Experimental Study on Dam-Break Hydrodynamic Characteristics Under Different Conditions

2017 ◽  
Vol 12 (1) ◽  
pp. 198-207 ◽  
Author(s):  
Hui Liu ◽  
◽  
Haijiang Liu ◽  
Keyword(s):  
Flow Velocity ◽  
Water Level ◽  
High Speed ◽  
Flow Characteristics ◽  
Dam Break ◽  
Hydrodynamic Characteristics ◽  
High Temporal Resolution ◽  
Initial Water ◽  
Water Head ◽  
Reservoir Length

In this study, a series of dam-break experiments was carried out to investigate the influence of the initial downstream water depth, water head settings, and upstream reservoir length on the dam-break wave movement. The instantaneous water level and flow velocity were measured at two specified downstream locations. Considering the requirements for precise data measurement with high temporal resolution, the synchronization of different instruments was realized based on high-speed camera recording. Even with the same initial water head setting, the water level and flow velocity variations of the dam-break wave propagating downstream on the wet bed show noteworthy differences in flow characteristics compared to the initial dry bed, caused by the interactions between the upstream and downstream water. Hydrodynamic formulae proposed by Lauber and Hager (1998) [1] are not applicable for the wet-bed condition, although their solution of wave profiles for the initial dry-bed condition performs well at the location farther from the gate. The non-dimensional average front velocity of the wet-bed condition, which mainly depends on the initial water head setting, is smaller than that of the dry-bed case. In addition, the maximum water level and flow velocity at the downstream location are mainly controlled by the initial water head setting, while the duration of the large values is influenced by the reservoir length.

An Experimental Study of the Run-Up Process of Breaking Bores Generated by Dam-Break Under Dry- and Wet-Bed Conditions

2018 ◽  
Vol 12 (02) ◽  
pp. 1840005 ◽  
Author(s):  
Senxun Lu ◽  
Haijiang Liu ◽  
Xiaohu Deng
Keyword(s):  
Water Depth ◽  
Laboratory Experiments ◽  
Bottom Friction ◽  
Dam Break ◽  
Hydrodynamic Characteristics ◽  
Initial Water ◽  
Water Head ◽  
Run Up ◽  
Front Profile ◽  
Two Stages

In this study, a series of dam-break laboratory experiments were carried out to investigate the run-up process of breaking bores under dry- and wet-bed conditions. Detailed measurements were conducted to reveal differences in the run-up hydrodynamic characteristics under these two conditions, e.g. the bore front profile, the maximum run-up height and duration, and the instantaneous bore front velocity. Two successive bores were observed under the wet-bed run-up process, while multiple bores (three bores in general) were generated during the dry-bed run-up process due to the significant bottom friction effect. A linear relationship with the uniform gradient is found between the maximum run-up height and the initial water head for both dry- and wet-bed conditions, indicating that difference in the maximum run-up height between the dry- and specified wet-bed cases or among various wet-bed cases is not sensitive to the initial water head. Under the same initial water head, although the dry-bed run-up process takes a longer duration than that of wet-bed cases, the maximum run-up height is smallest for the dry-bed case and gradually increases with the increase of the initial downstream water depth for wet-bed cases. Under the wet-bed conditions, temporal variation of the bore front run-up velocity can be classified into two stages, i.e. the acceleration stage induced by the relatively large incident bore front water depth (large onshore hydrostatic pressure gradient) and the deceleration stage governed by the offshore-directed gravity force and bottom friction. Nevertheless, due to the small incident bore front water depth, run-up process under the dry-bed conditions does not show the acceleration stage.

