hi I Mike Crowley and today at fluid
mechanics I'm going to give an
introduction to the Wanda software tool.
Wonda is a software program for
modeling pipeline systems it's very good
at doing steady state and transient flow
analysis particularly of long pipe lines
and long pipeline systems today I'll
give an introduction to the user
interface and i'll show you how to build
a model using Wanda. I'll build a
model of two reservoirs connected with a
pipeline with a valve between them and
i'll show you what happens when you
close the valve when the flow is running
and you'll get a surge event or a water
hammer event in the pipeline I'll show
you how to do this shortly at fluid
mechanics.
So this is the user interface you're
presented with when you start. Here is
the working area where you're actually
going to build your model. Over here we
have a palette of components which will
build the model with and here is a
property window. Now within the palette
of components or shapes you have various
components we have tanks pumps all the
sort of basic sort of hydraulic
components that you you could want to
use. Within wonder I'm not going to be
going into this today but they have
other modules they can do heat transfer
and basically if we click on the tab for
that then those components for doing
heat transfer and they also have
components for doing more sophisticated
control systems but we're going to be
just dealing with the the Wonder liquid
components today. So we want to have two
tanks so the first thing we need to do
is select the tank or a reservoir in
this case so we're going to just use two
reservoirs at different heights and
we're going to connect them together. So
we just drag and drop the reservoir into
into the working space now as I said
we're going to have two reservoirs. So
just move that over a little bit. So I
just click click on another one and I'm
going to drag that over there. Now what
I'm going to do is have an undulating
pipe and in the middle of the pipe I'm
going to have a an air vent valve. So the
next thing we need to do is select a
pipe so this is the pipe component here
and we'll drag this in. Now we can we'll
be putting a profile in for that
pipeline in a minute and as it showing
how it goes up and down over Hills but
because as I say we want an air vent we
need to select two pipes and between the
two pipes will put the air vent.
Down here we have an air vent so I
think it's that one there. As you hover
over the the components it tells you
what they are. So this is what we want
so this is the the air vent and we're
going to need a valve at the end of the
pipeline because we're going to do a
simulation later on where we actually
close the valve. so that's the valve that
we're going to use.
Okay so they're the the basic components.
I think that's all we need to do this
this model. We now need to connect the
the components up so we go over here to
the connection and this basically
creates nodes between the various
components and we just connect them up
so I connect that to that that pipe to
that pipe. Clearly it doesn't
really matter too much where you put
things on the sheet. And we
then connect up the air vent in between
those two pipes there. I'll go back to
that mode so the first thing we need to
do is set up the tank. so we'll set up
that tank there and I say tank reservoir
as I said there's a couple of different
types of reservoir we can use this is
what we call an infinite area reservoir
so it doesn't matter how much fluid
fluid comes out of this reservoir the
level is always going to stay the same
there are other options this is a tank
with so if I put that in this has got a
limited area so effectively as the fluid
comes out of the tank the level would
start to drop but just to keep things
simple for the time being we'll just
we'll have a intimate area reservoir so
once we click on the component you'll
notice the property window comes alive
and start showing the options now this
property window is used for putting in
the parameters for that component and
after we've run the model will be able
to look at the results in this window as
well so most of the component we don't
need to do anything but the thing we do
need to say is the height of the
reservoir so I'm going to just for this
particular example put the height at 25
meters now we also need to set the
heights at the nodes between the
components okay and I'm going to set
that 25 meters actually you might say
well why why we're saying that and the
tank it took lemon's we could have set
that to a lower lower level you know the
outlet could be at the bottom of the
reservoir but just keeps things simple
I'm gonna set that to 25 meters to now
we've got the pipes here and the
valve now what we can do is some of the
values are going to be the same for all of
these three here so we've got the two
pipes and we've got the valve I mean as
you click on
components you'll see that different
parameters come up so there's the valve
there's the pipe okay but one thing I
know if I if I hold the shift key I can
select all three components together and
what you'll notice here is some of
the components some of them the names
are in red and some of them black and
what it means is when it's in red it
means that the values between the
different components is different so I'm
going t0. what we're going to do is
is the thing that we have the same for
all of them is the size so I'm going to
just say the the diameter for those and
we'll just set it for this example to
150 millimeters okay now if I set that
to 150mm you'll notice straightaway
that that's only set it for that
component there and the numbers come up
red that means that all the other the
other components have got different
values so what you can do is you got
that selected if you select that just
copies it through to the other ones
which is what you want which I which is
what I wanted to do now if i go back to
just selecting the pipes next for the
pipes i'm going to also set the wall
roughness and i'm going to set that to
one millimeter okay there are various
ways of working out friction.
