Investigation of Stator Induced Unsteadiness on a Centrifugal Impeller Using a Mach-Independent Non-Linear Harmonic Method

2015 ◽  
Author(s):  
Benoît Tartinville ◽  
Charles Hirsch
Keyword(s):  
Experimental Data ◽  
Computing Time ◽  
Computational Effort ◽  
Centrifugal Impeller ◽  
Flow Solver ◽  
Wide Range ◽  
Non Linear ◽  
Unsteady Simulation ◽  
Number Flow ◽  
Short Time

The objective of this paper is to numerically investigate the unsteadiness generated by a bladed diffuser on an upstream centrifugal impeller. The Non-Linear Harmonic (NLH for short) time-spectral method has been retained here. The major advantage of such a method is that it requires much less computational effort than a standard unsteady simulation. In order to further reduce the computing time, the NLH method has been extended to low speed flows by using a preconditioning technic. Therefore, the NLH method can be accurately applied to any Mach number flow and even to purely incompressible fluids. This extension of the flow solver has been validated on a wide range of simple test cases at various reduce frequencies. Solutions have been compared to purely unsteady approach and also to experimental data. In a second step, the NLH method has been applied to a centrifugal impeller and its downstream diffuser. Numerical results have been analyzed and compared to the available experimental data showing the significant influence of the downstream diffuser on the impeller pressure load.

scholarly journals Short-time diffusion of charge-stabilized colloidal particles: generic features

2010 ◽  
Vol 43 (5) ◽  
pp. 970-980 ◽  
Author(s):  
Marco Heinen ◽  
Peter Holmqvist ◽  
Adolfo J. Banchio ◽  
Gerhard Nägele
Keyword(s):  
Experimental Data ◽  
Colloidal Particles ◽  
Stokesian Dynamics ◽  
Self Diffusion ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Dynamics Simulations ◽  
Short Time ◽  
Hydrodynamic Function

Analytical theory and Stokesian dynamics simulations are used in conjunction with dynamic light scattering to investigate the role of hydrodynamic interactions in short-time diffusion in suspensions of charge-stabilized colloidal particles. The particles are modeled as solvent-impermeable charged spheres, repelling each otherviaa screened Coulomb potential. Numerical results for self-diffusion and sedimentation coefficients, as well as hydrodynamic and short-time diffusion functions, are compared with experimental data for a wide range of volume fractions. The theoretical predictions for the generic behavior of short-time properties obtained from this model are shown to be in full accord with experimental data. In addition, the effects of microion kinetics, nonzero particle porosity and residual attractive forces on the form of the hydrodynamic function are estimated. This serves to rule out possible causes for the strikingly small hydrodynamic function values determined in certain synchrotron radiation experiments.

Implementation and adaptation of non-linear process mathematical modeling applied to vehicles and heavy equipment exploitation

2020 ◽  
Vol 10 (5) ◽  
pp. 522-534
Author(s):  
Vladimir S. Vlasov ◽  
Keyword(s):  
Mathematical Modeling ◽  
Computational Complexity ◽  
Linear Process ◽  
Data Handling ◽  
Modeling Methods ◽  
Heavy Equipment ◽  
Wide Range ◽  
Non Linear ◽  
Short Time ◽  
Work Done

The modern mathematical modeling methods provides a comprehensive toolkit for handling a most of data, on another hand more complicated tasks requires logic with higher computational complexity, which means a considerable influence at a Big Data handling. The most suitable method selection is a search of a compromise solution with the necessary accuracy and admissible computational complexity. Moreover, methods are to be adapted to the certain solution aimed at providing the greatest match of the modeling results to process class. This article discusses the selecting and adaptation of mathematical modeling methods to vehicles and heavy equipment MRO costs, which are a result of two different processes: regular maintenance and accidental repair that may be delayed due to the situation reasons. The work done not only allows to make a longterm (thirty years) forecast using accumulated during a short time (three years) statistics, but also provides a toolkit to handle a wide range of data including non-linear and stochastic processes.

