Three Dimensional Linearized Navier-Stokes Calculations for Flutter and Forced Response

1998 ◽  
pp. 211-224 ◽  
Author(s):  
D. Graham Holmes ◽  
Christopher B. Lorence
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes

Forced Response Variation of Aerodynamically and Structurally Mistuned Turbo-Machinery Rotors

2006 ◽  
Author(s):  
I. Sladojevic´ ◽  
E. P. Petrov ◽  
M. Imregun ◽  
A. I. Sayma
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Fe Model ◽  
Frequency Shifts ◽  
Aero Engine ◽  
Different Types ◽  
Aerodynamic Parameters ◽  
Reynolds Averaged Navier Stokes ◽  
Response Variation

The paper presents the results of a study looking into changes in the forced response levels of bladed disc assemblies subject to both structural and aerodynamic mistuning. A whole annulus FE model, representative of a civil aero-engine fan with 26 blades was used in the calculations. The forced response of all blades of 1000 random mistuned patterns was calculated. The aerodynamic parameters, frequency shifts and damping, were calculated using a three-dimensional Reynolds-averaged Navier-Stokes aero-elasticity code. They were randomly varied for each mistuning pattern, with the assumption that the system would remain stable, i.e. flutter would not occur due to aerodynamic mistuning. The results show the variation of the forced response with different types of mistuning, with structural mistuning only, with aerodynamic mistuning only and with both structural and aerodynamic mistuning.

scholarly journals Calculation and Correlation of the Unsteady Flowfield in a High Pressure Turbine

2002 ◽  
Author(s):  
Milind A. Bakhle ◽  
Jong S. Liu ◽  
Josef Panovsky ◽  
Theo G. Keith ◽  
Oral Mehmed
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Forced Vibrations ◽  
Forced Response ◽  
Operating Conditions ◽  
Test Facility ◽  
Navier Stokes ◽  
Turbine Stage ◽  
High Pressure Turbine

Forced vibrations in turbomachinery components can cause blades to crack or fail due to high-cycle fatigue. Such forced response problems will become more pronounced in newer engines with higher pressure ratios and smaller axial gap between blade rows. An accurate numerical prediction of the unsteady aerodynamics phenomena that cause resonant forced vibrations is increasingly important to designers. Validation of the computational fluid dynamics (CFD) codes used to model the unsteady aerodynamic excitations is necessary before these codes can be used with confidence. Recently published benchmark data, including unsteady pressures and vibratory strains, for a high-pressure turbine stage makes such code validation possible. In the present work, a three dimensional, unsteady, multi blade-row, Reynolds-Averaged Navier Stokes code is applied to a turbine stage that was recently tested in a short duration test facility. Two configurations with three operating conditions corresponding to modes 2, 3, and 4 crossings on the Campbell diagram are analyzed. Unsteady pressures on the rotor surface are compared with data.

Blade Aerodynamic Damping Variation With Rotor-Stator Gap: A Computational Study Using Single-Passage Approach

2003 ◽  
Vol 127 (3) ◽  
pp. 573-579 ◽  
Author(s):  
H. D Li ◽  
L. He
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
Single Passage ◽  
Finite Volume Discretization ◽  
Shape Correction ◽  
Gap Spacing

One of the outstanding issues in turbomachinery aeromechanic analysis is the intrarow interaction effects. The present work is aimed at a systematic examination of rotor-stator gap effects on blade aerodynamic damping by using a three-dimensional (3D) time-domain single-passage Navier-Stokes solver. The method is based on the upwind finite volume discretization and the single-passage shape-correction approach with enhanced accuracy and efficiency for unsteady transonic flows prediction. A significant speedup (by a factor of 20) over to a conventional whole annulus solution has been achieved. A parametric study with different rotor-stator gaps (56%–216% rotor tip chord) for a 3D transonic compressor stage illustrates that the reflection from an adjacent stator row can change rotor aerodynamic damping by up to 100% depending on the intrarow gap spacing. Furthermore, this rotor aerodamping dependency on the intrarow gap seems also to be affected by the number of stator blades. The predicted nonmonotonic relationship between the rotor blade aerodynamic damping and the gap spacing suggests the existence of an optimum gap regarding rotor flutter stability and/or forced response stress levels.

