Feedforward control to suppress the leading edge bulge in photopolymerization-based additive manufacturing

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Andrey Kozhevnikov ◽  
Rudie P.J. Kunnen ◽  
Gregor E. van Baars ◽  
Herman J.H. Clercx
Keyword(s):  
Feedforward Control ◽  
Leading Edge ◽  
Capillary Length ◽  
Length Scales ◽  
Content Type ◽  
Flow Recirculation ◽  
Part Geometry ◽  
Control Scheme ◽  
Computational Fluid Dynamics Cfd ◽  
Practical Implications

Purpose This study aims to examine the feasibility of feedforward actuation of the recoater blade position to alleviate the resin surface non-uniformity while moving over deep-to-shallow transitions of submerged (already cured) geometric features. Design/methodology/approach A two-dimensional computational fluid dynamics (CFD) model has been used to determine optimized blade actuation protocols to minimize the resin surface non-uniformity. An experimental setup has been designed to validate the feasibility of the proposed protocol in practice. Findings A developed protocol for the blade height actuation is applied to a rectangular stair-like configuration of the underlying part geometry. The evaluation of the actuation protocol revealed the importance of two physical length scales, the capillary length and the size of the flow recirculation cell below in the liquid resin layer below the blade. They determine, together with the length scales defining the topography (horizontal extent and depth), the optimal blade trajectory. This protocol has also shown its efficiency for application to more complicated shapes (and, potentially, for any arbitrary geometry). Practical implications This study shows that incorporation of a feedforward control scheme in the recoating system might significantly reduce (by up to 80%) the surface unevenness. Moreover, this improvement of performances does not require major modifications of the existing architecture. Originality/value The results presented in this work demonstrate the benefits of the integration of the feedforward control to minimize the leading edge bulges over underlying part geometries in stereolithography.

Numerical evaluation of separation efficiency in the diverging T-junction for slug flow

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Faheem Ejaz ◽  
William Pao ◽  
Hafiz Muhammad Ali
Keyword(s):  
Slug Flow ◽  
Design Methodology ◽  
Separation Efficiency ◽  
Fluid Model ◽  
Diameter Ratio ◽  
Maintenance Costs ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Practical Implications ◽  
High Separation

Purpose Offshore industries encounter severe production downtime due to high liquid carryovers in the T-junction. The diameter ratio and flow regime can significantly affect the excess liquid carryovers. Unfortunately, regular and reduce T-junctions have low separation efficiencies. Ansys as a commercial computational fluid dynamics (CFD) software was used to model and numerically inspect a novel diverging T-junction design. The purpose of diverging T-junction is to merge the specific characteristics of regular and reduced T-junctions, ultimately increasing separation efficiency. The purpose of this study is to numerically compute the separation efficiency for five distinct diverging T-junctions for eight different velocity ratios. The results were compared to regular and converging T-junctions. Design/methodology/approach Air-water slug flow was simulated with the help of the volume of the fluid model, coupled with the K-epsilon turbulence model to track liquid-gas interfaces. Findings The results of this study indicated that T-junctions with upstream and downstream diameter ratio combinations of 0.8–1 and 0.5–1 achieved separation efficiency of 96% and 94.5%, respectively. These two diverging T-junctions had significantly higher separation efficiencies when compared to regular and converging T-junctions. Results also revealed that over-reduction of upstream and downstream diameter ratios below 0.5 and 1, respectively, lead to declination in separation efficiency. Research limitations/implications The present study is constrained for air and water as working fluids. Nevertheless, the results apply to other applications as well. Practical implications The proposed T-junction is intended to reduce excessive liquid carryovers and frequent plant shutdowns. Thus, lowering operational costs and enhancing separation efficiency. Social implications Higher separation efficiency achieved by using diverging T-junction enabled reduced production downtimes and resulted in lower maintenance costs. Originality/value A novel T-junction design was proposed in this study with a separation efficiency of higher than 90%. High separation efficiency eliminates loss of time during shutdowns and lowers maintenance costs. Furthermore, limitations of this study were also addressed as the lower upstream and downstream diameter ratio does not always enhance separation efficiency.

