Experimental investigation of bedload transport processes under unsteady flow conditions

2004 ◽  
Vol 18 (13) ◽  
pp. 2439-2454 ◽  
Author(s):  
Kwan Tun Lee ◽  
Yi-Liang Liu ◽  
Kai-Hung Cheng
Keyword(s):  
Experimental Investigation ◽  
Unsteady Flow ◽  
Bedload Transport ◽  
Transport Processes ◽  
Flow Conditions

scholarly journals Impact of Unsteady Flow Events on Bedload Transport: A Review of Laboratory Experiments

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 907 ◽  
Author(s):  
Magdalena M. Mrokowska ◽  
Paweł M. Rowiński
Keyword(s):  
Unsteady Flow ◽  
Laboratory Experiments ◽  
Current Knowledge ◽  
Bedload Transport ◽  
Ephemeral Streams ◽  
Flow Conditions ◽  
Future Directions ◽  
Alluvial Rivers ◽  
Gravel Bed Streams ◽  
The Impact

Recent advances in understanding bedload transport under unsteady flow conditions are presented, with a particular emphasis on laboratory experiments. The contribution of laboratory studies to the explanation of key processes of sediment transport observed in alluvial rivers, ephemeral streams, and river reaches below a dam is demonstrated, primarily focusing on bedload transport in gravel-bed streams. The state of current knowledge on the impact of flow properties (unsteady flow hydrograph shape and duration, flood cycles) and sediment attributes (bed structure, sediment availability, bed composition) on bedload are discussed, along with unsteady flow dynamics of the water-sediment system. Experiments published in recent years are summarized, the main findings are presented, and future directions of research are suggested.

Variable Geometry and Waste-Gated Automotive Turbochargers: Measurements and Comparison of Turbine Performance

1992 ◽  
Vol 114 (3) ◽  
pp. 553-560 ◽  
Author(s):  
M. Capobianco ◽  
A. Gambarotta
Keyword(s):  
Experimental Investigation ◽  
Unsteady Flow ◽  
Transient Response ◽  
Test Facility ◽  
Variable Geometry ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Variable Geometry Turbine ◽  
The University ◽  
And Control

In turbocharging automotive Diesel engines, an effective method to extend the turbine flow range and control the boost level is the use of a variable geometry turbine (VGT): This technique can be very helpful to improve the transient response of the engine and reduce exhaust emissions. In order to compare the performance of variable geometry and conventional waste-gated turbines, a thorough experimental investigation was developed on a test facility at the Department of Energetic Engineering of the University of Genoa (DINE). Two VG turbines were considered: a variable area turbine (VAT) and a variable nozzle turbine (VNT). The VG turbines were compared with a fixed geometry waste-gated turbine in both steady and unsteady flow conditions, referring to mass flow and efficiency characteristics.

An Experimental Study on the Transport of Sediment in Sewer Pipes with a Permanent Deposit

1992 ◽  
Vol 25 (8) ◽  
pp. 115-122 ◽  
Author(s):  
G. S. Perrusquía
Keyword(s):  
Experimental Study ◽  
Critical Shear Stress ◽  
Side Wall ◽  
Bedload Transport ◽  
Flow Conditions ◽  
Sewer Pipes ◽  
Sediment Bed ◽  
Concrete Pipe ◽  
Geometric Factors ◽  
Particle Parameters

An experimental study of the transport of sediment in a part-full pipe was carried out in a concrete pipe. The experiments were confined to bedload transport. The purpose of this study was to analyze the flow conditions that characterize the stream traction in pipe channels and their relationship to flow resistance and sediment transport rate. Three procedures used in this kind of experimental study were tested and found valid: 1) the vertical velocity distribution near the sediment bed can be described by the velocity-defect law, 2) the side wall elimination procedure can be used to compute the hydraulic radius of the sediment bed, and 3) the critical shear stress of the sediment particles can be obtained by using Shields' diagram. A relationship to estimate bedload transport, based on dimensional analysis, was proposed. This was expressed in terms of both flow and particle parameters as well as geometric factors. Further experimental work is recommended before this relationship can be fully incorporated in a simulation model for the analysis of storm sewers.

Experimental investigation of gradually-varied unsteady flow passed a circular pile

2021 ◽  
pp. 103926
Author(s):  
Mehrnoush Kohandel Gargari ◽  
V.S. Ozgur Kirca ◽  
Oral Yagci
Keyword(s):  
Experimental Investigation ◽  
Unsteady Flow

The Estimation of Discharge in an Experimental Open Channel

2014 ◽  
Vol 905 ◽  
pp. 369-373
Author(s):  
Choo Tai Ho ◽  
Yoon Hyeon Cheol ◽  
Yun Gwan Seon ◽  
Noh Hyun Suk ◽  
Bae Chang Yeon
Keyword(s):  
Unsteady Flow ◽  
River Discharge ◽  
Open Channel ◽  
Flow Conditions ◽  
Mean Velocity ◽  
Velocity Equation ◽  
The Mean ◽  
Loop Form

The estimation of a river discharge by using a mean velocity equation is very convenient and rational. Nevertheless, a research on an equation calculating a mean velocity in a river was not entirely satisfactory after the development of Chezy and Mannings formulas which are uniform equations. In this paper, accordingly, the mean velocity in unsteady flow conditions which are shown loop form properties was estimated by using a new mean velocity formula derived from Chius 2-D velocity formula. The results showed that the proposed method was more accurate in estimating discharge, when compared with the conventional formulas.

