scholarly journals Probing into frictional contact dynamics by ultrasound and electrical simulations

2014 ◽  
Vol 1 (1) ◽  
pp. 943012
Author(s):  
Changshan Jin ◽  
Mei Jin ◽  
Duc Pham
Keyword(s):  
Frictional Contact ◽  
Contact Dynamics

Large-Scale Parallel Multibody Dynamics With Frictional Contact on the GPU

2008 ◽  
Author(s):  
Dan Negrut ◽  
Alessandro Tasora ◽  
Mihai Anitescu
Keyword(s):  
Large Scale ◽  
Frictional Contact ◽  
Complementarity Problems ◽  
Linear Complementarity Problems ◽  
Rigid Bodies ◽  
Contact Dynamics ◽  
Iteration Algorithm ◽  
Symmetric Convex ◽  
Processing Unit ◽  
Multiple Data

In the context of simulating the frictional contact dynamics of large systems of rigid bodies, this paper reviews a novel method for solving large cone complementarity problems by means of a fixed-point iteration algorithm. The method is an extension of the Gauss-Seidel and Gauss-Jacobi methods with overrelaxation for symmetric convex linear complementarity problems. Convergent under fairly standard assumptions, the method is implemented in a parallel framework by using a single instruction multiple data (SIMD) computation paradigm promoted by the Compute Unified Device Architecture (CUDA) library for graphical processing unit (GPU) programming. The framework is anticipated to become a viable tool for investigating the dynamics of complex systems such as ground vehicles running on sand, powder composites, and granular material flow.

scholarly journals Nonsmooth Thermoelastic Simulations of Blade–Casing Contact Interactions

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Anders Thorin ◽  
Nicolas Guérin ◽  
Mathias Legrand ◽  
Fabrice Thouverez ◽  
Patricio Almeida
Keyword(s):  
Numerical Scheme ◽  
Frictional Contact ◽  
Unilateral Contact ◽  
Contact Dynamics ◽  
Nonsmooth Dynamics ◽  
Integration Scheme ◽  
Strongly Coupled ◽  
Measure Differential Inclusions ◽  
Time Marching ◽  
Stability Issues

In turbomachinery, it is well known that tighter operating clearances improve the efficiency. However, this leads to unwanted potential unilateral and frictional contact occurrences between the rotating (blades) and stationary components (casings) together with attendant thermal excitations. Unilateral contact induces discontinuities in the velocity at impact times, hence the terminology nonsmooth dynamics. Current modeling strategies of rotor–stator interactions are either based on regularizing penalty methods or on explicit time-marching methods derived from Carpenter's forward Lagrange multiplier method. Regularization introduces an artificial time scale in the formulation corresponding to numerical stiffness, which is not desirable. Carpenter's scheme has been successfully applied to turbomachinery industrial models in the sole mechanical framework, but faces serious stability issues when dealing with the additional heat equation. This work overcomes the above issues by using the Moreau–Jean nonsmooth integration scheme within an implicit θ-method. This numerical scheme is based on a mathematically sound description of the contact dynamics by means of measure differential inclusions and enjoys attractive features. The procedure is unconditionally stable opening doors to quick preliminary simulations with time-steps one hundred times larger than with previous algorithms. It can also deal with strongly coupled thermomechanical problems.

A GPU-Based Implementation of a Cone Convex Complementarity Approach for Simulating Rigid Body Dynamics With Frictional Contact

2008 ◽  
Author(s):  
Alessandro Tasora ◽  
Dan Negrut ◽  
Mihai Anitescu
Keyword(s):  
Frictional Contact ◽  
Complementarity Problems ◽  
Linear Complementarity Problems ◽  
Rigid Bodies ◽  
Rigid Body Dynamics ◽  
Contact Dynamics ◽  
Iteration Algorithm ◽  
Symmetric Convex ◽  
Processing Unit ◽  
Multiple Data

In the context of simulating the frictional contact dynamics of large systems of rigid bodies, this paper reviews a novel method for solving large cone complementarity problems by means of a fixed-point iteration algorithm. The method is an extension of the Gauss-Seidel and Gauss-Jacobi methods with over-relaxation for symmetric convex linear complementarity problems. Convergent under fairly standard assumptions, the method is implemented in a parallel framework by using a single instruction multiple data computation paradigm promoted by the Compute Unified Device Architecture library for graphical processing unit programming. The framework supports the analysis of problems with a large number of rigid bodies in contact. Simulation thus becomes a viable tool for investigating the dynamics of complex systems such as ground vehicles running on sand, powder composites, and granular material flow.

