scholarly journals Improved structure of vertical flow velocity distribution in natural rivers based on mean vertical profile velocity and relative water depth

2017 ◽  
Vol 49 (3) ◽  
pp. 878-892
Author(s):  
S. Song ◽  
B. Schmalz ◽  
N. Fohrer
Keyword(s):  
Velocity Distribution ◽  
Flow Velocity ◽  
Water Depth ◽  
Vertical Velocity ◽  
Water Surface ◽  
Friction Velocity ◽  
Depth Direction ◽  
Relative Water ◽  
Estimated Error ◽  
New Formula

Abstract Logarithmic, power, and parabolic distribution laws were proven to be efficient for the prediction of vertical velocity distribution. Traditionally, the distribution formulas involve the friction velocity (u*) and the depth (y) of the measurement point. The low availability of friction velocity and limitation of real water depth data hindered the promotion and comparison of the available flow velocity formulas. In this paper, we proposed a new formula structure adopting a relative flow velocity based on mean vertical velocity (u/ū) and dimensionless relative water depth (y/H). The observations showed the following. (1) The substitution of u* and y with u/ū and y/H were reliable and applicable. Parabolic logarithmic and power fitting curves worked well, with an error of 7%, 10%, and 11%, respectively. (2) In water depth direction, the predicted results of the middle depth of the vertical profiles tend to be more reliable and precise. The highest estimated error appeared in the area near the water surface. (3) Higher catchment slope resulted in larger coefficients and constants in logarithmic and power fitting. (4) In the rivers with higher width-to-depth ratio, the maximum profile velocity occurred closer to the water surface, and mean profile velocity tended to happen more at the bottom.

The Effects of an Air/Water Surface on the Fast-Start Performance of Rainbow Trout (Oncorhynchus Mykiss)

1991 ◽  
Vol 155 (1) ◽  
pp. 219-226 ◽  
Author(s):  
PAUL W. WEBB ◽  
DOMINIQUE SIMS ◽  
WILLIAM W. SCHULTZ
Keyword(s):  
Rainbow Trout ◽  
Water Depth ◽  
Water Surface ◽  
The Body ◽  
Energy Dispersion ◽  
Cumulative Distance ◽  
Relative Water ◽  
Fast Start ◽  
Turning Radius ◽  
Water Depths

Fast-start performance of rainbow trout (mass 0.187±0.022kg; mean±2S.E., N= 10) was measured in water of various depths. Relative water depth was defined as z/B, where z is the water depth measured from the air/water surface to the longitudinal midline of the body and B is the span of the caudal fin, 0.062±0.004m. Relative water depths (at absolute depths) tested were; 0.31 (at 0.05m), 1.11 (at 0.1m), 1.92 (at 0.15m), 2.73 (at 0.2m) and 7.56 (at 0.5m). Performance was defined in terms of the motion of the centre of mass as measured by the turning radius and the cumulative distance travelled in a given elapsed time. Turning radius was not affected by water depth and averaged 0.018±0.003m. Distance travelled was a positive function of water depth, although paired t-tests showed no significant effect of depth at 0.15 and 0.2 m after about 70 ms. Energy dispersion due to the formation of surface waves increased with decreasing relative water depth. The largest energy dispersion in wave formation at a relative water depth of 0.31 averaged about 70% of the useful mechanical work performed in deep water. Energy dispersion in wave generation was negligible for relative water depths larger than approximately 3. Energy dispersion is similar to that for rigid streamlined bodies moving at constant speed

Flow Hydrodynamic Characteristics in the Dam-Break Induced Wave Tip Region

2020 ◽  
Vol 14 (05) ◽  
pp. 2040002
Author(s):  
Danhong Wu ◽  
Jia Shen ◽  
Haijiang Liu
Keyword(s):  
Velocity Distribution ◽  
Vertical Velocity ◽  
Water Surface ◽  
Momentum Equation ◽  
Dam Break ◽  
Force Balance ◽  
Hydrodynamic Characteristics ◽  
Uniform Structure ◽  
Flow Convergence ◽  
Layer Flow

