scholarly journals IFAR liner benchmark challenge #1 – DLR impedance eduction of uniform and axially segmented liners and comparison with NASA results

2021 ◽  
pp. 1475472X2110238
Author(s):  
Friedrich Bake ◽  
Ralf Burgmayer ◽  
Anita Schulz ◽  
Karsten Knobloch ◽  
Lars Enghardt ◽  
...  
Keyword(s):  
Test Facility ◽  
Axial Pressure ◽  
Design Data ◽  
One Dimensional ◽  
Pressure Profiles ◽  
Straightforward Method ◽  
Flow Test ◽  
The One ◽  
German Aerospace ◽  
Good Agreement

This paper presents the contribution from the German Aerospace Center (DLR) to the first liner benchmark challenge under the framework of the International Forum for Aviation Research (IFAR). Therefore, two sets of acoustically damping wall treatments, called ‘liner samples’, have been produced by additive manufacturing based on the design data provided by NASA coordinating this benchmark. These liner samples have been integrated and acoustically characterized in the liner flow test facility DUCT-R at DLR Berlin as well as in the liner flow test facility GFIT at NASA Langley. Besides the dissipation coefficients and the axial pressure profiles, the liner wall impedance was educed by first determining the axial wave numbers and then applying a straightforward method based on the one-dimensional Convected Helmholtz Equation. Finally, the comparison of the liner impedance values to the NASA results show a fairly good agreement.

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

scholarly journals Post-liquefaction reconsolidation of sand

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150745 ◽  
Author(s):  
O. Adamidis ◽  
G. S. P. Madabhushi
Keyword(s):  
Void Ratio ◽  
One Dimensional ◽  
Geotechnical Centrifuge ◽  
Significant Damage ◽  
Pore Water Pressures ◽  
The One ◽  
Crucial Parameter ◽  
Excess Pore ◽  
Good Agreement ◽  
Made In

Loosely packed sand that is saturated with water can liquefy during an earthquake, potentially causing significant damage. Once the shaking is over, the excess pore water pressures that developed during the earthquake gradually dissipate, while the surface of the soil settles, in a process called post-liquefaction reconsolidation. When examining reconsolidation, the soil is typically divided in liquefied and solidified parts, which are modelled separately. The aim of this paper is to show that this fragmentation is not necessary. By assuming that the hydraulic conductivity and the one-dimensional stiffness of liquefied sand have real, positive values, the equation of consolidation can be numerically solved throughout a reconsolidating layer. Predictions made in this manner show good agreement with geotechnical centrifuge experiments. It is shown that the variation of one-dimensional stiffness with effective stress and void ratio is the most crucial parameter in accurately capturing reconsolidation.

A new algorithm for numerical modelling of impurity transport in the frame of statistically homogeneous sharply contrasting media

2019 ◽  
Vol 34 (6) ◽  
pp. 339-351 ◽  
Author(s):  
Petr S. Kondratenko ◽  
Leonid V. Matveev ◽  
Alexander D. Vasiliev
Keyword(s):  
Numerical Modelling ◽  
Contaminant Transport ◽  
Integral Kernel ◽  
Time Intervals ◽  
One Dimensional ◽  
Time Representation ◽  
Impurity Transport ◽  
The One ◽  
Analytical Expressions ◽  
Good Agreement

Abstract A new method is developed to calculate characteristics of contaminant transport (including non-classical regimes) in statistically homogeneous sharply contrasting media. A transport integro-differential equation in the space-time representation is formulated on the basis of the model earlier proposed by one of the authors (L. M.). Analytical expressions for transport characteristics in limiting time intervals in the one-dimensional case are derived. An interpolation form is proposed for the integral kernel of the transport equation. On a basis of this expression, an algorithm is developed for numerical modelling the contaminant transport in statistically homogeneous sharply contrasting media. Trial numerical 1D calculations are performed based on this algorithm. Good agreement was found between the numerical simulation results and the asymptotic analytical expressions.

scholarly journals Study of Unsteady Flow in a Heat Exchanger by the Method of Characteristics

1992 ◽  
Vol 114 (4) ◽  
pp. 459-463 ◽  
Author(s):  
Yuan Mao Huang
Keyword(s):  
Heat Exchanger ◽  
Unsteady Flow ◽  
Transfer Rate ◽  
Method Of Characteristics ◽  
Governing Equations ◽  
One Dimensional ◽  
The Method Of Characteristics ◽  
Improvement Factor ◽  
The One ◽  
Good Agreement

The one-dimensional, unsteady flow in an air-to-air heat exchanger is studied. The governing equations are derived and the method of characteristics with the uniform interval scheme is used in the analysis. The effect of the fin improvement factor on the air temperature in the heat exchanger and the heat transfer rate of the heat exchanger, and air properties in the heat exchanger are analyzed. The numerical results are compared and show good agreement with the available data.

