Determination of volterra transfer functions of non-linear multiport networks

Model tests of a drillship with a rectangular moonpool opening were conducted in regular and irregular waves from the bow and bow-quarter. Most tests were conducted at zero speed, the rest was performed with the model towed to a speed of 10 kn. From the video-recordings and transfer functions of the measured relative water elevation inside the moonpool, the typical piston and first sloshing modes are well captured, for wave frequencies that agree relatively well with relevant formulations. A few tests conducted at varying wave amplitudes show that the water elevation is non-linear by nature, while repeat tests conducted with the moonpool fitted with two layers of side wall flanges shows that these can reduce the water motions by nearly 40 %.

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Influence of Non Linear Effects in the Determination of Transfer Functions

10.4271/1999-01-2349 ◽

1999 ◽

Author(s):

A. Ulmann ◽

V. Enjalbert

Keyword(s):

Transfer Functions ◽

Non Linear ◽

Linear Effects

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Determination of Concrete Cube Strength from Used Samples / Určení Krychelné Pevnosti Betonu U Použitých Zkušebních Trámců

Transactions of the VŠB - Technical University of Ostrava Civil Engineering Series ◽

10.2478/v10160-012-0033-3 ◽

2012 ◽

Vol 12 (2) ◽

pp. 186-194 ◽

Cited By ~ 2

Author(s):

Oldřich Sucharda ◽

David Mikolášek ◽

Jiří Brožovský

Keyword(s):

Compressive Strength ◽

Concrete Beams ◽

Linear Analysis ◽

Bending Tests ◽

Cube Strength ◽

Non Linear ◽

Compressive Strength Of Concrete ◽

Concrete Cube

Abstract This paper deals with the determination of compressive strength of concrete. Cubes, cylinders and re-used test beams were tested. The concrete beams were first subjected to three-point or fourpoint bending tests and then used for determination of the compressive strength of concrete. Some concrete beams were reinforced, while others had no reinforcement. Accuracy of the experiments and calculations was verified in a non-linear analysis.

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Offline method for determination of non‐linear dependence of machine magnetising inductance utilising parallel operation of current and voltage model

IET Power Electronics ◽

10.1049/iet-pel.2018.6321 ◽

2019 ◽

Vol 12 (11) ◽

pp. 2843-2850 ◽

Cited By ~ 3

Author(s):

Ondrej Lipcak ◽

Jan Bauer ◽

Pavel Kobrle

Keyword(s):

Linear Dependence ◽

Parallel Operation ◽

Non Linear

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Interaction of equivalence ratio fluctuations and flow fluctuations in acoustically forced swirl flames

International Journal of Spray and Combustion Dynamics ◽

10.1177/17568277211015544 ◽

2021 ◽

pp. 175682772110155

Author(s):

Vincent Kather ◽

Finn Lückoff ◽

Christian O. Paschereit ◽

Kilian Oberleithner

Keyword(s):

Equivalence Ratio ◽

Transfer Functions ◽

Transport Model ◽

Mode Conversion ◽

Fuel Injector ◽

One Dimensional ◽

Flow Fluctuations ◽

Non Linear ◽

Non Local ◽

Acoustic Forcing

The generation and turbulent transport of temporal equivalence ratio fluctuations in a swirl combustor are experimentally investigated and compared to a one-dimensional transport model. These fluctuations are generated by acoustic perturbations at the fuel injector and play a crucial role in the feedback loop leading to thermoacoustic instabilities. The focus of this investigation lies on the interplay between fuel fluctuations and coherent vortical structures that are both affected by the acoustic forcing. To this end, optical diagnostics are applied inside the mixing duct and in the combustion chamber, housing a turbulent swirl flame. The flame was acoustically perturbed to obtain phase-averaged spatially resolved flow and equivalence ratio fluctuations, which allow the determination of flux-based local and global mixing transfer functions. Measurements show that the mode-conversion model that predicts the generation of equivalence ratio fluctuations at the injector holds for linear acoustic forcing amplitudes, but it fails for non-linear amplitudes. The global (radially integrated) transport of fuel fluctuations from the injector to the flame is reasonably well approximated by a one-dimensional transport model with an effective diffusivity that accounts for turbulent diffusion and dispersion. This approach however, fails to recover critical details of the mixing transfer function, which is caused by non-local interaction of flow and fuel fluctuations. This effect becomes even more pronounced for non-linear forcing amplitudes where strong coherent fluctuations induce a non-trivial frequency dependence of the mixing process. The mechanisms resolved in this study suggest that non-local interference of fuel fluctuations and coherent flow fluctuations is significant for the transport of global equivalence ratio fluctuations at linear acoustic amplitudes and crucial for non-linear amplitudes. To improve future predictions and facilitate a satisfactory modelling, a non-local, two-dimensional approach is necessary.

