2418 Numerical and Experimental Investigations on Three-Dimensional Unsteady Aerodynamic Interaction in a Turbine Stage

In the present work, unsteady RANS simulations were performed to clarify several interesting features of the unsteady three-dimensional flow field in a turbine stage. The unsteady effect was investigated for two cases of axial spacing between stator and rotor, i.e. large and small axial spacing. Simulation results showed that the stator wake was convected from pressure side to suction side in the rotor. As a result, another secondary flow, which counter-rotated against the passage vortices, was periodically generated by the stator wake passing through the rotor passage. It was found that turbine stage efficiency with the small axial spacing was higher than that with the large axial spacing. This was because the stator wake in the small axial spacing case entered the rotor before mixing and induced the stronger counter-rotating vortices to suppress the passage vortices more effectively, while the wake in the large axial spacing case eventually promoted the growth of the secondary flow near the hub due to the migration of the wake towards the hub.

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Structural Characterization of Receptor–Receptor Interactions in the Allosteric Modulation of G Protein-Coupled Receptor (GPCR) Dimers

International Journal of Molecular Sciences ◽

10.3390/ijms22063241 ◽

2021 ◽

Vol 22 (6) ◽

pp. 3241

Author(s):

Raudah Lazim ◽

Donghyuk Suh ◽

Jai Woo Lee ◽

Thi Ngoc Lan Vu ◽

Sanghee Yoon ◽

...

Keyword(s):

G Protein ◽

Protein Interactions ◽

Metabotropic Glutamate Receptor ◽

Three Dimensional ◽

Allosteric Modulation ◽

Experimental Investigations ◽

G Protein Coupled Receptor ◽

Metabotropic Glutamate ◽

Gpcr Activation ◽

G Protein Coupled

G protein-coupled receptor (GPCR) oligomerization, while contentious, continues to attract the attention of researchers. Numerous experimental investigations have validated the presence of GPCR dimers, and the relevance of dimerization in the effectuation of physiological functions intensifies the attractiveness of this concept as a potential therapeutic target. GPCRs, as a single entity, have been the main source of scrutiny for drug design objectives for multiple diseases such as cancer, inflammation, cardiac, and respiratory diseases. The existence of dimers broadens the research scope of GPCR functions, revealing new signaling pathways that can be targeted for disease pathogenesis that have not previously been reported when GPCRs were only viewed in their monomeric form. This review will highlight several aspects of GPCR dimerization, which include a summary of the structural elucidation of the allosteric modulation of class C GPCR activation offered through recent solutions to the three-dimensional, full-length structures of metabotropic glutamate receptor and γ-aminobutyric acid B receptor as well as the role of dimerization in the modification of GPCR function and allostery. With the growing influence of computational methods in the study of GPCRs, we will also be reviewing recent computational tools that have been utilized to map protein–protein interactions (PPI).

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Assessment of Unsteady Flows in Turbines

Journal of Turbomachinery ◽

10.1115/1.2928001 ◽

1992 ◽

Vol 114 (1) ◽

pp. 79-90 ◽

Cited By ~ 57

Author(s):

O. P. Sharma ◽

G. F. Pickett ◽

R. H. Ni

Keyword(s):

Unsteady Flow ◽

Three Dimensional ◽

Flow Simulation ◽

Experimental Investigations ◽

Flow Parameters ◽

Research Activities ◽

Flow Features ◽

Computational Fluid Dynamics Cfd ◽

Turbine Design ◽

The Impact

The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

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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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Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage

Journal of Turbomachinery ◽

10.1115/1.2928368 ◽

1994 ◽

Vol 116 (2) ◽

pp. 327-332 ◽

Cited By ~ 29

Author(s):

T. Green ◽

A. B. Turner

Keyword(s):

Pressure Distribution ◽

Static Pressure ◽

Three Dimensional ◽

Computer Code ◽

Rotor Blades ◽

Rotor Speed ◽

Turbine Stage ◽

Flow Rates ◽

Static Pressure Distribution ◽

Axial Clearance

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGVs) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGVs and rotor blades on the level of mainstream ingestion for different seal flow rates. A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainstream flow rates by controlling the rotor speed with an air brake. The circumferential variation in hub static pressure was measured at the trailing edge of the NGVs upstream of the seal gap and was found to affect ingestion significantly. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton three-dimensional C.F.D. computer code was used to predict the smoothed time-dependent pressure field for the rotor together with the pressure distribution downstream of the NGVs. The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace. With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGVs were found to reduce mainstream ingestion seal flow rates significantly, but a small level of ingestion existed even for very high levels of seal flow rate.