Vibration of an elastic strip with varying curvature

1992 ◽  
Vol 339 (1655) ◽  
pp. 587-625 ◽  
Keyword(s):  
Total Internal Reflection ◽  
Normal Modes ◽  
Mode Shapes ◽  
Elastic Strip ◽  
Interesting Phenomenon ◽  
One Dimensional ◽  
End Conditions ◽  
The One ◽  
Fixed End ◽  
Good Agreement

The vibrational behaviour of an elastic strip with varying curvature is investigated. The case of vibration which is predominantly transverse is considered, and it is shown that when the strip is S-shaped, certain of the normal modes may be confined to the vicinity of the inflection point of the S by a process of total internal reflection from points where the curvature reaches critical values. This confinement can produce modes with extraordinarily low damping factors. Asymptotic analysis is compared with experimental measurements on a strip in several S-shaped configurations, and very good agreement is demonstrated for modal frequencies and shapes. Mathematically, the lower modes turn out to be analogous to those of the one-dimensional harmonic oscillator in quantum mechanics. This mode confinement behaviour occurs for all waveguide branches except the lowest, ‘bending beam ’, branch. In this particular case, wave propagation is insensitive to curvature. However, an interesting phenomenon associated with curvature is found : the successive mode shapes do not display the normal alternation of symmetry and antisymmetry with respect to the centre of the strip. The effect is shown to result from the constraint on axial movement produced by fixed end conditions. For the geometry of the experiments, this constraint raises the frequencies of antisymmetric modes in a characteristic way while leaving the symmetric modes unaltered, thus changing the mode sequence. Theory is developed which gives reasonable quantitive agreement with the observations.

scholarly journals The black hole retention fraction in star clusters

2018 ◽  
Vol 617 ◽  
pp. A69 ◽  
Author(s):  
Václav Pavlík ◽  
Tereza Jeřábková ◽  
Pavel Kroupa ◽  
Holger Baumgardt
Keyword(s):  
Binary Stars ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Star Clusters ◽  
One Dimensional ◽  
Mass Segregation ◽  
The One ◽  
Good Agreement ◽  
Effective Distribution ◽  
Retention Fraction

Context. Recent research has been constraining the retention fraction of black holes (BHs) in globular clusters by comparing the degree of mass segregation with N-body simulations. They are consistent with an upper limit of the retention fraction being 50% or less. Aims. In this work, we focus on direct simulations of the dynamics of BHs in star clusters. We aim to constrain the effective distribution of natal kicks that BHs receive during supernova (SN) explosions and to estimate the BH retention fraction.Methods. We used the collisional N-body code nbody6 to measure the retention fraction of BHs for a given set of parameters, which are: the initial mass of a star cluster, the initial half-mass radius, and σBH, which sets the effective Maxwellian BH velocity kick distribution. We compare these direct N-body models with our analytic estimates and newest observational constraints. Results. The numerical simulations show that for the one-dimensional velocity kick dispersion σBH < 50 km s−1, clusters with radii of 2 pc and that are initially more massive than 5 × 103 M⊙ retain more than 20% of BHs within their half-mass radii. Our simple analytic model yields a number of retained BHs that is in good agreement with the N-body models. Furthermore, the analytic estimates show that ultra-compact dwarf galaxies should have retained more than 80% of their BHs for σBH ≤ 190 km s−1. Although our models do not contain primordial binaries, in the most compact clusters with 103 stars, we have found evidence of delayed SN explosions producing a surplus of BHs compared to the IMF due to dynamically formed binary stars. These cases do not occur in the more populous or expanded clusters.