the one I'm going to be
using as a Darcy formula with Colebrook-White
friction calculation now let's go
back to this pipe well actually what I'm
going to do is going to put a profile in
for the pipe okay so if i wanted to i
could just set the length of the pipe
and then it will just take the levels
from the nodes on either end but i'm not
going to do that what i'm going to do is
put a profile in so this is length hight
so then then what happens is you can go
down and we get a table a profile table
okay and we can put the the chainage in
and then we can put the the actual enter
the pipe in so basically we're going to
start off at this end of the pipe at 35
meters. So 0 chainage and it's 35
meters and then that just for this
example I would say at 3,000 meters
we're going to go down to
0 enter will come up with a new line
and then I put it 7,000 meters and we're
going to put in 10 meters in there so
basically the pipe starts off at 30
meters drops down to zero then comes
back up to 10 meters so what we need to
do then is put on that on that node
there we just put in the level that we
had for that which is going to be 10
meters we'll keep that the same kind of
it's different and then for this pipe
here I'm just going to put in that the
the the pipe length is
we're going to go pipe length it's gonna
be 6,000 meters okay the valve I think
we've set up most of the things we
need for the valve yeah we've got the
diameter its initial position is
100% in other words it's
opened the other thing we need to set is
this level here so basically the
level at this end of that pipe is 10
meters in the middle there so that pipe
is 10 meters of that end how we're going
to set it dropping down to 5 meters at
that end there five meters okay and
that's also going to be 5 meters on the
other end of that size of that valve and
I think we put in the head of that tank
no we didn't head it's 5 meters so we've
got a tank in fact what we can do is
going to turn on that on some of the
numbers so that tells us that it's at
five meters and I just put that up there
and that's the 25 meters and it will
come up show you what the value is
that's just by clicking on that tick
box there that I just shows you on there on
the chart go be a bit careful if you
start putting too much of these down
you'll end up with them a very cluttered
screen we're going to just initially run
a steady state case and what you can do
is as an option here disuse in other
words we can turn it off and we're going
to i'm just going to turn it off yes so
you notice it goes a bit greyed out so
it's not connected okay so we should now
be in a position to run a sort of a
steady state anaysis
on that on that model so let's go
often when you tried to run the model
first there's always some error but
let's justjust see what happens so I
just first of all look at the fluid
window so this tells you the fluids
property now the standard fluid they
uses water and that's exactly what I'm
going to use so I don't need to change
any of these parameters here but but
clearly you could put in various
properties if you want to for
different fluids oils etc. Now
the other thing I should perhaps point
out is there's two modes of operation on
this model and the defaults when you
first start a model is what they call
engineering mode okay and this is what
sort of recommended to start a model
often and basically this is just going
to give you the steady state steady
state results and it's it's easiest to
run it in there's less likely that
you're going to get there's less
information needed so the model is going
to run if you went to go for the
transient case you'd need to put all the
transit information in and it wouldn't
run so we should better run the model
now so we go to calculate steady state
so value of wall so if I obviously
missed out saying value of all roughness
is missing so let's just go back to that
component and I thought I'd put that in
already but I had an obviously
1 millimeter I'm sure I put it for that
one yeah that's that one's correct so
let's just calculate steady state
okay so I needed to set the
characteristic for this valve we're
going to set it to standard valve and
the type of valve is going to be a
butterfly valve so I think there
might be other types yes but we're just
gonna use a butterfly valve for this for
this case and diameter D so now let's
just try and run that model calculate
steady-state just asking me do I want to
save it and I just say just say use them
so that little click there said that its
run the model that little beep you heard
okay so if we look at some of these
results we can see the pressures at
various nodes and actually so I just
clicked on that node there and the
pressure there if you look there the
it's got a negative gauge pressure so
there's something not quite right with
the mod load of expected the pressure
there to be around about 0 gauge so I
suspect I've probably done something not
quite right so we got that height there
as 25 meters and the tank is 25 meters
but let's just quickly look at the
profile of the main yeah I started that
off at 30 meters so in other words the
inlet to the pipe is higher than the
tank which is not quite right so we put
that to 25 meters and now let's try
running the model again okay so I click
on that yeah so now clicked on there
that the pressure there is 0 and you
would expect the pressure at this end as
well to be 0 that's great so that that
