scholarly journals Towards simulation of force and velocity fluctuations due to turbulence in the relay nozzle jet of an air jet loom

2020 ◽  
pp. 004051752096828
Author(s):  
Lucas Delcour ◽  
Lieva Van Langenhove ◽  
Joris Degroote
Keyword(s):  
Quality Criteria ◽  
Velocity Fluctuations ◽  
Force Fluctuations ◽  
Free Jet ◽  
Eddy Simulation ◽  
Air Jet ◽  
Flow Features ◽  
Set Up ◽  
Les Model ◽  
Air Jet Loom

This research was aimed at obtaining a first estimation of the effect of turbulent vortices present in the relay nozzle jets of an air jet loom on the weft. To this end a large eddy simulation (LES) model was set up and validated capable of simulating a highly underexpanded jet up to a point sufficiently far from the nozzle exit such that flow features at the weft location could be analyzed. The quality of the LES was evaluated based on several quality criteria as well as by comparing the results with experiments and data from the literature. The results show that for a free jet substantial velocity fluctuations are present at a representative yarn location. By inserting a rigid cylinder at this location, the corresponding force fluctuations on a smooth yarn were also obtained. The research shows that the unsteadiness in the jet is quite substantial, as are the corresponding force fluctuations. These fluctuations could have a profound impact on the yarn motion and should at least be considered when using numerical tools to evaluate the forces on or the motion of a yarn acted on by a relay nozzle jet.

Larger-Eddy Simulation of Velocity Fluctuation in a Mixing T-Junction

2012 ◽  
Vol 152-154 ◽  
pp. 1313-1318
Author(s):  
Tao Lu ◽  
Su Mei Liu ◽  
Ping Wang ◽  
Wei Yyu Zhu
Keyword(s):  
Experimental Data ◽  
Velocity Fluctuation ◽  
Flow Model ◽  
Numerical Results ◽  
Mean Square ◽  
Main Duct ◽  
Velocity Fluctuations ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

Velocity fluctuations in a mixing T-junction were simulated in FLUENT using large-eddy simulation (LES) turbulent flow model with sub-grid scale (SGS) Smagorinsky–Lilly (SL) model. The normalized mean and root mean square velocities are used to describe the time-averaged velocities and the velocities fluctuation intensities. Comparison of the numerical results with experimental data shows that the LES model is valid for predicting the flow of mixing in a T-junction junction. The numerical results reveal the velocity distributions and fluctuations are basically symmetrical and the fluctuation at the upstream of the downstream of the main duct is stronger than that at the downstream of the downstream of the main duct.

Flow Patterns and Temperature Distribution in an Underground Metro Station

2018 ◽  
Author(s):  
Alaa Hasan ◽  
Tarek ElGammal ◽  
Ryoichi S. Amano ◽  
Essam E. Khalil
Keyword(s):  
Thermal Comfort ◽  
Thermal Conditions ◽  
Large Space ◽  
Metro Station ◽  
Air Conditioning System ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Les Model

Accurate control of thermal conditions in large space buildings like an underground metro station is a significant issue because passengers’ thermal comfort must be maintained at a satisfactory level. The large eddy simulation (LES) model was adopted while using the computational fluid dynamics (CFD) software “STAR CCM+” to set up a CFD station model to predict static air temperature, velocity, relative humidity and predicted mean vote (PMV), which indicates the passengers’ thermal comfort. The increase in the number of passengers using the model station is taken into consideration. The studied cases covered all the possible modes of the station box, these modes are (1) the station box is empty of trains, (2) the presence of one train inside the station box, (3) the presence of two trains inside the station box. The objective is to bring the passengers’ thermal comfort in all modes to the acceptable level. The operation of under platform exhaust (UPE) system is considered in case of train presence inside the station box. The use of UPE is more energy efficient than depending entirely on the air conditioning system to maintain the thermal conditions comfortable.

scholarly journals Simulation of Motion of Long Flexible Fibers with Different Linear Densities in Jet Flow

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Peifeng Lin ◽  
Wenqian Xu ◽  
Yuzhen Jin ◽  
Zefei Zhu
Keyword(s):  
Linear Density ◽  
High Efficiency ◽  
Transient Flow ◽  
Great Influence ◽  
Simulation Method ◽  
Jet Flow ◽  
Eddy Simulation ◽  
Air Jet ◽  
Flexible Fibers ◽  
Air Jet Loom

