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Message
re: How do they measure the flow?
Posted on 5/15/11 at 9:02 pm to duchuntintiger
Posted on 5/15/11 at 9:02 pm to duchuntintiger
I'm sure it has something to do with math...
All BS aside, I'm sure they shoot sonar and other shite to measure the x section of the river, measure the velocity, and do some old fangled (velocity)(area)=flow rate
All BS aside, I'm sure they shoot sonar and other shite to measure the x section of the river, measure the velocity, and do some old fangled (velocity)(area)=flow rate
0
Posted on 5/15/11 at 9:38 pm to duchuntintiger
quote:
I don't know what it is but they have beed hanging this airplane looking deal over US 61 by my house in Montz (spillway bridge). Looks like some thing to read water speed or flow.
I was not there today but that was me on the bridge Wed-Sat.
On the Bonnet Carre Bridge on Hwy 61 this is how we measure the flow.
It is called a Price AA meter. See:
LINK
Under it is a 100 lb weight (yes it looks like a torpedo).
We mark off the bridge every 100 to 200 ft. We take theAA and weight and sound the bottom. Then we bring the AA and weight up to a point 0.6*the depth and count how many times the "cups" spin in 40 sec. We do that 30-40 times across the whole bridge.
This determines the velocity for that point. The depth times the distance between the two points gives the area.
Q(discharge)=V(Velocity)*A(Area).
There are few other things that need to be done but I can not tell all the secrets(job secruity).
Posted on 5/15/11 at 9:48 pm to ScottieP
Now on the big rivers we use basically this same equipment except with a 300lb weight under the AA meter. Instead of on a bridge we do it from a boat.
A new technology that we also use on the bigger rivers is :
LINK
We mount it to the front of the boat and using it and a laptop we start on one bank and drive a straight line across to the other bank.
It sends acoustic waves through the water to determine a depth and using the speed of sound it calculates the water velocity based on particles it hits in the water. These pulses are added up to get a Q.
This allows for alot of data points and is much easier than the AA. Although both do give the same Q within a few %.
A new technology that we also use on the bigger rivers is :
LINK
We mount it to the front of the boat and using it and a laptop we start on one bank and drive a straight line across to the other bank.
It sends acoustic waves through the water to determine a depth and using the speed of sound it calculates the water velocity based on particles it hits in the water. These pulses are added up to get a Q.
This allows for alot of data points and is much easier than the AA. Although both do give the same Q within a few %.
Posted on 5/16/11 at 12:04 am to ScottieP
Scottie just won't admit it but they do use a rubber ducky 
Posted on 5/16/11 at 3:15 am to ScottieP
I really do favor the Rubber Ducky theory...
Even in 2001 when I had my Lowrance depth finder on my bass boat all components were in place (at a '01 $1,200 cost) to determine rudimentary River flow (cfs).
Area could have been determined with GPS (to determine side to side width of the River) and sonar/depth finder depth (to determine depth at any chosen # of points while travelling from side to side of the River). The Lowrance depth finder also had a velocity meter input from a spinning blade velocity meter/transducer mounted at the bottom of the transom of the bass boat (just like depthfinder transducer). The readout of this was MPH (not ft./sec.) and was designed to indicate boat speed (not River speed). However, if stationary/anchored this same readout would indicate River speed in miles per hour.
Rudimentary - yes. The Q = VA math has not changed. These were measurements. Remove as many assumptions as possible, improve the accuracy of the measuring electronica and the accuracy of measurements is improved. Do this, transfer more calculation responsibility to the computerized electronics and the resultant calculation (and the answer) is improved.
This is what has happened. Note the above crude velocity meter on my bass boat is only measuring velocity at the surface. Improvements came first from measuring velocity from top to bottom (perhaps at 3 points, perhaps more) at any one GPS reading with a given depth. This determined a velocity profile from top to bottom (mentioned in your post with 100 lb. and 300 lb. weights on the velocity meters) - IMO. Problem is/was, this is/was labor intensive and time consuming to measure velocity at each point several times. If this was not done (or only partly done) the answer relied on "Top to Bottom" profile velocity assumptions. I got that.
Calculations were always done from measurements. Improvements came from producing computerized results of the measurements (computer programs did the calculations). Sonar is obvious - the electronics contain computerized programs to display results in depth (feet). GPS slowly became more accurate (accuracy was determined by the Government's willingness to release accuracy determination (3' instead of 30') to the general public through the years since the Government has long ago had that accuracy capability).
