NUMERICAL STUDY ON EFFECT OF DIFFRENCE BETWEEN SIDE WALL AND BOTTOM WALL ROUGHNESS COEFFICIENTS ON SECONDARY FLOW IN BEND CHANNEL

This article presents the results of the study of the influence of the most significant parameters of the side wall roughness of an ultra-thin silicon nitride lightguide layer of multimode integrated optical waveguides with widths of 3 and 8 microns. The choice of the waveguide width was made due to the need to provide multimode operation for telecommunication wavelengths, which is necessary to ensure high integration density. Scattering in waveguide structures was measured by optical frequency domain reflectometry (OFDR) of a backscattering reflectometer. The finite difference time domain method (FDTD) was used to study the effect of roughness parameters on optical losses in fabricated waveguides, the roughness parameters that most strongly affect optical scattering were determined, and methods of its significant reduction were specified. The prospects for implementing such structures on a quartz substrate are justified.

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Side-wall roughness of deep trenches in 1D and 2D periodic silicon structures fabricated by photoelectrochemical etching

physica status solidi (c) ◽

10.1002/pssc.201000138 ◽

2011 ◽

Vol 8 (6) ◽

pp. 1936-1940 ◽

Cited By ~ 8

Author(s):

E. V. Astrova ◽

G. V. Fedulova ◽

Yu. A. Zharova ◽

E. V. Gushchina

Keyword(s):

Side Wall ◽

Wall Roughness ◽

Photoelectrochemical Etching ◽

Silicon Structures

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Aerodynamics of Cooling Jets Introduced in the Secondary Flow of a Low-Speed Turbine Cascade

Journal of Turbomachinery ◽

10.1115/1.2927692 ◽

1990 ◽

Vol 112 (3) ◽

pp. 539-546 ◽

Cited By ~ 2

Author(s):

F. Bario ◽

F. Leboeuf ◽

A. Onvani ◽

A. Seddini

Keyword(s):

Secondary Flow ◽

Side Wall ◽

Velocity Fields ◽

Measuring Apparatus ◽

Flow Ratio ◽

Turbine Cascade ◽

Hot Wire ◽

Local Pressure ◽

Low Speed ◽

Jet Behavior

The aerodynamic behavior of cold discrete jets in a cold secondary flow is investigated. Configurations including single jets and rows of jets are studied. These jets are introduced through the side wall of a low-speed nozzle turbine cascade. The experimental setup and the jet behavior are fully described. The effects of location with respect to the blades, mass flow ratio, yaw, and incidence angles on the aerodynamics of single jets are investigated. The influence of neighboring jets is detailed in the case of multiple jet configurations. The interaction with the secondary flow is presented. The local pressure and velocity fields, trajectories, and visualizations are discussed. The measuring apparatus includes a five-hole probe and a hot wire for intermittency measurements.

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Numerical Simulation of Secondary Flow in Gas Turbine Disc Cavities, Including Conjugate Heat Transfer

Volume 1: Turbomachinery ◽

10.1115/96-gt-067 ◽

1996 ◽

Cited By ~ 7

Author(s):

Y.-H. Ho ◽

M. M. Athavale ◽

J. M. Forry ◽

R. C. Hendricks ◽

B. M. Steinetz

Keyword(s):

