bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delta Winglet Pairs in the Core of a Pipe and its Effect on Heat Transfer and Flow
Authors: Islam Md. , Chong Z. , Alam Md. 
Published: November 2019

Abstract
Vortex generators/turbulent promoters generate the longitudinal vortices which introduce the better mixing of the fluid with fluid circulation and enhance heat transfer. In this research, experimental investigations have been carried out to study the effect of delta winglet vortex generator (DWVG) in the core of the pipe on heat transfer and flow behavior. In this experiment, two pairs of delta winglet vortex generators (DWVG) were printed on the upside and downside of the thin plate using 3D printing technology in a ring and then placed in the core of the pipe to generate longitudinal vortices. Middle plate was very thin. The effect of heights (H = 5mm, 10mm, 15mm and 20mm) of DWVG for 10° angle of attack and 15mm spacing between leading edges of VG pairs on heat transfer and pressure drop was studied. The experiments were conducted for a fully developed turbulent flow of air in the range of Reynolds numbers (Re) 5000–25000. The influence of the DWVGs on heat transfer and pressure drop was investigated in terms of the Nusselt number (Nu) and friction factor (f). The experimental results indicate that DWVG in the core of the tube results in a considerable increase in Nu with some pressure penalty. It is found that DWVG increase Nu considerably only when H is over 10mm. Nu increases with Re and H. Friction factor decreases with Re but increase with H. The thermal performance enhancement (TPE) was noticed decreasing with Re. TPE could be obtain up to 1 only when the height is over 10mm for Re ≤ 7500. The experimental results show that the DWVG in the core of the pipe is not a good option to enhance the heat transfer at a higher Re.
Numerical Investigation on the Effect of Blade Loading on Unsteady Sheet Cavitation Patterns
Authors: Nahon Jeremy , Zangeneh Mehrdad , Nohmi Motohiko , Watanabe Hiroyoshi 
Published: November 2019

Abstract
Cavitation commonly manifests itself as vapour structures attached to the suction surfaces of impeller, runner or propeller blades. The numerical study carried out here seeks to correlate the changes in the behaviour of sheet cavitation to variations in blade geometry. The analysis is run for a two-dimensional stationary cascade. The streamwise loading distribution is the metric used to characterise the geometry. It determines the rate and amount of work generated across the channel and is directly connected to blade surface pressure.
In this study, the test sample consists of a set of varying blade profiles characterised by specific loading configurations: foreloaded, aft-loaded or bespoke distributions. Time-resolved simulations of the cavitating flow are generated to study cavity behaviour. Computations are run through Fluent using the SST URANS formulation. The Zwart-Gerber-Belamri homogeneous cavitation model is used to treat cavitation. A range of behaviours are observed for the cavitation patterns. Variations are found in inception conditions, shape and sheet stability. For the latter, two dynamic regimes are identified with a transition point that varies according to the loading profile. A pair of tradeoff relations are also observed: hydrodynamic efficiency versus suction performance and suction performance versus cavity stability. The results demonstrate the capacity of the loading distribution to affect cavitation dynamics.
Wake Flow Visualization of a Simplified Vehicle Model During Flow State Change
Authors: Nakashima Takuji , Moriuchi Takashi , Chao Yan , Kohri Itsuhei 
Published: November 2019

Abstract
A flow around a three-dimensional bluff body such as an automobile sometimes exhibits a bi-stable state wherein two stable flow states exist for a single condition. Better aerodynamic characteristics can be obtained if we suppress or promote the flow state change between such bi-stable states. Hence, it is necessary to understand the trigger conditions and process of the flow state change. In this study, we investigated the transient aerodynamics of the Ahmed model with the slant angle of 32°, exceeding the critical angle of 30°, known to exhibit bi-stable state under crosswind conditions. Changing the Yaw angle by rotating the model, produced change in the flow state, accompanied by time delay. While continuously measuring fluid force, we performed PIV measurement triggered by a sudden change in fluid dynamic force corresponding to the flow state change. Using these methods, we realized the synchronous measurement of the fluid force and wake flow during the flow state change. At the beginning of the flow state change, flow velocity changed around the trailing edge of the slant surface. Subsequently, the separated flow above the slant surface increased. A gradual decrease of drag coefficient was observed before the flow state change though flow behavior associated with the drag change was not observed in the velocity field of PIV measurement.
Experimental and Numerical Analysis of an Axial Piston Pump: A Comparison Between Lumped Parameter and 3D CFD Approaches
Authors: Frosina Emma , Marinaro Gianluca , Senatore Adolfo 
Published: November 2019