The simulation of single wraparound fin on a semi-cylindrical missile body

2020 ◽  
Vol 92 (3) ◽  
pp. 418-427 ◽  
Author(s):  
Nayhel Sharma ◽  
Rakesh Kumar
Keyword(s):  
Research Study ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Future Research ◽  
Aerodynamic Coefficients ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Predicted Values ◽  
Characteristic Trend ◽  
Practical Implications

Purpose The purpose of this paper is to establish a freestream computational fluid dynamics (CFD) model of a three-dimensional non-spinning semi-cylindrical missile model with a single wrap around fin in Mach 2.70-3.00M range and 0° angle of attack, and ultimately establishing itself for future research study. Design/methodology/approach In this study, the behaviour of flow around the fin was investigated using a κ-ϵ turbulence model of second-order of discretization. This was done using a highly structured mesh. Additionally, an inviscid CFD simulation involving the same boundary conditions have also been carried out for comparison. Findings The obtained values of aerodynamic coefficients and pressure contours visualizations are compared against their experimental and computational counterparts. A typical missile aerodynamic characteristic trend can be seen in the current CFD. Practical implications The predicted values of the aerodynamic coefficients of this single fin model have also been compared to those of the full missile body comprising of four fins from the previous research studies, and a similar aerodynamic trend can be seen. Originality/value This study explores the possibility of the use of turbulence modelling in a single fin model of a missile and provides a basic computational model for further understanding the flow behaviour near the fin.

RBF-based mesh morphing approach to perform icing simulations in the aviation sector

2019 ◽  
Vol 91 (4) ◽  
pp. 620-633 ◽  
Author(s):  
Corrado Groth ◽  
Emiliano Costa ◽  
Marco Evangelos Biancolini
Keyword(s):  
High Performance ◽  
Three Dimensional ◽  
Ansys Fluent ◽  
Content Type ◽  
Mesh Morphing ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses ◽  
2D And 3D ◽  
First Time ◽  
Practical Implications

Purpose Numerical simulation of icing has become a standard. Once the iced shape is known, however, the analyst needs to update the computational fluid dynamics (CFD) grid. This paper aims to propose a method to update the numerical mesh with ice profiles. Design/methodology/approach The present paper concerns a novel and fast radial basis functions (RBF) mesh morphing technique to efficiently and accurately perform ice accretion simulations on industrial models in the aviation sector. This method can be linked to CFD analyses to dynamically reproduce the ice growth. Findings To verify the consistency of the proposed approach, one of the most challenging ice profile selected in the LEWICE manual was replicated and simulated through CFD. To showcase the effectiveness of this technique, predefined ice profiles were automatically applied on two-dimensional (2D) and three-dimensional (3D) cases using both commercial and open-source CFD solvers. Practical implications If ice accreted shapes are available, the meshless characteristic of the proposed approach enables its coupling with the CFD solvers currently supported by the RBF4AERO platform including OpenFOAM, SU2 and ANSYS Fluent. The advantages provided by the use of RBF are the high performance and reliability, due to the fast application of mesh smoothing and the accuracy in controlling surface mesh nodes. Originality/value As far as authors’ knowledge is concerned, this is the first time in scientific literature that RBF are proposed to handle icing simulations. Due to the meshless characteristic of the RBF mesh morphing, the proposed approach is cross solver and can be used for both 2D and 3D geometries.

