. A one-DOF six-bar mechanism (Watt I) was designated as the model to be identified, and it was divided into two parts, i.e. a one-DOF four-bar linkage and a three-DOF series arm. Then we formed constraints and a loss function. The parameters of the model were identified based on the kinematic data of a marmoset jumping. As a result, we obtained the desired model. Then, a prototype derived from the model was fabricated, and the experiments verified the effectiveness of the method. Our method also can be applied to other motion simulation scenarios.
A Graph Partitioning Technique to Optimize the Physical Integration of Functional Requirements for Axiomatic Design
Authors: Green Emilyn , Estrada Spenser , Gopalakrishnan Praveen Kumare , Jahanbekam Sogol , Behdad Sara 
Published: October 2021

Abstract
According to the concept of physical integration as understood in axiomatic design, design parameters of a product should be integrated into a single physical part or a few parts with the aim of reducing the information content, while still satisfying the independence of functional requirement. However, no specific method is suggested in the literature for determining the optimal degree of physical integration in a given design. This is particularly important with the current advancement in technologies such as additive manufacturing. As new manufacturing technologies allow physical elements to be integrated in new ways, new methods are needed to help designers optimize physical integration given the specific constraints and conflicts of each design. This study proposes an algorithm that uses graph partitioning to allow a designer to optimize the integration of functional requirements into a target number of parts, with the goal of minimizing the co-allocation of incompatible functional requirements in the same part. The operation and viability of the algorithm are demonstrated via two numerical examples and a practical example of designing a pencil.
Multi-Material Integrated Three-Dimensional Printing of Cylindrical Li-Ion Battery
Authors: Zhou Weiping , Li Xiying , Duan Huiling , Lv Pengyu 
Published: October 2021

Abstract
A simple, low-cost and highly efficient method of fabrication has always been the goal of manufacturing technology. In order to improve the speed of fabrication and simplify the preparation steps, this work proposes a multi-material integrated 3D printing method, aiming to obtain the desired structure from the print head in one step. As a typical example, a cylindrical Li-ion battery (LIB) with core–shell structure was integrally fabricated using this one-step multi-material integrated printing method. A multi-material print head is designed based on the structure to be printed. The inks with the characteristics of non-Newtonian fluid are developed for battery printing. Anode, cathode, separator layer, and packaging layer are easily printed simultaneously by coaxial wrapping layer by layer. The parameters of ink viscosity, printing pressure, and printing speed are studied. Electrochemical performance of the printed battery is tested with the charge and discharge capacities of the printed battery up to 147 and 99 mAh g−1 at 0.1 C rate, respectively. Compared with the traditional step-by-step printing, the proposed multi-material integrated printing method realizes the one-step printing of the battery structure, which improves manufacturing efficiency. This system can be directly extended to fabricate other integrated devices such as supercapacitors. Based on this idea, it should also be possible to design different print heads to print other multi-material devices in one step.
Rigid Spool & Riser Slugging Induced Vibrations
Authors: Aljarah Raghid , Le Prin Kevin , Saunier Claire , Minguez Matthieu 
Published: October 2021

Abstract
The paper addresses response of subsea components subject to internal intermittent slug flows. The proposed work pursues experiments already published last year (OMAE2020-18620) and focuses on the way to numerically model such complex coupled physics for both rigid spool and steel lazy wave riser.
The first part of the paper relies on the coupling approach already presented in OTC-29306 and OMAE2020-18620 mixing (i) Finite Element solver to predict the mechanical behavior of the system and (ii) a Unit Cell solver to recover the intermittent slug flow. It accounts for both (i) the complexity of the slug flow properties at the spool inlet and (ii) their variability along the system. This approach is successfully compared to the experimental (large scale) results already published. This preliminary step validates the ability of the proposed numerical model to recover real-life behavior and underlines some limitations resulting from the Industry Best Practices use.
The second part of the paper extends the applicability of the proposed coupling philosophy to a steel lazy wave riser where a classical Flow Assurance software (e.g. Olga) is considered for the characterization of the intermittent flow and then coupled with a mechanical solver. This one-way coupling accounts for the slugging variability along the riser length and consequently exhibits a finer granularity of the mechanical behavior of the riser. This modelling is then compared to the industry best practices to open a discussion on the observed differences.
Advanced Intelligent Control Strategy in Dynamic Positioning (DP) System Applied to a Semi-Submersible Drilling Platform in the North Sea
Authors: Alremeihi Mohamad , Norman Rosemary , Pazouki Kayvan , Dev Arun , Bashir Musa 
Published: October 2021