The third ingredient (velocity) improvement is what has blown me away. ScottieP, once again thanks for the info. I appreciate candor! Sounds like the labor intensive top to bottom velocity measurement (as well as the electronic computerized calculation of cfs at a given point) has been tamed. Wow. Ain't technology somethin'????
Next up: Captain Kirk asks Scottie to shoot a reading of the River flow - can whales still swim upstream during this terible torrent? Stay tuned... Tryin' to lighten' up, not belittle anyone's plight.
Cliff Notes: Although mankind cannot measure flow (it must be calculated), measurement devices and calculating electronic devices are making flow determination of any body of water a Walk In The Park/Piece Of Cake!!!!!
BTW - I still like the Duckies and Bunnies ("Johnny Dangerously" movie) theory.
Even in 2001 when I had my Lowrance depth finder on my bass boat all components were in place (at a '01 $1,200 cost) to determine rudimentary River flow (cfs).
Area could have been determined with GPS (to determine side to side width of the River) and sonar/depth finder depth (to determine depth at any chosen # of points while travelling from side to side of the River). The Lowrance depth finder also had a velocity meter input from a spinning blade velocity meter/transducer mounted at the bottom of the transom of the bass boat (just like depthfinder transducer). The readout of this was MPH (not ft./sec.) and was designed to indicate boat speed (not River speed). However, if stationary/anchored this same readout would indicate River speed in miles per hour.
Rudimentary - yes. The Q = VA math has not changed. These were measurements. Remove as many assumptions as possible, improve the accuracy of the measuring electronica and the accuracy of measurements is improved. Do this, transfer more calculation responsibility to the computerized electronics and the resultant calculation (and the answer) is improved.
This is what has happened. Note the above crude velocity meter on my bass boat is only measuring velocity at the surface. Improvements came first from measuring velocity from top to bottom (perhaps at 3 points, perhaps more) at any one GPS reading with a given depth. This determined a velocity profile from top to bottom (mentioned in your post with 100 lb. and 300 lb. weights on the velocity meters) - IMO. Problem is/was, this is/was labor intensive and time consuming to measure velocity at each point several times. If this was not done (or only partly done) the answer relied on "Top to Bottom" profile velocity assumptions. I got that.
Calculations were always done from measurements. Improvements came from producing computerized results of the measurements (computer programs did the calculations). Sonar is obvious - the electronics contain computerized programs to display results in depth (feet). GPS slowly became more accurate (accuracy was determined by the Government's willingness to release accuracy determination (3' instead of 30') to the general public through the years since the Government has long ago had that accuracy capability).
The third ingredient (velocity) improvement is what has blown me away. ScottieP, once again thanks for the info. I appreciate candor! Sounds like the labor intensive top to bottom velocity measurement (as well as the electronic computerized calculation of cfs at a given point) has been tamed. Wow. Ain't technology somethin'????
Next up: Captain Kirk asks Scottie to shoot a reading of the River flow - can whales still swim upstream during this terible torrent? Stay tuned... Tryin' to lighten' up, not belittle anyone's plight.
Cliff Notes: Although mankind cannot measure flow (it must be calculated), measurement devices and calculating electronic devices are making flow determination of any body of water a Walk In The Park/Piece Of Cake!!!!!
BTW - I still like the Duckies and Bunnies ("Johnny Dangerously" movie) theory.
Posted on 5/16/11 at 10:26 am to TaserTiger
quote:
BTW - I still like the Duckies and Bunnies ("Johnny Dangerously" movie) theory.
You laugh about the ducks but way back in the day oranges and a stop watch was used.
Posted on 5/16/11 at 11:24 am to duchuntintiger
I was told there would be no math.
Posted on 5/16/11 at 2:49 pm to Rocketvapor
quote:
Scottie just won't admit it but they do use a rubber ducky
A rubber ducky would work fine if you have a stopwatch and know the geometry of the channel. I've done it several times were I've needed to estimate channel flow by simply using driftwood, floating debris, etc. If your channel geometry is symmetrical, like spillways, flow measurement is very accurate. However, if your channel is not symmetrical, like a river or bayou, you'll need to take several dept measurements across the the channel to get a better representation of the cross section. The more measurements the better. Then do a little elementary statistics and you can get a pretty damn accurate number.
Posted on 5/16/11 at 5:27 pm to GumboPot
Is this going to be on the test?
Posted on 5/16/11 at 8:15 pm to ScottieP
quote:
I was not there today but that was me on the bridge Wed-Sat.
On the Bonnet Carre Bridge on Hwy 61 this is how we measure the flow.
It is called a Price AA meter. See:
Thanks for the info that is very interesting, so how are things looking in the spillway. I live within a 1/4 mile so this is the highest I've seen it.
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