Transcript Mjerenje protoka vode

The Primeval
Power of Water
Methods of Measuring
the Speed Flow of the River Drava
RUNNING WATER
STAGNANT WATER
About Drava
• running water
• 725 km (springs in South Tirol)
Danube
• Varaždin, Legrad, Belišće, Osijek
• length: 719 km
• the size of the drainage basin:
40087 km2
• depth: 4-7 m
• spring – maximum water level
• zima – minimum water level
• the bottom substratum either
muddy or sandy
• the shore – strewn with rocks
• a river which is fast and strong
The History of Drava as an Important
Water Resource
• in the 19th century many hydro-regulatory measures
have been taken (before that, a lot of surrounding
villages nearby Drava were often flodded – Bukevlje,
Levača, Repaš…)
• water-mills
• hydro-electric power plants (Donja Dubrava)
The purpose of water-mills
• grinding of grains and
making flour
• sawing of boards
• processing of textile
• manufacture of cast iron,
etc.
What can we measure on a river?
pH
• pH is a measure of the acidity or basicity of an
aqueous solution
TEMPERATURE
• a physical value by which we express the
thermal state of something
RIVER WIDTH
l
RIVER DEPTH
h
CROSS SECTION
DETERMINING THE
CROSS SECTION OF
THE RIVER DRAVA
1ST PROBLEM OF THE COMENIUS TEAM
• utenslis: a ferry, 15 m long cord, grapples, 200
m long cord, measuring tape, an iron object
• the problem:
– 1. find an equation with the help of which we can
determine the surface of the cross section of the
river Drava
– 2. draw a curve which describes how the depth of
the river Drava changes with its width
INSTRUCTIONS
Secure the iron object on a 15 m cord. First
measure the width of the river: secure the
longer cord on the right bank of the river, and
transfer onto the left bank. While returning
towards the right bank, measure the depth
with the shorter cord.
FLOW SPEED
• the volume of water which passes through
the observed point in a certain time interval
Ways of Measuring the Flow Speed
Q = V/t
3
(m /s)
Ultrasonic Flow Meter
• based on high-frequent sound waves which are generated by
introducing a certain alternative voltage onto the piezoelectric
crystal
Electromagnetic Flow Meter
• the fluid itself works as a voltage conductor, and
there are two electrodes on the inner walls of the
tube (which are isolated from the tube itself)
The Bucket Method
• measure the volume of
the bucket
• find a location along the stream
that has a waterfall (or using a weir)
• with a stopwatch, time how long it takes the
waterfall to fill the bucket with water
• repeat steps two and three about six or seven
times and take the average
THE STREAMING SPEED
• the speed by which the fluid passes
through the observed cross section
v = s/t (m/s)
MEASURING THE
STREAMING SPEED
OF THE RIVER DRAVA
2ND PROBLEM OF THE COMENIUS TEAM
• utensils: a ferry, stopwatch, measuring tape, bits of
paper
• the problem:
– 1. determine the streaming speed of the river Drava at Brodić
– 2. determine the maximum absolute and the maximum
relative errors
INSTRUCTIONS
• climb onto the ferry
• measure the width of the ferry
• after the width of the ferry has been measured, throw
bits of paper into the water from one end of the ferry
• measure the time needed for one bit of paper to get to
the other end of the ferry
The Primeval and Unpredictable
Power of Water  FLOODS
• November 2013, Karlovac (Kupa)
• February 2014, Sisak surroundings (Sava)
We often forget that the circle of water
is the same thing as the circle of life.
Jacques Yves Cousteau
The noblest of the elements
is water. (Pindar)
Who does not care for the water,
does not care for a better tomorrow.
(Old Irish saying)
To a good man, one drop of water is the
ocean; to an evil man, the ocean is but one
drop of water. (Indian saying)
The Primeval
Power of Water
Methods of Measuring
the Speed Flow of the River Drava