Influence of non-uniform inflow on unsteady internal flow characteristics of waterjet pump

2021 ◽  
Author(s):  
Chao Liu ◽  
Hongxun Chen ◽  
Zheng Ma
Keyword(s):  
High Speed ◽  
Pressure Pulsation ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Energy Performance ◽  
Hydrodynamic Characteristics ◽  
Area Formula ◽  
Low Speed ◽  
Waterjet Pump

Waterjet propulsion has many advantages when operating at high-speed conditions. As a special way of navigation, it is mostly used in high-speed ships and shallow draft ships. In this paper, a mixed-flow waterjet pump was taken as the research object. For the two cases of non-uniform inflow and uniform inflow, a modified RANS/LES method was adopted for unsteady calculation of the whole channel, aiming at investigating the influence mechanism of the non-uniform inflow on the energy performance and pressure pulsation characteristics of the waterjet pump. The hydrodynamic characteristics of the waterjet pump were comprehensively analyzed such as head, efficiency, axial-force, internal flow and pressure pulsation. It is found that the non-uniform inflow will reduce the external characteristics of the waterjet pump and lead to the huge fluctuation of energy performance with time. Low-speed swirls occur locally in the intake duct for non-uniform inflow, in which condition the vorticity is much higher than that for uniform inflow. In terms of the low-speed area, [Formula: see text] and [Formula: see text], the values under non-uniform inflow condition are generally larger than those under uniform flow condition when in the impeller and guide vane zone. The dominant frequencies of pressure pulsation are, respectively, [Formula: see text], 7[Formula: see text] and 4[Formula: see text] in the intake duct, impeller and diffuser, which are almost consitent for the two cases. However, the frequency features are more diverse, and the amplitudes corresponding to the same frequencies are more intense for non-uniform inflow.

scholarly journals Experimental Study of Dam-Break-Like Tsunami Bore Impact Mechanism on a Container Model

2020 ◽  
Vol 27 (1) ◽  
pp. 53-59
Author(s):  
Cheng Chen ◽  
Jun Chen ◽  
Peng Lin ◽  
Chiwei Chen ◽  
Haozhe Chen
Keyword(s):  
Water Level ◽  
High Speed ◽  
Tsunami Wave ◽  
Dam Break ◽  
Water Levels ◽  
Level Gauge ◽  
Impact Mechanism ◽  
Tsunami Waves ◽  
Movement Distance ◽  
Container Model

AbstractTsunami disasters have frequently occurred in recent years. More and more researchers are focusing on this topic. To investi-gate the tsunami bore impact mechanism on a container model, a multi-functional slope-changing tsunami flume is built in this study. To simulate a tsunami bore, a dam-break wave was generated by a free-falling gate in a reservoir. A needle water level gauge and a high-speed camera were used to measure the tsunami wave heights and velocities for different storage water levels in the test flume, and the corresponding Froude numbers of tsunami waves were also calculated. The factors af-fecting the movement distance of the tsunami wave impacting the container model are explored in this experiment, and the results show that the movement distance is positively correlated with the storage water level, and negatively correlated with the container density and the coast slope.

Study on Flow Characteristics inside a Spillway Tunnel of Hydropower Station

2014 ◽  
Vol 716-717 ◽  
pp. 219-222
Author(s):  
Hong Qing Zhang ◽  
Bing Cao ◽  
Yi Long Lou ◽  
Wei Kai Tan
Keyword(s):  
Flow Velocity ◽  
High Speed ◽  
Flow Characteristic ◽  
Flow Characteristics ◽  
Hydropower Station ◽  
Turbulent Model ◽  
Cross Sectional ◽  
Vof Model ◽  
Spillway Tunnel ◽  
The Right

VOF model and turbulent model were used in this paper to study on flow characteristic inside a certain spillway tunnel of hydropower station, which includes cross sectional distributions of flow velocity in pressure section and non-pressure section. The results show that flow velocity distribution in the pressure section of the spillway tunnel is basically symmetrical. After turning, flow velocity is well-distributed and move ahead; flow velocity in the right side of non-pressure section in the spillway tunnel is 1m/s faster than that in the left side. When two high-speed water flow come together after passing through the central division pier, flow velocity distributions in the both sides of the spillway tunnel are all uniform. The conclusions obtained can improve the design of the spillway tunnel.

