scholarly journals Directionality and Crest Length Statistics of Steep Waves in Open Ocean Waters

2005 ◽  
Vol 22 (3) ◽  
pp. 272-281 ◽  
Author(s):  
Nicholas Scott ◽  
Tetsu Hara ◽  
Paul A. Hwang ◽  
Edward J. Walsh
Keyword(s):  
Ocean Waves ◽  
Open Ocean ◽  
One Dimensional ◽  
Analysis Methodology ◽  
Wave Slope ◽  
The Mean ◽  
Steep Waves ◽  
The One ◽  
Crest Length ◽  
Steep Wave

Abstract A new wavelet analysis methodology is applied to open ocean wave height data from the Southern Ocean Waves Experiment (1992) and from a field experiment conducted at Duck, North Carolina, in 1997 with the aim of estimating the directionality and crest lengths of steep waves. The crest directionality statistic shows that most of the steep wave crests are normal to the direction of the mean wind. This is inconsistent with the Fourier wavenumber spectrum that shows a broad bimodal directional spreading at high wavenumbers. The crest length statistics demonstrate that the wave field is dominated by short-crested waves with small crest length/wavelength ratios. The one-dimensional steep wave statistic obtained from the integration of the directional (two dimensional) steep wave statistic is consistent with the one-dimensional steep wave statistic obtained from the one-dimensional analysis at high wave slope thresholds.

scholarly journals Observations of Steep Wave Statistics in Open Ocean Waters

2005 ◽  
Vol 22 (3) ◽  
pp. 258-271 ◽  
Author(s):  
Nicholas Scott ◽  
Tetsu Hara ◽  
Edward J. Walsh ◽  
Paul A. Hwang
Keyword(s):  
Wind Speed ◽  
Ocean Waves ◽  
Open Ocean ◽  
Breaking Wave ◽  
Wave Statistics ◽  
Analysis Methodology ◽  
Wide Range ◽  
Wave Slope ◽  
Steep Waves ◽  
Steep Wave

Abstract A new wavelet analysis methodology is proposed to estimate the statistics of steep waves. The method is applied to open ocean wave height data from the Southern Ocean Waves Experiment (1992) and from a field experiment conducted at Duck, North Carolina (1997). Results show that high wave slope crests appear over a wide range of wavenumbers, with a large amount being much shorter than the dominant wave. At low wave slope thresholds, all wave fields have roughly the same amount of wave crests regardless of wind forcing. The steep wave statistic decays exponentially with the square of the wave slope threshold, with a decay rate that is larger for the low wind cases than the high wind cases. Comparison of the steep wave statistic with independent measurements of the breaking wave statistic suggests a breaking wave slope threshold of about 0.12. The steep wave statistic does not scale with the cube of the wind speed, suggesting that other factors besides the wind speed also affect its level. Comparison of the steep wave statistic to the saturation spectrum reveals a reasonable correlation at moderate wave slope thresholds.

scholarly journals Assessment of CFD turbulence models for free surface flow simulation and 1-D modelling for water level calculations over a broad-crested weir floodway

Water SA ◽  
2019 ◽  
Vol 45 (3 July) ◽  
Author(s):  
Ahmed M Helmi
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Water Level ◽  
Dimensional Analysis ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Cfd Simulations ◽  
One Dimensional ◽  
The Mean ◽  
The One

