scholarly journals Suppressing the pressure-source instability in modeling deep-draft vessels with low under-keel clearance in FUNWAVE-TVD

2021 ◽  
Author(s):  
Matt Malej ◽  
Fengyan Shi
Keyword(s):  
High Frequency ◽  
Wave Model ◽  
Technical Note ◽  
Shock Capturing ◽  
Army Corps ◽  
Far Field ◽  
Pressure Source ◽  
Houston Ship Channel ◽  
Friction Method ◽  
Large Container

This Coastal and Hydraulics Engineering Technical Note (CHETN) documents the development through verification and validation of three instability-suppressing mechanisms in FUNWAVE-TVD, a Boussinesq-type numerical wave model, when modeling deep-draft vessels with a low under-keel clearance (UKC). Many large commercial ports and channels (e.g., Houston Ship Channel, Galveston, US Army Corps of Engineers [USACE]) are traveled and affected by tens of thousands of commercial vessel passages per year. In a series of recent projects undertaken for the Galveston District (USACE), it was discovered that when deep-draft vessels are modeled using pressure-source mechanisms, they can suffer from model instabilities when low UKC is employed (e.g., vessel draft of 12 m¹ in a channel of 15 m or less of depth), rendering a simulation unstable and obsolete. As an increasingly large number of deep-draft vessels are put into service, this problem is becoming more severe. This presents an operational challenge when modeling large container-type vessels in busy shipping channels, as these often will come as close as 1 m to the bottom of the channel, or even touch the bottom. This behavior would subsequently exhibit a numerical discontinuity in a given model and could severely limit the sample size of modeled vessels. This CHETN outlines a robust approach to suppressing such instability without compromising the integrity of the far-field vessel wave/wake solution. The three methods developed in this study aim to suppress high-frequency spikes generated nearfield of a vessel. They are a shock-capturing method, a friction method, and a viscosity method, respectively. The tests show that the combined shock-capturing and friction method is the most effective method to suppress the local high-frequency noises, while not affecting the far-field solution. A strong test, in which the target draft is larger than the channel depth, shows that there are no high-frequency noises generated in the case of ship squat as long as the shock-capturing method is used.

A dynamic model for far-field acceleration

1982 ◽  
Vol 72 (4) ◽  
pp. 1049-1068
Author(s):  
John Boatwright
Keyword(s):  
Stress Drop ◽  
High Frequency ◽  
Dynamic Stress ◽  
The Body ◽  
Body Waves ◽  
Far Field ◽  
Rupture Velocity ◽  
Frequency Level ◽  
Average Change ◽  
Dynamic Stress Drop

abstract A model for the far-field acceleration radiated by an incoherent rupture is constructed by combining Madariaga's (1977) theory for the high-frequency radiation from crack models of faulting with a simple statistical source model. By extending Madariaga's results to acceleration pulses with finite durations, the peak acceleration of a pulse radiated by a single stop or start of a crack tip is shown to depend on the dynamic stress drop of the subevent, the total change in rupture velocity, and the ratio of the subevent radius to the acceleration pulse width. An incoherent rupture is approximated by a sample from a self-similar distribution of coherent subevents. Assuming the subevents fit together without overlapping, the high-frequency level of the acceleration spectra depends linearly on the rms dynamic stress drop, the average change in rupture velocity, and the square root of the overall rupture area. The high-frequency level is independent, to first order, of the rupture complexity. Following Hanks (1979), simple approximations are derived for the relation between the rms dynamic stress drop and the rms acceleration, averaged over the pulse duration. This relation necessarily depends on the shape of the body-wave spectra. The body waves radiated by 10 small earthquakes near Monticello Dam, South Carolina, are analyzed to test these results. The average change of rupture velocity of Δv = 0.8β associated with the radiation of the acceleration pulses is estimated by comparing the rms acceleration contained in the P waves to that in the S waves. The rms dynamic stress drops of the 10 events, estimated from the rms accelerations, range from 0.4 to 1.9 bars and are strongly correlated with estimates of the apparent stress.