Investigation of the Influence of Aerodynamic Coupling on Response Levels of Mistuned Bladed Discs With Weak Structural Coupling

2005 ◽  
Author(s):  
I. Sladojevic´ ◽  
E. P. Petrov ◽  
A. I. Sayma ◽  
M. Imregun ◽  
J. S. Green
Keyword(s):  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Response Distribution ◽  
Aerodynamic Forces ◽  
Torsional Mode ◽  
Structural Coupling ◽  
Unsteady Aerodynamic ◽  
The Difference ◽  
Statistical Results

The paper summarises the results of a study investigating the correlation between the aerodynamic blade-to-blade coupling in mistuned bladed disc assemblies and the level of forced response. The focus was placed on the torsional mode of vibration, where blades’ coupling through the disc is weak, exposing the effects of aerodynamic coupling. The forced response of a large number of mistuned discs was computed, using whole-annulus finite element (FE) models. The unsteady aerodynamic forces that act upon the disc were calculated using a three-dimensional Reynolds-averaged Navier-Stokes CFD code. The results show the difference in response with and without aerodynamic coupling, exposing higher blade-to-blade interaction in the latter case. The statistical results show the change of the forced response distribution curves with the introduction of aero-coupling and their deviation from Gaussian distribution.

Prediction of Flutter and Inlet Distortion Driven Response of a Transonic Fan Rotor Using Phase-Lagged Boundary Conditions

2001 ◽  
Author(s):  
H. D. Li ◽  
L. He
Keyword(s):  
Computing Time ◽  
Three Dimensional ◽  
Correction Method ◽  
Forced Response ◽  
Navier Stokes ◽  
Design Environment ◽  
Inlet Distortion ◽  
Single Passage ◽  
Shape Correction ◽  
Transonic Fan

Prediction of blade forced response and flutter is of great importance to turbomachinery designers. However, calculations of unsteady turbomachinery flows using conventional time-domain methods typically would lead to the use of multi-passage/whole-annulus domains due to the required direct periodic condition. This makes numerical computations extremely time-consuming and is one of the major difficulties for nonlinear unsteady calculations to be applied in a blading design environment. A single-passage approach to three-dimensional unsteady Navier-Stokes calculations using the Fourier-series based Shape-Correction method has been developed, and been applied to analyze inlet distortion driven response and flutter of a transonic fan rotor (NASA Rotor-67). The key feature is that the Shape-Correction method enables a single-passage solution to unsteady flows in blade rows under influences of multiple disturbances with arbitrary inter-blade phase angles. The results show that the single-passage solution can capture deterministic unsteadiness as well as time-averaged flows in good agreement with conventional multi-passage solutions, while the corresponding computing time can be reduced dramatically.

A Multi Blade-Row Linearised Analysis Method for Flutter and Forced Response Predictions in Turbomachinery

2006 ◽  
Author(s):  
Gabriel Saiz ◽  
Mehmet Imregun ◽  
Abdulnaser I. Sayma
Keyword(s):  
Travelling Waves ◽  
Three Dimensional ◽  
Forced Response ◽  
Navier Stokes ◽  
Test Case ◽  
Test Cases ◽  
Simple Test ◽  
Analysis Method ◽  
Turbine Stage ◽  
Blade Row

A three-dimensional time-linearised unsteady Navier-Stokes solver is presented for the computation of multistage unsteady flow in turbomachinery. The objective is to address multistage aeroelastic effects for both flutter and forced response. Since the method is currently being developed, only forced response applications are studied in this paper. With this approach, travelling waves, known as spinning modes, are propagated across the multistage domain in order to take into account the interaction between the blade-rows. The method is first validated over two simple test cases for which analytical solutions were available. It is then tested on a turbine stage test case and multistage effects are evaluated from the contribution of one spinning mode included in the model. The results are compared with both time-linearised single-row and nonlinear multirow methods. Multi-row effects are shown not to be important in this case. However, the test case serves as a validation for the implementation of the methodology and further work will focus on the implementation of several spinning modes and the computations of forced response and flutter cases with several blade-rows.

