Phase-Lagged Boundary Condition Methods for Aeroelastic Analysis of Turbomachines: A Comparative Study

In the present work a comparative study of phase-lagged boundary condition methods is carried out. The relative merits and advantages of time-shifted and the Fourier decomposition methods are compared. Both methods are implemented in a time marching Euler/Navier-Stokes solver and are applied to a flat plate helical fan with harmonically oscillating blades to perform the study. Results were obtained for subsonic as well as supersonic inflows. Results for subsonic inflow showed good comparisons with published results and between the two methods along with comparable computational costs. For the supersonic inflow, despite the presence of shocks at the periodic boundary results from both the methods compared well, however, Fourier decomposition method was computationally more expensive. For linear flowfield Fourier decomposition method is best suited, especially for work-station environment. The time-shifted method is better suited for CRAY category of computers where fast input-output devices are available.

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Application of Time-Shifted Boundary Conditions to a 3D Euler/Navier-Stokes Aeroelastic Code

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education ◽

10.1115/98-gt-042 ◽

1998 ◽

Author(s):

R. Srivastava ◽

Milind A. Bakhle ◽

Theo G. Keith ◽

G. L. Stefko

Keyword(s):

Boundary Condition ◽

Boundary Conditions ◽

Inviscid Flow ◽

Computer Time ◽

Aerodynamic Characteristics ◽

Navier Stokes ◽

Blade Passage ◽

Unsteady Aerodynamic ◽

Time Marching ◽

Phase Angles

In the present work the unsteady aerodynamic characteristics of harmonically oscillating fan blades are investigated by applying a time-shifted boundary condition at the periodic boundaries. The direct-store method is used to implement the time-shifted boundary condition in a time-marching Euler/Navier-Stokes solver. Inviscid flow calculations for a flat plate helical fan, in a single-blade passage domain, are used to verify the analysis. The results obtained show good correlation with other published results as well as with the same solver using multiple blade passages stacked together. Significant savings in computer time is realized, especially for smaller phase angles.

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A domain decomposition method for the time-dependent Navier-Stokes-Darcy model with Beavers-Joseph interface condition and defective boundary condition

Journal of Computational Physics ◽

10.1016/j.jcp.2020.109400 ◽

2020 ◽

Vol 411 ◽

pp. 109400 ◽

Cited By ~ 3

Author(s):

Changxin Qiu ◽

Xiaoming He ◽

Jian Li ◽

Yanping Lin

Keyword(s):

Boundary Condition ◽

Domain Decomposition ◽

Decomposition Method ◽

Domain Decomposition Method ◽

Time Dependent ◽

Interface Condition ◽

Navier Stokes ◽

Darcy Model

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A STUDY OF ENDOMETRIAL THICKNESS IN TRANS VAGINAL SONOGRAPHY IN RELATION WITH HISTOPATHOLOGY REPORT IN DILATION & CURRATAGE IN AUB WOMEN

10.36106/paripex/1 ◽

2019 ◽

pp. 1-2

Keyword(s):

Comparative Study ◽

Endometrial Thickness ◽

P Value ◽

First Line ◽

Non Invasive ◽

Dilation And Curettage ◽

Study Results ◽

Vaginal Sonography ◽

In Trans

A study of of endometrial thickness on TVS in relation with histopathology report on dilation and curettage. AIM AND OBJECTIVE-To set a cut off limit of endometrial thickness on TVS for differtiating between normal and abnormal endometrium. MATERIAL AND METHOD-hospital based comparative study. RESULTS-TVS is non invasive ,simple first line procedure in AUB women. Mean endometrial thickness in normal endometrial group was 8.00±2.44 mm and in abnormal endometrial group was 15.16±33 mm.The difference was found highly significant (p value<.001)

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Nonlinear singular one dimensional thermo-elasticity coupled system and double Laplace decomposition methods

Filomat ◽

10.2298/fil1720269g ◽

2017 ◽

Vol 31 (20) ◽

pp. 6269-6280

Author(s):

Hassan Gadain

Keyword(s):

Laplace Transform ◽

Decomposition Method ◽

Adomian Decomposition Method ◽

Coupled System ◽

Decomposition Methods ◽

One Dimensional ◽

Convergence Proof ◽

Double Laplace Transform ◽

Adomian Decomposition

In this work, combined double Laplace transform and Adomian decomposition method is presented to solve nonlinear singular one dimensional thermo-elasticity coupled system. Moreover, the convergence proof of the double Laplace transform decomposition method applied to our problem. By using one example, our proposed method is illustrated and the obtained results are confirmed.

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A Note on the Decomposition Methods for Support Vector Regression

Neural Computation ◽

10.1162/089976602753712936 ◽

2002 ◽

Vol 14 (6) ◽

pp. 1267-1281 ◽

Cited By ~ 14

Author(s):

Shuo-Peng Liao ◽

Hsuan-Tien Lin ◽

Chih-Jen Lin

Keyword(s):

Support Vector Regression ◽

Decomposition Method ◽

Decomposition Methods ◽

Support Vector ◽

Dual Formulation ◽

Working Set ◽

Number Of Iterations

The dual formulation of support vector regression involves two closely related sets of variables. When the decomposition method is used, many existing approaches use pairs of indices from these two sets as the working set. Basically, they select a base set first and then expand it so all indices are pairs. This makes the implementation different from that for support vector classification. In addition, a larger optimization subproblem has to be solved in each iteration. We provide theoretical proofs and conduct experiments to show that using the base set as the working set leads to similar convergence (number of iterations). Therefore, by using a smaller working set while keeping a similar number of iterations, the program can be simpler and more efficient.

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Vibration analysis and combustion parameter evaluation of CI engine based on Fourier Decomposition Method

International Journal of Engine Research ◽

10.1177/1468087420988195 ◽

2021 ◽

pp. 146808742098819

Author(s):

Wang Yang ◽

Cheng Yong

Keyword(s):

Vibration Analysis ◽

Decomposition Method ◽

Combustion Process ◽

Pressure Rise ◽

Maximum Pressure ◽

Vibration Signals ◽

Loop Control ◽

Fourier Decomposition ◽

Surface Vibration ◽

Rise Rate

As a non-intrusive method for engine working condition detection, the engine surface vibration contains rich information about the combustion process and has great potential for the closed-loop control of engines. However, the measured engine surface vibration signals are usually induced by combustion as well as non-combustion excitations and are difficult to be utilized directly. To evaluate some combustion parameters from engine surface vibration, the tests were carried out on a single-cylinder diesel engine and a new method called Fourier Decomposition Method (FDM) was used to extract combustion induced vibration. Simulated and test results verified the ability of the FDM for engine vibration analysis. Based on the extracted vibration signals, the methods for identifying start of combustion, location of maximum pressure rise rate, and location of peak pressure were proposed. The cycle-by-cycle analysis of the results show that the parameters identified based on vibration and in-cylinder pressure have the similar trends, and it suggests that the proposed FDM-based methods can be used for extracting combustion induced vibrations and identifying the combustion parameters.

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