Dynamic effects on high frequency unsteady flow structures

1990 ◽  
Author(s):  
JOHN KLINGE ◽  
SCOTT SCHRECK ◽  
MARVIN LUTTGES
Keyword(s):  
Unsteady Flow ◽  
High Frequency ◽  
Flow Structures ◽  
Dynamic Effects

Unsteady flow structures behind a shark denticle replica on the wall: Time-resolved particle image velocimetry measurements

2021 ◽  
Vol 33 (7) ◽  
pp. 075109
Author(s):  
Qian Mao ◽  
Peng Wang ◽  
Chuangxin He ◽  
Yingzheng Liu
Keyword(s):  
Particle Image Velocimetry ◽  
Unsteady Flow ◽  
Particle Image ◽  
Flow Structures ◽  
Time Resolved ◽  
Image Velocimetry

Helical Flow Disturbances in a Multi-Nozzle Combustor

2014 ◽  
Author(s):  
Michael Aguilar ◽  
Michael Malanoski ◽  
Gautham Adhitya ◽  
Benjamin Emerson ◽  
Vishal Acharya ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Field Measurements ◽  
Flow Fields ◽  
Helical Flow ◽  
Forced Response ◽  
Flow Structures ◽  
Response Dynamics ◽  
Flow Disturbances ◽  
Nozzle Configuration ◽  
Jet Interactions

This paper describes an experimental investigation of a transversely forced, swirl stabilized combustor. Its objective is to compare the unsteady flow structures in single and triple nozzle combustors and determine how well a single nozzle configuration emulates the characteristics of a multi-nozzle one. The experiment consists of a series of velocity field measurements captured on planes normal to the jet axis. As expected, there are differences between the single and triple-nozzle flow fields, but the differences are not large in the regions upstream of the jet merging zone. Direct comparisons of the time averaged flow fields reveal a higher degree of non-axisymmetry for the flowfields of nozzles in a multi-nozzle configuration. Azimuthal decompositions of the velocity fields show that the transverse acoustic forcing has an important influence on the dynamics, but that the single and multi-nozzle configurations have similar forced response dynamics near the dump plane. Specifically, the axial dependence of the amplitude in the highest energy axisymmetric and helical flow structures is quite similar in the two configurations. This result suggests that the hydrodynamic influence of one swirling jet on the other is minimal and, as such, that jet-jet interactions in this configuration do not have a significant influence on the unsteady flow structures.

scholarly journals Numerical modelling and flow analysis of a centrifugal pump running as a turbine: Unsteady flow structures and its effects on the global performance

2011 ◽  
Vol 65 (5) ◽  
pp. 542-562 ◽  
Author(s):  
Carlos Santolaria Morros ◽  
Jesús Manuel Fernández Oro ◽  
Katia María Argüelles Díaz
Keyword(s):  
Numerical Modelling ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Flow Analysis ◽  
Flow Structures ◽  
Global Performance

3D numerical analysis of unsteady flow structures around inclined spur dikes by means of a non-linear k-_ model

Shallow Flows ◽  
2004 ◽  
pp. 651-660 ◽  
Author(s):  
T Hosoda ◽  
A Tominaga ◽  
S Onda ◽  
I Kimura
Keyword(s):  
Numerical Analysis ◽  
Unsteady Flow ◽  
Flow Structures ◽  
Non Linear ◽  
Spur Dikes

Analysis of Unsteady Flow Structures in a Radial Turbomachine by Using Proper Orthogonal Decomposition

2018 ◽  
Author(s):  
Matthias Witte ◽  
Benjamin Torner ◽  
Frank-Hendrik Wurm
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Proper Orthogonal Decomposition ◽  
Orthogonal Decomposition ◽  
Mode Shapes ◽  
Flow Structures ◽  
Periodic Flow ◽  
Noise Emission ◽  
Turbulent Flow Field ◽  
Proper Orthogonal

Tonalities in hydro and airborne noise emission are a known problem of turbomachines, wherein the tonalities in the noise spectrum are associated with the different orders of the blade passing frequency (BPF). The proper orthogonal decomposition (POD) method was utilized to find the relationship between the fluctuations in the pressure field at the BPF orders which are the origin of the noise emission and the correlated fluctuations in the turbulent velocity field in terms of coherent, periodic flow structures. In order the provide the input data for the POD analysis, a URANS k-ω-SST scale adaptive simulation (SAS) of the turbulent flow field in a single stage radial pump under part load conditions was performed. Compared to traditional two equation turbulence models this approach is less dissipative and allows the development of small scale turbulence structures and is therefore an appropriate method for this study. In order to compute the POD correlation matrix Sirovich’s “Methods of Snapshots” was applied to the unsteady pressure and velocity fields from the CFD simulation. The discrimination of coherent, periodic flow structures and the incoherent, chaotic turbulence was carried out by analyzing the POD eigenvalue distributions, the POD mode shapes and the spectral properties of the POD time coefficients. Five coupled POD mode pairs were identified in total, which were strictly correlated with the 1st, 2nd, 3rd, 4th and 5th order of the BPF and therefore responsible for the noise emission at these discrete frequencies. The coherent structures were explored on the basis of the spatial POD velocity und pressure mode shapes and in terms of vortical structures after an additional phase averaging. The scope of this study is to introduce an enhanced collection of post processing techniques which are capable of analyzing highly unsteady flow fields from numerical simulations in a better way than is possible by just using traditional techniques like the evaluation of integral or time averaged quantities. The identified coherent flow structures and their associated pressure fluctuations are key elements for a proper comprehension of the internal dynamics of the turbulent flow field in a turbomachine and therefore essential for the understanding of the noise generation processes and the optimization of such machines.