looks okay so if we look at the profile
so what we can do is we can select a
pipe and we can look at the pressure
profile along the pipe which is this one
here and that's showing the pressure so
it starts off at 0 at the tank increases
as the level descends and then as a
level comes back up so the pressure
increases decreases again what's more
useful actually a better way to look at
is we can select the two pipes okay and
we can look at the pressure profile over
the whole main and that's what's
happening so basically as the level goes
down the pressure goes up and then at
the end it comes down or alternatively
normally you look in terms of head the
red line there is showing you the
profile of the main okay so that's
actually that the level of the main so
so initially it starts off at 25 meters
and if you remember the table we put it
it goes down 20 meters at 3,000 meters
along it comes back where the air valve
is up to 7,000 meters up to 10 and then
it goes back down to five at the end so
that's the the profile of the main and
this is showing you the head the total
header along the main as you'd expect it
because it's a it's got a constant
diameter pipe it just decreases
gradually to the end so that's the
steady-state case and of course you can
look at the flow velocities in the pipe
so we can look at the velocity obviously
the velocity in the pipe is going to be
the same all the way along because it's
just a steady state case 0.36 m/s
or it's probably got
discharged flow rate so actually the
flow rate along the main 23 cubic meters
an hour before we go on to look at the
transient case we need to put in the the
air valve now looking at this if we look
at the pressure at this point here the
pressure sorry the pressure is positive
so I don't think we're going to get any
air coming in and out of that Val but
but still we'll set up the air valve now
and we'll just say yes to that so we
do want to use it now. now I'll just go
through these air valve some of these
terms are a bit
not very obvious so first of all we need
to get the level right so it's 10 meters
there so we need to put the elevation of
the air valves so normally actually you
might put the elevation the air valve
slightly higher than the pipe itself
because it would be above the ground and
the pipe would be below it but I'll just
keep it the same the Laplace coefficenct
when I first start using the stuff I
found this a bit confusing what Laplace
me what they really mean by this is the
the the ratios of specific heat
capacities you know the CP over which is
1.4 for air okay ambient temperature
would you say 20 degrees inlet discharge
coefficient this is about how much the
the contraction as it goes through i
usually put 0.7 in and
0.7 for this as well inlet discharge
area okay so I'm just going to say that
this is based on a sort of a 70
millimeter valve and you need
to put this in m^2 you
could put it in mm^2
and put it in m^2 and it's I
think it's 3850e-6
meters squared okay 3850 that that's
basically a 70 millimeter valve. to the
minus 6 initial air volume so this is
the actual air volume that you've
actually got in the valve when you start
and it's going to be zero there's
usually with these air valve some sort
of residual volume left in there and
where the float goes and I need to put a
number in for that so I need to put a
volume for that and I'm going to put in
0.1 okay
I think that's all the parameters we
need for that we'll just check that now
that the model still runs before we move
on to the steady state okay so when I
run the model just then I got an error
signal I've got two screens here and on
the other screen it's come up with the
error error that's just showing an error
there and just looking at this thing I'm
not so what's so I think what's actually
wrong is this elevation I've got
actually its elevation offset not
elevation so so what I should have said
is the offset 0 so it sort will change
that 20 i think yeah that probably solve
the problem and it's just um model run
that again calculate steady oh yeah and
that worked or okay now so we can see
the pressures and everything in there
but if we should actually look at the
valve if we look down here the air flow
is 0 because there is no negative
pressure the pressure is positive at
that at that point because it's a
positive pressure so now we are ready to
go for the the transient case so we first
of all need to swap over modes so
initially we were doing this engineering
mode we now need to go to transient mode
okay if these two yes okay now one we go
to the transient mode what you'll find
is if we look at the the model there's
more parameters to put in particular for
the pipes so we need to put in some
information for the pipes and the thing
that we really need to do is is first of
all we need to set the mode that we're
going to use and we're going to talk
about water hammer or
surge you can there's a number of
ways you could model it water hammer is
is is the proper way to do it that's
using what they call the method of
characteristics to to work out the water
hammer wave speed now you can you can
specify wave speed I have done another
video on how you actually calculate the
wave speed in water hammer events and it
may be well looking at that if you
actually want to
work out how to calculate it you can
actually put in the physical parameters
of the wall thickness and that and
that's actually what I showed you in the
other show in the other video how to
