Current meter - Revision history

António at 16:08, 10 April 2020

2020-04-10T16:08:28Z

António at 16:02, 10 April 2020

2020-04-10T16:02:19Z

António: /* Other information */

2020-04-10T15:57:06Z

Other information

António: /* Application */

2020-04-10T15:55:31Z

Application

António: /* Application */

2020-04-10T15:54:37Z

Application

António: /* Application */

2020-04-10T15:51:10Z

Application

António: /* Application */

2020-04-10T15:48:23Z

Application

António: /* Application */

2020-04-10T15:47:04Z

Application

António at 15:41, 10 April 2020

2020-04-10T15:41:17Z

Bendikhansen at 13:12, 5 April 2020

2020-04-05T13:12:55Z

@@ Line 1: / Line 1: @@
 =Quick summary=
 [[file:current_meter_types.png|thumb|250px|Figure 1: Current meter: a) mechanic, b) electromagnetic, c) acoustic (Sources: SEBA hydrométrie, OTT, Sontek).]]
-[[file:current_meter_section.png|thumb|250px|Figure 2: Cutting of a section during the measurement by a flow meter, in red the verticals, the black dots correspond to the measurement points.]]
+[[file:current_meter_section.png|thumb|250px|Figure 2: Flow cross-section with the verticals (in red) and the  points (black dots) for velocity measurement with the current meter]]
-[[file:current_meter_operator.png|thumb|250px|Figure 3: Operator in the downstream migration channel for measurements with a current meter.]]
+[[file:current_meter_operator.png|thumb|250px|Figure 3: Operator in the downstream migration channel performing measurements with a current meter.]]
 Developed by:

@@ Line 1: / Line 1: @@
 =Quick summary=
-[[file:current_meter_types.png|thumb|250px|Figure 1: Current meter: a) mechanic, b) electro-magnetic, c) acoustic. Sources: SEBA hydrométrie, OTT, Sontek.]]
+[[file:current_meter_types.png|thumb|250px|Figure 1: Current meter: a) mechanic, b) electromagnetic, c) acoustic (Sources: SEBA hydrométrie, OTT, Sontek).]]
 [[file:current_meter_section.png|thumb|250px|Figure 2: Cutting of a section during the measurement by a flow meter, in red the verticals, the black dots correspond to the measurement points.]]
 [[file:current_meter_operator.png|thumb|250px|Figure 3: Operator in the downstream migration channel for measurements with a current meter.]]
@@ Line 14: / Line 14: @@
 The first devices to measure flow velocities appeared during the 1780s, with the first mechanical current meter which counts the rotations of a propeller and links it to the flow velocity (by proportionality principle).
-Today there are 3 different techniques to assess the flow velocity: mechanically, electromagnetically, and acoustically (Figure 1). The acoustic current meters using the Doppler Effect are not presented here, as these tools (ADCP, ADV, etc.) are presented separately.
+Today there are 3 different techniques to assess the flow velocity: mechanically, electromagnetically, and acoustically (Figure 1). The acoustic current meters using the Doppler Effect are not presented here, as these tools (e.g ADCP, ADV) are presented separately.
 =Application=
-For a mechanical flow meter, the rotation of the propeller produces an electrical impulse detected and recorded by a counter connected to the current meter.
+In a mechanical flow meter, the rotation of the propeller produces an electrical impulse detected and recorded by a counter connected to the current meter.
 The electromagnetic flow meter uses the Faraday law. The sensor creates a magnetic field between two electrodes located at the end of the probe. The flow velocity is deduced from the measurement of the electromagnetic force generated by the passage of water through the magnetic field.

@@ Line 56: / Line 56: @@
 =Other information=
-Several companies commercialise these technologies.
+Several companies commercialize these technologies.
-At the French Test Cases an electromagnetic flow meter Marsh McBirney, FLO-MATE 2000 is used.
+At the French Test Cases an electromagnetic flow meter Marsh McBirney, FLO-MATE 2000 was used.
 =Relevant literature=

@@ Line 46: / Line 46: @@
 <math>Q_{section}=V_{mean section}*H_{water mean}*W</math>
-where <math>Hwatermean</math> is the mean water level and <math>W</math> is the width of the channel.
+where <math>H_{water mean}</math> is the mean water level and <math>W</math> is the width of the channel.
 The total discharge is the sum of all the discharges per section.