Floodways, where a road embankment is permitted to be overtopped by flood water, are usually designed as broad-crested weirs. Determination of the water level above the floodway is crucial and related to road safety. Hydraulic performance of floodways can be assessed numerically using 1-D modelling or 3-D simulation using computational fluid dynamics (CFD) packages. Turbulence modelling is one of the key elements in CFD simulations. A wide variety of turbulence models are utilized in CFD packages; in order to identify the most relevant turbulence model for the case in question, 96 3-D CFD simulations were conducted using Flow-3D package, for 24 broad-crested weir configurations selected based on experimental data from a previous study. Four turbulence models (one-equation, k-ε, RNG k-ε, and k-ω) ere examined for each configuration. The volume of fluid (VOF) algorithm was adopted for free water surface determination. In addition, 24 1-D simulations using HEC-RAS-1-D were conducted for comparison with CFD results and experimental data. Validation of the simulated water free surface profiles versus the experimental measurements was carried out by the evaluation of the mean absolute error, the mean relative error percentage, and the root mean square error. It was concluded that the minimum error in simulating the full upstream to downstream free surface profile is achieved by using one-equation turbulence model with mixing length equal to 7% of the smallest domain dimension. Nevertheless, for the broad-crested weir upstream section, no significant difference in accuracy was found between all turbulence models and the one-dimensional analysis results, due to the low turbulence intensity at this part. For engineering design purposes, in which the water level is the main concern at the location of the flood way, the one-dimensional analysis has sufficient accuracy to determine the water level.

Microscale temperature and velocity spectra in the atmospheric boundary layer

1977 ◽  
Vol 83 (3) ◽  
pp. 547-567 ◽  
Author(s):  
R. M. Williams ◽  
C. A. Paulson
Keyword(s):  
Reynolds Number ◽  
Prandtl Number ◽  
Temperature Fluctuations ◽  
Inertial Subrange ◽  
Velocity Fluctuations ◽  
One Dimensional ◽  
Temperature Spectra ◽  
The Mean ◽  
Velocity Spectra ◽  
The One

High-frequency fluctuations in temperature and velocity were measured at a height of 2 m above a harvested, nearly level field of rye grass. Conditions were both stably and unstably stratified. Reynolds numbers ranged from 370000 to 740000. Measurements of velocity were made with a hot-wire anemometer and measurements of temperature with a platinum resistance element which had a diameter of 0[sdot ]5 μm and a length of 1 mm. Thirteen runs ranging in length from 78 to 238 s were analysed.Spectra of velocity fluctuations are consistent with previously reported universal forms. Spectra of temperature, however, exhibit an increase in slope with increasing wavenumber as the maximum in the one-dimensional dissipation spectrum is approached. The peak of the one-dimensional dissipation spectrum for temperature fluctuations occurs at a higher wavenumber than that of simultaneous spectra of the dissipation of velocity fluctuations. It is suggested that the change in slope of the temperature spectra and the dissimilarity between temperature and velocity spectra may be due to spatial dissimilarity in the dissipation of temperature and velocity fluctuations. The temperature spectra are compared with a theoretical prediction for fluids with large Prandtl number, due to Batchelor (1959). Even though air has a Prandtl number of 0[sdot ]7, the observations are in qualitative agreement with predictions of the theory. The non-dimensional wavenumber at which the increase in slope occurs is about 0[sdot ]02, in good agreement with observations in the ocean reported by Grantet al. (1968).For the two runs for which the stratification was stable, the normalized spectra of the temperature derivative fall on average slightly below the mean of the spectra of the remaining runs in the range in which the slope is approximately one-third. Hence the Reynolds number may not have always been sufficiently high to satisfy completely the conditions for an inertial subrange.Universal inertial-subrange constants were directly evaluated from one-dimensional dissipation spectra and found to be 0[sdot ]54 and 1[sdot ]00 for velocity and temperature, respectively. The constant for velocity is consistent with previously reported values, while the value for temperature differs from some of the previous direct estimates but is only 20% greater than the mean of the indirect estimates. This discrepancy may be explained by the neglect in the indirect estimates of the divergence terms in the conservation equation for the variance of temperature fluctuations. There is weak evidence that the one-dimensional constant, and hence the temperature spectra, may depend upon the turbulence Reynolds number, which varied from 1200 to 4300 in the observations reported.

scholarly journals Tomographic retrievals of ozone with the OMPS Limb Profiler: algorithm description and preliminary results

