scholarly journals Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion)

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1900
Author(s):  
Christian Marschik ◽  
Wolfgang Roland ◽  
Marius Dörner ◽  
Sarah Schaufler ◽  
Volker Schöppner ◽  
...  
Keyword(s):  
High Performance ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Wave Dispersion ◽  
Pressure Profile ◽  
Design And Optimization ◽  
Single Screw ◽  
Modeling Approach ◽  
Single Screw Extrusion ◽  
Pressure Flows

Due to progress in the development of screw designs over recent decades, numerous high-performance screws have become commercially available in single-screw extrusion. While some of these advanced designs have been studied intensively, others have received comparatively less attention. We developed and validated a semi-numerical network-theory-based modeling approach to predicting flows of shear-thinning polymer melts in wave-dispersion screws. In the first part (Part A), we systematically reduced the complexity of the flow analysis by omitting the influence of the screw rotation on the conveying behavior of the wave zone. In this part (Part B), we extended the original theory by considering the drag flow imposed by the screw. Two- and three-dimensional melt-conveying models were combined to predict locally the conveying characteristics of the wave channels in a discretized flow network. Extensive experiments were performed on a laboratory single-screw extruder, using various barrel designs and wave-dispersion screws. The predictions of our semi-numerical modeling approach for the axial pressure profile along the wave-dispersion zone accurately reproduce the experimental data. Removing the need for time-consuming numerical simulations, this modeling approach enables fast analyses of the conveying behavior of wave-dispersion zones, thereby offering a useful tool for design and optimization studies and process troubleshooting.

scholarly journals Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part A (Pressure Flows)

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1488 ◽  
Author(s):  
Marschik ◽  
Dörner ◽  
Roland ◽  
Miethlinger ◽  
Schöppner ◽  
...  
Keyword(s):  
High Performance ◽  
Flow Analysis ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Polymer Melt ◽  
Wave Dispersion ◽  
Pressure Distributions ◽  
Extrusion Die ◽  
Wave Channel ◽  
Pressure Flows

Wave-dispersion screws have been used industrially in many types of extrusion processes, injection molding, and blow molding. These high-performance screws are constructed by replacing the metering section of a conventional screw with a melt-conveying zone consisting of two or more parallel flow channels that oscillate periodically in-depth over multiple cycles. With the barrier flight between the screw channels being selectively undercut, the molten resin is strategically forced to flow across the secondary flight, assuring repeated cross-channel mixing of the polymer melt. Despite the industrial relevance, very few scientific studies have investigated the flow in wave-dispersion sections in detail. As a result, current screw designs are often based on traditional trial-and-error procedures rather than on the principles of extrusion theory. This study, which was split into two parts, was carried out to systematically address this issue. The research reported here (Part A) was designed to reduce the complexity of the problem, exclusively analyzing the pressure-induced flows of polymer melts in wave sections. Ignoring the influence of the screw rotation on the conveying characteristics of the wave section, the results could be clearly assigned to the governing type of flow mechanism, thereby providing a better understanding of the underlying physics. Experimental studies were performed on a novel extrusion die equipped with a dual wave-channel system with alternating channel depth profiles. A seminumerical modeling approach based on network theory is proposed that locally describes the downchannel and cross-channel flows along the wave channels and accurately predicts the pressure distributions in the flow domain. The solutions of our seminumerical approach were, moreover, compared to the results of three-dimensional non-Newtonian CFD simulations. The results of this study will be extended to real screw designs in Part B, which will include the influence of the screw rotation in the flow analysis.

scholarly journals A Novel Modeling Approach for Plastics Melting within a CFD-DEM Framework

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 227
Author(s):  
Alptekin Celik ◽  
Christian Bonten ◽  
Riccardo Togni ◽  
Christoph Kloss ◽  
Christoph Goniva
Keyword(s):  
Three Dimensional ◽  
Melting Rate ◽  
Experimental Results ◽  
Single Screw ◽  
Modeling Approach ◽  
Single Screw Extrusion ◽  
Three Dimensional Modeling ◽  
Solids Transport ◽  
Joint Consideration ◽  
Liquid States

Existing three-dimensional modeling approaches to single-screw extrusion can be classified according to the process sections. The discrete element method (DEM) allows describing solids transport in the feed section. The melt flow in the melt section can be calculated by means of computational fluid dynamics (CFD). However, the current state of the art only allows a separate consideration of the respective sections. A joint examination of the process sections still remains challenging. In this study, a novel modeling approach is presented, allowing a joint consideration of solids and melt transport and, beyond that, the formation of melt. For this purpose, the phase transition from the solid to liquid states is modeled for the first time within the framework CFDEMCoupling®, combining CFD and DEM by a novel melting model implemented in this study. In addition, a melting apparatus for the validation of the novel melting model is set up and put into operation. CFD-DEM simulations are carried out in order to calculate the melting rate and are compared to experimental results. A good agreement between the simulation and experimental results is found. From the findings, it can be assumed that the CFD-DEM simulation of single-screw extruder with a joint consideration of the feed and melt section is feasible.