Abstract
Dynamic Positioning (DP) systems play a crucial role in oil and gas drilling and production floaters used globally for deep-water operations. Drilling operations need to maintain automatic positioning of the platform in the horizontal-plane within the safe zone. Operating DP systems typically require highly responsive control systems when encountering prevailing weather conditions. However, DP incident analysis demonstrates that control and thruster failures have been the leading causes of accidents for the past two decades, according to the International Marine Contractors Association (IMCA). In this paper, a Predictive Neural Network (PNN) strategy is proposed for thruster allocation on a platform; it has been developed by predicting the platform response and training the network to transform the required force commands from a nonlinear Proportional Integral Derivative (PID) motion controller for each thruster. The strategy is developed for increasing safety and zone keeping of DP-assisted-drilling operations in harsh weather. This is done by allowing the platform to recover the position more rapidly whilst decreasing the risk of losing the platform position and heading, which can lead to catastrophic damage. The operational performance of the DP system on a drilling platform subjected to the North Sea real environmental conditions of wind, currents and waves, is simulated with the model incorporating the PNN control algorithm, which deals with dynamic uncertainties, into the unstable conventional PID control system for a current drilling semi-submersible model. The simulation results demonstrate the improvement in DP accuracy and robustness for the semi-submersible drilling platform positioning and performance using the PNN strategy.
Nonlinear Behaviors of Three Dimensional Sloshing in the LNG Elastic Tank
Authors: Wang Zhongchang , Jiang Meirong , Yu Yang 
Published: October 2021

Abstract
Aiming at the nonlinear sloshing in the LNG tank, a three-dimensional elastic model is established to investigate the fluid structure interaction effect. For the transient flow and the tank motion, the direct coupling method is employed to calculate the interaction between the sloshing and the bulkhead. The finite element software ADINA is adopted to do the computation. The sloshing natural frequency is verified with the results of the theoretical formula. Different wall thicknesses, filling ratios and external excitations are considered and the structure natural frequency, surface elevation and sloshing pressure are obtained. The results of the elastic case are further compared with the rigid results and the nonlinear characteristics are extracted to see the hydro-elastic effect. The sloshing natural frequencies are agreed well with the theoretical results. Due to the influence of the fluid structure interaction, the couple frequencies are obviously less than those of the empty tank. With the increase of the wall thickness, the frequencies of the empty tank and the couple frequencies all increase gradually. For the surface elevation, the thinner the bulkhead thickness is, the more the high frequency component is. The free surface is relatively flat and stable in the rigid tank but tend to be chaotic for the elastic one. Due to the fluid structure interaction, the sloshing pressure of the elastic case presents obvious high-frequency fluctuation and the sloshing pressure in the elastic tank is smaller than that in the rigid tank. This model clearly shows the valuable ability to solve the three dimensional sloshing in the elastic tank.
Resistance Tests of an Articulated Pusher Barge System in Deep and Shallow Water
Authors: Zhang Li , Xing Lei , Dong Mingyu , Chen Weimin 
Published: October 2021