HPC-LES for Unsteady Aerodynamics of a Heavy Duty Truck in Wind Gust - 1st report: Validation and Unsteady Flow Structures

2010 ◽  
Author(s):  
Makoto Tsubokura ◽  
Kaito Takahashi ◽  
Tomofuyu Matsuuki ◽  
Takuji Nakashima ◽  
Takeshi Ikenaga ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Unsteady Aerodynamics ◽  
Flow Structures ◽  
Wind Gust ◽  
Heavy Duty ◽  
Heavy Duty Truck

scholarly journals Experimental and Computational Study of the Unsteady Flow in a 1.5 Stage Axial Turbine With Emphasis on the Secondary Flow in the Second Stator

1998 ◽  
Author(s):  
Ralf E. Walraevens ◽  
Heinz E. Gallus ◽  
Alexander R. Jung ◽  
Jürgen F. Mayer ◽  
Heinz Stetter
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Computational Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Axial Flow ◽  
Time Dependent ◽  
Flow Structures ◽  
Mean Flow ◽  
Dependent Flow

A study of the unsteady flow in an axial flow turbine stage with a second stator blade row is presented. The low aspect ratio blades give way to a highly three-dimensional flow which is dominated by secondary flow structures. Detailed steady and unsteady measurements throughout the machine and unsteady flow simulations which include all blade rows have been carried out. The presented results focus on the second stator flow. Secondary flow structures and their origins are identified and tracked on their way through the passage. The results of the time-dependent secondary velocity vectors as well as flow angles and Mach number distributions as perturbation from the time-mean flow field are shown in cross-flow sections and azimuthal cuts throughout the domain of the second stator. At each location the experimental and numerical results are compared and discussed. A good overall agreement in the time-dependent flow behaviour as well as in the secondary flow structures is stated.

Characterization of Unsteady Flow Structures Near Leading-Edge Slat: Part I: PIV Measurements

2004 ◽  
Author(s):  
Luther Jenkins ◽  
Mehdi Khorrami ◽  
Meelan Choudhari
Keyword(s):  
Unsteady Flow ◽  
Leading Edge ◽  
Flow Structures ◽  
Piv Measurements

Unsteady Flow Interactions Between a High- and Low-Pressure Turbine: Part 1 — Time-Resolved Flow

2019 ◽  
Author(s):  
P. Z. Sterzinger ◽  
S. Zerobin ◽  
F. Merli ◽  
L. Wiesinger ◽  
M. Dellacasagrande ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Low Pressure ◽  
Flow Fields ◽  
System Level ◽  
Flow Structures ◽  
Pressure Probe ◽  
Time Resolved ◽  
Low Pressure Turbine ◽  
Aerodynamic Pressure ◽  
Flow Interactions

Abstract This two-part paper presents the unsteady flow interactions between an engine-representative high-pressure turbine (HPT) and low-pressure turbine (LPT) stage, connected by a turbine center frame (TCF) duct with non-turning struts. The setup was tested at the high-speed two-spool test turbine facility at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology and includes relevant purge and turbine rotor tip leakage flows. Due to the complexity of such a test, the unsteady component interactions in an HPT-TCF-LPT module have not received much attention in the past and require additional analysis to determine new approaches for further performance improvements on the system level. The flow downstream of an HPT is highly unsteady and dominated by statorrotor interactions, which affect the flow behavior through the downstream TCF and LPT. To capture the unsteady flow structures, time-resolved aerodynamic measurements were carried out with a fast-response aerodynamic pressure probe (FRAPP) at three different measurement planes. In this first part of the paper, the time-resolved and phase-averaged flow fields with respect to the HPT and LPT trigger are studied. Since the two rotors are uncorrelated, the applied method allows the identification of the flow structures induced by either of them. Upstream of the LPT stage, the HPT flow structures evolving through the TCF duct dominate the flow fields. Downstream of the LPT stage, the flow is affected by both the HPT and the LPT secondary flow structures. The interactions between the various stator rows and the two rotors are detected by means of time-space plots and modal decomposition. To describe the fluctuations induced by both rotors, particularly the rotor-rotor interaction, the Rotor Synchronic Averaging (RSA) is used to analyze the flow field downstream of the LPT. The second part of the paper decomposes the flow fields to gain additional insight into the rotor-rotor interactions using the Proper Orthogonal Decomposition (POD) and RSA methods. The paper highlights the need to account for the HPT-induced unsteady mechanisms in addition to the LPT flow structures and the interaction of both to arrive at improved LPT designs.

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