scholarly journals Porosity Effects on the Dispersion Relation of Water Waves through Dense Array of Vertical Cylinders

2020 ◽  
Vol 8 (12) ◽  
pp. 960
Author(s):  
Joffrey Jamain ◽  
Julien Touboul ◽  
Vincent Rey ◽  
Kostas Belibassakis
Keyword(s):  
Dispersion Relation ◽  
Water Waves ◽  
Environmental Flows ◽  
Numerical Study ◽  
Wave Number ◽  
Coastal Vegetation ◽  
The Finite Element Method ◽  
Dense Array ◽  
Wide Range ◽  
Vertical Cylinders

There is growing interest for water-wave flows through arrangements of cylinders with application to the performance of porous marine structures and environmental flows in coastal vegetation. For specific few cases experimental data are available in the literature concerning the modification of the dispersion equation for waves through a dense array of vertical cylinders. This paper presents a numerical study of the porosity effects on the dispersion relation of water waves through such configurations. To this aim, the sloshing problem in a tank full of vertical cylinders intersecting the free surface is studied using the finite element method, and the influence of the porosity on the wave number is quantified. On the basis of numerical results, a new modification of a dispersion relation for porous medium is suggested based on a wide range of collected data. Moreover, the domain of validity of this new dispersion relation is examined considering the number of cylinders and the extrapolation to the infinite medium.

A Nonhydrostatic Two-Layer Staggered Scheme for Transient Waves due to Anti-Symmetric Seabed Thrust

2017 ◽  
Vol 11 (01) ◽  
pp. 1740002 ◽  
Author(s):  
S. R. Pudjaprasetya ◽  
I. Magdalena ◽  
S. S. Tjandra
Keyword(s):  
Dispersion Relation ◽  
Water Depth ◽  
Numerical Scheme ◽  
Vertical Direction ◽  
Wave Number ◽  
Transient Waves ◽  
Wide Range ◽  
Staggered Scheme ◽  
Wave Trains ◽  
2004 Tsunami

The development of transient waves generated by bottom motion is studied numerically in this work. A nonhydrostatic numerical scheme, based on solving the two-dimensional Euler equations using two-layer approximation for the vertical direction, is implemented. The dispersion relation of this scheme is shown to agree with the analytical dispersion relation over a wide range of [Formula: see text], where [Formula: see text] denotes the wave number and [Formula: see text] the characteristic water depth. To ensure that a good balance between nonlinearity and dispersion is accommodated by the scheme, the propagation of a solitary wave (undisturbed in shape) was simulated. Our next focus was on the simulation of transient waves generated by bottom motion. After conducting a benchmark test against Hammack’s experimental results for downward bottom motion, an anti-symmetric bottom thrust was considered. The resulting transient waves developed different behavior depending on the water depth. Finally, to mimic the December 2004 tsunami, a seabed motion was generated over Aceh bathymetry. This simulation showed that a package of wave trains developed and propagated towards the Aceh coast, and exhibited inter alia the feature of shoreline withdrawal often observed.

scholarly journals Mean drift forces on arrays of bodies due to incident long waves

1987 ◽  
Vol 185 ◽  
pp. 469-482 ◽  
Author(s):  
P. McIver
Keyword(s):  
Water Waves ◽  
Low Frequency ◽  
Frequency Limit ◽  
Numerical Work ◽  
Single Body ◽  
Force Ratio ◽  
Wide Range ◽  
The Mean ◽  
Drift Force ◽  
Vertical Cylinders

The scattering of long water waves by an array of bodies is investigated using the method of matched asymptotic expansions. Two particular geometries are considered: a group of vertical cylinders extending throughout the depth and a group of floating hemispheres. From these solutions, the low-frequency limit of the ratio of the mean drift force on a group of N bodies to that on a single body is calculated. For a wide range of circumstances this drift-force ratio is N2, which is in agreement with previous numerical work. Further drift-force enhancement is possible for certain configurations of vertical cylinders.

scholarly journals A non-hydrostatic two-layer staggered scheme for transient waves due to anti-symmetric seabed thrust

2018 ◽  
Author(s):  
Sri Redjeki Pudjaprasetya ◽  
Ikha Magdalena ◽  
Sugih Sudharma Tjandra
Keyword(s):  
Dispersion Relation ◽  
Numerical Scheme ◽  
Vertical Direction ◽  
Wave Number ◽  
Transient Waves ◽  
Good Balance ◽  
Wide Range ◽  
Staggered Scheme ◽  
Wave Trains ◽  
2004 Tsunami

