scholarly journals Analytical Models of Velocity, Reynolds Stress and Turbulence Intensity in Ice-Covered Channels

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1107
Author(s):  
Jiao Zhang ◽  
Wen Wang ◽  
Zhanbin Li ◽  
Qian Li ◽  
Ya Zhong ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Reynolds Stress ◽  
Turbulence Intensity ◽  
Vertical Profile ◽  
Open Channel ◽  
Longitudinal Velocity ◽  
Analytical Formula ◽  
Ice Cover ◽  
Analytical Models ◽  
The Vertical Distribution

Ice cover in an open channel can influence the flow structure, such as the flow velocity, Reynolds stress and turbulence intensity. This study analyzes the vertical distributions of velocity, Reynolds stress and turbulence intensity in fully and partially ice-covered channels by theoretical methods and laboratory experiments. According to the experimental data, the vertical profile of longitudinal velocities follows an approximately symmetry form. Different from the open channel flow, the maximum value of longitudinal velocity occurs near the middle of the water depth, which is close to the channel bed with a smoother boundary roughness compared to the ice cover. The measured Reynolds stress has a linear distribution along the vertical axis, and the vertical distribution of measured turbulence intensity follows an exponential law. Theoretically, a two-power-law function is presented to obtain the analytical formula of the longitudinal velocity. In addition, the vertical profile of Reynolds stress is obtained by the simplified momentum equation and the vertical profile of turbulence intensity is investigated by an improved exponential model. The predicted data from the analytical models agree well with the experimental ones, thereby confirming that the analytical models are feasible to predict the vertical distribution of velocity, Reynolds stress and turbulence intensity in ice-covered channels. The proposed models can offer an important theoretical reference for future study about the sediment transport and contaminant dispersion in ice-covered channels.

scholarly journals Optimal estimation of catch by the continuous underway fish egg sampler based on a model of the vertical distribution of American plaice (Hippoglossoides platessoides) eggs

2006 ◽  
Vol 64 (1) ◽  
pp. 18-30 ◽  
Author(s):  
P. Pepin ◽  
K. A. Curtis ◽  
P. V. R. Snelgrove ◽  
B. de Young ◽  
J. A. Helbig
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
Vertical Profile ◽  
Negative Binomial ◽  
Optimal Estimation ◽  
Eddy Diffusivity ◽  
Model Parameters ◽  
Error Structure ◽  
The Vertical Distribution ◽  
Hippoglossoides Platessoides

Abstract Pepin, P., Curtis, K.A., Snelgrove, P.V.R., de Young, B., and Helbig, J.A. 2007. Optimal estimation of catch by the continous underway fish egg sampler based on a model of the vertical distribution of American plaice (Hippoglossoides platessoides) eggs – ICES Journal of Marine Science, 64, 18–30. We investigate how the vertical stratification of the water column (specifically density) affects predictions of the catch of American plaice eggs (Hipploglossoides platessoides) from a fixed-depth sampler [the continuous underway fish egg sampler (CUFES)] relative to the integrated abundance in the water column measured in bongo tows. A steady-state model of the vertical distribution of fish eggs coupled with a simple model of the vertical profile of eddy diffusivity (i.e. mixing) is applied. Key model parameters are estimated through optimization of a one-to-one relationship between predicted and observed catches fit, using a generalized linear model with a Poisson, negative binomial, or gamma error structure. The incorporation of data on the vertical structure of the water column significantly improved the ability to forecast CUFES catches when using Poisson or negative binomial error structure, but not using a gamma distribution. Optimal maximum likelihood parameter estimates for eddy diffusivity and egg buoyancy fell within the range of expected values. The degree of uncertainty in the parameterization of eddy diffusivity suggests, however, that greater understanding of the forces that determine the vertical profile of mixing is critical to achieving strong predictive capabilities. The inverse problem of predicting integrated abundance from CUFES catches did not benefit from the environmental-driven model because of the high uncertainty in the catches from the CUFES.

scholarly journals Pollen-ovule relation in Adesmia tristis and reflections on the seed–ovule ratio by interaction with pollinators in two vertical strata

2014 ◽  
Vol 86 (3) ◽  
pp. 1327-1336 ◽  
Author(s):  
NADILSON R. FERREIRA ◽  
LUCIA B. FRANKE ◽  
BETINA BLOCHTEIN
Keyword(s):  
Vertical Distribution ◽  
Breeding System ◽  
Vertical Profile ◽  
Rio Grande ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Catholic University ◽  
Pollination Deficit ◽  
Foraging Pattern ◽  
The Vertical Distribution

