How Does a Queuing Network React to a Change of Different Flow Control Parameters?

2016 ◽  
pp. 73-82
Author(s):  
Mais Farkhadov ◽  
Nina Petukhova ◽  
Alexander Abramenkov ◽  
Olga Blinova
Keyword(s):  
Flow Control ◽  
Control Parameters ◽  
Queuing Network

scholarly journals 3D Printed Structured Porous Treatments for Flow Control around a Circular Cylinder

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 136
Author(s):  
Pranjal Bathla ◽  
John Kennedy
Keyword(s):  
Flow Control ◽  
Coating Thickness ◽  
Lattice Structure ◽  
Porous Coating ◽  
Lattice Structures ◽  
Control Parameters ◽  
Multiple Control ◽  
Flow Measurements ◽  
Porous Coatings ◽  
Flow Stabilization

The use of porous coatings is one of the passive flow control methods used to reduce turbulence, noise and vibrations generated due to fluid flow. Porous coatings for flow stabilization have potential for a light-weight, cost-effective, and customizable solution. The design and performance of a structured porous coating depend on multiple control parameters like lattice size, strut thickness, lattice structure/geometry, etc. This study investigated the suitability of MSLA 3D printers to manufacture porous coatings based on unit cell designs to optimize porous lattices for flow control behind a cylinder. The Reynolds number used was 6.1×104–1.5×105 and the flow measurements were taken using a hotwire probe. Different experiment sets were conducted for single cylinder with varying control parameters to achieve best performing lattice designs. It was found that lattice structures with higher porosity produced lower turbulence intensity in the wake of the cylinder. However, for constant porosity lattice structures, there was negligible difference in turbulence and mean wake velocity levels. Coating thickness did not have a linear relationship with turbulence reduction, suggesting an optimal thickness value. For constant porosity coatings, cell count in coating thickness did not influence the turbulence or mean wake velocity. Partial coating designs like helical and spaced coatings had comparable performance to that of a full coating. MSLA printers were found capable of manufacturing thin and complex porous lattices.

Improvement of Flat-Plate Film Cooling Performance by Double Flow Control Devices: Part II — Optimization of Device Shape and Arrangement by Experiment- and CFD-Based Taguchi Method

2014 ◽  
Author(s):  
Hirokazu Kawabata ◽  
Ken-ichi Funazaki ◽  
Ryota Nakata ◽  
Hisato Tagawa ◽  
Yasuhiro Horiuchi
Keyword(s):  
Taguchi Method ◽  
Flow Control ◽  
Flat Plate ◽  
Film Cooling ◽  
Optimal Parameter ◽  
Control Device ◽  
Noise Factor ◽  
Control Parameters ◽  
Flow Control Device ◽  
Cooling Air

This paper, as a second part of the study on the double flow control device (DFCD) which has been proven in Part I [1] to improve the flat plate film cooling considerably, describes an approach to optimize the device shape and arrangement using Taguchi method. The target cooling holes are conventional cylindrical ones of 3.0d pitch with 35 deg angle to the flat plate surface. The shape of the double flow control device to be optimized is based on the hemi-spheroid used in Part I. The optimization process in this study is categorized as “static problem”, in which S/N ratios of “larger-the-better” characteristics are calculated for control parameters against their noise factor. The “larger-the-better” characteristics adopted in this study is the area averaged film effectiveness over the downstream region of the cooling hole. L18 orthogonal array is used to accommodate the experiment. Blowing ratios of the cooling air to the main flow used in this study are 0.5, 0.75 and 1.0, which are regarded as noise factor. Seven control parameters such as fillet radius, installation angle of the device are chosen and their effects on the film effectiveness are evaluated by the measurement as well as by RANS simulation. In this research, the optimization which used Taguchi method was at the same time carried out by an experiment and numerical simulation. From a comparison between the optimal parameter combinations attained from the measurement-based and CFD-based approaches, one can have an idea about the dependency of the optimal parameter combination on the characteristic evaluation approach. Additional investigation is also made on the effects of turbulence model upon the optimal parameter combination. The flow fields in the downstream region of the optimal DFCD are observed using 3D Laser Doppler Velocimeter in order to understand how the device works on the ejected cooling air. In addition, Large-Eddy-Simulation (LES) is also executed in order to grasp unsteady flow structures created by the device and their interaction with the cooling air. It is found from the measurement as well as the LES analysis that the optimal DFCD generates comparatively large-scale longitudinal vortices, causing the drastic increase in film effectiveness.

scholarly journals Prediction of Better Flow Control Parameters in MHD Flows Using a High Accuracy Finite Difference Scheme

2017 ◽  
Vol 07 (03) ◽  
pp. 243-275
Author(s):  
A. D. Abin Rejeesh ◽  
S. Udhayakumar ◽  
T. V. S. Sekhar ◽  
R. Sivakumar
Keyword(s):  
Finite Difference ◽  
Flow Control ◽  
Difference Scheme ◽  
Finite Difference Scheme ◽  
High Accuracy ◽  
Control Parameters ◽  
Mhd Flows

Active Flow Control Concepts on a Highly Loaded Subsonic Compressor Cascade: Résumé of Experimental and Numerical Results

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Christoph Gmelin ◽  
Vincent Zander ◽  
Martin Hecklau ◽  
Frank Thiele ◽  
Wolfgang Nitsche ◽  
...  
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Suction Side ◽  
Numerical Results ◽  
Pressure Probe ◽  
Control Parameters ◽  
Compressor Cascade ◽  
Wide Range ◽  
Active Flow ◽  
Highly Loaded