The development of transient waves generated by bottom motion is studied numericallyin this work. A non-hydrostatic numerical scheme, based on solving the two dimensionalEuler equations using two-layer approximation for the vertical direction, is implemented.The dispersion relation of this scheme is shown to agree with the analytical dispersionrelation over a wide range of kd0, where k denotes the wave number and d0 the characteristic water depth. To ensure that a good balance between non-linearity and dispersion is accommodated by the scheme, the propagation of a solitary wave (undisturbed in shape) was simulated. Our next focus was on the simulation of transient waves generatedby bottom motion. After conducting a benchmark test against Hammack's experimentalresults for downward bottom motion, an anti-symmetric bottom thrust was considered.The resulting transient waves developed different behavior depending on the water depth.Finally, to mimic the December 2004 tsunami, a seabed motion was generated over Acehbathymetry. This simulation showed that a package of wave trains developed and propa-gated towards the Aceh coast, and exhibited inter alia the feature of shoreline withdrawaloften observed.

Damping of Regular Waves in Model Ice

2020 ◽  
Author(s):  
Moritz C. N. Hartmann ◽  
R. U. Franz von Bock und Polach ◽  
Marco Klein
Keyword(s):  
Dispersion Relation ◽  
Water Waves ◽  
Wave Amplitude ◽  
Wave Length ◽  
Open Water ◽  
Angular Frequency ◽  
Wave Number ◽  
Regular Waves ◽  
Incident Waves ◽  
The Waves

Abstract Wave characteristics change significantly when the waves propagate in a solid ice field. The damping of the incident waves due to the presence of the ice sheet has a significant impact on the modification of wave propagation and dispersion. In this study the interaction of waves with solid ice are investigated by means of model tests. The objective of the study is to measure wave and ice characteristics and analyze the data regarding wave damping and the change of wave parameters in model ice. The experiments were performed in the ice tank of the Hamburg ship model basin (HSVA) with a set of regular waves with varying wave number and steepness. The surface elevation of the waves is recorded by acoustic and motion capturing measurement devices. By comparing the measurements of the incident open water waves with the waves in ice, the change in terms of wave amplitude and dispersion due to the presence of ice is analyzed. It is shown that once the waves travels through the ice the angular frequency remains unchanged while the wave amplitude exponentially decays, with an increasing decay coefficient at smaller wave length. Furthermore, the dispersion relation in ice, represented by the measured angular frequency and wave number, is consistent with the theoretical dispersion relation.

Numerical Study of Film Thickness Averaging in Compressible Lubricating Films Incurring Stationary Surface Roughness

1990 ◽  
Vol 112 (2) ◽  
pp. 230-237 ◽  
Author(s):  
Y. Mitsuya ◽  
T. Hayashi
Keyword(s):  
Film Thickness ◽  
Numerical Study ◽  
Wave Number ◽  
Numerical Comparison ◽  
Load Carrying Capacity ◽  
Roughness Effects ◽  
Individual Unit ◽  
Wide Range ◽  
Load Carrying ◽  
Compressibility Effects

The compressibility effects of lubricating films incurring a roughness on film thickness averaging were studied numerically with a focus on the physical interpretation of the roughness effects. A numerical comparison between load-carrying capacities resulting from rough film thickness and from averaged film thickness are presented for a wide range of bearing numbers up to 107. It is found that currently indicated particular features such as the appearance of the maximum or minimum load-carrying capacity can be induced from the superimposition of local compressibility effects (LCEs) caused by individual unit roughness on compressibility effects owing to averaged film thickness. The most noticeable difference between the case of small LCEs and that of saturated LCEs is that the roughness phase results in a minimal effect with the increasing wave number for the former, while it creates a dominant effect for the latter. The results confirm that the same averaging method as that for incompressible films can be applied for small LCEs, and that Greengard’s method is applicable for nearly saturated LCEs. It should be noted that the averaged film thickness can be determined physically for small LCE regions, while it is defined mathematically for nearly saturated LCE regions.