The vertical distribution of pollinators is an important component in the foraging pattern of plants strata, and it influences the reproductive system (pollen/ovule ratio) and seed/ovule ratio. Niches in two different strata from Adesmia tristis Vogel were evaluated in these aspects. This plant is an endemic shrub from the Campos de Cima da Serra in Southern Brazil. The studies were carried out from January 2010, to January 2011, at Pró-Mata/PUCRS (Catholic University of Rio Grande do Sul) (29°27′-29°35′S and 50°08′-50°15′W), São Francisco de Paula, sate of Rio Grande do Sul, Brazil. Breeding system of A. tristis is mandatory allogamy. The vertical profile in A. tristis has differentiated foraging niches among the most common pollinators. Bees of Megachile genus forage in the upper stratum, and representative bees of the Andrenidae family explore the lower stratum. The upper stratum of the vertical profile had more contribution to seed production. Adesmia tristis showed evidence of pollination deficit.

scholarly journals Effect of a Lateral Jet on the Turbulent Flow Characteristics of an Open Channel Flow with Rigid Vegetation

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1204 ◽  
Author(s):  
Sufen Teng ◽  
Minquan Feng ◽  
Kailin Chen ◽  
Weijie Wang ◽  
Bangmin Zheng
Keyword(s):  
Flow Velocity ◽  
Reynolds Stress ◽  
Water Flow ◽  
Channel Flow ◽  
Turbulence Intensity ◽  
Open Channel ◽  
Aquatic Vegetation ◽  
Open Channel Flow ◽  
Rigid Vegetation ◽  
Bodies Of Water

Aquatic vegetation can purify polluted bodies of water and beautify the environment, as well as alter the structure of water flow and affect the migration and diffusion of pollutants in bodies of water. Vegetation can significantly change the original water flow, especially in cases in which aquatic vegetation interacts with a jet. Characteristics of jet flow open channels without vegetation have been studied, but research on the characteristics of open-channel flows under the action of lateral jets and in the presence of vegetation are rare. High-frequency particle image velocimetry (PIV) was used to measure a lateral jet in water with rigid vegetation and our results were compared to the lateral jet flow field in water without vegetation. The results show that the vegetation arrangement and vegetation resistance cause significant changes. The presence of vegetation increased the surface velocity of the water, and the flow velocity decreased in the interior area of the vegetation and near the bottom of the water tank. The changes in flow velocity with changes in water depth displayed “S” type and anti-“S” type distributions, and the flow velocity of free layer was approximately logarithmic. Due to vegetation resistance and jet pressure differences, the lateral jet trajectory in water with vegetation was more likely to bend than in water without vegetation. The turbulence intensity and Reynolds stress had different distributions for water with and without vegetation. At the top of the vegetation and near the water surface, turbulent mixing of the water flow was strong, the flow velocity gradient was large and the turbulence intensity and the Reynolds stress reached their maxima. The effects of a lateral jet on an open-channel flow were compared for different vegetation conditions, revealing that a rhombic vegetation arrangement has a stronger deceleration effect than other arrangements. The theoretical results can be applied to wastewater discharge into vegetation channels.

scholarly journals TURBULENCE GENERATED BY WAVE BREAKING ON BEACH

1982 ◽  
Vol 1 (18) ◽  
pp. 1 ◽  
Author(s):  
T. Sakai ◽  
Y. Inada ◽  
I. Sandanbata
Keyword(s):  
Vertical Distribution ◽  
Turbulence Intensity ◽  
Wave Breaking ◽  
Surf Zone ◽  
Turbulent Wake ◽  
Wave Period ◽  
Laser Doppler Velocimeter ◽  
Two Component ◽  
Hot Film ◽  
The Vertical Distribution

Horizontal and vertical velocities are measured with a hot-film anemometer (HFA) and a two-component laser-doppler velocimeter(LDV) in surf zones on uniform slopes of about 1/30 in two wave tanks. The turbulence generated by wave breaking is detected from the records. Following three aspects of the turbulence are discussed : (1) the distribution of the turbulence intensity in the surf zone, (2) the variation of the vertical distribution of the turbulence during one wave period and (3) the variation of the Reynolds stress during one wave period. It is found that the pattern of the distribution of the turbulence in the surf zone depends on the breaker type. A model is proposed, by extending the turbulent wake theory, to explain the variation of the vertical distribution of the turbulence during one wave period.

scholarly journals Experimental and Numerical Investigations of Turbulent Open Channel Flow over a Rough Scour Hole Downstream of a Groundsill

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1488
Author(s):  
Cheng-Kai Chang ◽  
Jau-Yau Lu ◽  
Shi-Yan Lu ◽  
Zhong-Xiang Wang ◽  
Dong-Sin Shih
Keyword(s):  
Numerical Simulation ◽  
Reynolds Stress ◽  
Turbulence Intensity ◽  
Open Channel ◽  
Measured Data ◽  
Experimental Results ◽  
Attachment Point ◽  
Scour Hole ◽  
Scour Holes ◽  
Non Equilibrium

