scholarly journals Determination of the separation points for the flow around blunt bodies: experimental and numerical studies

2021 ◽  
Vol 664 (1) ◽  
pp. 012015
Author(s):  
N O Tănase ◽  
Ş M Simionescu ◽  
M M Păduroiu ◽  
C Bălan
Keyword(s):  
Numerical Studies ◽  
Blunt Bodies

scholarly journals EXPERIMENTAL AND NUMERICAL STUDIES OF PRESSURE AND GAP LENGTH EFFECTS ON ENERGY DEPOSITION IN SPARK DISCHARGE

2021 ◽  
pp. 92-97
Author(s):  
K.V. Korytchenko ◽  
I.S. Varshamova ◽  
D.V. Meshkov ◽  
D.P. Dubinin ◽  
R.I. Kovalenko ◽  
...  
Keyword(s):  
Energy Input ◽  
Energy Deposition ◽  
Initial Pressure ◽  
Numerical Studies ◽  
Voltage Probe ◽  
Spark Channel ◽  
Discharge Gap ◽  
Total Discharge ◽  
Channel Development

A study of the influence of the discharge gap length and the initial gas pressure on the energy deposition into the discharge channel was done. The study was conducted at the same total discharge energy. It is experimentally shown that the connection of the voltage probe to the discharge circuit significantly affects the discharge current. The determination of the energy deposited into the spark channel is based on the results of numerical simulation of the spark channel development. Experimentally measured discharge currents at different pressures and the gap length were used as initial data for the calculation. Based on the obtained results, it is determined which of the factors (the initial pressure or the gap length) has the strongest influence on the energy input into the spark channel.

scholarly journals Rechnerische Bestimmung der lonenbeweglichkeit in Ziegelstein unter Zuhilfenahme von Ergebnissen aus nichtstationären Diffusionsversuchen / Numerical Determination of Ion Diffusivity in Bricks Based on Non-Stationary Diffusion Experiments

1999 ◽  
Vol 5 (1) ◽  
pp. 3-14
Author(s):  
H. Sadouki ◽  
A. Buchwald ◽  
F.H. Wittmann ◽  
Ch. Kaps
Keyword(s):  
Diffusion Coefficients ◽  
Inverse Analysis ◽  
Water Saturation ◽  
Optimization Technique ◽  
Ion Concentration ◽  
Ion Diffusion ◽  
Ion Migration ◽  
Numerical Studies ◽  
Stationary Diffusion

Abstract Ion concentration profiles in sandwich-brick specimens have been determined experimentally at different degrees of water saturation. Based on the experimental data, ion diffusion coefficients were determined by inverse analysis. The diffusion equation served as a basis for an optimization technique. It has been shown that the ion diffusivity in bricks decreases markedly as the moisture content decreases. The interface between two adjacent bricks slows down the ion migration at low water content in particular. It is planed to investigate the interface between mortar and bricks in further experimental and numerical studies.

Damage Assessment of Reinforced Concrete Beams by Complex Ratios of Transfer Functions

2006 ◽  
Vol 321-323 ◽  
pp. 357-362 ◽  
Author(s):  
Chih Peng Yu ◽  
Chia Chi Cheng ◽  
Chih Hung Chiang
Keyword(s):  
Reinforced Concrete ◽  
Transfer Functions ◽  
Concrete Beams ◽  
Field Tests ◽  
High Sensitivity ◽  
Reinforced Concrete Beams ◽  
Numerical Studies ◽  
Complex Ratio ◽  
Local Defects

In this paper, a newly developed approach for the determination of characteristics associated with local defects of a beam is briefly introduced. From the numerical studies carried out in this study, the complex ratio between two transfer functions associated with an imaginary intact beam and a damaged beam can provide such information. Based on the numerical studies, the rules in determining degree of damages and locations of defects were first briefly outlined. These idealized rules were then verified by experimental data obtained from dynamic tests of realistic specimens of simply-supported reinforced concrete beams. The preliminary results indicate that the defined ratio of transfer functions can potentially serve as an exaggerated indication for the degree of changes in certain modal responses. Thus, the proposed ratio of transfer functions can be used to assist system identification, while the nature of high sensitivity also restricts its direct application to certain complicated data associated with field tests. A variety of test setup for both receivers and impact sources were studied and the test results appear to agree with designated conditions of the specimens.