scholarly journals Self-similarity of wind-driven seas

2005 ◽  
Vol 12 (6) ◽  
pp. 891-945 ◽  
Author(s):  
S. I. Badulin ◽  
A. N. Pushkarev ◽  
D. Resio ◽  
V. E. Zakharov
Keyword(s):  
Water Waves ◽  
Numerical Solutions ◽  
Wind Wave ◽  
Numerical Study ◽  
Wave Age ◽  
Self Similarity ◽  
Limited Growth ◽  
Wide Range ◽  
Wind Input ◽  
Self Similar

Abstract. The results of theoretical and numerical study of the Hasselmann kinetic equation for deep water waves in presence of wind input and dissipation are presented. The guideline of the study: nonlinear transfer is the dominating mechanism of wind-wave evolution. In other words, the most important features of wind-driven sea could be understood in a framework of conservative Hasselmann equation while forcing and dissipation determine parameters of a solution of the conservative equation. The conservative Hasselmann equation has a rich family of self-similar solutions for duration-limited and fetch-limited wind-wave growth. These solutions are closely related to classic stationary and homogeneous weak-turbulent Kolmogorov spectra and can be considered as non-stationary and non-homogeneous generalizations of these spectra. It is shown that experimental parameterizations of wind-wave spectra (e.g. JONSWAP spectrum) that imply self-similarity give a solid basis for comparison with theoretical predictions. In particular, the self-similarity analysis predicts correctly the dependence of mean wave energy and mean frequency on wave age Cp / U10. This comparison is detailed in the extensive numerical study of duration-limited growth of wind waves. The study is based on algorithm suggested by Webb (1978) that was first realized as an operating code by Resio and Perrie (1989, 1991). This code is now updated: the new version is up to one order faster than the previous one. The new stable and reliable code makes possible to perform massive numerical simulation of the Hasselmann equation with different models of wind input and dissipation. As a result, a strong tendency of numerical solutions to self-similar behavior is shown for rather wide range of wave generation and dissipation conditions. We found very good quantitative coincidence of these solutions with available results on duration-limited growth, as well as with experimental parametrization of fetch-limited spectra JONSWAP in terms of wind-wave age Cp / U10.

scholarly journals Interaction of Very Large Scale Motion of Coherent Structures with Sediment Particle Exposure

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 248
Author(s):  
Sencer Yücesan ◽  
Daniel Wildt ◽  
Philipp Gmeiner ◽  
Johannes Schobesberger ◽  
Christoph Hauer ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Large Scale ◽  
Numerical Study ◽  
Local Maximum ◽  
Wave Number ◽  
Exposure Level ◽  
Sediment Particle ◽  
High Wave Number ◽  
Large Scale Motion ◽  
Scale Motion

A systematic variation of the exposure level of a spherical particle in an array of multiple spheres in a high Reynolds number turbulent open-channel flow regime was investigated while using the Large Eddy Simulation method. Our numerical study analysed hydrodynamic conditions of a sediment particle based on three different channel configurations, from full exposure to zero exposure level. Premultiplied spectrum analysis revealed that the effect of very-large-scale motion of coherent structures on the lift force on a fully exposed particle resulted in a bi-modal distribution with a weak low wave number and a local maximum of a high wave number. Lower exposure levels were found to exhibit a uni-modal distribution.

scholarly journals Strain Sensor via Wood Anomalies in 2D Dielectric Array

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1022
Author(s):  
Rashid G. Bikbaev ◽  
Ivan V. Timofeev ◽  
Vasiliy F. Shabanov
Keyword(s):  
Higher Plants ◽  
Numerical Study ◽  
Reciprocal Lattice ◽  
Strain Sensing ◽  
Photonic Materials ◽  
Sensing Applications ◽  
Wide Range ◽  
Sensor Structure ◽  
Optical Behavior ◽  
Chlorophyll Absorption

Optical sensing is one of many promising applications for all-dielectric photonic materials. Herein, we present an analytical and numerical study on the strain-responsive spectral properties of a bioinspired sensor. The sensor structure contains a two-dimensional periodic array of dielectric nanodisks to mimic the optical behavior of grana lamellae inside chloroplasts. To accumulate a noticeable response, we exploit the collective optical mode in grana ensemble. In higher plants, such a mode appears as Wood’s anomaly near the chlorophyll absorption line to control the photosynthesis rate. The resonance is shown persistent against moderate biological disorder and deformation. Under the stretching or compression of a symmetric structure, the mode splits into a couple of polarized modes. The frequency difference is accurately detected. It depends on the stretch coefficient almost linearly providing easy calibration of the strain-sensing device. The sensitivity of the considered structure remains at 5 nm/% in a wide range of strain. The influence of the stretching coefficient on the length of the reciprocal lattice vectors, as well as on the angle between them, is taken into account. This adaptive phenomenon is suggested for sensing applications in biomimetic optical nanomaterials.