This study discusses the mechanism for the occurrence of equilibrium and non-equilibrium scour holes. By using a particle image velocimetry (PIV) measurement system, it measures the turbulent flow fields in an open channel moving through the rough bed below a groundsill. Then, the Reynolds-stress model (RSM), embedded in FLUENT software, is applied to perform a numerical simulation. The experimental results show that at equilibrium, the location of the re-attachment point is significantly affected by the flow discharge. Further, the re-attachment point of the scour hole affects the size and range of the counterflow zone, which becomes the main region for deposits in the natural channel. In addition, the formation of erosion is mainly affected by turbulence intensity and Reynolds stress. However, in non-equilibrium scour holes, our results clearly show that the turbulence intensity and the Reynolds stress are significantly larger at the end of the scour holes near the bed due to the continual development of the scouring. The correlation between the numerical simulation and experimental results are also examined. Overall, it can be seen that the simulated mean velocity profiles are quite consistent with the measured data. However, in terms of turbulence intensities and Reynolds stress, the simulated results could be overestimated when compared with the measured data; they are overestimated with a sudden decrease near the liquid surface. Although, the simulations in the near bed area show some divergence and the trend in the scour hole is quite consistent. Therefore, numerical simulations can be performed in advance to act as an important reference when evaluating the safety of downstream structures.

scholarly journals Vertical Measurement of Equivalent Black Carbon Concentration at Low Altitude

2020 ◽  
Vol 10 (15) ◽  
pp. 5142
Author(s):  
Jeonghoon Lee ◽  
Jiseung Park ◽  
Juhyung Kim
Keyword(s):  
Vertical Distribution ◽  
Black Carbon ◽  
Vertical Profile ◽  
Ground Level ◽  
Measurement Noise ◽  
Average Scheme ◽  
Above Ground Level ◽  
Low Altitude ◽  
Averaging Time ◽  
The Vertical Distribution

The vertical profile of equivalent black carbon (eBC) concentrations has been measured together with the temperature up to 130 m above ground level at several locations. A hexacopter was deployed for the measurement of eBC, and the temperature on typical days in winter, spring, summer and early autumn. We observed high eBC concentrations between 10 m and 90 m above ground level, which was related to the vertical distribution of temperature. We examined that the measurement noise could be reduced by using a box-average scheme. Furthermore, the negative values at low eBC concentration could be removed for an averaging time of 30 min or longer.

scholarly journals Impact of Aerosol Vertical Distribution on Aerosol Optical Depth Retrieval from Passive Satellite Sensors

2020 ◽  
Vol 12 (9) ◽  
pp. 1524 ◽  
Author(s):  
Chong Li ◽  
Jing Li ◽  
Oleg Dubovik ◽  
Zhao-Cheng Zeng ◽  
Yuk L. Yung
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Vertical Profile ◽  
Retrieval Algorithm ◽  
Retrieval Error ◽  
Satellite Sensors ◽  
Absorbing Aerosols ◽  
The Impact ◽  
The Vertical Distribution

When retrieving Aerosol Optical Depth (AOD) from passive satellite sensors, the vertical distribution of aerosols usually needs to be assumed, potentially causing uncertainties in the retrievals. In this study, we use the Moderate Resolution Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) sensors as examples to investigate the impact of aerosol vertical distribution on AOD retrievals. A series of sensitivity experiments was conducted using radiative transfer models with different aerosol profiles and surface conditions. Assuming a 0.2 AOD, we found that the AOD retrieval error is the most sensitive to the vertical distribution of absorbing aerosols; a −1 km error in aerosol scale height can lead to a ~30% AOD retrieval error. Moreover, for this aerosol type, ignoring the existence of the boundary layer can further result in a ~10% AOD retrieval error. The differences in the vertical distribution of scattering and absorbing aerosols within the same column may also cause −15% (scattering aerosols above absorbing aerosols) to 15% (scattering aerosols below absorbing aerosols) errors. Surface reflectance also plays an important role in affecting the AOD retrieval error, with higher errors over brighter surfaces in general. The physical mechanism associated with the AOD retrieval errors is also discussed. Finally, by replacing the default exponential profile with the observed aerosol vertical profile by a micro-pulse lidar at the Beijing-PKU site in the VIIRS retrieval algorithm, the retrieved AOD shows a much better agreement with surface observations, with the correlation coefficient increased from 0.63 to 0.83 and bias decreased from 0.15 to 0.03. Our study highlights the importance of aerosol vertical profile assumption in satellite AOD retrievals, and indicates that considering more realistic profiles can help reduce the uncertainties.

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