Implementation of the Ffowcs Williams-Hawkings Equation: Predicting the Far Field Noise From Airfoils While Using Boundary Layer Tripping Mechanisms

2018 ◽  
Author(s):  
Andrew L. Bodling ◽  
Anupam Sharma
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
Permeable Surface ◽  
Far Field ◽  
Trailing Edge ◽  
Extraneous Noise ◽  
Field Noise ◽  
High Frequency Waves

A study was done to investigate how boundary layer tripping mechanisms can affect the ability of a permeable surface FW-H solver to predict the far field noise emanating from an airfoil trailing edge. The far field noise in a baseline airfoil as well as the baseline airfoil fitted with fin let fences was analyzed. Two numerical boundary layer tripping mechanisms were implemented. The results illustrated the importance of choosing a permeable integration surface that is outside any high frequency waves emanating from the trip region. The results also illustrated the importance of choosing a boundary layer tripping mechanism that minimizes any extraneous noise so that an integration surface can be taken close to the airfoil.

scholarly journals Emulation of Radius-to-Fix legs in Departure Routes via Fly-By Turns

2019 ◽  
Vol 11 (4) ◽  
pp. 93-106
Author(s):  
Carlos GONZAGA-LOPEZ ◽  
Florian Michael BUCHMANN ◽  
Henrik EKSTRAND ◽  
Andreas LINNÉR ◽  
Philipp Daniel SCHAAD
Keyword(s):  
High Frequency ◽  
Weather Conditions ◽  
Technical Note ◽  
Optimal Management ◽  
Traffic Flows ◽  
Bank Angle ◽  
Constant Radius ◽  
First Results ◽  
Preliminary Study ◽  
Aircraft Type

The results of a preliminary study on the emulation of radius-to-fix legs in turning departures by means of standard track-to-fix legs are presented in this technical note. While radius-to-fix equipage rates keep gradually increasing over time, a traffic mix containing aircraft with and without this navigation capability can impede an optimal management of the traffic flows whenever precise and repeatable curved flight paths are required. After test-flying various sequences of track-to-fix segments to emulate a reference constant-radius arc in a typical departure environment, the deviations to the desired flight path and the flyability aspects were assessed. The first results for a given scenario and aircraft type show an adequate path conformance for a navigation specification RNAV/RNP 1 within a certain range of aircraft performances and weather conditions. However, the reduced predictability of the roll steering when transitioning between track-to-fix segments and the high frequency in the oscillations of the bank angle may pose a problem to flight crews and passengers, respectively.

Suppression Approaches of Far-Field Radiated Emission Using Common-Mode Inductor

2021 ◽  
Vol 1 (2) ◽  
pp. 1-5
Author(s):  
Mengzi Li ◽  
◽  
Shishan Wang ◽  
Jian Guo
Keyword(s):  
High Frequency ◽  
Reference Value ◽  
Power Converter ◽  
Practical Significance ◽  
Far Field ◽  
Common Mode ◽  
Suppression Method ◽  
Switching Mode ◽  
Emc Design ◽  
Radiated Emission

The miniaturization and integration of Switching Mode Power Supply (SMPS) is increasing, making it more complicated to analyze and predict its far-field radiated emission, and, consequently, studying the suppression method of far-field radiated emission of SMPS is of practical significance and engineering value. In this paper, a high-frequency SMPS is selected as the research object, whose far-field radiated emission is measured under the condition of three typical suppression methods. The experimental results verified the effectiveness of common-mode inductor and are of reference value for EMC design of power converter. Keywords: SMPS; EMC; Far-field Radiated Emission;

scholarly journals FRF WAVE TEST BED AND BATHYMETRY INVERSION

2017 ◽  
pp. 22 ◽  
Author(s):  
Jane McKee Smith ◽  
Spicer Bak ◽  
Tyler Hesser ◽  
Mary A. Bryant ◽  
Chris Massey
Keyword(s):  
Numerical Models ◽  
Field Research ◽  
Wave Model ◽  
Army Corps ◽  
Army Corps Of Engineers ◽  
Test Bed ◽  
Inversion Algorithm ◽  
Us Army ◽  
Spectral Wave Model ◽  
Limited Application