Structures and Dynamics Committee Best Paper of 1996 Award: Inlet Distortion Generated Forced Response of a Low-Aspect-Ratio Transonic Fan

1997 ◽  
Vol 119 (4) ◽  
pp. 665-676 ◽  
Author(s):  
S. R. Manwaring ◽  
D. C. Rabe ◽  
C. B. Lorence ◽  
A. R. Wadia
Keyword(s):  
Aspect Ratio ◽  
Steady Flow ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Forced Response ◽  
Navier Stokes ◽  
Surface Boundary ◽  
Unsteady Pressure ◽  
Low Aspect Ratio ◽  
Transonic Fan

This paper describes a portion of an experimental and computational program (ADLARF), which incorporates, for the first time, measurements of all aspects of the forced response of an airfoil row, i.e., the flow defect, the unsteady pressure loadings, and the vibratory response. The purpose of this portion was to extend the knowledge of the unsteady aerodynamics associated with a low-aspect-ratio transonic fan where the flow defects were generated by inlet distortions. Measurements of screen distortion patterns were obtained with total pressure rakes and casing static pressures. The unsteady pressure loadings on the blade were determined from high response pressure transducers. The resulting blade vibrations were measured with strain gages. The steady flow was analyzed using a three-dimensional Navier–Stokes solver while the unsteady flow was determined with a quasi-three-dimensional linearized Euler solver. Experimental results showed that the distortions had strong vortical, moderate entropic, and weak acoustic parts. The three-dimensional Navier–Stokes analyses showed that the steady flow is predominantly two-dimensional, with radially outward flow existing only in the blade surface boundary layers downstream of shocks and in the aft part of the suction surface. At near resonance conditions, the strain gage data showed blade-to-blade motion variations and thus, linearized unsteady Euler solutions showed poorer agreement with the unsteady loading data than comparisons at off-resonance speeds. Data analysis showed that entropic waves generated unsteady loadings comparable to vortical waves in the blade regions where shocks existed.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

Experimental and Numerical Analysis of a Motorcycle Air Intake System Aerodynamics and Performance

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
M. A. Abd Halim ◽  
N. A. R. Nik Mohd ◽  
M. N. Mohd Nasir ◽  
M. N. Dahalan
Keyword(s):  
Combustion Process ◽  
Three Dimensional ◽  
Engine Performance ◽  
Internal Flow ◽  
Rapid Expansion ◽  
Navier Stokes ◽  
Turbulent Fluctuation ◽  
Ansys Fluent ◽  
Induction System ◽  
Acceleration And Deceleration

Induction system or also known as the breathing system is a sub-component of the internal combustion system that supplies clean air for the combustion process. A good design of the induction system would be able to supply the air with adequate pressure, temperature and density for the combustion process to optimizing the engine performance. The induction system has an internal flow problem with a geometry that has rapid expansion or diverging and converging sections that may lead to sudden acceleration and deceleration of flow, flow separation and cause excessive turbulent fluctuation in the system. The aerodynamic performance of these induction systems influences the pressure drop effect and thus the engine performance. Therefore, in this work, the aerodynamics of motorcycle induction systems is to be investigated for a range of Cubic Feet per Minute (CFM). A three-dimensional simulation of the flow inside a generic 4-stroke motorcycle airbox were done using Reynolds-Averaged Navier Stokes (RANS) Computational Fluid Dynamics (CFD) solver in ANSYS Fluent version 11. The simulation results are validated by an experimental study performed using a flow bench. The study shows that the difference of the validation is 1.54% in average at the total pressure outlet. A potential improvement to the system have been observed and can be done to suit motorsports applications.

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