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![Relation between the blockage by a groyne and its drag coefficient C D normalised by F r 2. Data points are defined in legend, solid line is a data-fit line for [C D /F r 2 = a (h g /H t ) b ], with a = 76.4 and b = 3.7](profile/Mohamed-Yossef/publication/259840682/figure/fig3/AS:667618096713746@1536183966694/Relation-between-the-blockage-by-a-groyne-and-its-drag-coefficient-C-D-normalised-by-F-r.png)
Relation between the blockage by a groyne and its drag coefficient C D normalised by F r 2. Data points are defined in legend, solid line is a data-fit line for [C D /F r 2 = a (h g /H t ) b ], with a = 76.4 and b = 3.7
Source publication
In this study, the resistance of groynes is investigated for different submergence levels. For this reason, experiments have been conducted in a physical model with a scale of 1:40 for a schematised river reach, which is based on the geometry of the Dutch River Waal. Four electromagnetic flowmeters (EMF) were employed in order to obtain the horizon...
Contexts in source publication
Context 1
... eliminate that effect, the values of the estimated C D were divided by Froude number squared (F r 2 ) (see Fenton 2003). The result of this operation is presented in Figure 5, from which we can observe that; excluding the last point estimated from test case (SD06) which has a blockage ratio near unity; the calculated (C D /F r 2 ) shows an obvious increasing trend with increasing blockage ratio (h g /H t ). ...
Context 2
... functions could fit the data points in Figure 5, e.g. linear, exponential, or power. ...
Context 3
... a and b are constants, and F r is calculated for the main channel region. The result of the fitting is shown in Figure 5 as a solid line, where the constants a and b were found to equal 76.4, and 3.72 consecutively ...
Context 4
... C D deduced from Eq. 3, and the values of a and b estimated from the laboratory data in Figure 5, it is possible to calculate C effective for any given prototype conditions, see Figure 6. Furthermore, it is now possible to assess the effect of lowering the crest level of the existing groynes on the resistance of the groynes region. ...
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Citations
... These recirculating flows consume energy from the bulk flow field, which causes increases in effective resistance near wing dikes and through wing dike fields. The impact of wing dikes on flow resistance was quantified by Yossef (2004Yossef ( , 2005, who proposed a relationship that allows for an initial assessment of wing dike impact on water levels (e.g., Azinfar 2010). According to Yossef's laboratory experiments, the effective cumulative hydraulic roughness of the bank zone relates to the size and longitudinal distance between the wing dikes as follows (presented in this paper in terms of Manning's n): ...
... where H = depth of flow in the primary channel; h wd − h 0 = relative height of the wing dike as measured from the channel bed (use h à 0 instead of h 0 for case T2); and a and b are regression coefficients given in Yossef (2004Yossef ( , 2005 as a ¼ 76.4 and b ¼ 3.7. The expression is scaled to the channel's Froude number, Fr ¼ U mc =ðgHÞ 1=2 , where U mc = mean flow velocity of the primary channel. ...
The question of whether wing dikes (bank-perpendicular river training structures or groynes) cause higher flood levels has been debated in the United States for many years. Some researchers point to empirical data that show large stage increases which are associated with wing dike construction, whereas other researchers have suggested that such increases are contrary to engineering theory. In a recent report, the U. S. Government Accountability Office (USGAO) presented this question as a priority to be resolved by engineers and scientists. As a first step to better understand the connection between navigation structures and flood levels on the Middle Mississippi River (MMR), a simplified theoretical analysis is presented to test the assertion (made in the USGAO report and elsewhere) that such increases are contrary to hydraulic theory. This analysis predicts that wing dike construction may lead to water level lowering for in-bank flows and to water level increases for out-of-bank (flood) flows. This confirms that, in principle, wing dikes may have contributed to the observed flood water level trends in the MMR. More detailed follow-up studies are required to accurately quantify the impact of wing dikes on flood levels. DOI: 10.1061/(ASCE)HY.1943-7900.0000698. (C) 2013 American Society of Civil Engineers.
... These recirculating flows consume energy from the bulk flow field, which causes increases in effective resistance near wing dikes and through wing dike fields. The impact of wing dikes on flow resistance was quantified by Yossef (2004 Yossef ( , 2005), who proposed a relationship that allows for an initial assessment of wing dike impact on water levels (e.g., Azinfar 2010). According to Yossef's laboratory experiments , the effective cumulative hydraulic roughness of the bank zone relates to the size and longitudinal distance between the wing dikes as follows (presented in this paper in terms of Manning's n): ...
The question of whether wing dikes (bank-perpendicular river training structures or groynes) cause higher flood levels has been
debated in the United States for many years. Some researchers point to empirical data that show large stage increases which are associated
with wing dike construction, whereas other researchers have suggested that such increases are contrary to engineering theory. In a recent
report, the U.S. Government Accountability Office (USGAO) presented this question as a priority to be resolved by engineers and scientists.
As a first step to better understand the connection between navigation structures and flood levels on the Middle Mississippi River (MMR), a
simplified theoretical analysis is presented to test the assertion (made in the USGAO report and elsewhere) that such increases are contrary to
hydraulic theory. This analysis predicts that wing dike construction may lead to water level lowering for in-bank flows and to water level
increases for out-of-bank (flood) flows. This confirms that, in principle, wing dikes may have contributed to the observed flood water
level trends in the MMR. More detailed follow-up studies are required to accurately quantify the impact of wing dikes on flood levels.
... Investigations of the flow pattern and turbulence structures around groynes are necessary for desirable design and construction. For the past few years, a number of researches dealing with the flow structures and scour process around the groynes have been done both experimentally and numerically including: Molls et al (1995), Ouillon et al (1997), Tominaga et al (1997), Zhou et al (2000), Uijttewaal et al (2001), Kuhnle et al (2002), Ettema et al (2004), Yossef (2004), Uijtewaal (2005), Nagata et al (2005) and more recently Xuelin et al (2006). The scour process is the phenomenon of which most of the coastal and hydraulics structures are usually suffering. ...
The groynes which are typical of shore protective structures can provide several aims. Although these structures may partly help to shoreline protection, they would also create some major problems in adjacent regions. Therefore the real performance of these structures needs to be considered carefully before going to construction. In this research, the effects of the cross shore and groyne wall slopes on flow pattern around an impermeable groyne were considered using a three-dimensional numerical CFD model (i.e., FLUENT). The widely accepted eddy viscosity concept and k-ε turbulence model were used to evaluate the Reynolds stresses and eddy viscosity coefficients, respectively. The finite volume method used in the software makes attractive flexibility to use any shape of grids to cover the cross and structural slopes in the computational domain. The model was first applied to a vertical groyne on a flat bed and the numerical model results were compared with experimental data. The model results of this numerical test showed a very good agreement with the corresponding experimental measurements, in terms of water elevation and velocity magnitudes. The model was then applied to a series of structures with different lateral slopes on various cross sectional bed slope. It was found that the flow pattern around the groyne was not changed significantly when the slopes of the structure and bed were slightly changed. The numerical model results, however, showed that by increasing the cross shore slope in any case of the lateral slope of the structure, the magnitude of the maximum velocity was decreased. The bed shear stresses were also decreased when the cross shore slope was increased. Moreover, these values were further decreased when the groyne-wall slope was reduced.
