scholarly journals Computation of the Diffraction Transfer Matrix and the Radiation Characteristics in the Open-Source BEM Code NEMOH

2016 ◽  
Author(s):  
Francesc Fàbregas Flavià ◽  
Cameron McNatt ◽  
François Rongère ◽  
Aurélien Babarit ◽  
Alain H. Clément
Keyword(s):  
Open Source ◽  
Transfer Matrix ◽  
Body Wave ◽  
Finite Depth ◽  
Interaction Theory ◽  
Floating Bodies ◽  
Radiation Characteristics ◽  
Speed Up ◽  
Multi Body ◽  
Good Agreement

Until now, widely available boundary element method (BEM) codes did not allow the calculation of two non-conventional hydrodynamic operators, which characterize the way a body diffracts and radiates waves, known as Diffraction Transfer Matrix and Radiation Characteristics respectively. When embedded into the finite-depth interaction theory developed by [1], they drastically speed up the computation of the added mass, damping and excitation force coefficients of a group (“farm”) of floating bodies. This paper presents the implementation of their computation in the open source BEM solver NEMOH using the methodology proposed by [2]. Results for two different geometries, a cylinder and a square box, are presented and compared to an alternative computational approach developed by [3]. A very good agreement between them is found. In addition, the hydrodynamic operators of the cylinder are compared to a semi-analytical solution available in the literature showing a good match. Results obtained using the finite-depth interaction theory are shown for a generic multi-body wave energy converter (WEC) demonstrating how the capabilities added to the BEM software NEMOH can facilitate the numerical modeling of the hydrodynamic interactions in large arrays of bodies.

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.

Asymptotic modal approximation of nonlinear resonant sloshing in a rectangular tank with small fluid depth

2002 ◽  
Vol 470 ◽  
pp. 319-357 ◽  
Author(s):  
ODD M. FALTINSEN ◽  
ALEXANDER N. TIMOKHA
Keyword(s):  
Finite Depth ◽  
Modal System ◽  
Full Account ◽  
Inviscid Flows ◽  
State Response ◽  
Linear Damping ◽  
Convergence Problems ◽  
Run Up ◽  
Fourth Order Polynomial ◽  
Good Agreement

The modal system describing nonlinear sloshing with inviscid flows in a rectangular rigid tank is revised to match both shallow fluid and secondary (internal) resonance asymptotics. The main goal is to examine nonlinear resonant waves for intermediate depth/breadth ratio 0.1 [lsim ] h/l [lsim ] 0.24 forced by surge/pitch excitation with frequency in the vicinity of the lowest natural frequency. The revised modal equations take full account of nonlinearities up to fourth-order polynomial terms in generalized coordinates and h/l and may be treated as a modal Boussinesq-type theory. The system is truncated with a high number of modes and shows good agreement with experimental data by Rognebakke (1998) for transient motions, where previous finite depth modal theories failed. However, difficulties may occur when experiments show significant energy dissipation associated with run-up at the walls and wave breaking. After reviewing published results on damping rates for lower and higher modes, the linear damping terms due to the linear laminar boundary layer near the tank's surface and viscosity in the fluid bulk are incorporated. This improves the simulation of transient motions. The steady-state response agrees well with experiments by Chester & Bones (1968) for shallow water, and Abramson et al. (1974), Olsen & Johnsen (1975) for intermediate fluid depths. When h/l [lsim ] 0.05, convergence problems associated with increasing the dimension of the modal system are reported.

Reduced-Order Time-Domain Simulation of Floating Bodies for Efficient Design Analysis

2015 ◽  
Author(s):  
Hyun Y. Kim ◽  
Stephanie L. Fitzpatrick ◽  
David C. Kring
Keyword(s):  
Memory Function ◽  
Computational Effort ◽  
Impulse Response Functions ◽  
Time Domain Simulation ◽  
Efficient Design ◽  
Floating Bodies ◽  
Order Model ◽  
Reduced Order ◽  
Multi Body ◽  
Multiple Floating Bodies

This paper describes the development and implementation of a reduced-order model to represent the hydrodynamic forces acting on a ship using Impulse-Response Functions (IRF). The approach will be conducted using Aegir, a timedomain seakeeping program that uses an advanced, Non-Rational Uniform B-Spline (NURBS) based, high-order boundary element method. The Cummins equation is slightly modified such that the memory function is decomposed into two terms: one for the impulsive velocity and the other term for the impulsive displacement. The present approach also further develops a method to simulate interactions between multiple floating bodies. The IRF convolutions for the free surface memory effect significantly reduce the computational effort compared to direct simulation. This will be demonstrated for both single and multi-body forward-speed, seakeeping simulations.

scholarly journals An Open-Source Cloud-FPGA Gene Regulatory Accelerator

2021 ◽  
Author(s):  
Lucas Bragança ◽  
Jeronimo Penha ◽  
Michael Canesche ◽  
Dener Ribeiro ◽  
José Augusto M. Nacif ◽  
...  
Keyword(s):  
Open Source ◽  
Gene Regulatory Networks ◽  
High Performance ◽  
Regulatory Networks ◽  
Cloud Services ◽  
On Demand ◽  
Speed Up ◽  
Gene Regulatory ◽  
High Level ◽  
Better Than

FPGAs are suitable to speed up gene regulatory network (GRN) algorithms with high throughput and energy efficiency. In addition, virtualizing FPGA using hardware generators and cloud resources increases the computing ability to achieve on-demand accelerations across multiple users. Recently, Amazon AWS provides high-performance Cloud's FPGAs. This work proposes an open source accelerator generator for Boolean gene regulatory networks. The generator automatically creates all hardware and software pieces from a high-level GRN description. We evaluate the accelerator performance and cost for CPU, GPU, and Cloud FPGA implementations by considering six GRN models proposed in the literature. As a result, the FPGA accelerator is at least 12x faster than the best GPU accelerator. Furthermore, the FPGA reaches the best performance per dollar in cloud services, at least 5x better than the best GPU accelerator.

