The Uncertainty of Measurements in River Hydraulics: Evaluation of Friction Velocity Based on an Unrepeatable Experiment

This paper intends to present the theoretical background as well as practical illustrations for good laboratory practices in conductivity measurements, ways to increase the accuracy of conductivity measurements as well as how one may evaluate the uncertainty of conductivity measurements for the electrolyte solutions. Practical measurements for prepared standards of 1 M KCl and 0.1 M KCl solutions are carried out and the values of repeatability, composed uncertainty and expanded uncertainty are presented.

Download Full-text

Considering the impact of intermittent discharges when modelling overflows

Water Science & Technology ◽

10.2166/wst.1998.0370 ◽

1998 ◽

Vol 38 (10) ◽

pp. 23-30

Author(s):

Sarah Jubb ◽

Philip Hulme ◽

Ian Guymer ◽

John Martin

Keyword(s):

Water Quality ◽

Dissolved Oxygen ◽

Preliminary Investigation ◽

Oxygen Demand ◽

Sediment Oxygen Demand ◽

Combined Sewer Overflows ◽

River Hydraulics ◽

Combined Sewer ◽

The Impact ◽

Curve Equation

This paper describes a preliminary investigation that identified factors important in the prediction of river water quality, especially regarding dissolved oxygen (DO) concentration. Intermittent discharges from combined sewer overflows (CSOs) within the sewerage, and overflows at water reclamation works (WRW) cause dynamic conditions with respect to both river hydraulics and water quality. The impact of such discharges has been investigated under both wet and dry weather flow conditions. Data collected from the River Maun, UK, has shown that an immediate, transient oxygen demand exists downstream of an outfall during storm conditions. The presence of a delayed oxygen demand has also been identified. With regard to modelling, initial investigations used a simplified channel and the Streeter-Phelps (1925) dissolved oxygen sag curve equation. Later, a model taking into account hydrodynamic, transport and dispersion processes was used. This suggested that processes other than water phase degradation of organic matter significantly affect the dissolved oxygen concentration downstream of the location of an intermittent discharge. It is proposed that the dynamic rate of reaeration and the sediment oxygen demand should be the focus of further investigation.

Download Full-text

Modelling Weirs in Two-Dimensional Shallow Water Models

Water ◽

10.3390/w13162152 ◽

2021 ◽

Vol 13 (16) ◽

pp. 2152

Author(s):

Gonzalo García-Alén ◽

Olalla García-Fonte ◽

Luis Cea ◽

Luís Pena ◽

Jerónimo Puertas

Keyword(s):

Experimental Data ◽

Shallow Water ◽

Shallow Water Equations ◽

Water Model ◽

Two Dimensional ◽

Shallow Water Model ◽

Experimental Dataset ◽

River Hydraulics ◽

Shallow Water Models ◽

Water Models

2D models based on the shallow water equations are widely used in river hydraulics. However, these models can present deficiencies in those cases in which their intrinsic hypotheses are not fulfilled. One of these cases is in the presence of weirs. In this work we present an experimental dataset including 194 experiments in nine different weirs. The experimental data are compared to the numerical results obtained with a 2D shallow water model in order to quantify the discrepancies that exist due to the non-fulfillment of the hydrostatic pressure hypotheses. The experimental dataset presented can be used for the validation of other modelling approaches.

Download Full-text

The asymptotic stage of longitudinal turbulent dispersion within a tube

Journal of Fluid Mechanics ◽

10.1017/s0022112077001682 ◽

1977 ◽

Vol 80 (2) ◽

pp. 293-303 ◽

Cited By ~ 11

Author(s):

R. Dewey ◽

Paul J. Sullivan

Keyword(s):

Turbulent Flows ◽

Friction Velocity ◽

Turbulent Dispersion ◽

Time Interval ◽

Longitudinal Diffusion ◽

A Value ◽

Discharge Velocity ◽

Concentration Curves ◽

Temporal Growth Rate ◽

Short Times

This paper describes an experimental investigation of the conditions for which the asymptotic description of longitudinal dispersion given by Taylor (1954) would apply. At non-dimensional times following the release of a dye pulse that are significantly larger than those previously investigated, the integrated concentration curves were observed to be skewed. At relatively short times from release the concentration curves appear to be well described by the models presented by Sullivan (1971) and by Chatwin (1973). Some features of the asymptotic behaviour, namely the translation of the modal value of the integrated concentration curve at the discharge velocity and the constant temporal growth rate of the variance, are observed at the longest times following release. On the basis of these observations it is estimated that a non-dimensional time interval oftu*/d=O(105/R*), whereR*=u*d/v,u*is the friction velocity,vthe kinematic viscosity anddthe tube diameter, is required for the Taylor result to become applicable. Thus application of Taylor's theory is significantly restricted in turbulent flows, especially those with irregular boundaries and those that are not stationary. There the variations in the flow must be small with respect to an equivalent ‘development time’ if a value of the ‘local’ longitudinal diffusion coefficient is to have meaning.