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A Time-Domain Fluid-Structure Interaction Analysis of Fan Blades

Volume 5: Structures and Dynamics, Parts A and B ◽

10.1115/gt2008-50479 ◽

2008 ◽

Author(s):

Seung Ho Cho ◽

Taehyoun Kim ◽

Seung Jin Song

Keyword(s):

Time Domain ◽

Vortex Lattice ◽

Interaction Analysis ◽

Three Dimensional ◽

Incoming Flow ◽

Structure Interaction ◽

Unsteady Aerodynamic ◽

Aerodynamic Model ◽

Blade Row ◽

Fan Blade

This paper presents aerodynamic and aeromechanical analyses for an entire row of fan blades (i.e. tens of blades with a finite aspect ratio) subject to a uniform incoming flow. In this regard, a new unsteady three-dimensional vortex lattice model has been developed for multiple blades in discrete time domain. Using the new model, the characteristics of the unsteady aerodynamic forces on vibrating blades, including their temporal development, are examined. Also, the new aerodynamic model is applied to examine the aeromechanical behavior of fan blades by using a standard eigenvalue analysis. For this analysis, the fan blades have been modeled as three-dimensional plates, and, increasing the number of blades (or solidity) is predicted to destabilize the fan blade row.

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Experimental Investigations of Interactions between Sand Wave Movements, Flow Structure, and Individual Aquatic Plants in Natural Rivers: A Case Study of Potamogeton Pectinatus L.

Water ◽

10.3390/w10091166 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1166 ◽

Cited By ~ 8

Author(s):

Łukasz Przyborowski ◽

Anna Łoboda ◽

Robert Bialik

Keyword(s):

Flow Velocity ◽

Three Dimensional ◽

Potamogeton Pectinatus ◽

Sand Wave ◽

Experimental Investigations ◽

Cross Sectional ◽

Bending Tests ◽

Long Duration ◽

Elevation Changes

Long-duration measurements were performed in two sandy bed rivers, and three-dimensional (3D) flow velocity and bottom elevation changes were measured in a vegetated area and in a clear region of a river. Detailed flow velocity profiles downstream and upstream of a single specimen of Potamogeton pectinatus L. were obtained and the bed morphology was assessed. Potamogeton plants gathered from each river were subjected to tensile and bending tests. The results show that the existence of the plants was influenced by both bottom and flow conditions, as the plants were located where water velocity was lower by 12% to 16% in comparison to clear region. The characteristics of the flow and sand forms depended on the cross-sectional arrangement of the river, e.g., dunes were approximately four times higher in the middle of the river than in vegetated regions near the bank. Furthermore, the studied hydrophytes were too sparse to affect water flow and had no discernible impact on the sand forms’ movements. The turbulent kinetic energy downstream of a single plant was reduced by approximately 25%. Additionally, the plants’ biomechanical characteristics and morphology were found to have adjusted to match the river conditions.

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Effect of Temperature Nonuniformity on Heat Transfer in an Unshrouded Transonic HP Turbine: An Experimental and Computational Investigation

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2010-22700 ◽

2010 ◽

Cited By ~ 1

Author(s):

Imran Qureshi ◽

Andy D. Smith ◽

Kam S. Chana ◽

Thomas Povey

Keyword(s):

Heat Transfer ◽

Three Dimensional ◽

Aerodynamic Characteristics ◽

Test Facility ◽

Effect Of Temperature ◽

Inlet Temperature ◽

Experimental Measurements ◽

Turbine Stage ◽

Cfd Simulations ◽

Turbine Inlet

Detailed experimental measurements have been performed to understand the effects of turbine inlet temperature distortion (hot-streaks) on the heat transfer and aerodynamic characteristics of a full-scale unshrouded high pressure turbine stage at flow conditions that are representative of those found in a modern gas turbine engine. To investigate hot-streak migration, the experimental measurements are complemented by three-dimensional steady and unsteady CFD simulations of the turbine stage. This paper presents the time-averaged measurements and computational predictions of rotor blade surface and rotor casing heat transfer. Experimental measurements obtained with and without inlet temperature distortion are compared. Time-mean experimental measurements of rotor casing static pressure are also presented. CFD simulations have been conducted using the Rolls-Royce code Hydra, and are compared to the experimental results. The test turbine was the unshrouded MT1 turbine, installed in the Turbine Test Facility (previously called Isentropic Light Piston Facility) at QinetiQ, Farnborough UK. This is a short duration transonic facility, which simulates engine representative M, Re, Tu, N/T and Tg /Tw at the turbine inlet. The facility has recently been upgraded to incorporate an advanced second-generation temperature distortion generator, capable of simulating well-defined, aggressive temperature distortion both in the radial and circumferential directions, at the turbine inlet.

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Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage

Journal of Turbomachinery ◽

10.1115/1.2929197 ◽

1993 ◽

Vol 115 (1) ◽

pp. 128-136 ◽

Cited By ~ 14

Author(s):

J. Zeschky ◽

H. E. Gallus

Keyword(s):

Flow Field ◽

Three Dimensional ◽

Axial Flow ◽

Tip Clearance ◽

Hot Wire ◽

Turbine Stage ◽

Static Pressure Distribution ◽

Inlet Conditions ◽

Experimental Values ◽

Rotor Flow

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data include the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The paper presents the formation of the tip clearance vortex and the passage vortices, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.

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