scholarly journals Scour Features at Wood Bundles

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2118
Author(s):  
Simone Pagliara ◽  
Deep Roy ◽  
Michele Palermo
Keyword(s):  
Froude Number ◽  
Storage Site ◽  
Curved Channels ◽  
Wide Range ◽  
Hydraulic Conditions ◽  
Wood Debris ◽  
Channel Curvature ◽  
Fluvial Habitat ◽  
Dune Height ◽  
Scour Morphology

Structures like blunt-nosed chevrons, log deflectors and double-winged log frames help in modifying the flow regime in the channel by concentrating the flow and increasing navigability. Moreover, they create scour pools in the downstream stilling basin, which can be used either as fish refuge or as an in-stream storage site for previously dredged material. In this respect, the use of wood debris in the channel in the form of wood bundles has gained attention for the ability of these structures to integrate into the surrounding fluvial habitat and to divert the flow partially towards the central part of the channel when placed in curves. Considering the absence of studies dealing with wood bundles as a restoration structure, the aim of this paper is to analyse the scour mechanism and equilibrium scour morphology of wood bundles in straight and curved channels. In doing so, a wide range of hydraulic conditions, structure positions and configurations were tested. Thereafter, dimensional analysis was carried out to derive useful empirical relationships to predict the maximum scour depth and length as well as the maximum dune height based on a novel, equivalent Froude number, which accounts for the effects of channel curvature and structure position. Moreover, the various resulting scour morphology types were classified, and conditions of their existence were determined depending on the abovementioned Froude number and other key hydraulic parameters.

scholarly journals Experimental Analysis of Scour Features at Chevrons in Straight Channel

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 971
Author(s):  
Deep Roy ◽  
Simone Pagliara ◽  
Michele Palermo
Keyword(s):  
River Restoration ◽  
Disposal Site ◽  
Scour Depth ◽  
Straight Channel ◽  
Wake Region ◽  
Densimetric Froude Number ◽  
Hydraulic Conditions ◽  
In Series ◽  
Dune Height ◽  
Scour Morphology

Eco-friendly river restoration structures are used to create localized scour pools which serve as fish nurseries and promote biodiversity. In this category, chevrons are relatively new structures designed to maintain navigability in rivers. The scour hole formed in the wake region of chevrons can either act as a disposal site for dredged material or as a resting spot for different fish species. However, only few studies are present in the literature dealing with the scour mechanism due to chevrons. Therefore, this work aims to analyze the scour features at equilibrium, under different hydraulic conditions and transversal locations in a straight channel. Tests were conducted with both isolated and multiple chevrons in series arrangement. Scour morphology types were classified and their fields of existence were established as well. A detailed dimensional analysis was conducted, allowing us to identify the main parameters governing the scour phenomenon and derive a novel equivalent densimetric Froude number. Finally, empirical equations were developed to predict the maximum scour depth and length as well as the maximum dune height.

Checking The Hydraulic Efficiency and Improving Safety of the Internal Water Supply 

2018 ◽  
Vol 20 (2) ◽  
pp. 121-125
Author(s):  
Sarka Krocova ◽  
Karla Barcova
Keyword(s):  
Water Supply ◽  
Water Supply Systems ◽  
Safety Hazard ◽  
Industrial Facilities ◽  
Internal Water ◽  
Operational Capabilities ◽  
Wide Range ◽  
Hydraulic Conditions ◽  
Industrial Zones ◽  
Supply Systems

Water management systems in industrial facilities, industrial zones, hospitals and other internal water systems relatively frequently fail to meet the intended purpose for which they were built when an extraordinary event occurs. They may even pose a safety hazard. The causes of this condition may be of internal or external origin. Given that internal water supply systems of large premises always have a multipurpose character, i.e. to provide enough drinking water for drinking and sanitation purposes and also as a source of fire water for the fire safety of buildings, they must meet a wide range of hydraulic conditions and technical-operational capabilities. By what means and methods it is possible to achieve the desired state in economically-acceptable dimensions, while maintaining all the necessary hydraulic capabilities of the supply points of drinking and fire water, is briefly described in this article.