Numerical and experimental analysis of rotating wheel in contact with the ground

2018 ◽  
Vol 28 (5) ◽  
pp. 1203-1217 ◽  
Author(s):  
Michal Kulak ◽  
Maciej Karczewski ◽  
Pawel Lesniewicz ◽  
Krzysztof Olasek ◽  
Bas Hoogterp ◽  
...  
Keyword(s):  
Aerodynamic Drag ◽  
Cfd Simulations ◽  
Content Type ◽  
Car Body ◽  
Aerodynamic Properties ◽  
University Of Technology ◽  
Ansys Cfx ◽  
Key Factor ◽  
Computational Fluid Dynamics Cfd ◽  
Practical Implications

Purpose This paper aims to provide the results of investigations concerning an influence of the tyre with longitudinal grooves on the car body aerodynamics. It is considered as an important aspect affecting the vehicle aerodynamic drag. Design/methodology/approach To investigate a contribution of grooved tyres to the overall vehicle drag, three wind tunnel experimental campaigns were performed (two by Peugeot Société Anonyme Peugeot Citroen, one at the Lodz University of Technology). In parallel, computational fluid dynamics (CFD) simulations were conducted with the ANSYS CFX software to enable formulation of wider conclusions. Findings The research shows that optimised tread patterns can be derived on a single tyre via a CFD study in combination with a controlled experiment to deliver designs actively lowering the overall vehicle aerodynamic drag. Practical implications A reduction in the aerodynamic drag is one of ways to decrease vehicle fuel consumption. Alternatively, it can be translated into an increase in the maximum travel velocity and the maximum distance driven (key factor in electric vehicles), as well as in a reduction of CO2 emissions. Finally, it can improve the vehicle driving and steering stability. Originality/value The tyre tread pattern analysis on isolated wheels provides an opportunity to cut costs of R&D and could be a step towards isolating aerodynamic properties of tyres, irrespective of the car body on which they are applied.

Vortex force of an impulsively started plate at high angle of attack

2017 ◽  
Vol 27 (11) ◽  
pp. 2402-2414
Author(s):  
Xiang Fu ◽  
Gaohua Li ◽  
Fuxin Wang
Keyword(s):  
Aerodynamic Force ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Aerodynamic Forces ◽  
Total Drag ◽  
Content Type ◽  
Vortical Structures ◽  
Edge Vortex ◽  
The Individual ◽  
Practical Implications

Purpose A quantitative study that can identify the primary aerodynamic forces and relate them to individual vortical structures is lacking. The paper aims to clarify the quantitative relationships between the aerodynamic forces and vortical structures. Design/methodology/approach The various contributions to the aerodynamic forces on the two-dimensional impulsively started plate are investigated from the perspective of the vorticity moment theorem. The angles of attacks are set to 45°, 58.5° and 72°, while the Reynolds number is 10,000 based on the chord length. Compared with the traditional pressure force analysis, this theorem not only tells us the total aerodynamic force during the motion, but also enables us to quantify the forces contributed from the fluid elements with non-zero vorticity. Findings It is found that the time-dependent force behaviors are dominated by the formations and evolutions of these vortical structures. The analysis of the time-averaged forces demonstrates that the lift contributed from the leading edge vortex (LEV) is nearly four times larger than the total lift and the drag contributed from the starting vortex (SV) is almost equal to the total drag when the angle of attack (AoA) increases to 72°, which means the LEV is “lift structure” whereas the SV is “drag structure”. Practical implications The present method provides a better perspective for flow control and drag reduction by relating the forces directly to the individual vorticity structures. Originality/value In this paper, the Vorticity Moment Theory is first used to study the quantitative relationships between the aerodynamic forces and the vortices.

Blade stacking and clocking effects in two-stage high-pressure axial turbine

2019 ◽  
Vol 91 (8) ◽  
pp. 1133-1146
Author(s):  
Kaddour Touil ◽  
Adel Ghenaiet
Keyword(s):  
High Pressure ◽  
Leading Edge ◽  
Maximum Efficiency ◽  
Two Stage ◽  
Axial Turbine ◽  
Content Type ◽  
Second Stage ◽  
Blade Row ◽  
Practical Implications ◽  
Isentropic Efficiency

