Sensitivity Analysis of Implementing CFD-based Distributed Flame Transfer Functions in a Nonlinear Euler Solver

This article revisits the problem of indirect combustion noise in nozzles of finite length. The analytical model proposed by Moase et al. (JFM 2007) for indirect combustion noise is red-erived and applied to subcritical nozzles having shapes of increasing complexity. This model is based on the equations formulated by Marble & Candel (JSV 1977) for which an explicit solution is obtained in the subsonic framework. The discretization of the nozzle into n elementary units of finite length implies the determination of 2n integration constants for which a set of linear equations is provided in this article. The analytical method is applied to configurations of increasing complexity. Analytical solutions are compared to numerical results obtained using SUNDAY (a 1D non linear Euler solver in temporal space) and CEDRE (3D Navier-Stokes flow solver). An excellent agreement is found for all configurations thereby showing that acceleration discontinuities at the boundaries between adjacent elements do not influence the actual acoustic transfer functions. The issue of nozzle compactness is addressed. It is found that in the subcritical domain, spectral results should be nondimensionalized using the flow-through-time of the entire nozzle. Doing so, transfer functions of nozzles of different lengths are successfully compared and a compactness criterion is proposed that writes ω*∫0Ldζ/uζ<1 where L is the axial length of the nozzle. Finally, the EWG experimental setup of Bake et al. (JSV 2009) is considered. Analytical results are compared to the results reported by Howe (JFM 2010). Both models give similar trends and show the important role of the rising time of the fluctuating temperature front on the amplitude of the indirect acoustic emission. The experimental temperature profile and the impedance coefficients at the inlet and outlet provided by Bake et al. (JSV 2009) and Leyko et al. (JSV 2011) are introduced into the analytical formulation. Results show that the indirect combustion noise mechanism cannot be held responsible alone for the acoustic emission in the subcritical case.

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A Study on the Influence of Ship Roll Characteristics on the Risk of Cargo Shifting

Marine Technology and SNAME News ◽

10.5957/mt1.2004.41.2.51 ◽

2004 ◽

Vol 41 (02) ◽

pp. 51-59

Author(s):

Anna Ryrfeldt

Keyword(s):

Sensitivity Analysis ◽

Transfer Function ◽

Computational Efficiency ◽

Transfer Functions ◽

Resonance Peak ◽

Roll Motion ◽

Ship Motions ◽

Load Case ◽

Contributing Factors ◽

Ship Roll

In a previous work a methodology for assessing the risk of cargo shifting has been developed and used to study the influence of different parameters on the risk of cargo shifting. It has been found that ship rolling is one of the major contributing factors of cargo shifting. Linear theory of ship motions is presently used in the methodology because of computational efficiency and simplicity. Because the roll motion is complex and difficult to predict because of nonlinearities, the present study has been performed in order to study the influence of the roll motion on the risk of cargo shifting. This study may be seen as a sensitivity analysis of roll motion with respect to cargo shifting. The risk has been studied by the number of potentially dangerous conditions and how they depend on such parameters as wave height and period, and ship heading toward waves. The influence of roll amplitude and phase, as well as the influence of roll stabilizing devices, on the number of dangerous conditions is studied for two vessels and two load cases each. Roll amplitude influence is analyzed by changing the amplitude of the transfer function, and the results show that the influence of roll amplitude is very large. This influence is especially marked when the roll amplitude is large and the vertical and horizontal accelerations are small to moderate. The influence of roll stabilizing devices is studied by cutting of the resonance peak in the transfer functions. The results show that roll stabilizing is often efficient but that it can be more important to choose load case in order to attain good seakeeping characteristics, especially with respect to roll motion.