calculate the wave speed or actually can
just specify what the wave speed is I
tend to prefer to just specify what the
wave speed is and we're going to set
both of them both pipes the same wave
speed and we're going to set it at a
typical sort of wave speed for a plastic pipe
would be about 1200 meters a second
actually how quite right
so 1,200 meter but I need to obviously
copy that across to the other one okay
and also that needs to be specified for
both of them so we're going to do it
that way ok so this uses a system called
the method of characteristics to plot
the progression of the wave speed the
wave front going along the pipe it
basically breaks the pipe up into small
sections and we have what's known as a
fixed stepped solver so actually if
we go up here we need to change the time
parameters so what we need to do is
the time step so we can set set how the
short of the time step we set the more
accurate the results are going to be I'm
going to set it to a time step of about
0.1s I think that's good enough
foot for what we need here and we can
run the model for say 200 seconds of
simulation time there are other methods
that other softwares use I have given a
demonstration on simulation X and
modelica modeling that uses a different
way of modeling the progression of
waves along a pipe it's not really as
accurate as the method of
characteristics for long pipes this is
by far the most accurate method of using
it other methods basically what they do
is split the pipe up again into small
sections which is what this does but
then they look at the bulk modulus of
the sections and
actually the wave speed sort of
propagates along the whole whole pipe
almost instantaneously so it doesn't
quite give you the same characteristics
definitely the method of characteristics
for long pipes is by far the best the
reason why other software you use a
different method is because they use
variable type step solvers MATLAB
Simulink sim hydraulics use that as well
in their in their software this does
require fixed step time solver of them okay so
let's try running the model now and see
what happens honor we need to fit all so
what we're going to do here now is we're
going to actually close the valve so
we've got a valve we've got the position
and what we're going to do is we're
going to set up a table of closing it
over a period of time initial position
is 100% use action table that's what
we're going to do yes so action table so
at time 0 the valve is going to be a
hundred percent open so we put one
hundred percent in there then at time
one second it's still going to be a
hundred percent so initially what I'm
going to do is initially for the first
one second this will this will provide
steady state conditions that we want and
then what will say is over say a period
of 20 seconds will close the valve will
save 30 seconds to start with and we'll
go down to zero and then at 200 seconds
which is the end of the run you will
still be 0 okay so that's going to give
you your profile of the valve closing so
that's just come across your screen so
effectively that's what we've got going
down to zero
let's try running that and see what
happens so we're now going to do this
the transient case so that has run I
think and what we can do is we can now
if we click on the valve we can look at
the discharge now that should give us
the discharge over time so what you can
see is is the valve closing. Now
actually this is the flow rate through
the valve and i'll just show something
else as well on this valve the position
so this is showing you the position and
actually what we can do is we can bring
the two graphs in together what if you
click on if you click and drag it in you
bring the two in together so the valve
is closing and actually what you find
with a butterfly valve which is typical
is that butterfly valves they don't
actually start to shut off the flow rate
until you've got to quite closed. so if i
can if i zoom into this zoom if we zoom
into this safe for the first 20 30
seconds you'll find that it's only when
you get to about 20 seconds which is
about sorry looking over this way sort
of when you get to about twenty-five
percent closed that the the flow rate
actually starts to drop off okay close
that down so what happens what's
happening to the pressure so we can look
at that point there and we can see the
pressure and this is a sort of a typical
surge analysis of water hammer event so
as you close the valve the pressure
builds up and actually it's on the
second thing that you get the highest
pressure in the system and then it's
slowly decays away over time let's just
have a look at the whole pipeline so we
can click both of those pipes
and we can actually look at the pressure
through the whole pipe now what this
tells you is this is giving you the
maximum and minimum pressure up over the
whole pipeline okay this is showing you
the centerline of the pipe or the
pressure for the centerline of the pipe
and going up and down this is the
minimum pressure that's the maximum
pressure now it's perhaps a bit more
useful to actually show what's happening
in the transient case so what you can do is
we'll bring down this time navigator bar
let's put onto the screen so just bring
it across and this this will allow you
to see what's actually happening to
think so what we do is we press the
start button and it basically runs
through the model and it tells you
what's actually actually happening.