Air-jet loom is a textile machine designed to drive the long fiber using a combination flow of high-pressure air from a main nozzle and a series of assistant nozzles. To make the suggestion of how to make the fiber fly with high efficiency and stability in the jet flow, in which vortices also have great influence on fiber movement, the large eddy simulation method was employed to obtain the transient flow field of turbulent jet, and a bead-rod chain fiber model was used to predict long flexible fiber motion. The fluctuation and velocity of fibers with different linear densities in jet flow were studied numerically. The results show that the fluctuation amplitude of a fiber with a linear density of 0.5 × 10−5 kg·m−1 is two times larger than that of a fiber with a linear density of 2.0 × 10−5 kg·m−1. The distance of the first assistant nozzle from the main nozzle should be less than 120 mm to avoid collision between the fiber and the loom. The efficient length of the main nozzle to carry the fiber flying steadily forward is about 100–110 mm. For fibers with a linear density of 0.5 × 10−5 kg·m−1, it is suggested that the distance of the first assistant nozzle from the main nozzle is about 110 mm. With the increase of fiber linear density, the distance could be appropriately increased to 140 mm. The simulation results provide an optimization option for the air-jet loom to improve the energy efficiency by reasonably arranging the first assistant nozzle.

Nonlinear Dynamic Analysis of Back-Rest System of Type WG-2000 Air-Jet Loom

2010 ◽  
Vol 43 ◽  
pp. 722-725
Author(s):  
Lang Sun ◽  
Zhi Hua Feng ◽  
Si Yong Wang
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Rest System ◽  
Rotating Speed ◽  
Air Jet ◽  
Weaving Technology ◽  
Set Up ◽  
Air Jet Loom ◽  
Back Rest

The dynamic model of the back-rest system of type WG-2000 air-jet loom is set up and the relevant nonlinear vibration analysis is investigated when principal parametric resonance is taken into consideration. Results show that the system will be unstable when the corresponding frequency of the rotating-speed meets Ω≈2ω0/n, it may have unstable region. The higher speed is, the wider the region is. The nonlinear dynamic analysis of the back-rest system can be benefit for engineering design and improvement of weaving technology.

Numerical Study of the Mean and Filtered Characteristics of Turbulent Jets Impinging on Convex and Flat Surfaces Using LES

2012 ◽  
Author(s):  
Adra Benhacine ◽  
Zoubir Nemouchi ◽  
Lyes Khezzar ◽  
Nabil Kharoua
Keyword(s):  
Convex Surface ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulent Jets ◽  
Scale Model ◽  
Wall Jet ◽  
Potential Core ◽  
Flat Surfaces ◽  
Free Jet ◽  
Eddy Simulation

A numerical study of a turbulent plane jet impinging on a convex surface and on a flat surface is presented, using the large eddy simulation approach and the Smagorinski-Lilly sub-grid-scale model. The effects of the wall curvature on the unsteady filtered, and the steady mean, parameters characterizing the dynamics of the wall jet are addressed in particular. In the free jet upstream of the impingement region, significant and fairly ordered velocity fluctuations, that are not turbulent in nature, are observed inside the potential core. Kelvin-Helmholtz instabilities in the shear layer between the jet and the surrounding air are detected in the form of wavy sheets of vorticity. Rolled up vortices are detached from these sheets in a more or less periodic manner, evolving into distorted three dimensional structures. Along the wall jet the Coanda effect causes a marked suction along the convex surface compared with the flat one. As a result, relatively important tangential velocities and a stretching of sporadic streamwise vortices are observed, leading to friction coefficient values on the curved wall higher than those on the flat wall.