A Rational Study of the Origin and Generality of Anti-Enthalpy–Entropy Compensation (AEEC) Phenomenon

2018 ◽  
Vol 232 (3) ◽  
pp. 373-391
Author(s):  
Animesh Pan ◽  
Bithika Mandal ◽  
Animesh K. Rakshit ◽  
Satya P. Moulik
Keyword(s):  
Experimental Data ◽  
Chemical Processes ◽  
Energy Window ◽  
Close Attention ◽  
Solid Materials ◽  
Physical Chemical ◽  
Wide Range ◽  
Entropy Of Formation ◽  
Non Linear ◽  
Enthalpy And Entropy

AbstractIn addition to enthalpy–entropy compensation (EEC), anti-enthalpy–entropy compensation (AEEC) phenomenon is also found in literature. The reports on the latter are limited, and analyses and justifications are so far unclear. Herein we present demonstration on the nature and possibility of the AEEC phenomenon. Although literature reports so far have mostly shown linear AEEC, we have found both linear and non-linear dependences. The non-linearity we consider arises from large “free energy window” (FEW) like EEC, recently presented and discussed. Attempts have been made to rationalize the observations in terms of solvation–desolvation phenomenon of the involved processes anticipated in previous studies. We have found that enthalpy and entropy of formation of gaseous and solid materials may also exhibit AEEC, it can be thus classified as a global phenomenon. In addition to AEEC, the phenomenon of no-enthalpy–entropy compensation (NEEC) is also reported. Thus, the phenomena EEC, AEEC and NEEC are thermodynamic puzzles that require close attention and analysis. With the help of wide range of physical chemical processes, an elaborate general understanding of the linear and non-linear AEEC phenomena has been attempted. The experimental data herein used are collected from literature reports, new measurements were not done. A variety of examples have supported possible generality of AEEC.

LIQUIDUS THERMO-BAROMETER FOR THE MODELING OF MAGNETITE — MELT EQUILIBRIUM

2018 ◽  
pp. 71-80
Author(s):  
N. S. Aryaeva ◽  
E. V. Koptev-Dvornikov ◽  
D. A. Bychkov
Keyword(s):  
Experimental Data ◽  
Liquidus Temperature ◽  
Vertical Structure ◽  
Maximum Error ◽  
Silicate Melt ◽  
System Of Equations ◽  
Wide Range ◽  
Basaltic Melts ◽  
Multidimensional Statistics

A system of equations of thermobarometer for magnetite-silicate melt equilibrium was obtained by method of multidimensional statistics of 93 experimental data of a magnetite solubility in basaltic melts. Equations reproduce experimental data in a wide range of basalt compositions, temperatures and pressures with small errors. Verification of thermobarometers showed the maximum error in liquidus temperature reproducing does not exceed ±7 °C. The level of cumulative magnetite appearance in the vertical structure of Tsypringa, Kivakka, Burakovsky intrusions predicted with errors from ±10 to ±50 m.

scholarly journals Influence of the Porosity of Polymer Foams on the Performances of Capacitive Flexible Pressure Sensors

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 1968 ◽  
Author(s):  
Sylvie Bilent ◽  
Thi Hong Nhung Dinh ◽  
Emile Martincic ◽  
Pierre-Yves Joubert
Keyword(s):  
Experimental Data ◽  
Linear Model ◽  
Dielectric Material ◽  
Pressure Sensors ◽  
Volume Ratio ◽  
Measurement Range ◽  
Polymer Foams ◽  
First Order ◽  
Non Linear ◽  
Flexible Pressure Sensors