Abstract
In this paper an axial piston pump is studied using numerical and experimental approaches. The pump, manufactured by the company Continental Hydraulic Inc., has a maximum operating pressure limit of 280 bar and a displacement of 65.9 cm3/rev; it is a variable swashplate design with nine-piston, suitable for open circuit application, medium to high pressure.
Two numerical approaches have been compared to simulate the pump units. First of all, an accurate 3D -CFD model has been built up putting emphasis on the description of the detailed features of the flow through the unit. Specific attention has been reserved to the flow losses due to cavitation. Then a fast-lumped parameter approach has been built up focusing the attention on the valve plate geometry. Using the proposed numerical approaches, it is possible to fully understand the unit operation with, obviously, different assumptions and level of result details.
Numerical models have been validated with an experimental data performed by the pump manufactured on their test ring with high agreement.
As results, the proposed analysis permit to gain a high level of understanding of the operation of the unit finding the critical aspects and giving important information to the designer in order to improve the pump performance.
By the end a new valve plate has been designed to improve the pump volumetric efficiency and to reduce the flow ripples and the reverse flow.
Investigation of Turbulent Flow Behavior in a Heated Boundary Layer
Authors: Dennis Kadeem , Siddiqui Kamran 
Published: November 2019

Abstract
The boundary layers are known to play key roles in many engineering systems. The hydrodynamic boundary layer found in these systems is often turbulent in nature and heat transfer is involved which further increases flow complexity due to the influence of buoyancy. One of the constituent layers of the turbulent boundary layer, the inner layer, has been established as home to key dynamical turbulent phenomena which can be influenced by the buoyant force. In the mixed convection flow regime, flow inertia and buoyant force are on the same order of magnitude. In this regime, buoyant thermals rising from the wall interact with the inertia-driven turbulent flow field resulting in highly complex three-dimensional flow dynamics. Past research studies conducted in this flow regime have been mostly computational in nature with little experimental work. The current knowledge on the impact of the relative contributions by the buoyant force and flow inertia on turbulent phenomena in the mixed convection flow regime is very limited.
This study reports on an investigation into the turbulent flow phenomena present in mixed convection turbulent boundary layer flow over a heated smooth horizontal flat plate. Experiments were performed in a closed loop wind tunnel where the turbulent boundary layer was heated from below. The multi-plane particle image velocimetry (PIV) technique was used to capture two-dimensional velocity fields over two planes with respect to the flow direction. Experiments were conducted over a range of Richardson numbers (Ri) between 0.0 and 2.0 to control the relative contribution of the buoyant force with respect to flow inertia. The measured velocity fields are used to describe the influence of buoyancy on the three-dimensional turbulent boundary layer flow.
Experimental Investigation of Nozzle Orientation Effects on Mixing Characteristics of Elliptic Triple Free Jets
Authors: Morris Ella M. , Aleyasin Seyed S. , Biswas Neelakash , Tachie Mark F. 
Published: November 2019

Abstract
An experimental investigation of nozzle orientation effects on turbulent characteristics of elliptic triple free jets was carried out for three nozzle configurations. The first configuration had all three nozzles oriented along the minor plane (3_Minor), the next had two nozzles oriented along the minor plane and one along the major plane (2_Minor_1_Major) and the last configuration had one nozzle oriented along the minor plane and two along the major plane (1_Minor_2_Major). The experiments were conducted using modified contoured nozzles with a sharp linear contraction for a nozzle-to-nozzle distance of 4.1, a nozzle equivalent diameter of 9 mm and a Reynolds number of 10,000. The effects of nozzle orientation on the mean velocity, turbulence intensity and Reynolds shear stress were discussed. The velocity decay, jet spread, merging point, combined point and potential core length were used to characterize the effects of nozzle orientation on the mixing performance. The results show that the 3_Minor configuration had shorter potential core length and closer merging point location which are indicative of a faster mixing in the converging region. Two-point correlation, skewness and flatness factors were used to provide insight into the effects of nozzle orientation on turbulence structure and higher order turbulence statistics.
Open-Source Computational Fluid Dynamics in Engineering Education
Authors: Nedyalkov Ivaylo 
Published: November 2019

Abstract
Computational Fluid Dynamics (CFD) is widely used in industry but is not discussed sufficiently in undergraduate engineering education. In some cases, CFD is studied only from a mathematical perspective, focusing on computational partial differential equations, and in some cases it is introduced as a black-box tool. A hybrid CFD class was developed for undergraduate and graduate students at the University of New Hampshire, which combines the two approaches. The students are exposed to the mathematics and physics behind CFD, and they also utilize OpenFOAM — an open source CFD package — to work on practical problems. Since the code is open-source, the students are able to see and modify it. Although OpenFOAM is challenging due to the minimum graphical user interface, the code-base environment forces the students to learn what the code is doing. Sample assignments and project submissions from the students are presented in the paper.
Validation of Numerical Simulation of Drop Motion on Surfaces With Micro Patterns
Authors: Onishi Junya , Shikazono Naoki 
Published: November 2019