Heat Transfer ◽

Secondary Flow ◽

Conjugate Heat Transfer ◽

Gas Flow ◽

Numerical Study ◽

Labyrinth Seal ◽

Temperature Fields ◽

Heat Transfer Analysis ◽

Flow Rates ◽

Turbine Disc

A numerical study of the flow and heat transfer in secondary flow elements of the entire inner portion of the turbine section of the Allison T-56/501D engine is presented. The flow simulation included the interstage cavities, rim seals and associated main path flows, while the energy equation also included the solid parts of the turbine disc, rotor supports, and stator supports. Solutions of the energy equations in these problems usually face the difficulty in specifications of wall thermal boundary conditions. By solving the entire turbine section this difficulty is thus removed, and realistic thermal conditions are realized on all internal walls. The simulation was performed using SCISEAL, an advanced 2D/3D CFD code for predictions of fluid flows and forces in turbomachinery seals and secondary flow elements. The mass flow rates and gas temperatures at various seal locations were compared with the design data from Allison. Computed gas flow rates and temperatures in the rim and labyrinth seal show a fair 10 good comparison with the design calculations. The conjugate heat transfer analysis indicates temperature gradients in the stationary intercavity walls, as well as the rotating turbine discs. The thermal strains in the stationary wall may lead to altered interstage labyrinth seal clearances and affect the disc cavity flows. The temperature, fields in the turbine discs also may lead to distortions that can alter the rim seal clearances. Such details of the flow and temperature fields are important in designs of the turbine sections to account for possible thermal distortions and their effects on the performance. The simulation shows that the present day CFD codes can provide the means to understand the complex flow field and thereby aid the design process.

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Investigation of Three-Dimensional Flow in Microchannels With Patterned Surfaces

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30052 ◽

2007 ◽

Cited By ~ 1

Author(s):

Auro Ashish Saha ◽

Sushanta K. Mitra

Keyword(s):

Surface Tension ◽

Flow Instability ◽

Numerical Study ◽

Three Dimensional ◽

Surface Characteristics ◽

Bottom Wall ◽

Surface Tension Effect ◽

Hydrophobic Region ◽

Side Walls ◽

Dimensional Simulation

A three-dimensional numerical simulation of flow in patterned microchannel with alternate layers of hydrophilic and hydrophobic surfaces at the bottom wall is studied here. Surface characteristics of the microchannel are accounted by specifying the contact angle and the surface tension of the fluid. Meniscus profiles with varying amplitude and shapes are obtained under the different specified surface conditions. Flow instability increases as the fluid at the bottom wall traverses alternately from hydrophilic region to hydrophobic region. To understand the surface tension effect of the side walls, a two-dimensional numerical study has also been carried out for the microchannel and the results are compared with three-dimensional simulation. The surface tension effect of the side walls enhances the capillary effect for three-dimensional case.

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Numerical Investigation of Secondary Flow Vortex Core Structure in the Two-Pass Rectangular Channel With 45° Ribs

Volume 5A: Heat Transfer ◽

10.1115/gt2015-42782 ◽

2015 ◽

Cited By ~ 4

Author(s):

Jiangnan Zhu ◽

Tieyu Gao ◽

Jun Li ◽

Guojun Li ◽

Jianying Gong

Keyword(s):

Heat Transfer ◽

Heat Transfer Enhancement ◽

Secondary Flow ◽

Gas Turbine ◽

Vortex Core ◽

Side Wall ◽

Main Flow ◽

Transfer Enhancement ◽

Cooling Channels ◽

Flow Vortex

The secondary flow which is generated by the angled rib is one of the key factors of heat transfer enhancement in gas turbine blade cooling channels. However, the current studies are all based on the velocity vector and streamline, which limit the research on the detailed micro-structure of secondary flow. In order to make further targeted optimization on the flow and heat transfer in the cooling channels of gas turbine blade, it is necessary to firstly investigate the generation, interaction, dissipation and the influence on heat transfer of secondary flow with the help of new topological method. This paper reports the numerical study of the secondary flow and the effect of secondary flow on heat transfer enhancement in rectangular two-pass channel with 45° ribs. Based on the vortex core technology, the structure of secondary flow can be clearly shown and studied. The results showed that the main flow secondary flow is thrown to the outer side wall after the corner due to the centrifugal force. Then it is weakened in the second pass and a new main flow secondary flow is generated at the same time near the opposite side wall in the second pass. The Nusselt number distribution has also been compared with the secondary flow vortex core distribution. The results shows that the heat transfer strength is weakened in the second pass due to the interaction between the old main flow secondary flow and the new one. These two secondary flows are in opposite rotation direction, which reduces the disturbance and mass transfer strength in the channel.