A Detailed Description of Flow-Deck Interaction in Consecutive Green Water Events

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Jassiel V. Hernández-Fontes ◽  
Edgar Mendoza ◽  
Irving D. Hernández ◽  
Rodolfo Silva
Keyword(s):  
High Speed ◽  
Effective Interaction ◽  
Dam Break ◽  
Green Water ◽  
Hydrodynamic Characteristics ◽  
Wave Flume ◽  
Series Of Experiments ◽  
Run Up ◽  
Fixed Structure ◽  
Air Cavities

Abstract This paper gives a detailed description of the main hydrodynamic characteristics of different types of green water events occurring on a fixed structure in a series of experiments. High-speed video, at 250 fps, was used to capture the flow details from regular waves produced inside a wave flume. The green water events were classified according to their type and the results of the evaluation from the apparent and effective interaction features. The air cavities in the plunging-dam-break (PDB)-type events were almost spherical for longer waves. PDB with large, elliptical cavities, and hammer-fist (HF)-type events occurred with steeper waves. The highest wave front and bow run-up velocities were found in PDB and HF events, respectively. The size of the cavities in PDB events increases and becomes more elliptical for higher bow run-up velocities. The results of these experiments show that not all events can be treated in the same way as the dam-break (DB)-type events when designing structures or implementing models, as not all interactions with the deck happen when the shipping water crosses the bow edge.

scholarly journals Stochastic Uncertainty in a Dam-Break Experiment with Varying Gate Speeds

2021 ◽  
Vol 9 (1) ◽  
pp. 67
Author(s):  
Hiroshi Takagi ◽  
Fumitaka Furukawa
Keyword(s):  
High Speed ◽  
Pressure Sensors ◽  
Dam Break ◽  
Maximum Pressure ◽  
Vertical Acceleration ◽  
Ship Wakes ◽  
Dam Break Flow ◽  
Statistical Relationships ◽  
Flow Propagation ◽  
Impulsive Pressure

Uncertainties inherent in gate-opening speeds are rarely studied in dam-break flow experiments due to the laborious experimental procedures required. For the stochastic analysis of these mechanisms, this study involved 290 flow tests performed in a dam-break flume via varying gate speeds between 0.20 and 2.50 m/s; four pressure sensors embedded in the flume bed recorded high-frequency bottom pressures. The obtained data were processed to determine the statistical relationships between gate speed and maximum pressure. The correlations between them were found to be particularly significant at the sensors nearest to the gate (Ch1) and farthest from the gate (Ch4), with a Pearson’s coefficient r of 0.671 and −0.524, respectively. The interquartile range (IQR) suggests that the statistical variability of maximum pressure is the largest at Ch1 and smallest at Ch4. When the gate is opened faster, a higher pressure with greater uncertainty occurs near the gate. However, both the pressure magnitude and the uncertainty decrease as the dam-break flow propagates downstream. The maximum pressure appears within long-period surge-pressure phases; however, instances considered as statistical outliers appear within short and impulsive pressure phases. A few unique phenomena, which could cause significant bottom pressure variability, were also identified through visual analyses using high-speed camera images. For example, an explosive water jet increases the vertical acceleration immediately after the gate is lifted, thereby retarding dam-break flow propagation. Owing to the existence of sidewalls, two edge waves were generated, which behaved similarly to ship wakes, causing a strong horizontal mixture of the water flow.

scholarly journals Automatic Dissolution Testing with High-Temporal Resolution for Both Immediate-Release and Fixed-Combination Drug Tablets

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhongmei Chi ◽  
Irfan Azhar ◽  
Habib Khan ◽  
Li Yang ◽  
Yunxiang Feng
Keyword(s):  
High Speed ◽  
Sequential Analysis ◽  
Immediate Release ◽  
Drug Dissolution ◽  
High Temporal Resolution ◽  
Dissolution Profile ◽  
Dissolution Testing ◽  
Combination Drug ◽  
Efficient Separation ◽  
High Efficient

