Air Permeability of Thick Foams: Flow Numerical Simulations

From measured data are determined permeability parameters of thick perforated foam samples, used as car seats cushions. Parameters are used for numerical flow simulations in foam samples. Model of detailed geometry gives good view about detailed flow field (pressure and velocity) in foam volume, influenced by perforations and grooves. However, simulated flow is several times different from measured one. The main flow is through perforations (99%) and flow through foam is of two orders lower. Using homogenous geometry with “averaged” permeability parameters, evaluated from measured values, the coincidence of measured and simulated flow is very good, difference of 1-5%. However, it is not possible to get any details of flow in foam volume. Using inlet layer, the flow is decreasing, first in perforations and the ratio between perforation and foam flows is more balanced.

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Manifold reduction techniques for the comparison of crank angle-resolved particle image velocimetry (PIV) data and Reynolds-averaged Navier-Stokes (RANS) simulations in a spark ignition direct injection (SIDI) engine

International Journal of Engine Research ◽

10.1177/14680874211013134 ◽

2021 ◽

pp. 146808742110131

Author(s):

Xiaohang Fang ◽

Li Shen ◽

Christopher Willman ◽

Rachel Magnanon ◽

Giuseppe Virelli ◽

...

Keyword(s):

Flow Field ◽

Particle Image ◽

Direct Injection ◽

Linear Manifold ◽

Main Flow ◽

Navier Stokes ◽

Reduction Techniques ◽

Image Velocimetry ◽

Manifold Reduction ◽

Relevance Index

In this article, different manifold reduction techniques are implemented for the post-processing of Particle Image Velocimetry (PIV) images from a Spark Ignition Direct Injection (SIDI) engine. The methods are proposed to help make a more objective comparison between Reynolds-averaged Navier-Stokes (RANS) simulations and PIV experiments when Cycle-to-Cycle Variations (CCV) are present in the flow field. The two different methods used here are based on Singular Value Decomposition (SVD) principles where Proper Orthogonal Decomposition (POD) and Kernel Principal Component Analysis (KPCA) are used for representing linear and non-linear manifold reduction techniques. To the authors’ best knowledge, this is the first time a non-linear manifold reduction technique, such as KPCA, has ever been used in the study of in-cylinder flow fields. Both qualitative and quantitative studies are given to show the capability of each method in validating the simulation and incorporating CCV for each engine cycle. Traditional Relevance Index (RI) and two other previously developed novel indexes: the Weighted Relevance Index (WRI) and the Weighted Magnitude Index (WMI), are used for the quantitative study. The results indicate that both POD and KPCA show improvements in capturing the main flow field features compared to ensemble-averaged PIV experimental data and single cycle experimental flow fields while capturing CCV. Both methods present similar quantitative accuracy when using the three indexes. However, challenges were highlighted in the POD method for the selection of the number of POD modes needed for a representative reconstruction. When the flow field region presents a Gaussian distribution, the KPCA method is seen to provide a more objective numerical process as the reconstructed flow field will see convergence with an increasing number of modes due to its usage of Gaussian properties. No additional criterion is needed to determine how to reconstruct the main flow field feature. Using KPCA can, therefore, reduce the amount of analysis needed in the process of extracting the main flow field while incorporating CCV.

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Influence of Seal Cavity Leakage Flow on Compressor Performance Investigated with a Circumferentially Averaged Method

Applied Sciences ◽

10.3390/app11020780 ◽

2021 ◽

Vol 11 (2) ◽

pp. 780

Author(s):

Dong Liang ◽

Xingmin Gui ◽

Donghai Jin

Keyword(s):

Flow Field ◽

Pressure Ratio ◽

Interaction Mechanism ◽

Main Flow ◽

Leakage Flow ◽

Destructive Effect ◽

Through Flow ◽

Compressor Performance ◽

Overall Performance ◽

Flow Blockage

In order to investigate the effect of seal cavity leakage flow on a compressor’s performance and the interaction mechanism between the leakage flow and the main flow, a one-stage compressor with a cavity under the shrouded stator was numerically simulated using an inhouse circumferentially averaged through flow program. The leakage flow from the shrouded stator cavity was calculated simultaneously with main flow in an integrated manner. The results indicate that the seal cavity leakage flow has a significant impact on the overall performance of the compressor. For a leakage of 0.2% of incoming flow, the decrease in the total pressure ratio was 2% and the reduction of efficiency was 1.9 points. Spanwise distribution of the flow field variables of the shrouded stator shows that the leakage flow leads to an increased flow blockage near the hub, resulting in drop of stator performance, as well as a certain destructive effect on the flow field of the main passage.

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Prediction of flow through swirl generator and validation by measured data

Journal of Physics Conference Series ◽

10.1088/1742-6596/318/2/022026 ◽

2011 ◽

Vol 318 (2) ◽

pp. 022026 ◽

Cited By ~ 2

Author(s):

Jiří Vondál ◽

Jiří Hájek

Keyword(s):

Measured Data ◽

Swirl Generator ◽

Flow Through

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Research on the Pollution Diffusion Regularity near Sewage Outlet Areas in Yuncheng Reach of the Fen River

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.383-390.2430 ◽

2011 ◽

Vol 383-390 ◽

pp. 2430-2436

Author(s):

Jian Hua Hou ◽

Min Quan Feng ◽

Xiao Peng Xing ◽

Zhen Hua Hou

Keyword(s):

Water Quality ◽

Flow Field ◽

Water Depth ◽

Concentration Gradient ◽

River Flow ◽

Measured Data ◽

Quality Model

The purpose of this paper is to find the pollution diffusion regularity near sewage outlet area of Yuncheng reach of the Fen River. A 2-D water hydrodynamic and quality model was used to simulate flow field, the water quality and contamination dispersion. The parameters of the model were calibrated with measured data of the water depth, flow and water quality in Yuncheng reach of the Fen River. According to the simulated result, the total area of pollution belt with 19 sewage outlets is 8.89km2 in normal year. And 3.89% of the reach has a worse water quality than V class in standard. The percentage of V and Ⅳ Class of water is 69.17% and 26.94%.In dry year, the total area of pollution belt with 19 sewage outlets is 8.89km2.The percentage of inferior V, V and Ⅳ Class of water is 27.80%, 69.46% and 2.74%. It was shown by the simulated results that the concentration gradient decreases with increasing distance to the outlets and the dilution and dispersion of pollutants was enhanced by a greater river flow.