Download Full-text

The application of a Ku-band scatterometer model function for friction velocity to SEASAT measurements and to airborne scatterometer measurements

Proceedings of OCEANS '93 ◽

10.1109/oceans.1993.326039 ◽

2002 ◽

Author(s):

D.E. Weissman

Keyword(s):

Friction Velocity ◽

Model Function ◽

Ku Band

Download Full-text

Controlled storage conditions prolong stability of biochemical components in whole blood

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm.2005.036 ◽

2005 ◽

Vol 43 (2) ◽

Cited By ~ 8

Author(s):

Marta Stahl ◽

Ivan Brandslund

Keyword(s):

Whole Blood ◽

Storage Conditions ◽

Ion Concentration ◽

Potassium Ions ◽

Uncertainty Of Measurements ◽

Biochemical Components ◽

Turn Around Time ◽

Analytical Result ◽

Blood Specimens ◽

Doctor's Office

AbstractBlood specimens from primary care centres are normally transported to central laboratories by mail. This necessitates centrifugation and separation, especially since the potassium ion concentration in whole blood changes during storage at ambient temperature. Thus, because of the growing awareness of and concern for pre-analytical contributions to the uncertainty of measurements, we investigated 27 components and their stability under controlled temperature conditions from 17 to 23°C. We found that storage of whole blood can be prolonged by up to 8–12h for all components examined, including potassium ions, when stored at 20±0.2°C. We conclude that this opens the possibility for establishing a pick-up service, by which whole blood specimens stored at 20–21°C can be collected at the doctor's office, making centrifugation, separation and mailing superfluous. In addition, the turn-around time from sample drawing to reporting the analytical result would be shortened. After investments in thermostatted boxes and logistics, the system could reduce costs for transporting blood samples from general practice centres to central laboratories.

Download Full-text

River Hydraulics

10.1007/978-3-030-81768-8 ◽

2022 ◽

Keyword(s):

River Hydraulics

Download Full-text

Turbulence and Flow–Sediment Interactions in Open-Channel Flows

Water ◽

10.3390/w12113169 ◽

2020 ◽

Vol 12 (11) ◽

pp. 3169

Author(s):

Roberto Gaudio

Keyword(s):

Open Channel ◽

Field Experiments ◽

State Of The Art ◽

Channel Flows ◽

Special Issue ◽

Panoramic View ◽

Open Channel Flows ◽

River Hydraulics ◽

The World ◽

Computing Skills

The main focus of this Special Issue of Water is the state-of-the-art and recent research on turbulence and flow–sediment interactions in open-channel flows. Our knowledge of river hydraulics is becoming deeper and deeper, thanks to both laboratory/field experiments related to the characteristics of turbulence and their link to the erosion, transport, deposition, and local scouring phenomena. Collaboration among engineers, physicists, and other experts is increasing and furnishing new inter/multidisciplinary perspectives to the research in river hydraulics and fluid mechanics. At the same time, the development of both sophisticated laboratory instrumentation and computing skills is giving rise to excellent experimental–numerical comparative studies. Thus, this Special Issue, with ten papers by researchers from many institutions around the world, aims at offering a modern panoramic view on all the above aspects to the vast audience of river researchers.

Download Full-text

Towards a reasoned 1D river model calibration

Journal of Hydroinformatics ◽

10.2166/hydro.2005.0009 ◽

2005 ◽

Vol 7 (2) ◽

pp. 91-104 ◽

Cited By ~ 9

Author(s):

Jean-Philippe Vidal ◽

Sabine Moisan ◽

Jean-Baptiste Faure ◽

Denis Dartus

Keyword(s):

Model Calibration ◽

Expert Knowledge ◽

Fixed Bed ◽

Rainfall Runoff ◽

Simulation Code ◽

Hydraulic Simulation ◽

Flow Equations ◽

Knowledge Based ◽

River Hydraulics ◽

Knowledge Levels

Model calibration remains a critical step in numerical modelling. After many attempts to automate this task in water-related domains, questions about the actual need for calibrating physics-based models are still open. This paper proposes a framework for good model calibration practice for end-users of 1D hydraulic simulation codes. This framework includes a formalisation of objects used in 1D river hydraulics along with a generic conceptual description of the model calibration process. It was implemented within a knowledge-based system integrating a simulation code and expert knowledge about model calibration. A prototype calibration support system was then built up with a specific simulation code solving subcritical unsteady flow equations for fixed-bed rivers. The framework for model calibration is composed of three independent levels related, respectively, to the generic task, to the application domain and to the simulation code itself. The first two knowledge levels can thus easily be reused to build calibration support systems for other application domains, like 2D hydrodynamics or physics-based rainfall–runoff modelling.

Download Full-text