AbstractDissolution testing plays many important roles throughout the pharmaceutical industry, from the research and development of drug products to the control and evaluation of drug quality. However, it is a challenging task to perform both high-efficient separation and high-temporal detection to achieve accurate dissolution profile of each active ingredient dissolved from a drug tablet. In our study, we report a novel non-manual-operation method for performing the automatic dissolution testing of drug tablets, by combining a program-controlled sequential analysis and high-speed capillary electrophoresis for efficient separation of active ingredients. The feasibility of the method for dissolution testing of real drug tablets as well as the performance of the proposed system has been demonstrated. The accuracy of drug dissolution testing is ensured by the excellent repeatability of the sequential analysis, as well as the similarity of the evaluation of dissolution testing. Our study show that the proposed method is capable to achieve simultaneous dissolution testing of multiple ingredients, and the matrix interferences can be avoided. Therefore it is of potential valuable applications in various fields of pharmaceutical research and drug regulation.

scholarly journals Investigate Impact Force of Dam-Break Flow against Structures by Both 2D and 3D Numerical Simulations

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 344
Author(s):  
Le Thi Thu Hien ◽  
Nguyen Van Chien
Keyword(s):  
Impact Force ◽  
Numerical Models ◽  
Splitting Method ◽  
Dam Break ◽  
Navier Stokes ◽  
Dynamic Force ◽  
Exact Mass ◽  
Initial Water ◽  
Dam Break Flow ◽  
2D And 3D

The aim of this paper was to investigate the ability of some 2D and 3D numerical models to simulate flood waves in the presence of an isolated building or building array in an inundated area. Firstly, the proposed 2D numerical model was based on the finite-volume method (FVM) to solve 2D shallow-water equations (2D-SWEs) on structured mesh. The flux-difference splitting method (FDS) was utilized to obtain an exact mass balance while the Roe scheme was invoked to approximate Riemann problems. Secondly, the 3D commercially available CFD software package was selected, which contained a Flow 3D model with two turbulent models: Reynolds-averaged Navier-Stokes (RANs) with a renormalized group (RNG) and a large-eddy simulation (LES). The numerical results of an impact force on an obstruction due to a dam-break flow showed that a 3D solution was much better than a 2D one. By comparing the 3D numerical force results of an impact force acting on building arrays with the existence experimental data, the influence of velocity-induced force on a dynamic force was quantified by a function of the Froude number and the water depth of the incident wave. Furthermore, we investigated the effect of the initial water stage and dam-break width on the 3D-computed results of the peak value of force intensity.

scholarly journals Study on the 3D Hydrodynamic Characteristics and Velocity Uniformity of a Gravity Flow Circular Flume

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 927
Author(s):  
Yi Zhang ◽  
Longxi Han ◽  
Lina Chen ◽  
Chenfang Wang ◽  
Bo Chen ◽  
...  
Keyword(s):  
Flow Field ◽  
Environmental Science ◽  
Structural Characteristics ◽  
Longitudinal Velocity ◽  
Flow Characteristics ◽  
Science Research ◽  
Hydrodynamic Characteristics ◽  
Straight Channel ◽  
Uniformity Coefficient ◽  
Annular Flume

Flumes have been widely used in water conservancy science and environmental science research. It is of great significance to obtain the hydrodynamic characteristics and flow field uniformity in the flume. In this study, a new type of annular flume was taken as an example. The 3D flow field was simulated by using a commercial computational fluid dynamics (CFD) code, and was also measured by acoustic doppler velocimeter (ADV) to verify the simulation results. The average relative error range was between 8.37% and 9.95%, the simulated results basically reflected the actual situation of the flow field. On this basis, the structural characteristics of flow field were analyzed. A new calculation method of flow velocity uniformity was presented according to the flow characteristics of natural open channels. The velocity uniformity in the straight channel was calculated and analyzed based on this method, and the influence of speed on the velocity uniformity was further discussed. The length of uniform section was negatively correlated with the rotational speed (average velocity), which was between 39 cm and 101 cm in the straight, and the uniformity coefficient was less than 10%. Finally, the water flow characteristics in the straight channel without wheel were compared with the natural open channel flow. The longitudinal velocity was well fitted with the Prandtl logarithmic distribution formula (R2 > 0.977), and the application feasibility of the flume was analyzed. This study can provide technical support for the development and application of annular flume.

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