Numerical and theoretical study of the shock stand-off distance in non-equilibrium flows

2008 ◽  
Vol 607 ◽  
pp. 167-197 ◽  
Author(s):  
N. BELOUAGGADIA ◽  
H. OLIVIER ◽  
R. BRUN
Keyword(s):  
Vibrational Energy ◽  
Physical Modelling ◽  
Relaxation Processes ◽  
Blunt Bodies ◽  
Explicit Formulae ◽  
Insight Into ◽  
Simple Ideal ◽  
Good Agreement ◽  
Non Equilibrium

A theoretical model based on a quasi-one-dimensional formulation is developed which allows determination of the shock stand-off distance at the stagnation point of blunt bodies in hypersonic non-equilibrium flows. Despite the simple ideal dissociating gas model implemented in the theoretical approach, it gives insight into the main physics governing the shock stand-off problem. More detailed and precise data are obtained by a numerical simulation where vibrational and chemical relaxation processes as well as their interactions are taken into account. The physical modelling of these processes is based on a kinetic approach and on a generalized Chapman–Enskog method of solving the Boltzmann equation. Explicit formulae for rate constants and vibrational energy consumption are derived and incorporated into the general conservation equations. Good agreement between theoretical, numerical and experimental results is achieved which ensures a reliable and mutual validation of the different methods.

scholarly journals Determination of the Electromagnetic Field on the Surface of the Beam Splitter of Laser Interferometer by Measuring the Displacements of Control Object Surfaces

2018 ◽  
Vol 8 (11) ◽  
pp. 2137 ◽  
Author(s):  
Igor Miroshnichenko ◽  
Ivan Parinov ◽  
Shun-Hsyung Chang ◽  
Hung-Yu Wang
Keyword(s):  
Numerical Simulation ◽  
Electromagnetic Field ◽  
Beam Splitter ◽  
Laser Interferometer ◽  
Control Object ◽  
Numerical Studies ◽  
Simulation Results ◽  
Optical Circuits ◽  
Theoretical Results

The paper describes in detail the governing relationships for the electromagnetic field on the surface of the laser beam splitter of a laser interferometer. These expressions are intended for numerical simulation of measuring the displacements of control object surfaces by using a laser interferometer. We consider the cases of perpendicular and parallel polarizations of the radiation source. Moreover, the most relevant particular cases of constructing optical circuits of the interferometer in question are treated. The presented theoretical results have been used in numerical studies of the functional characteristics of promising contactless optical means of measuring displacements. The use of the described results has improved the quality and informativeness of the numerical simulation results of the measurement process of displacements by a laser interferometer.

Online identification of torsionally coupled shear buildings using virtual synchronization method

2020 ◽  
pp. 107754632093203
Author(s):  
Pedram Ghaderi ◽  
Fereidoun Amini ◽  
Mohammad Emamian
Keyword(s):  
Design Parameters ◽  
Virtual Model ◽  
Unknown Parameters ◽  
Online Identification ◽  
Synchronization Method ◽  
Numerical Studies ◽  
Modeling Uncertainties ◽  
Design Scenario ◽  
Shear Buildings

In this study, the virtual synchronization method is developed for online identification of parameters in torsionally coupled shear buildings. In this method, first, a virtual model of the building is made and excited simultaneously with the actual building. Then, a proper virtual controller is designed, which forces the virtual model to follow the dynamic response of the actual building by converging the unknown parameters to the actual values. A major difficulty of the virtual synchronization method originates from the determination of its design parameters, which greatly affects the final performance. The main contribution of this study is an optimum scenario for defining the design parameters of the virtual synchronization method to maintain desirable accuracy and convergence speed. Provided numerical studies show that the proposed design scenario makes the virtual synchronization method a competitor to the other well-known methods. Also, the effect of building height and excitation on the performance of the virtual synchronization method is studied. Besides, robustness against measurement noise and modeling uncertainties are investigated.

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