Abstract
Articulated pusher barge vessel is a short-distance transport vessel with good economic performance and practicability, which is widely used in the Yangtze River of China. In this present work, the resistance performance of articulated pusher barge vessel in deep water and shallow water was studied by model tests in the towing tank and basin of Shanghai Ship and Shipping Research Institute. During the experimental investigation, the articulated pusher barge vessel was divided into three parts: the pusher, the barge and the articulated pusher barge system. Firstly, the deep water resistance performance of the articulated pusher barge system, barge and the pusher at design draught T was studied, then the water depth h was adjusted, and the shallow water resistance at h/T = 2.0, 1.5 and 1.2 was tested and studied respectively, and the difference between deep water resistance and shallow water resistance at design draught were compared. The results of model tests and analysis show that: 1) in the study of deep water resistance, the total resistance of the barge was larger than that of the articulated pusher barge system. 2) for the barge, the shallow water resistance increases about 0.4–0.7 times at h/T = 2.0, 0.5–1.1 times at h/T = 1.5, and 0.7–2.3 times at h/T = 1.2. 3) for the pusher, the shallow water resistance increases about 1.0–0.4 times at h/T = 2.7, 1.2–0.9 times at h/T = 2.0, and 1.7–2.4 times at h/T = 1.6. 4) for the articulated pusher barge system, the shallow water resistance increases about 0.2–0.3 times at h/T = 2.0, 0.5–1.3 times at h/T = 1.5, and 1.0–3.5 times at h/T = 1.2. Furthermore, the water depth Froude number Frh in shallow water was compared with the changing trend of resistance in shallow water.
Automated Iterative Gap Filling Method for Drilling Logs and Other Data Series
Authors: Tunkiel Andrzej T. , Sui Dan , Wiktorski Tomasz 
Published: October 2021

Abstract
Data scientists are facing multiple issues when working with real-life data. Logs are rarely devoid of incorrect values and one of the common categories of data problems is missing values. Gaps in logs are of various shapes, sizes, and quantities, with a plethora of techniques to infill, or restore missing values. No single algorithm will perform best for all scenarios, hence in pursuit of best results exploration of various options is necessary. Furthermore, gap filling in single step may be impossible for certain methods, where gaps exist for multiple attributes. This paper explores an automated iterative approach, where a selection of common algorithms and different input combinations are evaluated on existing data to select the best method based on R2 score. With the ability to perform iterative infilling, where previously imputed data is re-used as training data to patch other gaps, this represents the most automated and universal approach for gap filling in real-life data-series. This paper presents the methodologies and issues behind automated iterative approach to gap filling, and discusses what is necessary to achieve the final goal of high quality, one-click and optimal data infilling.
Scale and Configuration Effects of an Airchamber on PTO of Oscillating Water Column Type Wave Energy Converters
Authors: Ikoma Tomoki , Hirai Shota , Aida Yasuhiro , Masuda Koichi 
Published: October 2021

Abstract
Wave energy converters (WECs) have been extensively researched. The behaviour of the oscillating water column (OWC) in OWC WECs is extremely complex due to the interaction of waves, air, and turbines. Several problems must be overcome before such WECs can be put to practical use. One problem is that the effect of the difference in scale between a small-scale experimental model and a full-scale model is unclear. In this study, several OWC models with different scales and geometries were used in forced oscillation tests. The wave tank was 7.0 m wide, 24.0 m long, and 1.0 m deep. In the static water experiment, we measured the air pressure and water surface fluctuations in an air chamber. For the experiments, models with a box shape with an open bottom, a manifold shape with an open bottom, and a box shape with a front opening, respectively, were fabricated. Furthermore, 1/1, 1/2, and 1/4 scale models were fabricated for each shape to investigate the effects of scale and shape on the air chamber characteristics. Numerical calculations were carried out by applying linear potential theory and the results were compared with the experimental values. The results confirmed that the air chamber shape and scale affect the air pressure fluctuation and water surface fluctuation inside the OWC system.
Hydrodynamic Analysis of Tandem Flapping Hydrofoils
Authors: Joshi Vaibhav , Chaithanya Mysa Ravi 
Published: October 2021