This paper reports on the study of microporous polydimethylsiloxane (PDMS) foams as a highly deformable dielectric material used in the composition of flexible capacitive pressure sensors dedicated to wearable use. A fabrication process allowing the porosity of the foams to be adjusted was proposed and the fabricated foams were characterized. Then, elementary capacitive pressure sensors (15 × 15 mm2 square shaped electrodes) were elaborated with fabricated foams (5 mm or 10 mm thick) and were electromechanically characterized. Since the sensor responses under load are strongly non-linear, a behavioral non-linear model (first order exponential) was proposed, adjusted to the experimental data, and used to objectively estimate the sensor performances in terms of sensitivity and measurement range. The main conclusions of this study are that the porosity of the PDMS foams can be adjusted through the sugar:PDMS volume ratio and the size of sugar crystals used to fabricate the foams. Additionally, the porosity of the foams significantly modified the sensor performances. Indeed, compared to bulk PDMS sensors of the same size, the sensitivity of porous PDMS sensors could be multiplied by a factor up to 100 (the sensitivity is 0.14 %.kPa−1 for a bulk PDMS sensor and up to 13.7 %.kPa−1 for a porous PDMS sensor of the same dimensions), while the measurement range was reduced from a factor of 2 to 3 (from 594 kPa for a bulk PDMS sensor down to between 255 and 177 kPa for a PDMS foam sensor of the same dimensions, according to the porosity). This study opens the way to the design and fabrication of wearable flexible pressure sensors with adjustable performances through the control of the porosity of the fabricated PDMS foams.

scholarly journals Experimental analysis and ANN prediction on performances of finned oval-tube heat exchanger under different air inlet angles with limited experimental data

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 968-980
Author(s):  
Xueping Du ◽  
Zhijie Chen ◽  
Qi Meng ◽  
Yang Song
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Correlation Equation ◽  
Tube Heat Exchanger ◽  
Flow Friction ◽  
Air Inlet ◽  
Comparison Results ◽  
Wide Range ◽  
Oval Tube

Abstract A high accuracy of experimental correlations on the heat transfer and flow friction is always expected to calculate the unknown cases according to the limited experimental data from a heat exchanger experiment. However, certain errors will occur during the data processing by the traditional methods to obtain the experimental correlations for the heat transfer and friction. A dimensionless experimental correlation equation including angles is proposed to make the correlation have a wide range of applicability. Then, the artificial neural networks (ANNs) are used to predict the heat transfer and flow friction performances of a finned oval-tube heat exchanger under four different air inlet angles with limited experimental data. The comparison results of ANN prediction with experimental correlations show that the errors from the ANN prediction are smaller than those from the classical correlations. The data of the four air inlet angles fitted separately have higher precisions than those fitted together. It is demonstrated that the ANN approach is more useful than experimental correlations to predict the heat transfer and flow resistance characteristics for unknown cases of heat exchangers. The results can provide theoretical support for the application of the ANN used in the finned oval-tube heat exchanger performance prediction.

scholarly journals Effects of local isolates of Beauveria bassiana (Balsamo) Vuillemin on the two-spotted spider mite, Tetranychus urticae (Koch) (Acari: Tetranychidae)

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Cenk Yucel
Keyword(s):  
Tetranychus Urticae ◽  
Beauveria Bassiana ◽  
Spider Mite ◽  
Lethal Effect ◽  
Probit Analysis ◽  
Plant Feeding ◽  
Wide Range ◽  
Two Spotted Spider Mite ◽  
Short Time ◽  
Tetranychus Urticae Koch

Abstract Background The two-spotted spider mite, Tetranychus urticae (Koch) (Acari: Tetranychidae), is a widely distributed plant-feeding pest that causes significant yield losses in a wide range of crops. Newly developed or improved environmentally friendly biocontrol agents serve as an alternative to traditional pest control tools. Experiment of the effects of 2 local fungal isolates of Beauveria bassiana (BGF14 and BCA32) was carried out against T. urticae under laboratory conditions. Results Both tested isolates had lethal effect in a short time after application, and this effect increased as time progressed. BGF14 and BCA32 isolates caused T. urticae mortality rates ranging from 25.88 to 61.92 and 32.36 to 62.03% when applied at the concentrations between 1×105 and 1×108 conidia/ml, respectively. According to the Probit analysis performed on the effect of fungi on T. urticae adults, the LC50 values of BGF14 and BCA32 isolates on the 7th day after inoculation were 2.6×106 and 6.3×104 conidia/ml, respectively, and the LT50 values for both fungi applied at a concentration of 108 conidia/ml were 2.14 and 2.23 days, respectively. Conclusions The 2 isolates of B. bassiana (BGF14 and BCA32) had the potentials to suppress T. urticae population and can be recommended as promising biocontrol agent candidates for control of T. urticae.