Hybrid LES Approach for Practical Turbomachinery Flows—Part I: Hierarchy and Example Simulations

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Paul Tucker ◽  
Simon Eastwood ◽  
Christian Klostermeier ◽  
Richard Jefferson-Loveday ◽  
James Tyacke ◽  
...  
Keyword(s):  
Convex Surface ◽  
Computational Cost ◽  
Companion Paper ◽  
Navier Stokes ◽  
Computationally Efficient ◽  
Turbulent Structures ◽  
Hybrid Strategy ◽  
Eddy Simulation ◽  
Related Approach ◽  
Les Model

Unlike Reynolds-averaged Navier–Stokes (RANS) models that need calibration for different flow classes, LES (where larger turbulent structures are resolved by the grid and smaller modeled in a fashion reminiscent of RANS) offers the opportunity to resolve geometry dependent turbulence as found in complex internal flows—albeit at substantially higher computational cost. Based on the results for a broad range of studies involving different numerical schemes, large eddy simulation (LES) models and grid topologies, an LES hierarchy and hybrid LES related approach is proposed. With the latter, away from walls, no LES model is used, giving what can be termed numerical LES (NLES). This is relatively computationally efficient and makes use of the dissipation present in practical industrial computational fluid dynamics (CFD) programs. Near walls, RANS modeling is used to cover over numerous small structures, the LES resolution of which is generally intractable with current computational power. The linking of the RANS and NLES zones through a Hamilton–Jacobi equation is advocated. The RANS-NLES hybridization makes further sense for compressible flow solvers, where, as the Mach number tends to zero at walls, excessive dissipation can occur. The hybrid strategy is used to predict flow over a rib roughened surface and a jet impinging on a convex surface. These cases are important for blade cooling and show encouraging results. Further results are presented in a companion paper.

Research on the response characteristics of solenoid valve of the air-jet loom by simulation

2013 ◽  
Vol 22 (6) ◽  
pp. 606-612 ◽  
Author(s):  
Yuzhen Jin ◽  
Ruoyu Deng ◽  
Yingzi Jin ◽  
Xudong Hu
Keyword(s):  
Solenoid Valve ◽  
Response Characteristics ◽  
Air Jet ◽  
Air Jet Loom

scholarly journals Air Stream ejected from Sub-nozzles of Air Jet Loom

1996 ◽  
Vol 42 (3-4) ◽  
pp. 80-85 ◽  
Author(s):  
Ryuji Shintani ◽  
Ikuei Donjou ◽  
Kazuhide Chikaoka ◽  
Atsushi Okajima
Keyword(s):  
Air Jet ◽  
Air Stream ◽  
Air Jet Loom

Numerical Investigation of Energy Saving Device Effects on Ships With Propeller-Hull Interactions

2018 ◽  
Author(s):  
Ravi Chaithanya Mysa ◽  
Le Quang Tuyen ◽  
Ma Shengwei ◽  
Vinh-Tan Nguyen
Keyword(s):  
Energy Saving ◽  
Full Scale ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Propulsion Efficiency ◽  
Operational Conditions ◽  
Ship Resistance ◽  
The Past ◽  
Eddy Simulation ◽  
Flow Features

Energy saving devices (ESD) such as propeller ducts, pre-swirl stators, pre-nozzles, etc have been explored as a more economic and reliable approach to reduce energy consumption for both in-operation and newly design ships over the past decades. Those energy saving devices work in the principle of reducing ship resistance and improving propulsion efficiency as well as hull-propeller interactions. Potential saving from various types of ESD have been reported in literature from the range of 3–9% [1] for propulsion efficiency dependent on different measures. Deployment of those devices on actual full-scale ships has been limited over the past years. One of the key obstacles in application of ESD is the lack of confidence in measuring its efficiency on full-scale ships in actual operational conditions. Advances in computational fluid dynamics (CFD) has provided an alternative approach from model scale test to better understand uncertainties in prediction of ESD efficiency in full-scale ship operations [Shin et al, 2013]. In this work a high fidelity CFD model is presented for investigation effects of pre-nozzles on propulsion efficiency and ship resistance. The model is based on the Reynolds Average Navier-Stokes (RANS) solver with different turbulent models including a hybrid detached eddy simulation (DES) approach for predictions of complex near body flow features as well as in the wake regions from hull and propeller. The model is validated with model test for both towing and self-propulsion conditions. Finally a study of pre-nozzle effects on propeller efficiency as well as hull-propeller interaction is presented and compared with available experimental data (Tokyo 2015 Workshop). The current work constitutes a fundamental approach towards designing more efficient ESD for a specific hull form and propeller.

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