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Error analyses of a Multi-Input-Multi-Output cantilever beam test

Journal of Vibration and Control ◽

10.1177/10775463211033733 ◽

2021 ◽

pp. 107754632110337

Author(s):

Arup Maji ◽

Fernando Moreu ◽

James Woodall ◽

Maimuna Hossain

Keyword(s):

Transfer Function ◽

Frequency Domain ◽

Cantilever Beam ◽

Transfer Functions ◽

Linear Superposition ◽

Transfer Function Matrix ◽

Error Analyses ◽

Pseudo Inverse ◽

Function Matrix

Multi-Input-Multi-Output vibration testing typically requires the determination of inputs to achieve desired response at multiple locations. First, the responses due to each input are quantified in terms of complex transfer functions in the frequency domain. In this study, two Inputs and five Responses were used leading to a 5 × 2 transfer function matrix. Inputs corresponding to the desired Responses are then computed by inversion of the rectangular matrix using Pseudo-Inverse techniques that involve least-squared solutions. It is important to understand and quantify the various sources of errors in this process toward improved implementation of Multi-Input-Multi-Output testing. In this article, tests on a cantilever beam with two actuators (input controlled smart shakers) were used as Inputs while acceleration Responses were measured at five locations including the two input locations. Variation among tests was quantified including its impact on transfer functions across the relevant frequency domain. Accuracy of linear superposition of the influence of two actuators was quantified to investigate the influence of relative phase information. Finally, the accuracy of the Multi-Input-Multi-Output inversion process was investigated while varying the number of Responses from 2 (square transfer function matrix) to 5 (full-rectangular transfer function matrix). Results were examined in the context of the resonances and anti-resonances of the system as well as the ability of the actuators to provide actuation energy across the domain. Improved understanding of the sources of uncertainty from this study can be used for more complex Multi-Input-Multi-Output experiments.

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Bias Truck Tire Deformation Analysis with Finite Element Modeling

Applied Sciences ◽

10.3390/app10124326 ◽

2020 ◽

Vol 10 (12) ◽

pp. 4326

Author(s):

Józef Pelc

Keyword(s):

Incompressible Material ◽

Axisymmetric Deformation ◽

Thermal Shrinkage ◽

Deformation Analysis ◽

Truck Tire ◽

Non Linear ◽

Strain Relationship ◽

Tire Modeling ◽

Total Lagrangian Formulation

This paper presents a method for modeling of pneumatic bias tire axisymmetric deformation. A previously developed model of all-steel radial tire was expanded to include the non-linear stress–strain relationship for textile cord and its thermal shrinkage. Variable cord density and cord angle in the cord-rubber bias tire composite are the major challenges in pneumatic tire modeling. The variabilities result from the tire formation process, and they were taken into account in the model. Mechanical properties of the composite were described using a technique of orthotropic reinforcement overlaying onto isotropic rubber elements, treated as a hyperelastic incompressible material. Due to large displacements, the non-linear problem was solved using total Lagrangian formulation. The model uses MSC.Marc code with implemented user subroutines, allowing for the description of the tire specific properties. The efficiency of the model was verified in the simulation of mounting and inflation of an actual bias truck tire. The shrinkage negligence effect on cord forces and on displacements was examined. A method of investigating the influence of variation of cord angle in green body plies on tire apparent lateral stiffness was proposed. The created model is stabile, ensuring convergent solutions even with large deformations. Inflated tire sizes predicted by the model are consistent with the actual tire sizes. The distinguishing feature of the developed model from other ones is the exact determination of the cord angles in a vulcanized tire and the possibility of simulation with the tire mounting on the rim and with cord thermal shrinkage taken into account. The model may be an effective tool in bias tire design.

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