scholarly journals Velocity profile distribution in steep channels with low relative submergence conditions

2021 ◽  
Author(s):  
Blanca Marin-Esteve ◽  
Allen Bateman Pinzón ◽  
Raul Sosa Pérez
Keyword(s):  
Velocity Profile ◽  
Profile Distribution

scholarly journals The Visual Measurement of Velocity Profile Distribution in Silt Carrying Flow by Using Ultrasound PIV and Iterative Multi-Grid Deformation Technique

2021 ◽  
Vol 11 (15) ◽  
pp. 6952
Author(s):  
Xianjian Zou ◽  
Wenbin Hu ◽  
Huan Song ◽  
Bingrui Chen
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Measurement Technique ◽  
Imaging System ◽  
Single Point ◽  
Interrogation Window ◽  
Measured Velocity ◽  
Visual Measurement ◽  
Grid Deformation ◽  
Profile Distribution

Flow velocity in silt carrying flow is one key parameter to many river engineering problems. A visual measurement technique of velocity profile distribution in silt carrying flow is provided using a portable ultrasound imaging system and an improved iterative multi-grid deformation algorithm. A convex array probe in the system is used to obtain a series of ultrasonic images at different times. Window offset and an iterative computing scheme for reducing interrogation window size in the algorithm improve the accuracy and efficiency of flow velocity measurement in regions with velocity gradients. Results show that the measured profile velocities can be more acceptable after being compared with time-averaged stream-wise velocities of profiles at ten positions in the same silt carrying flow and subsequently verified by comparing the point-by-point standard value. The measured velocity is more in agreement with the theoretical value, with the minimum root mean square error in the ultrasound beam sweep effect calculated by using optimal interrogation size parameters. The system is a feasible alternative to the single-point measurement technique in silt carrying flow. The iterative multi-grid deformation algorithm can analyze velocity profile distribution with gradients simultaneously, which can help the real-time measurement of multiple spatial velocity distribution and turbulence.

How to Improve Accuracy of Existing Ultrasonic Water Meters

2021 ◽  
Author(s):  
Iryna Gryshanova ◽  
Ivan Korobko
Keyword(s):  
Velocity Profile ◽  
Measurement Range ◽  
Calibration Factor ◽  
Flow Profile ◽  
Cfd Modelling ◽  
Flow Transducer ◽  
Flow Parameters ◽  
Ultrasonic Time ◽  
Profile Distribution ◽  
Water Meters

Abstract In present paper, the focus is given to possible ways of increasing accuracy for existing ultrasonic time-of-flight water meters. We will consider transducers with coaxial reflectors working at laminar, transitional and turbulent regimes within their measurement range. Considering error curves of such meters, we can easily resume that they are non-linear and not simply corrected using only one polynomic function. Measurements in laboratory and field conditions demonstrate that there is a shift in the ultrasonic meter’s calibration factor. The deviation of readings starts at Re = 5 000–10 000 and the maximum value is reached at Re = 160. Great inaccuracies referred to the transition from laminar flow to turbulent take place abruptly, which lead to undesirable errors. To understand this phenomenon, the theoretical basis of ultrasonic measurements was analyzed and revealed that typical algorithm for determination of the calibration factor is very questionable since it contains simplified information about velocity profile distribution. Trying to fix this problem, we applied computational fluid dynamics (CFD) modelling of ultrasonic meters with different variants of flow straighteners. Ranges of applicability of a particular turbulence model for a correct description of the velocity profile and other flow parameters in metrological purposes have been evaluated. Due to applied techniques, the flow profile sensitivities of various meter configurations are investigated at different Reynolds numbers comparing to real experiments. To get an improved ultrasonic meter design recirculation zones and flow separation regions inside the flow transducer have been eliminated. As a result, the accuracy of the ultrasonic water meter has increased. Simulations demonstrated reasonable agreement to the error curves obtained on the calibration facility for a whole measurement range.

Velocity profile distribution along an arterial vessel: way to improve detection of stenotic sites

1995 ◽  
Vol 33 (3) ◽  
pp. 247-251 ◽  
Author(s):  
S. Cavalcanti ◽  
L. Carota
Keyword(s):  
Velocity Profile ◽  
Arterial Vessel ◽  
Profile Distribution

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

Theoretical Principles of Streaming Current Detection

1989 ◽  
Vol 21 (6-7) ◽  
pp. 443-453 ◽  
Author(s):  
S. K. Dentel ◽  
K. M. Kingery
Keyword(s):  
Velocity Profile ◽  
Electrophoretic Mobility ◽  
Double Layer ◽  
Initial Attempt ◽  
Streaming Current ◽  
Coagulant Dosage ◽  
Model Predictions ◽  
Double Layer Model ◽  
Simplifying Assumptions ◽  
Current Detection

In spite of the increased use of streaming current detectors (SCDs) as a means of monitoring and/or controlling coagulant dosage, knowledge regarding fundamental workings is incomplete. This paper provides an initial attempt at predicting and verifying functioning compared to electrophoretic mobility. The instrument's components -- the sensor and the signal processor -- are first described. Equations modelling electro-double layer behavior in its sensor are then developed. Simplifying assumptions include the use of a capacitance model of the double layer and a triangular velocity profile for fluid within the sensor's annulus. More complex modelling approaches are also suggested which incorporate the Gouy-Chapman electro-double layer model and an exact solution for the velocity profile. Experimental results confirm predictions of the simplified model under conditions of low potential. A monotonic relationship exists between streaming current electrophoretic mobility, which is required for its use as a control parameter. Deviations from model predictions are suggested to be due to charge characteristics of the sensor surfaces themselves.

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