scholarly journals Motion of large bubbles in curved channels

2007 ◽  
Vol 570 ◽  
pp. 455-466 ◽  
Author(s):  
METIN MURADOGLU ◽  
HOWARD A. STONE
Keyword(s):  
Film Thickness ◽  
Liquid Velocity ◽  
Circular Cross Section ◽  
Lubrication Theory ◽  
Bubble Velocity ◽  
Straight Tube ◽  
Curved Channel ◽  
Front Tracking Method ◽  
Curved Channels ◽  
Channel Curvature

We study the motion of large bubbles in curved channels both semi-analytically using the lubrication approximation and computationally using a finite-volume/front-tracking method. The steady film thickness is governed by the classical Landau–Levich–Derjaguin–Bretherton (LLDB) equation in the low-capillary-number limit but with the boundary conditions modified to account for the channel curvature. The lubrication results show that the film is thinner on the inside of a bend than on the outside of a bend. They also indicate that the bubble velocity relative to the average liquid velocity is always larger in a curved channel than that in a corresponding straight channel and increases monotonically with increasing channel curvature. Numerical computations are performed for two-dimensional cases and the computational results are found to be in a good agreement with the lubrication theory for small capillary numbers and small or moderate channel curvatures. For moderate capillary numbers the numerical results for the film thickness, when rescaled to account for channel curvature as suggested in the lubrication calculation, essentially collapse onto the corresponding results for a bubble in a straight tube. The lubrication theory is also extended to the motion of large bubbles in a curved channel of circular cross-section.

On the Inflow Phenomenon in Near Field of Buoyant Jet at Low Froude Number

2012 ◽  
Author(s):  
Atsushi Maeda ◽  
Takayuki Yamagata ◽  
Nobuyuki Fujisawa
Keyword(s):  
Reynolds Number ◽  
Froude Number ◽  
Near Field ◽  
Quantitative Information ◽  
Experimental Result ◽  
Inflow Rate ◽  
Buoyant Jet ◽  
Square Duct ◽  
Wide Range ◽  
Low Froude Number

In the present paper, the inflow phenomenon in the near-field of a buoyant jet issuing from a square duct is studied by using scanning LIF and scanning PIV measurements. The scanning LIF visualization allows an insight into the critical condition of the inflow phenomenon in a wide range of Froude number and Reynolds number. While, the scanning PIV allows the quantitative information on the inflow rate through the duct exit. The experimental result shows that the critical Froude number increases with an increase in Reynolds number in the duct exit up to Reynolds number 2,000, though it is weakened at higher Reynolds number. The examination of the inflow rate indicates that the large magnitude of the inflow rate occurs in the lower Froude number and Reynolds number.

Can the Dean number Alone Characterize Flow Similarity in Differently Bent Tubes?

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Krzysztof Cieślicki ◽  
Adam Piechna
Keyword(s):  
Flow Resistance ◽  
Classical Problem ◽  
Nonlinear Flow ◽  
Nonlinear Dependence ◽  
Dean Number ◽  
Curvature Ratio ◽  
Coiled Tube ◽  
Newtonian Flows ◽  
Curved Channels ◽  
Wide Range

Although flows of fluids in curved channels belong to a classical problem of fluid dynamics, most publications are restricted to investigations of flows in tube coils, or in single bends. This paper presents experimental and numerical (CFD) results concerning Newtonian flows in a set of multiple S-type bends of various orientations. Investigations were conducted for a wide range of Re values (0–3500) and for a significant curvature ratio lying between 0.05 and 0.29, which corresponds to De value falling within the range 0.02–1200. A coiled tube was also examined and treated as the reference geometry. It was shown, that despite a completely different velocity pattern, the nonlinear dependence of normalized flow resistance of wavy tubes and coiled tube of the same curvature ratio overlap within a significant range of De. A novel, close phenomenological formula to estimate the nonlinear flow resistance of tortuous tube in a wide range of De was proposed and compared with those in the literature. The conditions were also determined in which the De might be the only dimensionless group that characterizes such flows.