Computational Study of the Risø-B1-18 Airfoil with a Hinged Flap Providing Variable Trailing Edge Geometry

2005 ◽  
Vol 29 (2) ◽  
pp. 89-113 ◽  
Author(s):  
Niels Troldborg
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Computational Study ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Flow Conditions ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Fully Developed Turbulent Flow

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice.

Exploring probability distribution functions best-fitting the kinetic energy of coarse particles at above threshold flow conditions

2021 ◽  
Author(s):  
Hamed Farhadi ◽  
Manousos Valyrakis
Keyword(s):  
Probability Distribution ◽  
Kinetic Energy ◽  
Test Section ◽  
Particle Transport ◽  
River Flow ◽  
Distribution Functions ◽  
Transport Processes ◽  
Flow Conditions ◽  
Probability Distribution Functions ◽  
Transport Regime

<p>Applying an instrumented particle [1-3], the probability density functions of kinetic energy of a coarse particle (at different solid densities) mobilised over a range of above threshold flow conditions conditions corresponding to the intermittent transport regime, were explored. The experiments were conducted in the Water Engineering Lab at the University of Glasgow on a tilting recirculating flume with 800 (length) × 90 (width) cm dimension. Twelve different flow conditions corresponding to intermittent transport regime for the range of particle densities examined herein, have been implemented in this research. Ensuring fully developed flow conditions, the start of the test section was located at 3.2 meters upstream of the flume outlet. The bed surface of the flume is flat and made up of well-packed glass beads of 16.2 mm diameter, offering a uniform roughness over which the instrumented particle is transported. MEMS sensors are embedded within the instrumented particle with 3-axis gyroscope and 3-axis accelerometer. At the beginning of each experimental run, instrumented particle is placed at the upstream of the test section, fully exposed to the free stream flow. Its motion is recorded with top and side cameras to enable a deeper understanding of particle transport processes. Using results from sets of instrumented particle transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of the instrumented particles kinetic energy, were generated. The best-fitted PDFs were selected by applying the Kolmogorov-Smirnov test and the results were discussed considering the light of the recent literature of the particle velocity distributions.</p><p>[1] Valyrakis, M.; Alexakis, A. Development of a “smart-pebble” for tracking sediment transport. In Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2016), St. Louis, MO, USA, 12–15 July 2016.</p><p>[2] Al-Obaidi, K., Xu, Y. & Valyrakis, M. 2020, The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards, Journal of Sensors and Actuator Networks, vol. 9, no. 3, 36.</p><p>[3] Al-Obaidi, K. & Valyrakis, M. 2020, Asensory instrumented particle for environmental monitoring applications: development and calibration, IEEE sensors journal (accepted).</p>

Analysing surface water-groundwater interactions on selected sites of the River Moselle: Identifying transport processes along an important inland waterway in Germany

2021 ◽  
Author(s):  
Simon Mischel ◽  
Michael Engel ◽  
Sabrina Quanz ◽  
Dirk Radny ◽  
Axel Schmidt ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Surface Water ◽  
Transport Processes ◽  
Main Stream ◽  
Flow Conditions ◽  
Inland Waterway ◽  
Trace Compounds ◽  
Organic Trace Compounds ◽  
Longitudinal Sampling ◽  
Organic Trace

<p>Hydraulic engineering structures like locks affect the natural hydraulic conditions and have a relevant impact on surface water – groundwater interactions due to enlarging the hydraulic gradient. For this, these sites are excellent areas to study associated flow paths, mass transport and their spatial and temporal variability in higher detail. However, no large-scale study at an inland waterway is available in Germany until now.</p><p>Our work aims to close this gap by applying a multiparameter approach for analyzing surface water-groundwater-interactions by using pH, electrical conductivity, major ions in combination with various other tracers like stable water isotopes, 222-Rn, and tritium. In this context, we also investigate the usability of organic trace compounds and their associated transformation products as potential new tracers.</p><p>The main study approach is based on the hypothesis that i) gaining stream sections show relatively high 222-Rn concentrations originating from discharging groundwater and ii) losing stream sections which are characterized by low 222-Rn concentrations as well as lower tritium and organic trace compounds inventories compared to unaffected areas.</p><p>During different flow-scenarios of the river Moselle, we test these hypotheses by means of a high-resolution longitudinal sampling at 2 km intervals of the main stream (along 242 km) and its major tributaries in combination with groundwater sampling at numerous wells.</p><p>Here, we present the first results of the longitudinal sampling campaign of the river Moselle in October 2020, which took place during intermediate flow conditions (Q=200 m³/s). We used on-site and in-situ 222-Rn measurements and electrical conductivity as a tracer to immediately identify zones along the Moselle with increased groundwater inflow.</p><p>With the use of these tracers, we will deepen the conceptual process understanding of surface water – groundwater interactions occurring at larger streams and during different flow conditions, which may lead to a general river characterization of losing and gaining stream reaches. Moreover, understanding the sources of water compounds and the processes involved during transportation and transformation is crucial for maintaining a good quality of the water body, which is key for proper water management. The findings obtained in the region of the Moselle river might be further transferred to other waterways and support decision making.</p>

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