@@ Line 22: / Line 22: @@
 The measurement conditions of discharge through flow velocity fields are regulated by the European standard NF EN ISO 748.
 The velocities are measured along a cross section at verticals. The number of verticals (n) depends on the width of the channel (w):
-* w < 0.5 m,  n = 5 or 6
+* W < 0.5 m,  n = 5 or 6
-* w > 0.5 m and < 1 m,  n = 6 or 7
+* W > 0.5 m and < 1 m,  n = 6 or 7
-* w > 1 m and < 3 m,    n = 7 or 12
+* W > 1 m and < 3 m,    n = 7 or 12
-* w > 3 m and < 5 m,    n = 13 to 16
+* W > 3 m and < 5 m,    n = 13 to 16
-* w > 5 m,   n ≥ 22
+* W > 5 m,   n ≥ 22
 One method among others to measure the mean velocity on each vertical is to measure the velocity in one or several measurement points at different water levels on the vertical. The number of measurements points for each vertical depends on the water level. For example, only one point is needed for water level <20 cm at 60% of the water level. If there are only 2 measurement points, they should be at 20 and 80% of the flow depth, and the mean velocity corresponds to the average of the two measured velocities. In the following example, 6 measurements were selected (Figure 2). The example is linked to the velocity profile inside a downstream migration channel, which is not logarithmic.
@@ Line 44: / Line 44: @@
 The discharge per section can be calculated according to standard EN ISO 748:2007:
-<math>Q_{section}=V_{mean section}*H_{water mean}*w</math>
+<math>Q_{section}=V_{mean section}*H_{water mean}*W</math>
-where Hwatermean is the mean water level and w is the width of the channel.
+where <math>Hwatermean</math> is the mean water level and <math>W</math> is the width of the channel.
 The total discharge is the sum of all the discharges per section.

@@ Line 44: / Line 44: @@
 The discharge per section can be calculated according to standard EN ISO 748:2007:
-<math>Q_{section}=V_{mean section}*H_{water mean}*L_{flow}</math>
+<math>Q_{section}=V_{mean section}*H_{water mean}*w</math>
-where Hwater mean is the mean water level and Lflow is the width of the channel.
+where Hwatermean is the mean water level and w is the width of the channel.
-The total discharges the sum of all the discharges per section.
+The total discharge is the sum of all the discharges per section.
-The most recent devices have the possibility to directly treat the data and give the total discharge.
+The most recent devices have the possibility to directly treat the data and provide the total discharge.
 =Relevant mitigation measures and test cases=

@@ Line 21: / Line 21: @@
 The measurement conditions of discharge through flow velocity fields are regulated by the European standard NF EN ISO 748.
-The velocities are measured along a cross section at verticals. The number of verticals (n) depends on the width of the channel:
+The velocities are measured along a cross section at verticals. The number of verticals (n) depends on the width of the channel (w):
-*Width of channel < 0.5 m, n = 5 or 6
+* w < 0.5 m            n = 5 or 6
-*Width of channel > 0.5 m and < 1 m, n = 6 or 7
+* w > 0.5 m and < 1 m  n = 6 or 7
-*Width of channel > 1 m and < 3 m, n = 7 or 12
+* w > 1 m and < 3 m    n = 7 or 12
-*Width of channel > 3 m and < 5 m, n = 13 to 16
+* w > 3 m and < 5 m    n = 13 to 16
-*Width of channel > 5 m, n ≥ 22
+* w > 5 m              n ≥ 22
 One method among others to measure the mean velocity on each vertical is to measure the velocity in one or several measurement points at different water levels on the vertical. The number of measurements points for each vertical depends on the water level. For example, only one point is needed for water level <20 cm at 60% of the water level. If there are only 2 measurement points, they should be at 20 and 80% of the flow depth, and the mean velocity corresponds to the average of the two measured velocities. In the following example, 6 measurements were selected (Figure 2). The example is linked to the velocity profile inside a downstream migration channel, which is not logarithmic.
@@ Line 40: / Line 40: @@
 <math>V_{mean section}=\frac{m}{(m+1)}*V_{mean closer vertical}</math>
-where m is a parameter depicting the characteristics of the river bed or of the wall. m is generally comprised between 5 and 7 but can be equal to 10 if the walls are really smooth. If m=4 the river bed and the walls are rough.
+where m is a parameter depicting the characteristics of the river bed or of the wall. m is generally comprised between 5 and 7, but can be equal to 10 if the walls are really smooth. If the river bed and the walls are rough, m=4.
 The discharge per section can be calculated according to standard EN ISO 748:2007:
@@ Line 46: / Line 46: @@
 <math>Q_{section}=V_{mean section}*H_{water mean}*L_{flow}</math>
-Where Hwater mean is the mean water level and Lflow is the width of the channel.
+where Hwater mean is the mean water level and Lflow is the width of the channel.
-In order to have the total discharge, all discharges per section have to be added.
+The total discharges the sum of all the discharges per section.
-The most recent devices have the possibility to directly treat the data and give the discharge on the cross section.
+The most recent devices have the possibility to directly treat the data and give the total discharge.
 =Relevant mitigation measures and test cases=

← Older revision		Revision as of 13:12, 5 April 2020
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−	~~NOTE: fix equations [[file broken]]~~
−
	=Quick summary=		=Quick summary=
	[[file:current_meter_types.png\|thumb\|250px\|Figure 1: Current meter: a) mechanic, b) electro-magnetic, c) acoustic. Sources: SEBA hydrométrie, OTT, Sontek.]]		[[file:current_meter_types.png\|thumb\|250px\|Figure 1: Current meter: a) mechanic, b) electro-magnetic, c) acoustic. Sources: SEBA hydrométrie, OTT, Sontek.]]