This paper presents experimental and numerical results for a highly loaded, low speed, linear compressor cascade with active flow control. Three active flow control concepts employing steady jets, pulsed jets, and zero mass flow jets (synthetic jets) are investigated at two different forcing locations: at the end walls and the blade suction side. Investigations are performed at the design incidence for jet-to-inlet velocity ratios of approximately 0.7 to 3.0 and two different Reynolds numbers. Detailed flow field data are collected using a five-hole pressure probe, pressure tabs on the blade surfaces, and time-resolved particle image velocimetry. Unsteady Reynolds-Averaged Navier-Stokes simulations are performed for a wide range of flow control parameters. The experimental and numerical results are used to understand the interaction between the jet and the passage flow. Variation of jet amplitude, forcing frequency and blowing angle of the different control concepts at both locations allows determination of beneficial control parameters and offers a comparison between similar control approaches. This paper combines the advantages of an expensive yet reliable experiment and a fast but limited numerical simulation. Excellent agreement in control effectiveness is found between experiment and simulation.

scholarly journals Effect of the location of a gas flow control element in an ejector unit on the flow pattern

2020 ◽  
Vol 2020 (3) ◽  
pp. 54-63
Author(s):  
O.D. Ihnatev ◽  
◽  
H.M. Shevelova ◽  
Keyword(s):  
Numerical Simulation ◽  
Flow Control ◽  
Flow Pattern ◽  
Flow Rate ◽  
Gas Flow ◽  
Energy Carrier ◽  
Control Element ◽  
Gas Flows ◽  
Control Parameters ◽  
Processing Technologies

This article is devoted to a numerical simulation of the flow in a jet mill ejector equipped with a gas flow control element. This element is a channel wherefrom an additional gas flow enters the accelerating tube of the ejector. The gas flows in the mill ejector are controlled using the energy of additional gas flows, thus increasing the velocity of the main flow at the outlet of the ejector accelerating tube and producing a protective layer around the tube walls to prevent their wear. At the same time, there is no substantiation for the choice of optimal control parameters, a methodology, or scientific methods for gas flow control in the ejector channels. The purpose of this work is to investigate the effect of the location of the gas flow control element on gas-dynamic ejector performance and the flow pattern in the ejector channels. A numerical study was carried out using the Ansys Fluent software package and the SST k-? turbulence model. In the course of the study, the pressure of the additional gas flow and the distance from the accelerating tube inlet to the energy carrier supply channel were varied. The angle of the additional gas flow was 20 ?. The numerical simulation gave flow patterns in the ejector as a function of the location of the gas flow control element. Streamlines of the additional gas flow were constructed. The article presents the average flow velocity at the accelerating tube outlet and the energy carrier flow rate as a function of the pressure of the additional flow of the energy carrier and the location of the gas flow control element and the maximum values of the average outlet velocity for given pressure ranges. The article substantiates the choice of the gas flow control parameters that maximize the velocity of the mixed flow at the accelerating tube outlet at a minimum gas flow rate. The results may be used in improving material processing technologies.

Optimization of Active/Passive Flow Control Parameters on Airfoils at Transonic Speeds

2011 ◽  
Vol 48 (1) ◽  
pp. 212-219 ◽  
Author(s):  
Y. Volkan Pehlivanoglu ◽  
Bedri Yagiz
Keyword(s):  
Flow Control ◽  
Control Parameters ◽  
Passive Flow Control ◽  
Passive Flow

scholarly journals The effect of Reynolds number on turbulent drag reduction by streamwise travelling waves

2014 ◽  
Vol 759 ◽  
pp. 28-55 ◽  
Author(s):  
Edward Hurst ◽  
Qiang Yang ◽  
Yongmann M. Chung
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Flow Control ◽  
Travelling Waves ◽  
Reynolds Numbers ◽  
Travelling Wave ◽  
Control Parameters ◽  
Scaling Parameter ◽  
High Reynolds Numbers ◽  
High Reynolds

AbstractThis paper exploits the turbulent flow control method using streamwise travelling waves (Quadrio et al. J. Fluid Mech., vol. 627, 2009, pp. 161–178) to study the effect of Reynolds number on turbulent skin-friction drag reduction. Direct numerical simulations (DNS) of a turbulent channel flow subjected to the streamwise travelling waves of spanwise wall velocity have been performed at Reynolds numbers ranging from $\mathit{Re}_{{\it\tau}}=200$ to 1600. To the best of the authors’ knowledge, this is the highest Reynolds number attempted with DNS for this type of flow control. The present DNS results confirm that the effectiveness of drag reduction deteriorates, and the maximum drag reduction achieved by travelling waves decreases significantly as the Reynolds number increases. The intensity of both the drag reduction and drag increase is reduced with the Reynolds number. Another important finding is that the value of the optimal control parameters changes, even in wall units, when the Reynolds number is increased. This trend is observed for the wall oscillation, stationary wave, and streamwise travelling wave cases. This implies that, when the control parameters used are close to optimal values found at a lower Reynolds number, the drag reduction deteriorates rapidly with increased Reynolds number. In this study, the effect of Reynolds number for the travelling wave is quantified using a scaling in the form $\mathit{Re}_{{\it\tau}}^{-{\it\alpha}}$. No universal constant is found for the scaling parameter ${\it\alpha}$. Instead, the scaling parameter ${\it\alpha}$ has a wide range of values depending on the flow control conditions. Further Reynolds number scaling issues are discussed. Turbulent statistics are analysed to explain a weaker drag reduction observed at high Reynolds numbers. The changes in the Stokes layer and also the mean and root-mean-squared (r.m.s.) velocity with the Reynolds number are also reported. The Reynolds shear stress analysis suggests an interesting possibility of a finite drag reduction at very high Reynolds numbers.

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