okay so there we go this is showing you
the initial pressure the blue line is
the initial pressure in the pipeline and
as you can see as the valve closed at
the end so let's just stop that for a
second so if we go back we start again
so we're now up to nine seconds and not
much is happening this is because the
valve is just starting to close now
we're getting to sort of 20 seconds and
the valve is closing and the pressure at
the end of the pipe is starting to shoot
up as it closed down that pressure wave
is then moving all the way along the
pipe to the end and it's sort of like a
40 seconds it's getting to the end and
and now we can see what's happening over
a period of time as the pressure waves
fluctuate in the pipe okay that's
showing you what's happening I'm going
to speed it up a bit and you can see the
propagation of the wave over time that
will start to die down and eventually
you'll get to the final condition which
is well that's not quite the final
because I stopped it before it
completely settled but we can also look
at the pressure in at the point here and
that's the way the pressure at various
points okay so if I if I looked at that
other plot and plotted out that various
times this is what we would get
okay so looking at the pressure here.
This is showing you the pressure
characteristic we got for that valve
closing so let's see what we can do to
try and smooth that out a little bit so
what I'm going to do is I'm going to
freeze that screen and when we make the
changes we can you can see what happens
to it freeze all series okay I'm just
minimize that for a minute now we had
look at this valve and as I said the
valve as I showed previously it didn't
actually do any didn't actually help
reduce the flow until we got down to
about twenty-five percent so if we
rapidly close the valve term to
twenty-five percent and then do the rest
of it slowly I think that will help
quite a bit so what we'll do is I'll
change this time so if we say in two
seconds it closes so the first second it
closes really rapidly down to
twenty-five percent and then if I put in
that in 20 seconds it's now down to zero
percent so it's actually going to close
the last bit over a lot longer period of
time and then in 200 seconds it's down
to well it's still at zero percent okay
so that's that's that's what we're going
to do let's bring back that sorry let's
just over here the the graph so if I
bring back that graph and I'll run the
model calculate transient yes okay so
that's run
so if I now go back to this point here
and I take those pressure and I put that
onto that graph right well you can see
it's it's it's obviously gone down and
it's the pressure started to rise a bit
earlier because it's actually doing
something useful at the start now and
because the pressure rise because it was
actually the closure is over a longer
period of time the actual effective
pleasure along is over long a period of
time the surge pressures that rise have
been reduced and clearly I mean this is
quite a long pipeline so to have any
sort of effect i mean this this is that
it's got a length of 7,000 meters and
and that one there is forgot what was
that we put down so I that that that
pipe their length is seven sets that's
thirteen thousand meters so if we have
thirteen thousand meters and we got a
wave speed of 1200 so obviously so
that's going to be about 10s
so 20 seconds is sort of
basically the minimum that you would
need. At 20 seconds you're still going to
get significant surge so we need to sort
of which increase the speed or reduce
the increase the time to close to it for
about 40 seconds I think to make any
significant difference to this so let's
go back to the valve but at 40 seconds
okay that's where you run the model
hopefully should just put the model back
in so as you can see it's time to now
smooth it out more and we can just make
one more effort on that I mean I think
you need to 80 seconds with probability
about as good as you're going to get so
try 80 seconds in there plus 80 seconds
as we run the model so i think that's
about as good as you can get without
using sort of search or some sort of
damping system in there and if we look
at the profile of the flow rate through
there you go coming down nice and slowly
and if we look at the whole pipeline now
what's happening in the whole pipeline
the surge pressure should now be a lot
less over the whole pipeline and so so
we're not going up as high as we were
previously. So in summary Wonda is an
excellent program for doing surge
analysis on long pipelines and pipeline
systems it uses the method of
characteristics which is proven to be
the best method of solving surge
analysis particularly in long pipe lines
if you have any general questions then
please leave a comment on my website
blog and I will endeavor to answer them
there I cannot answer any questions
directly of our email but if you need
more detail advice or help on a surge
on a consultancy type
basis then please contact me my
contact details are on my website please
subscribe to my youtube channel i think
there is a link above over there
somewhere and please like my video if
you found it useful thank you for listen
that's it's a day form fluid mechanics
goodbye
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