Abstract
Numerical simulation of drop motion on surfaces with micro patterns is conducted. The results are compared with existing experimental and analytical studies to validate the reliability of the numerical simulations. In the comparison of the liquid phase morphology on a surface with straight grooves, it is confirmed that a variety of liquid shapes, including droplets, filaments with positive/negative Laplace pressure and so on are successfully reproduced by the numerical simulation. Moreover, the numerically observed transition between these morphologies in a broad range of the groove aspect ratio and the static contact angle agrees with the morphology diagram which is obtained by a semi-analytic approach based on the surface free energy minimization. Furthermore, in the comparison of the spreading behaviors of a liquid drop on a surface with square pillars, it is shown that the numerical simulations can predict the time-dependent drop deformation during the spreading process. The comparison of the length of two spreading modes shows a quantitative agreement with the experimental results.
Experimental Investigation of the Flow Inside the Rotor Passage of an Axial Ventricular Assist Device
Authors: Chen Huang , Drešar Primož , Lynch Bryan , Sharma Paarth , Williams Christopher , Katz Joseph 
Published: November 2019

Abstract
Ventricular assist devices (VAD) are designed to provide circulatory support to patients suffering from advanced-stage heart failure. While not pulsatile, the advantages of continuous axial flow VADs include a compact size and low mechanical failure rate. However, being compact, they operate at high speed, resulting in adverse effects, such as hemolysis caused by high flow shear and thrombosis formation in stagnant regions are common and threaten the successful use of the device. While state-of-the-art computational fluid dynamics (CFD) is widely used in designing these devices, detailed high-resolution experimental measurements of the flow within them are not readily available in the literature. Such experimental data is crucial for understanding the flow inside the VAD and its interaction with blood cells as well as for validating the CFD predictions. The present study investigates the flow inside a 1:1 exact replica of a VAD – ReliantHeart HeartAssist5®. This 12mm diameter device consists of an inlet guide vane (IGV), a rotor and a stator. However, unlike in the real machine, the rotor is driven by a thin shaft that penetrates through the center of the IGV. Refractive index-matching is used to facilitate optical measurements. Hence, all the blades and housing of the pump are made of transparent acrylic. The working fluid is a mixture of water, sodium iodide and glycerin, which matches the refractive index of acrylic, and the kinematic viscosity of blood. Performance tests have been carried out at speeds ranging from 7000 to 9000 RPM. Trends of the results are consistent with those of the actual machine. While scaled data for the pressure rise across the rotor at different speeds collapse, the total head rise across the entire machine does not. High-resolution 2D PIV measurements with vector spacing of 30μm have been conducted in meridional planes of the rotor passage at several blade orientations. They have been performed at 8000RPM and flowrate of 4.5L/min, consistent with physiological requirements. They show that near the rotor front end, the flow in the tip region is dominated by the tip leakage vortex (TLV), associated blockage effects, and very high turbulence level. The upstream end of this domain remains aligned with the leading edge, implying that blades persistently dissect the remnants of a previous TLVs. Interaction of the hub boundary layer with the blades also generates secondary flows. Downstream of the helical section of the rotor, the axial flow is high near the hub and low in the outer part of the passage due to leakage flow-related blockage. Hub boundary layer separation occurs upstream of the stator, generating a large circumferential vortex that occupies nearly half of the rotor span. The complexity of the flow structure and turbulence in this machine would be a challenge to model.
Research and Design of In-Arm Torsional Electromagnetic Active Suspension
Authors: Han Chengleng , Xu Lin , Abdelkareem Mohamed A. A. , Cui Enkang , Zou Junyi , Rono Kipkorir , Zhao Zhen , Yang Bo 
Published: November 2019

Abstract
This paper introduced a new type of an active suspension named as In-Arm Torsional Electromagnetic Active Suspension (ITEAS) according to its suspension characteristics. The proposed ITEAS is capable of actively controlling body attitude and adjusting the stiffness and damping of a suspension system in a larger scale. The structure of the ITEAS system is composing of a mechanical displacement adjustment device, a two-chamber vane damper connected by an electromagnetic valve, two torsion bars and necessary connection units such as trailing arms. Based on the hydraulic theory and fluid mechanics, the mathematical model of the vane damper was established and the external characteristic curve of the damper was obtained through the simulations. Regarding to the ITEAS stiffness and damping analysis, a quarter dynamic vehicle model was established and simulated by the AMESim platform. The results showed that the automobile ride based on the ITEAS system was reasonable as well as the functions of body height adjustment and suspension controllability were available. Thereafter, a small-scale prototype has been built to calibrate the unknown parameters for further research on ITEAS.
Topological Reconfigurations Based on a Concatenation of Bennett and RPRP Mechanisms
Authors: Hsu Kuan-Lun , Ting Kwun-Lon 
Published: November 2019