scholarly journals A Network-Theory-Based Comparative Study of Melt-Conveying Models in Single-Screw Extrusion: A. Isothermal Flow

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 929 ◽  
Author(s):  
Christian Marschik ◽  
Wolfgang Roland ◽  
Jürgen Miethlinger
Keyword(s):  
Comparative Study ◽  
Network Theory ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Polymer Melt ◽  
Pressure Profile ◽  
Single Screw ◽  
Single Screw Extrusion ◽  
Power Law Fluids ◽  
Flow Theories

In many extrusion processes, the metering section is the rate-controlling part of the screw. In this functional zone, the polymer melt is pressurized and readied to be pumped through the die. We have recently proposed a set of heuristic models for predicting the flow behavior of power-law fluids in two- and three-dimensional metering channels. These novel theories remove the need for numerical simulations and can be implemented easily in practice. Here we present a comparative study designed to validate these new methods against experimental data. Extensive experiments were performed on a well-instrumented laboratory single-screw extruder, using various materials, screw designs, and processing conditions. A network-theory-based simulation routine was written in MATLAB to replicate the flow in the metering zones in silico. The predictions of the three-dimensional heuristic melt-conveying model for the axial pressure profile along the screw are in excellent agreement with the experimental extrusion data. To demonstrate the usefulness of the novel melt-flow theories, we additionally compared the models to a modified Newtonian pumping model known from the literature.

Mechanism of the Transition From In-Plane Buckling to Helical Buckling for a Stiff Nanowire on an Elastomeric Substrate

2016 ◽  
Vol 83 (4) ◽  
Author(s):  
Youlong Chen ◽  
Yong Zhu ◽  
Xi Chen ◽  
Yilun Liu
Keyword(s):  
High Performance ◽  
Three Dimensional ◽  
Stretchable Electronics ◽  
Buckling Mode ◽  
Design And Optimization ◽  
Out Of Plane ◽  
Plane Direction ◽  
Plane Displacement ◽  
Helical Buckling ◽  
Selection Of

In this work, the compressive buckling of a nanowire partially bonded to an elastomeric substrate is studied via finite-element method (FEM) simulations and experiments. The buckling profile of the nanowire can be divided into three regimes, i.e., the in-plane buckling, the disordered buckling in the out-of-plane direction, and the helical buckling, depending on the constraint density between the nanowire and the substrate. The selection of the buckling mode depends on the ratio d/h, where d is the distance between adjacent constraint points and h is the helical buckling spacing of a perfectly bonded nanowire. For d/h > 0.5, buckling is in-plane with wavelength λ = 2d. For 0.27 < d/h < 0.5, buckling is disordered with irregular out-of-plane displacement. While, for d/h < 0.27, buckling is helical and the buckling spacing gradually approaches to the theoretical value of a perfectly bonded nanowire. Generally, the in-plane buckling induces smaller strain in the nanowire, but consumes the largest space. Whereas the helical mode induces moderate strain in the nanowire, but takes the smallest space. The study may shed useful insights on the design and optimization of high-performance stretchable electronics and three-dimensional complex nanostructures.

Blade Excitation in Pulse-Charged Mixed-Flow Turbocharger Turbines

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Stephan M. Senn ◽  
Martin Seiler ◽  
Ottmar Schaefer
Keyword(s):  
Three Dimensional ◽  
Numerical Approach ◽  
Forced Response ◽  
Computational Fluid Mechanics ◽  
Response Analysis ◽  
Mixed Flow ◽  
Design And Optimization ◽  
Modeling Approach ◽  
Measured Stress ◽  
Turbine Design

In this article, a fully three-dimensional computational modeling approach in the time and frequency domain is presented, which allows to accurately predicting fluid-structure interactions in pulse-charged mixed-flow turbocharger turbines. As part of the approach, a transient computational fluid mechanics analysis is performed based on the compressible inviscid Euler equations covering an entire engine cycle. The resulting harmonic orders of aerodynamic excitation are imposed in a forced response analysis of the respective eigenvector to determine effective stress amplitudes. The modeling approach is validated with experimental results based on various mixed-flow turbine designs. It is shown that the numerical results accurately predict the measured stress levels. The numerical approach can be used in the turbine design and optimization process. Aerodynamic excitation forces are the main reason for high cycle fatigue in turbocharger turbines and therefore a fundamental understanding is of key importance.

Blade Excitation in Pulse-Charged Mixed-Flow Turbocharger Turbines

2009 ◽  
Author(s):  
Stephan M. Senn ◽  
Martin Seiler ◽  
Ottmar Schaefer
Keyword(s):  
Three Dimensional ◽  
Numerical Approach ◽  
Forced Response ◽  
Computational Fluid Mechanics ◽  
Response Analysis ◽  
Mixed Flow ◽  
Design And Optimization ◽  
Modeling Approach ◽  
Measured Stress ◽  
Turbine Design

In this article, a fully three-dimensional computational modeling approach in the time and frequency domain is presented which allows to accurately predicting fluid-structure interactions (FSI) in pulse-charged mixed-flow turbocharger turbines. As part of the approach, a transient computational fluid mechanics analysis is performed based on the compressible inviscid Euler equations covering an entire engine cycle. The resulting harmonic orders of aerodynamic excitation are imposed in a forced response analysis of the respective eigenvector to determine effective stress amplitudes. The modeling approach is validated with experimental results based on various mixed-flow turbine designs. It is shown that the numerical results accurately predict the measured stress levels. The numerical approach can be used in the turbine design and optimization process. Aerodynamic excitation forces are the main reason for high cycle fatigue in turbocharger turbines and therefore, a fundamental understanding is of key importance.