Traditional models assuming a vertically uniform structure of the horizontal flow velocity and neglecting the vertical velocity distribution cannot accurately describe the complex boundary layer flow features in the dam-break induced wave tip region. Based on the assumption that the horizontal velocity profile in the wave tip region follows a vertically parabolic distribution with shear extending to the water surface, new solutions for the hydrodynamic characteristics in the wave tip region were derived with respect to the simplified force balance or the steady momentum equation, respectively. The force balance-based models show the relation between water depth [Formula: see text] and distance from the tip [Formula: see text] in the wave tip region as [Formula: see text], whereas a complex and implicit [Formula: see text] relation is confirmed after applying the momentum equation. Comparing with other models, the present momentum equation-based model gives the best agreements with experiments, which can illustrate the general spatial distribution of the wave profile in the wave tip region. Model predicted characteristics of surface particles’ motion are consistent with the experimental observation of Baldock et al. ([ 2014 ] “Flow convergence at the tip and edges of a viscous swash front — experimental and analytical modeling,” Coast Eng. 88, 123–130). As for the vertical velocity distribution in the wave tip region (being downward direction), it increases monotonically from the bed to the water surface and its magnitude increases when approaching the wave tip. Taking into account the relative streamline distribution and total flow field feature in the wave tip region, the present model can reproduce the uniform flow convergence pattern at the wave tip front, as experimentally observed in Baldock et al. [ 2014 ].

scholarly journals A study of the hydraulic parameters and ecological significance of braided rivers under flow variations

2021 ◽  
Author(s):  
Wang Hao ◽  
Hong Li ◽  
Lihua You ◽  
Lu Yun ◽  
Zaixiang Zhu ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Water Depth ◽  
Water Surface ◽  
Hydraulic Parameters ◽  
Braided River ◽  
Cross Sectional ◽  
Spawning Grounds ◽  
Spawning Period ◽  
Braided Rivers ◽  
Fish Spawning

Numerical modeling of braided channels showed no significant differences in the number of cross-sectional branches between different water periods in the middle reaches of the Yarlung Tsangpo River. During most of the year (wet, normal and dry periods), flow velocities in the higher-branching (HB) channels were significantly lower than in the other two branching categories, while the overall distribution of depth in the higher-branching channels maintained a high degree of consistency with the moderate-branching channels (MB), which partly explains why the HB channels are important habitats for fish spawning, nursery and baiting (lower flow velocity distribution with a wider range of depth). Based on the examination of the water surface width, the water surface width may not be a limiting factor for fish habitat within braided rivers. Simulation of the hydrodynamic parameters of the fish-spawning grounds revealed that the average cross-sectional flow velocity and water depth fluctuated the least at different flows during the fish-spawning period for the HB channels. By counting the hydraulic parameters of the spawning grounds during the spawning period, it can be seen that the most preferred flow velocity for fish in the braided river in the study section was 0.1-0.4 m/s, and the water depth was 0-1.2 m. This article analyses the characteristics of the hydraulic parameters of the braided river and provides theoretical support for the restoration of fish habitats in braided rivers.

scholarly journals MAGNITUDE OF THE B-FACTOR UNDER WAVE ACTION

1986 ◽  
Vol 1 (20) ◽  
pp. 67
Author(s):  
J. Van de Graaff ◽  
R.C. Steijn
Keyword(s):  
Velocity Distribution ◽  
Water Depth ◽  
Sediment Concentration ◽  
Wave Action ◽  
Practical Applications ◽  
Wave Flume ◽  
Sediment Size ◽  
Flume Tests ◽  
Waves And Currents ◽  
The Moment

The sediment transport due to waves and currents depends on the distribution of sediment concentration and on the distribution of the velocity over the water depth. Our knowledge of both phenomena for practical applications is still rather poor. Some results of wave flume tests concerning the distribution of sediment concentrations due to wave action will be discussed. It turns out that the sediment size of the bottom material has a rather unexpected effect hereupon. With respect to the velocity distribution only some qualitative remarks can be made at the moment.

scholarly journals A NEW FULLY-AUTOMATIC PROCEDURE FOR THE IDENTIFICATION AND THE COUPLING OF THE OVERTOPPING WAVES

2018 ◽  
pp. 36 ◽  
Author(s):  
Sara Mizar Formentin ◽  
Barbara Zanuttigh
Keyword(s):  
Flow Velocity ◽  
Water Surface ◽  
Automatic Identification ◽  
Practical Relevance ◽  
Threshold Values ◽  
Flow Conditions ◽  
Fully Automatic ◽  
The Individual ◽  
Coupling Algorithm ◽  
Submerged Conditions

This contribution presents a new procedure for the automatic identification of the individual overtopping events. The procedure is based on a zero-down-crossing analysis of the water-surface-elevation signals and, based on two threshold values, can be applied to any structure crest level, i.e. to emerged, zero-freeboard, over-washed and submerged conditions. The results of the procedure are characterized by a level of accuracy comparable to the human-supervised analysis of the wave signals. The procedure includes a second algorithm for the coupling of the overtopping events registered at two consecutive gauges. This coupling algorithm offers a series of original applications of practical relevance, a.o. the possibility to estimate the wave celerities, i.e. the velocities of propagation of the single waves, which could be used as an approximation of the flow velocity in shallow water and broken flow conditions.

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