scholarly journals A Wideband End-Fire Conformal Vivaldi Antenna Array Mounted on a Dielectric Cone

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Zengrui Li ◽  
Xiaole Kang ◽  
Jianxun Su ◽  
Qingxin Guo ◽  
Yaoqing (Lamar) Yang ◽  
...  
Keyword(s):  
Antenna Array ◽  
Antenna Element ◽  
Radiation Characteristics ◽  
Antenna Measurement ◽  
Radiation Beam ◽  
Conformal Antenna ◽  
Single Antenna ◽  
Measurement Results ◽  
Vivaldi Antenna ◽  
Good Agreement

The characteristics of a novel antipodal Vivaldi antenna array mounted on a dielectric cone are presented. By employing antipodal Vivaldi antenna element, the antenna array shows ultrawide bandwidth and end-fire radiation characteristics. Our simulations show that the cone curvature has an obvious influence on the performance of the conformal antenna, in terms of both the bandwidth and the radiation patterns. The thickness and permittivity of the dielectric cone have an effect on the bandwidth of the conformal antenna. Measurement results of both single antenna and conformal antenna array show a good agreement with the simulated results. The measured conformal antenna can achieve a −10 dBS11with bandwidth of 2.2–12 GHz and demonstrate a typical end-fire radiation beam. These findings provide useful guidelines and insights for the design of wideband end-fire antennas mounted on a dielectric cone.

Design of compact frequency agile filter-antenna using reconfigurable ring resonator bandpass filter for future cognitive radios

2018 ◽  
Vol 10 (4) ◽  
pp. 487-496 ◽  
Author(s):  
Hany A. Atallah ◽  
Adel B. Abdel-Rahman ◽  
Kuniaki Yoshitomi ◽  
Ramesh K. Pokharel
Keyword(s):  
Bandpass Filter ◽  
Ring Resonator ◽  
Cognitive Radios ◽  
Ultra Wideband ◽  
Planar Antenna ◽  
Radiation Characteristics ◽  
Total Size ◽  
Frequency Agile ◽  
Narrow Bands ◽  
Good Agreement

AbstractIn this paper, a new miniaturized frequency agile filter-antenna with a wide reconfigurable frequency band is proposed for interweave cognitive radios (CRs). A tunable bandpass filter (BPF) composed of a symmetrical ring resonator is cascaded to the feed line of an ultra-wideband planar antenna. The structure of the proposed ring resonator BPF is simple and compact so that the total size of the proposed filter-antenna is smaller than that of a conventional system made of a separate antenna and BPF. The reconfigurability of the proposed filter-antenna is achieved by changing the operating frequency of the BPF by loading the ring resonator with a single varactor diode at its center. The fabricated prototype has successfully achieved a wide operational bandwidth of 1.43 GHz which covers continuous narrow bands from 4.65 to 6.08 GHz. Moreover, the operating tunable narrow bands have stable radiation characteristics. Good agreement between measurement and simulation results is demonstrated.

Modeling the flow around and the hydrodynamic drag on net meshes using REEF3D

2021 ◽  
pp. 1-21
Author(s):  
Gang Wang ◽  
Tobias Martin ◽  
Liuyi Huang ◽  
Hans Bihs
Keyword(s):  
Open Source ◽  
Empirical Formula ◽  
Hydrodynamic Forces ◽  
Hydrodynamic Drag ◽  
Hydrodynamic Coefficients ◽  
Flume Experiments ◽  
Simulation Accuracy ◽  
Flow Interactions ◽  
Fluid Properties ◽  
Good Agreement

Abstract The hydrodynamics and flow around net meshes has recently drawn more and more attention because it is closely related to the expected forces on aquaculture. In terms of modelling the hydrodynamic forces on nets, Morison or screen force models are ordinarily. However, they mainly rely on empirical, experimental or cylindrical hydrodynamic coefficients, neglecting the flow interactions between adjacent net twines. In this study, the open-source hydrodynamic toolbox REEF3D is adopted to analyze the flow around net meshes and investigate the hydrodynamic drag on the structure. The simulation accuracy is in good agreement with flume experiments and previous research. The results demonstrate that 2 × 2 or 3 × 3 mesh cases are more reliable for studying the flow around net meshes including the flow interactions around adjacent twines. It is further shown that controlling the solidity of the net through changing net bar diameters has different effects on the flow around meshes than controlling it by the twine length. This paper presents a first step in the aim to derive a new empirical formula for the drag coefficients depending on the solidity and fluid properties which is more appropriate for to the physics involved in offshore conditions.

Mobile E-Health Information System

2011 ◽  
Vol 2 (4) ◽  
pp. 1-28
Author(s):  
Flora S. Tsai
Keyword(s):  
Health Care ◽  
Information System ◽  
Open Source ◽  
Health Information ◽  
Smart Card ◽  
Mobile Applications ◽  
Health Information System ◽  
Order Entry ◽  
Medical Centers ◽  
Speed Up

A mobile e-Health information system (MEHIS) aims to speed up the operations of health care in medical centers and hospitals. However, the proper implementation of MEHIS involves integrating many subsystems for MEHIS to be properly executed. A typical MEHIS can consist of many components and subsystems, such as appointments and scheduling; admission, discharge, and transfer (ADT); prescription order entry; dietary planning; and smart card sign-on. This paper describes the development of a MEHIS with open-source Eclipse, using currently available health care standards. The author discusses the issues of building a mobile e-Health information system which can help achieve the goal of ubiquitous and mobile applications for the personalization of e-Health.

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