High-performance ocean energy harvesting turbine design – Detailed flow analysis with blade leaning strategy

2018 ◽  
Vol 233 (3) ◽  
pp. 379-396 ◽  
Author(s):  
B Ranjith ◽  
Paresh Halder ◽  
Abdus Samad
Keyword(s):  
High Performance ◽  
Guide Vane ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Internal Flow ◽  
Principal Component ◽  
Geometrical Parameters ◽  
Impulse Turbine ◽  
Navier Stokes Equation ◽  
Low Efficiency

Oscillating water column wave energy converter is having low efficiency because of its principal component, a bidirectional turbine. An analysis of the internal flow of the turbine gives an idea of improving the performance through optimization of geometrical parameters. In this study, an impulse turbine of 0.3 m diameter with fixed guide vanes is numerically simulated by solving three-dimensional incompressible steady Reynolds averaged Navier-stokes equation with two-equation turbulence closure model. This study shows that the numerical results very well match with the experimental results. The detailed flow physics demonstrates that different types of losses occur in this type of turbine and shows that the downstream diverging path of the rotor and guide vane is responsible for low performance. In this study, the effect of guide vane lean, as well as the combined rotor and guide vane lean on the performance of the turbine, has been discussed in detail and found to increase the efficiency of the turbine.

Flow Property Measurements of Stirred-Tank Flow Across Three Reynolds Number Decades

2008 ◽  
Author(s):  
Yihong Yang ◽  
Roe-Hoan Yoon ◽  
Demetri P. Telionis ◽  
Asa Weber ◽  
Don Foreman
Keyword(s):  
High Performance ◽  
Three Dimensional ◽  
Flow Property ◽  
Vital Role ◽  
Stirred Tank ◽  
Stirred Tanks ◽  
Design And Optimization ◽  
Commercial Code ◽  
Tank Design ◽  
Design Characteristics

The flow in stirred tanks is very complicated because it passes around the rotating impeller blades, interacts with the stationary baffles or stator blades leading to high-intensity turbulence, and then goes through loops and returns to the impeller region. A penetrating understanding of the flow in stirred tanks is necessary for the tank design and optimization, because it could have a significant impact to the overall design characteristics, which will affect directly the production, the quality of the product and the maintenance costs. Despite the recent advances in computational fluid dynamics (CFD), testing still plays a vital role in the development of high-performance stirred tanks. This paper describes measurements and results obtained by traversing a five-hole probe in a 6-m3 stirred tank. The three-dimensional flow field was obtained. The separation region was also detected. The majority of the measurements were conducted in the 6-m3 tank, but unique to this investigation are measurements we have conducted with Pitot tubes in an 160-m3 geometrically-similar full-scale tank. We also have earlier results obtained by Particle Image Velocimetry (PIV) in another geometrically-similar but much smaller tank, namely a 0.1m3 tank. This provides the unique opportunity to explore how such flows scale with size and speed, extending to Reynolds numbers that approach ten million. Some numerical results were also conducted, using the commercial code FLUENT, and the results are presented together with the experimental data.

Improved 3-D reconstruction using stereo computer graphics and multiple tilt EM images

1995 ◽  
Vol 53 ◽  
pp. 630-631
Author(s):  
Lee D. Peachey ◽  
Lou Fodor ◽  
John C. Haselgrove ◽  
Stanley M. Dunn ◽  
Junqing Huang
Keyword(s):  
Computer Graphics ◽  
High Performance ◽  
Transverse Section ◽  
Three Dimensional ◽  
Stereo Pair ◽  
3D Reconstructions ◽  
Video Cameras ◽  
Biological Objects ◽  
Microscope Images ◽  
High Performance Computer

Stereo pairs of electron microscope images provide valuable visual impressions of the three-dimensional nature of specimens, including biological objects. Beyond this one seeks quantitatively accurate models and measurements of the three dimensional positions and sizes of structures in the specimen. In our laboratory, we have sought to combine high resolution video cameras with high performance computer graphics systems to improve both the ease of building 3D reconstructions and the accuracy of 3D measurements, by using multiple tilt images of the same specimen tilted over a wider range of angles than can be viewed stereoscopically. Ultimately we also wish to automate the reconstruction and measurement process, and have initiated work in that direction.Figure 1 is a stereo pair of 400 kV images from a 1 micrometer thick transverse section of frog skeletal muscle stained with the Golgi stain. This stain selectively increases the density of the transverse tubular network in these muscle cells, and it is this network that we reconstruct in this example.

Sign in / Sign up

Export Citation Format

Share Document