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Effects of Upstream Step Geometry on Axisymmetric Converging Vane Endwall Secondary Flow and Heat Transfer at Transonic Conditions

Journal of Turbomachinery ◽

10.1115/1.4041294 ◽

2018 ◽

Vol 140 (12) ◽

Cited By ~ 2

Author(s):

Zhigang Li ◽

Luxuan Liu ◽

Jun Li ◽

Ridge A. Sibold ◽

Wing F. Ng ◽

...

Keyword(s):

Heat Transfer ◽

Secondary Flow ◽

Thermal Load ◽

Numerical Study ◽

Guide Vane ◽

Leading Edge ◽

Step Height ◽

Temperature History ◽

Flow And Heat Transfer ◽

High Thermal Load

This paper presents a detailed experimental and numerical study on the effects of upstream step geometry on the endwall secondary flow and heat transfer in a transonic linear turbine vane passage with axisymmetric converging endwalls. The upstream step geometry represents the misalignment between the combustor exit and the nozzle guide vane endwall. The experimental measurements were performed in a blowdown wind tunnel with an exit Mach number of 0.85 and an exit Re of 1.5×106. A high freestream turbulence level of 16% was set at the inlet, which represents the typical turbulence conditions in a gas turbine engine. Two upstream step geometries were tested for the same vane profile: a baseline configuration with a gap located 0.88Cx (43.8 mm) upstream of the vane leading edge (upstream step height = 0 mm) and a misaligned configuration with a backward-facing step located just before the gap at 0.88Cx (43.8 mm) upstream of the vane leading edge (step height = 4.45% span). The endwall temperature history was measured using transient infrared thermography, from which the endwall thermal load distribution, namely, Nusselt number, was derived. This paper also presents a comparison with computational fluid dynamics (CFD) predictions performed by solving the steady-state Reynolds-averaged Navier–Stokes with Reynolds stress model using the commercial CFD solver ansysfluent v.15. The CFD simulations were conducted at a range of different upstream step geometries: three forward-facing (upstream step geometries with step heights from −5.25% to 0% span), and five backward-facing, upstream step geometries (step heights from 0% to 6.56% span). These CFD results were used to highlight the link between heat transfer patterns and the secondary flow structures and explain the effects of upstream step geometry. Experimental and numerical results indicate that the backward-facing upstream step geometry will significantly enlarge the high thermal load region and result in an obvious increase (up to 140%) in the heat transfer coefficient (HTC) level, especially for arched regions around the vane leading edge. However, the forward-facing upstream geometry will modestly shrink the high thermal load region and reduce the HTC (by ∼10% to 40% decrease), especially for the suction side regions near the vane leading edge. The aerodynamic loss appears to have a slight increase (0.3–1.3%) because of the forward-facing upstream step geometry but is slightly reduced (by 0.1–0.3%) by the presence of the backward upstream step geometry.

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Steady and unsteady flow of non-newtonian fluid in curved pipe with triangular

Baghdad Science Journal ◽

10.21123/bsj.3.3.470-480 ◽

2006 ◽

Vol 3 (3) ◽

pp. 470-480

Author(s):

Baghdad Science Journal

Keyword(s):

Unsteady Flow ◽

Pressure Gradient ◽

Secondary Flow ◽

Cross Section ◽

Numerical Study ◽

Equations Of Motion ◽

Curved Pipe ◽

First Case ◽

Stable Flow ◽

Flow Cross

This paper deals with numerical study of the flow of stable and fluid Allamstqr Aniotina in an area surrounded by a right-angled triangle has touched particularly valuable secondary flow cross section resulting from the pressure gradient In the first case was analyzed stable flow where he found that the equations of motion that describe the movement of the fluid

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