Numerical study of geometric morphing wings of the 1303 UCAV

2021 ◽  
pp. 1-17
Author(s):  
B. Nugroho ◽  
J. Brett ◽  
B.T. Bleckly ◽  
R.C. Chin
Keyword(s):  
Flight Control ◽  
Numerical Study ◽  
Aerodynamic Characteristics ◽  
Morphing Wing ◽  
Rolling Moment ◽  
Wide Range ◽  
Morphing Wings ◽  
Wing Geometry ◽  
Lift And Drag ◽  
Wing Morphing

ABSTRACT Unmanned Combat Aerial Vehicles (UCAVs) are believed by many to be the future of aerial strike/reconnaissance capability. This belief led to the design of the UCAV 1303 by Boeing Phantom Works and the US Airforce Lab in the late 1990s. Because UCAV 1303 is expected to take on a wide range of mission roles that are risky for human pilots, it needs to be highly adaptable. Geometric morphing can provide such adaptability and allow the UCAV 1303 to optimise its physical feature mid-flight to increase the lift-to-drag ratio, manoeuvrability, cruise distance, flight control, etc. This capability is extremely beneficial since it will enable the UCAV to reconcile conflicting mission requirements (e.g. loiter and dash within the same mission). In this study, we conduct several modifications to the wing geometry of UCAV 1303 via Computational Fluid Dynamics (CFD) to analyse its aerodynamic characteristics produced by a range of different wing geometric morphs. Here we look into two specific geometric morphing wings: linear twists on one of the wings and linear twists at both wings (wash-in and washout). A baseline CFD of the UCAV 1303 without any wing morphing is validated against published wind tunnel data, before proceeding to simulate morphing wing configurations. The results show that geometric morphing wing influences the UCAV-1303 aerodynamic characteristics significantly, improving the coefficient of lift and drag, pitching moment and rolling moment.

scholarly journals A Computational Study on the Role of Parameters for Identification of Thyroid Nodules by Infrared Images (and Comparison with Real Data)

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4459
Author(s):  
José R. González ◽  
Charbel Damião ◽  
Maira Moran ◽  
Cristina A. Pantaleão ◽  
Rubens A. Cruz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thyroid Nodules ◽  
Numerical Study ◽  
Computational Study ◽  
Internal Heat ◽  
Heat Transfer Process ◽  
The Body ◽  
Physical Parameters ◽  
Infrared Sensors ◽  
Wide Range

According to experts and medical literature, healthy thyroids and thyroids containing benign nodules tend to be less inflamed and less active than those with malignant nodules. It seems to be a consensus that malignant nodules have more blood veins and more blood circulation. This may be related to the maintenance of the nodule’s heat at a higher level compared with neighboring tissues. If the internal heat modifies the skin radiation, then it could be detected by infrared sensors. The goal of this work is the investigation of the factors that allow this detection, and the possible relation with any pattern referent to nodule malignancy. We aim to consider a wide range of factors, so a great number of numerical simulations of the heat transfer in the region under analysis, based on the Finite Element method, are performed to study the influence of each nodule and patient characteristics on the infrared sensor acquisition. To do so, the protocol for infrared thyroid examination used in our university’s hospital is simulated in the numerical study. This protocol presents two phases. In the first one, the body under observation is in steady state. In the second one, it is submitted to thermal stress (transient state). Both are simulated in order to verify if it is possible (by infrared sensors) to identify different behavior referent to malignant nodules. Moreover, when the simulation indicates possible important aspects, patients with and without similar characteristics are examined to confirm such influences. The results show that the tissues between skin and thyroid, as well as the nodule size, have an influence on superficial temperatures. Other thermal parameters of thyroid nodules show little influence on surface infrared emissions, for instance, those related to the vascularization of the nodule. All details of the physical parameters used in the simulations, characteristics of the real nodules and thermal examinations are publicly available, allowing these simulations to be compared with other types of heat transfer solutions and infrared examination protocols. Among the main contributions of this work, we highlight the simulation of the possible range of parameters, and definition of the simulation approach for mapping the used infrared protocol, promoting the investigation of a possible relation between the heat transfer process and the data obtained by infrared acquisitions.

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