Abstract
Flapping hydrofoils in tandem configuration find applications in wave gliders, dragonfly, dorsal-tail fin interaction in fishes, among others. The flapping motion consists of a combination of heaving and pitching motion. This type of motion involves complex interaction of the vortices shed from the upstream hydrofoil with the downstream hydrofoil, thus influencing the performance of the downstream hydrofoil. A two-dimensional stabilized finite element moving mesh framework is utilized for the current study. The important parameters which influence the flow interactions are the chord size ratio and the gap between the hydrofoils. The size ratio is defined as the ratio of the chord of the upstream hydrofoil to that of the downstream hydrofoil. The size ratio is varied from 0.25 to 1. The gap is varied from one chord length to 3 chord lengths of the downstream foil. The study focuses on the effect of the size ratio, gap and flapping kinematics based on sinusoidal heaving and pitching motion on the detailed flow dynamics of the tandem hydrofoils. The effect on the thrust coefficient and hydrodynamic efficiency is explored and compared with that of an isolated hydrofoil. The results obtained from the study can pave way for a better understanding with regard to engineering designs based on biomimetics.
Vibration Control of an Offshore Wind Turbine
Authors: Alkhoury Philip , Aït-Ahmed Mourad , Soubra Abdul-Hamid , Rey Valentine 
Published: October 2021

Abstract
In order to reduce their cost, offshore wind turbines (OWTs) must have a powerful generator and a minimum overall weight. This has the consequence of making the OWT structure sensitive to dynamic excitations even at low frequencies. Indeed, modern multi-megawatt OWTs are composed of slender flexible and lightly damped components. The excessive vibrations of the OWT structure can impact the wind energy conversion to electricity, decrease the fatigue lifetime and even result in a total collapse of the structure when exposed to harsh environmental conditions. It is therefore important to reduce the unwanted vibrations of an OWT by implementing an appropriate control device that enhances its structural safety.
Motivated by the potential of the structural control methods in suppressing OWTs vibration, this paper proposes the design of a controlled active tuned mass damper (ATMD) system to reduce the nacelle/tower out-of-plane vibration of a monopile-supported 10 MW DTU OWT subjected to combined wave and wind loads. Compared to previous works, the main originality of this paper is the inclusion of a state estimator, Linear Quadratic (LQ) observer, within an optimal control schema. The state observer aims to drastically reduce the number of required system states. Indeed, as some measurements are practically impossible, all system states cannot be obtained. In this study, a fully coupled multi-degree of freedom (MDOF) analytical model of a monopile-supported OWT developed in [4] is used for this purpose. The optimal control schema makes use of the robust LQR feedback controller to establish the ATMD actuator control force. The developed active control schema proved to efficiently reduce the nacelle/tower vibration.
Mean Wave Drift Force on a Barge-Type Floating Wind Turbine With Moonpools
Authors: Tan Lei , Ikoma Tomoki , Aida Yasuhiro , Masuda Koichi 
Published: October 2021

Abstract
The barge-type foundation with moonpool(s) is a promising type of platform for floating offshore wind turbines, since the moonpool(s) could improve the hydrodynamic performance at particular frequencies and reduce the costs of construction. In this paper, the horizontal mean drift force and yaw drift moment of a barge-type platform with four moonpools are numerically and experimentally investigated. Physical model tests are carried out in a wave tank, where a 2MW vertical-axis wind turbine is modelled in the 1:100 scale. By varying the rotating speed of the turbine and the mass of the blades, the gyroscopic effects due to turbine rotations on the mean drift forces are experimentally examined. The wave diffraction and radiation code WAMIT is used to carry out numerical analysis of wave drift force and moment. The experimental results indicate that the influence of the rotations of a vertical-axis wind turbine on the sway drift force is generally not very significant. The predictions by WAMIT are in reasonable agreement with the measured data. Numerical results demonstrate that the horizontal mean drift force and yaw drift moment at certain frequencies could be reduced by moonpool(s).