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Dr. JESSICA ***: Dr Bar-Meir is the founder of Potto Project.
He wrote three textbooks. Currently, has over a million readers
Dr Bar-Meir spend some of his time promoting open content ideology
Hello, my name is Genick Bar-Meir
I am from Potto Project.
I am very glad to have the opportunity to present this topic to distinguish audiences.
The topic of my discussion today is the maximum temperature in the shock tube.
In this discussion I will provide a short historical background,
I will discuss the motivations and the aims of this research.
I will show a physical model
I will discuss the dimensional analysis of the process.
I will compare the previous and the current model
I will conclude with some remarks.
Veille invented the short tube in the late nineteen century.
He invented this shock tube to find out how explosive act on things
or destroy things
Zel'dovich, von Neumann & Z"orin and others
re-invent the shock tube during world war two.
After that, there was a continuous development of the shock tube
but I did not see anything that is significant and or outstanding
that I found out.
Common to all these investigations about shock tube is how to destroy things
how to have atom bomb
for world war two and more explosives
This research is motivated
by looking on civilian applications of the shock tube.
and one of the benefit that google and other entities saying
that I am the most visible in the area of fluid mechanics
is that I have questions from all around the world.
I got questions from Australia and Germany
about the printing industry. Printing normally deals
when you sprayed some ink on the paper and bake it.
Baking requires temperature
and you want to have fast heating and you want to have
a cold paper at the end of the process.
Shock tube has the potential of doing that.
On the other hand, in the car industry people discussed
or asked me about how to absorb energy. When you stop the car, there is energy
and you want to move the energy in some place and then you want
to reuse this energy. So this is another potential of shock tube.
I also got some questions related to plasma and chemical reactions
but I have some ethical problems with these application
so I did not proceed with this line.
So, what is the aims of this research? To find out what is the
operational parameters of the shock tube.
For example, the pressure ratio between the two sides
and the effects of the geometrical parameters
for example, the length of the driver section
or the ratio between the length driver section to the driven section.
So, what is the shock tube?
Shock tube is a pipe that has two chambers
is separated by a diaphragm, this case
we have high pressure on one side and low pressure on the other side.
In blue indicates the cold chamber because it is going to get cold
the red indicates the hot chamber because it is going to be heated.
After the diaphragm is ruptured
the high pressure pushing the gas in the lower (driven) chamber
pushing it creates a shock wave.
this shock wave propagates toward the right
by doing so, is increasing the pressure and the temperature
this is well known and well documented.
and the shock wave reached to the other side
has reflected shock and is going backward
Here is the part where there we have a problem
when the shock reaching to the driver section
that's when the potential is eaten up
or the potential energy that we can have to increase the chamber temperature
On top of this, we have some areas
or almost entire area that is not fully used
This has to be noticed by the previous speaker that when you do
experimental research you have to do a dimensional analysis.
when you do dimensional analysis. In fluid mechanics when you teach it
the first thing when we look at dimensional analysis you look at
Buckingham Pi theory and Buckingham Pi theory
we have to look at the controlling parameters
and in this case, we have
the volume, the temperature, the density, the pressure,
the mass and the length. That is six parameters.
Then, we look on the basics fundamental parameters
which is the length, the temperature, the mass and time
and you going to get four basic parameters.
According to Buckingham Pi theory
That mean we have 2 dimensionless groups.
Then, there is a question, is that correct?
So, in order to do that we use a professional method
which is Nusselt method. What is Nusselt method?
To do that, we have to write the governing equations
when writing the governing equation, we have to look at the process and decide
what is the process that contribute the maximum temperature
in order to do that, we have the driver section pushing the other side.
has to be isentropic and adiabatic
On the other side (the driven section), it has to be only adiabatic
and does not have to be isentropic because does not matter.
In this way we can extract the most possible energy
that you can from the driver section.
when we write the governing equations and dimensionalize it
you are going to get 4 dimensionless parameters for the driver section
which is dimensionless work, dimensionless length,
dimensionless equilibrium length and the ratio of the lengths.
That is 4 dimensionless parameters.
when we write the governing equation for the driven section
we get additional 4 dimensionless parameters. In total, we have 8 dimensionless parameters.
We have two dimensionless groups methods.
One is Buckingham Pi theorem and one is Nusselt method
which provide 2 different results. One provides 2 and one provides 8.
and clearly one of them is not correct or is not complete
Since we are using the governing equations, Nusselt method
is the complete and I believe that it is the right way.
Therefore, I am imploring those who going to teach
fluid mechanics, it is essential that our students will know
what is Nusselt method and essentially if we want
them to be professional and able to solve problems they have to know this method.
Let's go back to the presentation.
We see that in the ruptured diaphragm,
we had the part that is eaten up and
the energy is not totally used and therefore, we cannot get the full potential.
In this case, we are going to get the temperature in the range of
3,000 to 14,000 degree
Very seldom we can get to 18,000
If we have what I call the moving diaphragm
between the two sections just move to the right
then we have the potential of getting the energy of
100,000 to half a million degree which significantly larger
What I learned from this thing investigation
that shock tube contain a larger amount of energy than previously thought
we can be identified and know where it (energy) was lost
So know the source of the problem we can design the shock tube.
we can redesign the shock tube to obtain the maximum temperature
I would appreciate if anyone who want
refer to this topic, will not use reference to this presentation
but my book because my book is open content and this is not.
Thank you very much
Dr. ***: thank you. Is there any question?
AUDIENCE: I have one when you talk about shock tube
do you have any idea how to build it. to build one.
is this theoretical analysis?
yes, this analysis essentially is very theoretical.
In building shock tube there are many things to be considered
and we need essentially make a pipe and between the two
sections you put a diaphragm that is ruptured
by different methods some mechanical and some electrical method.
There are a lot of discussions how to get the most efficient way.
but this analysis shows that the most efficient way
this analysis shows that instead of ruptured diaphragm we going to get
adiabatic or insulated
diaphragm and weight less that moves, we can
get huge amount of temperature increase to very very high degree
in the range of 100,000 degree
There is one guy in Chicago that has very expensive shock tube.
but if you will use the moving shock diaphragm
this method will get shock tube price to go down.
Because you going to have less pressure to achieve the same temperature.