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Sensitivity analysis of transfer functions of laminar flames

Combustion and Flame ◽

10.1016/j.combustflame.2011.05.013 ◽

2011 ◽

Vol 158 (12) ◽

pp. 2384-2394 ◽

Cited By ~ 54

Author(s):

F. Duchaine ◽

F. Boudy ◽

D. Durox ◽

T. Poinsot

Keyword(s):

Sensitivity Analysis ◽

Transfer Functions ◽

Laminar Flames

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Pyrolysis of Mixed Plastic Waste: II. Artificial Neural Networks Prediction and Sensitivity Analysis

Applied Sciences ◽

10.3390/app11188456 ◽

2021 ◽

Vol 11 (18) ◽

pp. 8456

Author(s):

Ibrahim Dubdub ◽

Mohammed Al-Yaari

Keyword(s):

Sensitivity Analysis ◽

Transfer Functions ◽

Pearson Correlation ◽

Input Parameter ◽

Propagation Model ◽

Ann Model ◽

Polymer Mixtures ◽

Feed Forward Back Propagation ◽

Proposed Model ◽

Artificial Neural

In this work, an artificial neural network (ANN) model was efficiently developed to predict the pyrolysis of mixed plastics, including pure polystyrene (PS), polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE), at a heating rate of 60 K/min using thermogravimetric analysis (TGA) data. The data of seventeen experimental tests of polymer mixtures with different compositions were used. A feed-forward back-propagation model, with 15 and 10 neurons in two hidden layers and TANSIG-TANSIG transfer functions, was constructed to predict the weight left percent during the pyrolysis of the mixed polymer samples. The model input variables include the composition of each polymer (PS, PP, LDPE, and HDPE), and temperature. The results showed an excellent agreement between the experimental and the predicted weight left percent values, where the correlation coefficient (R) is greater than 0.9999. In addition, to validate the proposed model, a highly efficient performance was found when the proposed model was simulated using new input data. Furthermore, a sensitivity analysis was performed using Pearson correlation to find the uncertainties associated with the relationship between the output and the input parameters. Temperature was found to be the most sensitive input parameter.

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Analytical Analysis of Indirect Combustion Noise in Subcritical Nozzles

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4007318 ◽

2012 ◽

Vol 134 (11) ◽

Cited By ~ 36

Author(s):

Alexis Giauque ◽

Maxime Huet ◽

Franck Clero

Keyword(s):

Acoustic Emission ◽

Finite Length ◽

Transfer Functions ◽

Linear Equations ◽

Combustion Noise ◽

Navier Stokes ◽

Subcritical Case ◽

Compactness Criterion ◽

Temporal Space ◽

Euler Solver

This article revisits the problem of indirect combustion noise in nozzles of finite length. The analytical model proposed by Moase for indirect combustion noise is rederived and applied to subcritical nozzles having shapes of increasing complexity. This model is based on the equations formulated by Marble and Candel for which an explicit solution is obtained in the subsonic framework. The discretization of the nozzle into n elementary units of finite length implies the determination of 2n integration constants for which a set of linear equations is provided in this article. The analytical method is applied to configurations of increasing complexity. Analytical solutions are compared to numerical results obtained using SUNDAY (a 1D nonlinear Euler solver in temporal space) and CEDRE (3D Navier–Stokes flow solver). Excellent agreement is found for all configurations thereby showing that acceleration discontinuities at the boundaries between adjacent elements do not influence the actual acoustic transfer functions. The issue of nozzle compactness is addressed. It is found that in the subcritical domain, spectral results should be nondimensionalized using the flow-through-time of the entire nozzle. Doing so, transfer functions of nozzles of different lengths are successfully compared and a compactness criterion is proposed that writes ω*∫0Ldζ/u(ζ)<1 where L is the axial length of the nozzle. Finally, the entropy wave generator (EWG) experimental setup is considered. Analytical results are compared to the results reported by Howe. Both models give similar trends and show the important role of the rising time of the fluctuating temperature front on the amplitude of the indirect acoustic emission. The experimental temperature profile and the impedance coefficients at the inlet and outlet are introduced into the analytical formulation. Results show that the indirect combustion noise mechanism is not alone responsible for the acoustic emission in the subcritical case.

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