scholarly journals LONG WAVES IN CHANNELS Of ARBITRARY CROSS-SECTION

1968 ◽  
Vol 1 (11) ◽  
pp. 12
Author(s):  
D.H. Peregrine
Keyword(s):  
Cross Section ◽  
Gravity Waves ◽  
Reasonable Agreement ◽  
Arbitrary Constant ◽  
Arbitrary Cross Section ◽  
Cross Sectional ◽  
Curved Channels ◽  
Channel Curvature ◽  
M Channels ◽  
Theoretical Results

This warier summarises some recent work on lone gravity waves on still water m channels of arbitrary constant cross-section. Theoretical results have been obtained for both straight and curved channels. Some experimental work has been performed m straight trapezoidal channels and shows reasonable agreement with theory. For straight channels some details of the second approximation are given, and the cases where the approximation breaks down are indicated. For curved channels it is found that the effect of channel curvature is more pronounced when the cross-sectional shane of the channel is not symmetric with resnect to its centre-line.

scholarly journals Uncertainty in regional estimates of capacity for carbon capture and storage

Solid Earth ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 1707-1715 ◽  
Author(s):  
Mark Wilkinson ◽  
Debbie Polson
Keyword(s):  
Carbon Capture ◽  
Storage Capacity ◽  
Significant Proportion ◽  
Carbon Capture And Storage ◽  
Saline Aquifers ◽  
Storage Site ◽  
Limited Data ◽  
Wide Range ◽  
Regional Estimates ◽  
And Storage

Abstract. Carbon capture and storage (CCS) is a potentially important technology for the mitigation of industrial CO2 emissions. However, the majority of the subsurface storage capacity is in saline aquifers, for which there is relatively little information. Published estimates of the potential storage capacity of such formations, based on limited data, often give no indication of the uncertainty, despite there being substantial uncertainty associated with the data used to calculate such estimates. Here, we test the hypothesis that the uncertainty in such estimates is a significant proportion of the estimated storage capacity, and should hence be evaluated as a part of any assessment. Using only publicly available data, a group of 13 experts independently estimated the storage capacity of seven regional saline aquifers. The experts produced a wide range of estimates for each aquifer due to a combination of using different published values for some variables and differences in their judgements of the aquifer properties such as area and thickness. The range of storage estimates produced by the experts shows that there is significant uncertainty in such estimates; in particular, the experts' range does not capture the highest possible capacity estimates. This means that by not accounting for uncertainty, such regional estimates may underestimate the true storage capacity. The result is applicable to single values of storage capacity of regional potential but not to detailed studies of a single storage site.

Natural Fluvial Ecohydraulics

2019 ◽  
Author(s):  
Gregory B. Pasternak
Keyword(s):  
Numerical Models ◽  
Spatial Scales ◽  
Multidisciplinary Teams ◽  
Widespread Occurrence ◽  
Societal Needs ◽  
Environmental Fluid Mechanics ◽  
Wide Range ◽  
Continuum Scale ◽  
Fluvial Habitat ◽  
Societal Problems

Ecohydraulics is the study of the mechanisms that explain hierarchically nested aquatic and riparian biotic phenomena. Mechanisms are sequential actions that can be physical, biological, or an interaction between the two. Biotic phenomena consist of individual, population, and community-level conditions, behaviors, and interactions. Hierarchical nesting means that phenomena are present across a wide range of spatial scales: from the smallest fluid continuum scale to the scale of the entire Earth. Many ecohydraulic studies prominently address scaling. Under this definitional framework and given the widespread occurrence of water on Earth, ecohydraulics is the “proximal” science mediating the influence of “distal” landscape drivers (e.g., climate, geology, and topography). Historically, scientists discovered empirical correlations relating biotic conditions to both proximal and distal abiotic variables. However, when such results are applied to practical societal problems (e.g., stream barrier passage, habitat rehabilitation, and flow regime specification), the accuracy and specificity is insufficient to solve them. That has led to widespread recognition of the need for a mechanistic understanding culminating in predictive numerical models. Driven by such necessity, physical and biological scientists and engineers have formed multidisciplinary teams to work out how water and biota interact. Through its marriage of conceptual understanding with quantitative analysis, ecohydraulics is playing a central role in methodological advancements to objectively, transparently, and repeatably explain biotic phenomena at multiple spatial scales. Students involved in ecohydraulics are part of an emerging interdisciplinary generation identifying more with problem-oriented applied science that responds to societal needs to solve specific ecological problems than disciplinarians driven by curiosity and traditional socio-scientific pathways. Nevertheless, it goes too far to conclude that ecohydraulics is nothing more than the application of other sciences, with no basic developments of its own. Necessity often motivates ecohydraulicists to undertake novel experiments revealing fundamental discoveries. As a result, a reasonable distinction can be made between basic ecohydraulics for studying natural phenomena and applied ecohydraulics for rehabilitating degraded phenomena. This annotated bibliography is the first of two spanning ecohydraulics, and it tackles the former, while the second addresses the latter. Due to space limitations, this article is narrowed to natural fluvial ecohydraulics. Within this domain, there are five essential topics: environmental fluid mechanics, flora ecohydraulics, fluvial habitat, faunal ecohydraulics, and fish migration. Finally, space limitations further limit the scope to an emphasis on observational studies over numerical modeling.