One-Dimensional Analysis of Energy Storage in Packed Capsules

1992 ◽  
Vol 114 (2) ◽  
pp. 127-130 ◽  
Author(s):  
S. L. Chen
Keyword(s):  
Energy Storage ◽  
Present Model ◽  
Engineering Application ◽  
Thermal Characteristics ◽  
One Dimensional ◽  
The One ◽  
Ice Water ◽  
Change Material ◽  
Porous Medium Model ◽  
Good Agreement

A one-dimensional porous-medium model to determine the thermal characteristics of energy storage for the utilization of phase change material (PCM) in packed capsules has been developed. Comparisons of this theory with experimental data obtained in the previous work show good agreement. Predictions from the present model have also been compared with the lumped capacitance model which assumes temperature uniformity in the packed capsules and in the coolant flow. The results show that the one-dimensional model has the advantage of predicting the temperature distributions of PCM and coolant. For engineering application, a useful correlation of the overall heat-transfer coefficient for ice-water cool storage in packed capsules has also been presented.

A Simplified One-Dimensional Thermal Model for Journal Bearings

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Daquan Liu ◽  
Wen Zhang ◽  
Tiesheng Zheng
Keyword(s):  
Thermal Effects ◽  
Thermal Model ◽  
Reynolds Equation ◽  
Computing Time ◽  
One Dimensional ◽  
Lubricating Film ◽  
Direct Solution Method ◽  
The One ◽  
Generalized Reynolds Equation ◽  
Good Agreement

The variational approach, which is used to solve the Reynolds equation based on the assumption of constant temperature, is extended to the generalized Reynolds equation calculation. The direct solution method of the generalized Reynolds equation is presented, where the pressure of the nodal points and the cavitation zone boundary of the film can be determined without iterating. A simplified one-dimensional thermal model is built on the basis of the original two-dimensional thermal model. The model not only concerns the thermal effects of the lubricating film, but also offers a direct and rapid numerical algorithm for solving lubricating film temperature field. The numerical results of the temperature distributions for the one model are in good agreement with experiment, and less computing time is needed.

The one-dimensional minesweeper game: What are your chances of winning?

2016 ◽  
Vol 27 (11) ◽  
pp. 1650127 ◽  
Author(s):  
M. Rodríguez-Achach ◽  
H. F. Coronel-Brizio ◽  
A. R. Hernández-Montoya ◽  
R. Huerta-Quintanilla ◽  
E. Canto-Lugo
Keyword(s):  
Numerical Simulations ◽  
Critical Density ◽  
Computer Game ◽  
Simple System ◽  
Two Dimensional ◽  
Dimensional Lattice ◽  
One Dimensional ◽  
Np Completeness ◽  
The One ◽  
Good Agreement

Minesweeper is a famous computer game consisting usually in a two-dimensional lattice, where cells can be empty or mined and gamers are required to locate the mines without dying. Even if minesweeper seems to be a very simple system, it has some complex and interesting properties as NP-completeness. In this paper and for the one-dimensional case, given a lattice of n cells and m mines, we calculate the winning probability. By numerical simulations this probability is also estimated. We also find out by mean of these simulations that there exists a critical density of mines that minimize the probability of winning the game. Analytical results and simulations are compared showing a very good agreement.

scholarly journals Computational modeling of classical and ablative Rayleigh–Taylor instabilities

2000 ◽  
Vol 18 (4) ◽  
pp. 583-593 ◽  
Author(s):  
W.M. WOOD-VASEY ◽  
K.S. BUDIL ◽  
B.A. REMINGTON ◽  
S.G. GLENDINNING ◽  
A.M. RUBENCHIK ◽  
...  
Keyword(s):  
Perturbation Analysis ◽  
Radiation Hydrodynamics ◽  
Saturation Model ◽  
Third Order ◽  
One Dimensional ◽  
Hydrodynamic Motion ◽  
Indirect Drive ◽  
The One ◽  
Ablation Front ◽  
Good Agreement

Modeling plus simulations using the one-dimensional Lagrangian radiation-hydrodynamics code HYADES are compared with data from classical and ablative Rayleigh–Taylor experiments conducted on the Nova laser. Comparisons between the experiments and modeling for both the gross hydrodynamic motion and the perturbation evolution are made and show good agreement. A third order perturbation analysis is applied to demonstrate the onset of nonlinearity. A simple, physically intuitive saturation model is used to describe the growth further into the nonlinear regime. Finally, we present the first comparison of the Betti ablation front theory with indirect-drive RT data and obtain good agreement.

Sign in / Sign up

Export Citation Format

Share Document