An automated Coastal Model Test Bed has been built for the US Army Corps of Engineers Field Research Facility to evaluate coastal numerical models. In October of 2015, the test bed was expanded during a multi-investigator experiment, called BathyDuck, to evaluate two bathymetry sources: traditional survey data and bathymetry generated through the cBathy inversion algorithm using Argus video measurements. Comparisons were made between simulations using the spectral wave model STWAVE with half-hourly cBathy bathymetry and the more temporally sparse surveyed bathymetry. The simulation results using cBathy bathymetry were relatively close to those using the surveyed bathymetry. The largest differences were at the shallowest gauges within 250 m of the coast, where wave model normalized root-mean-square was approximately twice are large using the cBathy bathymetry. The nearshore errors using the cBathy input were greatest during events with wave height greater than 2 m. For this limited application, the Argus cBathy algorithm proved to be a suitable bathymetry input for nearshore wave modeling. cBathy bathymetry was easily incorporated into the modeling test bed and had the advantage of being updated on approximately the same temporal scale as the other model input conditions. cBathy has great potential for modeling applications where traditional surveys are sparse (seasonal or yearly).

scholarly journals Technical note: A two-sided affine power scaling relationship to represent the concentration–discharge relationship

2020 ◽  
Vol 24 (4) ◽  
pp. 1823-1830 ◽  
Author(s):  
José Manuel Tunqui Neira ◽  
Vazken Andréassian ◽  
Gaëlle Tallec ◽  
Jean-Marie Mouchel
Keyword(s):  
Electrical Conductivity ◽  
Time Series ◽  
Power Law ◽  
High Frequency ◽  
Technical Note ◽  
Mathematical Representation ◽  
Power Scaling ◽  
Calibration And Validation ◽  
Numerical Criterion ◽  
Scaling Relationship

Abstract. This technical note deals with the mathematical representation of concentration–discharge relationships. We propose a two-sided affine power scaling relationship (2S-APS) as an alternative to the classic one-sided power scaling relationship (commonly known as “power law”). We also discuss the identification of the parameters of the proposed relationship, using an appropriate numerical criterion. The application of 2S-APS to the high-frequency chemical time series of the Orgeval-ORACLE observatory is presented here (in calibration and validation mode): it yields better results for several solutes and for electrical conductivity in comparison with the power law relationship.

scholarly journals Inclusion of landslide tsunamis generation into a depth integrated wave model

2010 ◽  
Vol 10 (11) ◽  
pp. 2259-2268 ◽  
Author(s):  
C. Cecioni ◽  
G. Bellotti
Keyword(s):  
Field Equation ◽  
Small Amplitude ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Wave Model ◽  
Dispersive Equations ◽  
Far Field ◽  
Mild Slope Equation ◽  
Calculation Results ◽  
Propagation Of Waves

Abstract. A numerical model based on the mild slope equation, suitable to reproduce the propagation of small amplitude tsunamis in the far field, is extended to reproduce the generation and the propagation of waves generated by landslides. The wave generation is modeled through a forcing term included in the field equation, which reproduces the effects of the movement of a submerged landslide on the fluid. The measurements of three dimensional laboratory experiments, which simulate tsunamis generated by landslide sliding along the flank of a conical island, are compared with the theoretical calculation results. The present approach is also compared with the similar method of Tinti et al. (2006) used for the generation of these waves in depth integrated model, and the different behavior when using frequency-dispersive and non-dispersive equations is highlighted.

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