2018 ◽  
Vol 11 (4) ◽  
pp. 2375-2393 ◽  
Author(s):  
Daniel J. Zawada ◽  
Landon A. Rieger ◽  
Adam E. Bourassa ◽  
Douglas A. Degenstein
Keyword(s):  
Polar Vortex ◽  
Retrieval Algorithm ◽  
Vertical Profiles ◽  
Two Dimensional ◽  
One Dimensional ◽  
Preliminary Results ◽  
Horizontal Gradients ◽  
The Mean ◽  
The One

Abstract. Measurements of limb-scattered sunlight from the Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) can be used to obtain vertical profiles of ozone in the stratosphere. In this paper we describe a two-dimensional, or tomographic, retrieval algorithm for OMPS-LP where variations are retrieved simultaneously in altitude and the along-orbital-track dimension. The algorithm has been applied to measurements from the center slit for the full OMPS-LP mission to create the publicly available University of Saskatchewan (USask) OMPS-LP 2D v1.0.2 dataset. Tropical ozone anomalies are compared with measurements from the Microwave Limb Sounder (MLS), where differences are less than 5 % of the mean ozone value for the majority of the stratosphere. Examples of near-coincident measurements with MLS are also shown, and agreement at the 5 % level is observed for the majority of the stratosphere. Both simulated retrievals and coincident comparisons with MLS are shown at the edge of the polar vortex, comparing the results to a traditional one-dimensional retrieval. The one-dimensional retrieval is shown to consistently overestimate the amount of ozone in areas of large horizontal gradients relative to both MLS and the two-dimensional retrieval.

scholarly journals Existence and nonexistence of entire solutions to the logistic differential equation

2003 ◽  
Vol 2003 (17) ◽  
pp. 995-1003 ◽  
Author(s):  
Marius Ghergu ◽  
Vicentiu Radulescu
Keyword(s):  
Blow Up ◽  
Entire Solutions ◽  
One Dimensional ◽  
Nonexistence Result ◽  
Nonnegative Solutions ◽  
Existence And Nonexistence ◽  
Logistic Problem ◽  
Whole Space ◽  
The Mean ◽  
The One

We consider the one-dimensional logistic problem(rαA(|u′|)u′)′=rαp(r)f(u)on(0,∞),u(0)>0,u′(0)=0, whereαis a positive constant andAis a continuous function such that the mappingtA(|t|)is increasing on(0,∞). The framework includes the case wherefandpare continuous and positive on(0,∞),f(0)=0, andfis nondecreasing. Our first purpose is to establish a general nonexistence result for this problem. Then we consider the case of solutions that blow up at infinity and we prove several existence and nonexistence results depending on the growth ofpandA. As a consequence, we deduce that the mean curvature inequality problem on the whole space does not have nonnegative solutions, excepting the trivial one.

scholarly journals Research on Intelligent Compaction Technology of Subgrade Based on Regression Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Ziyi Hou ◽  
Xiao Dang ◽  
Yezhen Yuan ◽  
Bo Tian ◽  
Sili Li
Keyword(s):  
Resilient Modulus ◽  
Single Point ◽  
Mean Value ◽  
Test Results ◽  
Intelligent Compaction ◽  
One Dimensional ◽  
Remote Monitoring System ◽  
The Mean ◽  
The One ◽  
Compaction Degree

A remote monitoring system with the intelligent compaction index CMV as the core is designed and developed to address the shortcomings of traditional subgrade compaction quality evaluation methods. Based on the actual project, the correlation between the CMV and conventional compaction indexes of compaction degree K and dynamic resilient modulus E is investigated by applying the one-dimensional linear regression equation for three types of subgrade fillers, clayey gravel, pulverized gravel, and soil-rock mixed fill, and the scheme of fitting CMV to the mean value of conventional indexes is adopted, which is compared with the scheme of fitting CMV to the single point of conventional indexes in the existing specification. The test results show that the correlation between the CMV and conventional indexes of clayey gravel and pulverized gravel is much stronger than that of soil-rock mixed subgrades, and the correlation coefficient can be significantly improved by fitting CMV to the mean of conventional indexes compared with single-point fitting, which can be considered as a new method for intelligent rolling correlation verification.