Purpose The purpose of this paper is to characterize the blade–row interaction and investigate the effects of axial spacing and clocking in a two-stage high-pressure axial turbine. Design/methodology/approach Flow simulations were performed by means of Ansys-CFX code. First, the effects of blade–row stacking on the expansion performance were investigated by considering the stage interface. Second the axial spacing and the clocking positions between successive blade–rows were varied, the flow field considering the frozen interface was solved, and the flow interaction was assessed. Findings The axial spacing seems affecting the turbine isentropic efficiency in both design and off-design operating conditions. Besides, there are differences in aerodynamic loading and isentropic efficiency between the maximum efficiency clocking positions where the wakes of the first-stage vanes impinge around the leading edge of the second-stage vanes, compared to the clocking position of minimum efficiency where the ingested wakes pass halfway of the second-stage vanes. Research limitations/implications Research implications include understanding the effects of stacking, axial spacing and clocking in axial turbine stages, improving the expansion properties by determining the adequate spacing and locating the leading edge of vanes and blades in both first and second stages with respect to the maximum efficiency clocking positions. Practical implications Practical implications include improving the aerodynamic design of high-pressure axial turbine stages. Originality/value The expansion process in a two-stage high-pressure axial turbine and the effects of blade–row spacing and clocking are elucidated thoroughly.

Aspirational guidance for wiser futures: toward open-sourced ascension from ego-centric to eco-centric human communities

foresight ◽  
2015 ◽  
Vol 17 (1) ◽  
pp. 1-34 ◽  
Author(s):  
Oliver Markley
Keyword(s):  
Leading Edge ◽  
Type Ii ◽  
Content Type ◽  
Institutional Processes ◽  
The Public ◽  
Epochal Change ◽  
High Degree ◽  
Technical Professionals ◽  
Practical Implications ◽  
High Credibility

Purpose – This paper aims to explore and demonstrate how the meme of aspiration can help guide human cultures through an epochal transformation triggered by a global megacrisis and leading to sustainable maturation of human cultures. Design/methodology/approach – Aspirational futures process, intuition-based visioning and “Type II” thinking that has high credibility for knowledgeable experts but low credibility to most others. Findings – Megacrisis is a Type II wild card needing anticipatory mitigation via strategies such as are suggested. While descent paths may be a suitable meme for technical professionals, ascent paths to higher levels of civilizational maturity are a better guiding image for the public. Aspirational methods whose core involves intuition-based creativity, wisdom and co-creative emergence are a vital complement to rational/analytic futures methods, especially in times of epochal change and uncertainty when a new “regime” of guiding world views, institutional processes and innovative technologies may emerge. Research limitations/implications – Results represent a high degree of uncertainly as well as “fringe” thinking needing to be more widely considered. Practical implications – Strategic suggestions based on Type II thinking are a unique category for “leading edge” funding and application. Originality/value – The Type II perspective offered here is unique and offers a promising approach for transformative megacrisis mitigation.

Optimal pitching schedules for a cycloidal rotor in hovering

2016 ◽  
Vol 88 (5) ◽  
pp. 623-635
Author(s):  
Andrea Andrisani ◽  
Diego Angeli ◽  
Antonio Dumas
Keyword(s):  
Power Efficiency ◽  
Geometrical Parameters ◽  
Mean Power ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean ◽  
Sinusoidal Functions ◽  
Definition Of ◽  
Propulsion Concept ◽  
Practical Implications

Purpose The purpose of this paper is to define an optimal pitching profile for the blades of a cycloidal rotor which minimizes the mean power consumption for a given mean thrust of the rotor. Design/methodology/approach A simple analytical model of the kinematics and aerodynamics of a cycloidal rotor is defined first to obtain expressions for thrust and power depending on the pitching profile and geometrical parameters of the rotor. Then, Lagrange optimization is applied to obtain the optimal pitching schedule under hovering conditions. Finally, results of the theoretical analysis are compared with those of a two-dimensional computational fluid dynamics (CFD) model. Findings Results of the optimization suggest that the optimal profile is a combination of sinusoidal functions. It is shown that the adoption of the optimal pitching schedule could improve the power efficiency of the rotor by approximately 25 per cent. Practical implications The possibility to increase the efficiency of a cycloidal rotor by acting on its pitching schedule could be a significant factor of success for this alternative propulsion concept. Originality/value The present work represents the first attempt at a definition of an optimal pitching profile for a cycloidal rotor. Moreover, although being carried out on the basis of simplified analytical considerations, the present investigation sets a methodological framework which could be successfully applied to the design of similar kinds of systems.