scholarly journals Nonsmooth Thermoelastic Simulations of Blade-Casing Contact Interactions

2018 ◽  
Author(s):  
Anders Thorin ◽  
Nicolas Guérin ◽  
Mathias Legrand ◽  
Fabrice Thouverez ◽  
Patricio Almeida
Keyword(s):  
Numerical Scheme ◽  
Frictional Contact ◽  
Unilateral Contact ◽  
Contact Dynamics ◽  
Nonsmooth Dynamics ◽  
Integration Scheme ◽  
Strongly Coupled ◽  
Measure Differential Inclusions ◽  
Time Marching ◽  
Stability Issues

In turbomachinery, it is well known that tighter operating clearances improve the efficiency. However, this leads to unwanted potential unilateral and frictional contact occurrences between the rotating (blades) and stationary components (casings) together with attendant thermal excitations. Unilateral contact induces discontinuities in the velocity at impact times, hence the terminology nonsmooth dynamics. Current modeling strategies of rotor-stator interactions are either based on regularizing penalty methods or on explicit time-marching methods derived from Carpenter’s forward Lagrange multiplier method. Regularization introduces an artificial time scale in the formulation corresponding to numerical stiffness which is not desirable. Carpenter’s scheme has been successfully applied to turbomachinery industrial models in the sole mechanical framework, but faces serious stability issues when dealing with the additional heat equation. This work overcomes the above issues by using the Moreau–Jean nonsmooth integration scheme within an implicit θ-method. This numerical scheme is based on a mathematically sound description of the contact dynamics by means of measure differential inclusions and enjoys attractive features. The procedure is unconditionally stable opening doors to quick preliminary simulations with time-steps one hundred times larger than with previous algorithms. It can also deal with strongly coupled thermomechanical problems.

Assessment of Tongue Position and Laryngeal Height in Two Professional Voice Populations

2020 ◽  
Vol 63 (1) ◽  
pp. 109-124
Author(s):  
Carly Jo Hosbach-Cannon ◽  
Soren Y. Lowell ◽  
Raymond H. Colton ◽  
Richard T. Kelley ◽  
Xue Bao
Keyword(s):  
Vocal Fold ◽  
Vocal Tract ◽  
Current Knowledge ◽  
Acoustic Resonance ◽  
Contact Dynamics ◽  
Voice Disorder ◽  
Music Program ◽  
Tongue Position ◽  
Singer Groups ◽  
Professional Voice

Purpose To advance our current knowledge of singer physiology by using ultrasonography in combination with acoustic measures to compare physiological differences between musical theater (MT) and opera (OP) singers under controlled phonation conditions. Primary objectives addressed in this study were (a) to determine if differences in hyolaryngeal and vocal fold contact dynamics occur between two professional voice populations (MT and OP) during singing tasks and (b) to determine if differences occur between MT and OP singers in oral configuration and associated acoustic resonance during singing tasks. Method Twenty-one singers (10 MT and 11 OP) were included. All participants were currently enrolled in a music program. Experimental procedures consisted of sustained phonation on the vowels /i/ and /ɑ/ during both a low-pitch task and a high-pitch task. Measures of hyolaryngeal elevation, tongue height, and tongue advancement were assessed using ultrasonography. Vocal fold contact dynamics were measured using electroglottography. Simultaneous acoustic recordings were obtained during all ultrasonography procedures for analysis of the first two formant frequencies. Results Significant oral configuration differences, reflected by measures of tongue height and tongue advancement, were seen between groups. Measures of acoustic resonance also showed significant differences between groups during specific tasks. Both singer groups significantly raised their hyoid position when singing high-pitched vowels, but hyoid elevation was not statistically different between groups. Likewise, vocal fold contact dynamics did not significantly differentiate the two singer groups. Conclusions These findings suggest that, under controlled phonation conditions, MT singers alter their oral configuration and achieve differing resultant formants as compared with OP singers. Because singers are at a high risk of developing a voice disorder, understanding how these two groups of singers adjust their vocal tract configuration during their specific singing genre may help to identify risky vocal behavior and provide a basis for prevention of voice disorders.

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