scholarly journals Tomographic retrievals of ozone with the OMPS Limb Profiler: algorithm description and preliminary results

2017 ◽  
Author(s):  
Daniel J. Zawada ◽  
Landon A. Rieger ◽  
Adam E. Bourassa ◽  
Douglas A. Degenstein
Keyword(s):  
Polar Vortex ◽  
Retrieval Algorithm ◽  
Vertical Profiles ◽  
Two Dimensional ◽  
One Dimensional ◽  
Preliminary Results ◽  
Horizontal Gradients ◽  
The Mean ◽  
The One

Abstract. Measurements of limb scattered sunlight from the Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) can be used to obtain vertical profiles of ozone in the stratosphere. In this paper we describe a two-dimensional, or tomographic, retrieval algorithm for OMPS-LP where variations are retrieved simultaneously in altitude and the along orbital track dimension. The algorithm has been applied to measurements from the center slit for the full OMPS-LP mission to create the publicly available USask OMPS-LP 2D v1.0.2 dataset. Tropical ozone anomalies are compared with measurements from the Microwave Limb Sounder (MLS) where differences are less than 5 % of the mean ozone value for the majority of the stratosphere. Examples of near coincident measurements with MLS are also shown, and agreement at the 5 % level is observed for the majority of the stratosphere. Both simulated retrievals and coincident comparisons with MLS are shown at the edge of the polar vortex, comparing the results to a traditional one-dimensional retrieval. The one-dimensional retrieval is shown to consistently overestimate the amount of ozone in areas of large horizontal gradients relative to both MLS and the two-dimensional retrieval.

Forward and Backward Running Waves in the Arteries: Analysis Using the Method of Characteristics

1990 ◽  
Vol 112 (3) ◽  
pp. 322-326 ◽  
Author(s):  
K. H. Parker ◽  
C. J. H. Jones
Keyword(s):  
Transient Flow ◽  
Impedance Analysis ◽  
Time Domain Analysis ◽  
Mean Velocity ◽  
One Dimensional ◽  
Acceleration And Deceleration ◽  
The Mean ◽  
The One ◽  
Made In

The one-dimensional equations of flow in the elastic arteries are hyperbolic and admit nonlinear, wavelike solutions for the mean velocity, U, and the pressure, P. Neglecting dissipation, the solutions can be written in terms of wavelets defined as differences of the Riemann invariants across characteristics. This analysis shows that the product, dUdP, is positive definite for forward running wavelets and negative definite for backward running wavelets allowing the determination of the net magnitude and direction of propagating wavelets from pressure and velocity measured at a point in the artery. With the linearizing assumption that intersecting wavelets are additive, the forward and backward running wavelets can be separately calculated. This analysis, applied to measurements made in the ascending aorta of man, shows that forward running wavelets dominate during both the acceleration and deceleration phases of blood flow in the aorta. The forward and backward running waves calculated using the linearized analysis are similar to the results of an impedance analysis of the data. Unlike the impedance analysis, however, this is a time domain analysis which can be applied to nonperiodic or transient flow.

Phase transition in one-dimensional random walk with partially reflecting boundaries

1985 ◽  
Vol 17 (03) ◽  
pp. 594-606 ◽  
Author(s):  
Ora E. Percus
Keyword(s):  
Random Walk ◽  
Transition Probability ◽  
Dimensional Lattice ◽  
One Dimensional ◽  
Boundary Case ◽  
Reflecting Boundaries ◽  
The Mean ◽  
The One ◽  
The Relationship ◽  
Asymptotic Forms

We consider an asymmetric random walk, with one or two boundaries, on a one-dimensional lattice. At the boundaries, the walker is either absorbed (with probability 1–ρ) or reflects back to the system (with probability p). The probability distribution (Pn (m)) of being at position m after n steps is obtained, as well as the mean number of steps before absorption. In the one-boundary case, several qualitatively different asymptotic forms of P n(m) result, depending on the relationship between transition probability and the reflection probability.

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