Alpha societies and requisite variety: a projected framework for governance, education, and work in the 21st century

2015 ◽  
Vol 23 (1) ◽  
pp. 16-24
Author(s):  
George H. Kubik
Keyword(s):  
Leading Edge ◽  
First Century ◽  
Content Type ◽  
Requisite Variety ◽  
Individual Enterprise ◽  
The Future ◽  
World Class ◽  
And Performance ◽  
Future Of Education ◽  
Practical Implications

Purpose – The purpose of this article is to define a framework for projecting future leading-edge alpha societies based on the principle of requisite variety. Alpha societies are advanced as a platform for creating future forms of work and workforce preparation premised on continuous creativity, invention, design and innovation. Design/methodology/approach – The principle of requisite variety is presented as the basis for a structured schema that incorporates trends and developments in anticipatory behaviors, systems thinking, creativity, design and innovation to produce a strategy for continuous leading-edge learning and performance. Findings – Growing global hypercompetition requires real-time ability to create and deliver world-class ideas and value-adding products and services in the shortest possible timeframes. This challenge requires societies, enterprises and individuals that are capable of continuously expanding and expressing their internal variety and complexity while rapidly decreasing the gaps between learning and doing. Research limitations/implications – The principle of requisite variety has been well known to cybernetics and systems communities since 1956. However, literature linking the principle of requisite variety to the future of learning and work is not well developed. Practical implications – This article establishes requisite variety generation as a valuable resource for twenty-first century societies and economies engaged in producing leading-edge outcomes. Social implications – The requisite variety framework developed in this article is intended to enhance the ability of leading-edge societies to continuously leapfrog existing educational, social and economic trajectories. Originality/value – The author defines the future of education and work in terms of enhancing individual, enterprise and societal abilities to absorb, generate and exploit variety, complexity and ambiguity.

Assessment of modelling strategies for film cooling

2017 ◽  
Vol 27 (5) ◽  
pp. 1118-1127 ◽  
Author(s):  
Lorenzo Mazzei ◽  
Antonio Andreini ◽  
Bruno Facchini
Keyword(s):  
Film Cooling ◽  
Computational Cost ◽  
Flat Plates ◽  
Cfd Simulations ◽  
Significant Saving ◽  
Content Type ◽  
Modelling Strategies ◽  
Computational Fluid Dynamics Cfd ◽  
Innovative Techniques ◽  
Practical Implications

Purpose Effusion cooling represents one the most innovative techniques for the thermal management of aero-engine combustors liners. The huge amount of micro-perforations implies a significant computational cost if cooling holes are included in computational fluid dynamics (CFD) simulations; therefore, many efforts are reported in literature to develop lower-order approaches aiming at limiting the number of mesh elements. This paper aims to report a numerical investigation for validating two approaches for modelling film cooling, distinguished according to the way coolant is injected (i.e. through either point or distributed mass sources). Design/methodology/approach The approaches are validated against experimental data in terms of adiabatic effectiveness and heat transfer coefficient distributions obtained for effusion cooled flat plates. Additional reynolds-averaged naver stokes (RANS) simulations were performed meshing also the perforation, so as to distinguish the contribution of injection modelling with respect to intrinsic limitations of turbulence model modelling. Findings Despite the simplified strategies for coolant injection, this work clearly shows the feasibility of obtaining a sufficiently accurate reproduction of coolant protection in conjunction with a significant saving in terms of computational cost. Practical/implications The proposed methodologies allow to take into account the presence of film cooling in simulations of devices characterized by a huge number of holes. Originality/value This activity represents the first thorough and quantitative comparison between two approaches for film cooling modelling, highlighting the advantages involved in their application.

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