scholarly journals Modelling the Inflation and Elastic Instabilities of Rubber-Like Spherical and Cylindrical Shells Using a New Generalised Neo-Hookean Strain Energy Function

2021 ◽  
Author(s):  
Afshin Anssari-Benam ◽  
Andrea Bucchi ◽  
Giuseppe Saccomandi
Keyword(s):  
Experimental Data ◽  
Energy Function ◽  
Limit Point ◽  
Strain Energy ◽  
Cylindrical Shells ◽  
Strain Energy Function ◽  
Model Parameters ◽  
Wide Range ◽  
Cylindrical Tubes ◽  
Gent Model

AbstractThe application of a newly proposed generalised neo-Hookean strain energy function to the inflation of incompressible rubber-like spherical and cylindrical shells is demonstrated in this paper. The pressure ($P$ P ) – inflation ($\lambda $ λ or $v$ v ) relationships are derived and presented for four shells: thin- and thick-walled spherical balloons, and thin- and thick-walled cylindrical tubes. Characteristics of the inflation curves predicted by the model for the four considered shells are analysed and the critical values of the model parameters for exhibiting the limit-point instability are established. The application of the model to extant experimental datasets procured from studies across 19th to 21st century will be demonstrated, showing favourable agreement between the model and the experimental data. The capability of the model to capture the two characteristic instability phenomena in the inflation of rubber-like materials, namely the limit-point and inflation-jump instabilities, will be made evident from both the theoretical analysis and curve-fitting approaches presented in this study. A comparison with the predictions of the Gent model for the considered data is also demonstrated and is shown that our presented model provides improved fits. Given the simplicity of the model, its ability to fit a wide range of experimental data and capture both limit-point and inflation-jump instabilities, we propose the application of our model to the inflation of rubber-like materials.

scholarly journals Optimal Perturbations of an Oceanic Vortex Lens

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 63 ◽  
Author(s):  
Thomas Meunier ◽  
Claire Ménesguen ◽  
Xavier Carton ◽  
Sylvie Le Gentil ◽  
Richard Schopp
Keyword(s):  
Normal Mode ◽  
Growth Rates ◽  
Time Interval ◽  
Time Intervals ◽  
Horizontal Structure ◽  
Azimuthal Wave ◽  
Wave Numbers ◽  
Non Linear ◽  
Long Time ◽  
Short Time

The stability properties of a vortex lens are studied in the quasi geostrophic (QG) framework using the generalized stability theory. Optimal perturbations are obtained using a tangent linear QG model and its adjoint. Their fine-scale spatial structures are studied in details. Growth rates of optimal perturbations are shown to be extremely sensitive to the time interval of optimization: The most unstable perturbations are found for time intervals of about 3 days, while the growth rates continuously decrease towards the most unstable normal mode, which is reached after about 170 days. The horizontal structure of the optimal perturbations consists of an intense counter-shear spiralling. It is also extremely sensitive to time interval: for short time intervals, the optimal perturbations are made of a broad spectrum of high azimuthal wave numbers. As the time interval increases, only low azimuthal wave numbers are found. The vertical structures of optimal perturbations exhibit strong layering associated with high vertical wave numbers whatever the time interval. However, the latter parameter plays an important role in the width of the vertical spectrum of the perturbation: short time interval perturbations have a narrow vertical spectrum while long time interval perturbations show a broad range of vertical scales. Optimal perturbations were set as initial perturbations of the vortex lens in a fully non linear QG model. It appears that for short time intervals, the perturbations decay after an initial transient growth, while for longer time intervals, the optimal perturbation keeps on growing, quickly leading to a non-linear regime or exciting lower azimuthal modes, consistent with normal mode instability. Very long time intervals simply behave like the most unstable normal mode. The possible impact of optimal perturbations on layering is also discussed.

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