scholarly journals Use of Multidimensional Models to Investigate Boundary Shear Stress through Meandering River Channels

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3506
Author(s):  
Timothy J. Randle
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Field Studies ◽  
River Channels ◽  
Meandering River ◽  
Boundary Shear ◽  
Wide Range ◽  
Channel Curvature ◽  
Boundary Shear Stress ◽  
Multidimensional Models

Three-dimensional hydraulics were simulated through a wide range of synthetically generated meandering river channels to determine how channel curvature and width would correlate with the maximum boundary shear stress. Multidimensional models were applied, similar to a computational flume to simulate a wide range of 72 meandering channels, developed from sine-generated curves. Cannel sinuosity ranged from 1.1 to 3.0 and included five consecutive meander bends. Longitudinal slopes of the various channels spanned four orders of magnitude, while bankfull discharges spanned three orders of magnitude. Using results from one-half of the simulation sets, an empirical correlation was found to predict the maximum boundary shear stress as a function of dimensionless ratios of channel curvature and width. The remaining simulation sets were used for verification. Multidimensional models were used to simulate channel hydraulics to efficiently investigate a wide range of channel sinuosity, width/depth ratios, bankfull discharges, and valley slopes. When simulating such a wide range of channel conditions, multidimensional models offer a more efficiency method of generating consistent datasets than either field studies or physical modeling. This paper demonstrates how multidimensional models can be used to identify important hydraulic relationships that are otherwise difficult to determine.

Hydraulic optimization of a combined sewer overflow (CSO) storage facility using numerical and physical modelingA paper submitted to the Journal of Environmental Engineering and Science.

2009 ◽  
Vol 36 (2) ◽  
pp. 363-373 ◽  
Author(s):  
Cheng He ◽  
Jiri Marsalek
Keyword(s):  
Numerical Model ◽  
Physical Models ◽  
Combined Sewer Overflow ◽  
Cfd Model ◽  
Structural Modifications ◽  
Wide Range ◽  
Hydraulic Conditions ◽  
Combined Sewer ◽  
Model Star ◽  
Sewer Overflow

A commercially available 3-D computational fluid dynamics (CFD) model (STAR-CD) was used to investigate capacity upgrading options for a combined sewer overflow (CSO) facility of inadequate capacity. The numerical model was verified against the data collected in two physical models. The need for verifying the CFD model was given by the complexity of the CSO facility, which comprises several interconnected tanks. The verified numerical model was then applied to analyze hydraulic conditions in the whole facility for major structural modifications with the aim of reducing or eliminating untreated overflows from the facility. Many scenarios were proposed and tested in the study and the two most promising structural modifications, scenarios 1 and 2, are presented in the paper. Both appeared to meet the design condition of increasing the facility capacity to 60 m3/s, but better performing scenario 1 would be significantly more costly to implement than scenario 2. Even though the study focused on a particular CSO facility, hydraulic conditions in the studied facility represent general flow conditions in typical CSO or stormwater settling facilities and, therefore, the numerical modeling methods used are applicable to solving a wide range of hydraulic problems encountered at similar facilities.

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