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Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1403460 ◽

2000 ◽

Vol 124 (1) ◽

pp. 140-146 ◽

Cited By ~ 22

Author(s):

V. Schramm ◽

K. Willenborg ◽

S. Kim ◽

S. Wittig

Keyword(s):

Flow Field ◽

Three Dimensional ◽

Theoretical Work ◽

Labyrinth Seal ◽

Honeycomb Structure ◽

Experimental Investigations ◽

Labyrinth Seals ◽

Numerical Predictions ◽

Flow Through ◽

Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

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Pitfalls for Accurate Steady-State Port Flow Simulations

Volume 11: Transportation Systems ◽

10.1115/imece2012-87534 ◽

2012 ◽

Cited By ~ 1

Author(s):

Xiaofeng Yang ◽

Zhaohui Chen ◽

Tang-Wei Kuo

Keyword(s):

Steady State ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Measured Data ◽

Steady State Flow ◽

Bench Tests ◽

Flow Simulations ◽

Mesh Topology ◽

State Flow

Steady-state port flow simulations were carried out with a commercial three dimensional (3D) Computational Fluid Dynamics (CFD) code using Cartesian mesh with cut cells to study the prediction accuracy. The accuracy is assessed by comparing predicted and measured mass-flow rate and swirl and tumble torques at various valve lifts using different boundary condition setup and mesh topology relative to port orientation. The measured data is taken from standard steady-state flow bench tests of a production intake port. The predicted mass-flow rates agree to within 1% with the measured data between the intermediate and high valve lifts. At low valve lifts, slight over prediction in mass-flow rate can be observed. The predicted swirl and tumble torques are within 25% of the flow bench measurements. Several meshing parameters were examined in this study. These include: inlet plenum shape and outlet plenum/extension size, embedded sphere with varying minimum mesh size, finer meshes on port and valve surface, orientation of valve and port centerline relative to the mesh lines. For all model orientations examined, only the mesh topology with the valve axis aligned closely with the mesh lines can capture the mass-flow rate drop for very high valve lifts due to flow separation. This study further demonstrated that it is possible to perform 3D CFD flow analyses to adequately simulate steady-state flow bench tests.

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New Approach for Determining Tortuosity in Fibrous Porous Media

Journal of Engineered Fibers and Fabrics ◽

10.1177/155892501000500302 ◽

2010 ◽

Vol 5 (3) ◽

pp. 155892501000500 ◽

Cited By ~ 10

Author(s):

Rahul Vallabh ◽

Pamela Banks-Lee ◽

Abdel-Fattah Seyam

Keyword(s):

Porous Medium ◽

Porous Media ◽

Fiber Diameter ◽

Empirical Relationship ◽

Air Permeability ◽

New Approach ◽

Upper Limits ◽

Fibrous Porous Media ◽

Flow Through

A method to determine tortuosity in a fibrous porous medium is proposed. A new approach for sample preparation and testing has been followed to establish a relationship between air permeability and fiberweb thickness which formed the basis for the determination of tortuosity in fibrous porous media. An empirical relationship between tortuosity and fiberweb structural properties including porosity, fiber diameter and fiberweb thickness has been proposed unlike the models in the literature which have expressed tortuosity as a function of porosity only. Transverse air flow through a fibrous porous media increasingly becomes less tortuous with increasing porosity, with the value of tortuosity approaching 1 at upper limits of porosity. Tortuosity also decreased with increase in fiber diameter whereas increase in fiberweb thickness resulted in the increase in tortuosity within the range of fiberweb thickness tested.

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Effect of punching on physical and mechanical properties of leathers: Focus on car seat covers

Journal of Engineered Fibers and Fabrics ◽

10.1177/1558925019890569 ◽

2019 ◽

Vol 14 ◽

pp. 155892501989056

Author(s):

Eui Kyung Roh

Keyword(s):

Mechanical Properties ◽

Apparent Density ◽

Coefficient Of Friction ◽

Dimensional Stability ◽

Physical And Mechanical Properties ◽

Air Permeability ◽

Car Seats ◽

Car Seat

As a lot of time is spent in the car, the comfort of not only the car seat but also the car seat cover itself has become of increasing importance. With increasing use of ventilated seats, the control of the physical and mechanical properties of leather in response to punching has become of prime importance in the design of car seats. This study evaluated the changes in the physical and mechanical properties of leather due to punching and proposes optimum punching intervals for car seats. Sixteen types of leather, punched at three spatial intervals (2, 3, and 5 mm), were evaluated in terms of their apparent density, softness, coefficient of friction, warm-cool feeling, and mechanical properties. Leather punching affected its physical and mechanical properties. However, there were differences in punching intervals that significantly affected each property, including the mechanical properties. Depending on the performance required when developing a product, a suitable punching interval must be selected. Therefore, punching at 5 mm intervals is preferred for obtaining physical and mechanical properties similar to those of untreated leathers, and punching at 3 mm intervals is recommended for achieving more softness. On the contrary, punching at 2 mm intervals increases air permeability but decreases dimensional stability.

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