Abstract
This paper presents a family of over-constrained mechanisms with revolute and prismatic joints. They are constructed by concatenating a Bennett 4R and a spatial RPRP mechanism. This is a major breakthrough because an assembly of two different source-modules, for the first time, will be used in the modular construction. A Bennett 4R mechanism and a spatial RPRP mechanism are mated for the purpose of demonstration. Topological reconfigurations of synthesized mechanisms are also discussed. The results indicate that synthesized mechanisms can be topologically reconfigured with either a plane-symmetric structure or a spatial four-bar RCRC loop. These synthesized mechanisms along with their reconfigurations represent the first and unique contribution in theoretical and applied kinematics. Academically, proposed methodology can be used to synthesize several families of over-constrained mechanisms. Each family of new mechanisms is unique and has its own academic significance because they are theoretical exceptions outside Chebychev–Grübler–Kutzbach criterion. The geometrical principles that address the combination of hybrid loops can treat the topological synthesis of over-constrained mechanisms as a systematic approach instead of a random search. Industrially, such paradoxical mechanisms could also be potentially valuable. The ambiguity of their structural synthesis stops ones from being aware of these theoretical exceptions. Hence, people fail to implement these mechanisms into real-world applications. The findings of this research can help people sufficiently acquire the knowledge of how to configure such mechanisms with desired mobility. From a practical point of view, over-constrained mechanisms can transmit motions with less number of links than the general types need. This means that engineers could achieve a compact design with fewer components. These features could be an attractive advantage to real world applications.
Design of Multi-DOF Spherical Piezoelectric Motor Using Electrode Configuration Based Actuating Units
Authors: Lin Chi-Ying , Sung Yu-Ting , Huang Yu-Hsi 
Published: November 2019

Abstract
Spherical piezoelectric motors (SPMs) apply piezoelectric materials as stators to generate modal responses for rotor orientation. The SPMs have the advantages of simple structure and compact size but may suffer from the difficulty of orientation manipulation. This paper presents a novel electrode configuration based SPM design for simple multi degree-of-freedom (DOF) orientation manipulation. Four piezoelectric actuating units are adopted as stators to generate 12 orientations through the integration and switch of two vibration modes of each piezoelectric actuator, including lateral mode and longitudinal mode. The dynamic characteristics associated with the design parameters at each vibration mode are experimentally obtained to evaluate the performance of the proposed SPM design.
Wireless Power and SIMO Control Based on Magnetic Coupling Resonance Using in Delta Robot
Authors: Wang Jue , Chen Genliang , Wang Hao 
Published: November 2019

Abstract
Resonance selectivity is a new way to achieve “Single-input Multi-output” (SIMO) system via wireless electromagnetic power transmission. But it is limited to low power and open loop systems. This paper presents a new method that uses the principle of resonance selectivity of which system is close loop and the power is over 10w. By using this method, we drive three DC motors to control a delta robot which is based on flexible linkages with feedback control. In this paper, we achieve the position control of delta robot through SIMO and wireless control. This paper introduces the principle of wireless control based on magnetic coupling resonance and the details about control system, and the fabrication and analysis of delta robot based on flexible linkages. According to the results of our experiment, we demonstrate that this method can be applied to control delta robot.
A Numerical Model to Predict Dynamic Performance of Layered Gears at Starved Lubrication
Authors: Dong Qingbing , Wei Jing , Li Yan , Xu Lixin 
Published: November 2019

Abstract
Gears of modern industry are required to have a good fatigue performance to transmit power and motion through the contact interfaces. Composite layered surfaces can effectively improve the damage resistance of gears and decrease the friction coefficients. However, improper surface modification may induce intensive stress concentrations at the joint interfaces of the strengthening layers and cause unexpected damages to the flanks. Furthermore, the amount of lubricant at the inlet may probably be insufficient to establish fully flooded condition, which may result in starvation and accelerate damages to the gear sets.
In this study, a starved elastohydrodynamic lubrication (EHL) model in three-dimensional (3D) line contact for layered gears is developed. The potential energy method is employed to determine the load distribution along the action line. The loading force is assumed to be balanced by the lubrication pressure, which is derived by discretizing the dimensional Reynolds equation into a solvable matrix with the consideration of the enforced boundary conditions due to the inlet oil supply. The transient evolution of lubrication is investigated to evaluate the load-carrying capability of the lubricant film at various starvation conditions. The influence coefficients related to the displacements and stresses of the layered material system are determined with the assistance of the fast Fourier transform (FFT) algorithm, and the effects of the layer properties and the fabrication methods are evaluated. Such analysis may provide insightful information for the optimization of material systems with fabricated layers and engineering design of gears.