It is amazing to do experiments on "fluidized bed" in which hard sand becomes undulating like a liquid with bath size

People will not sink on the sandy beach, but as air is sent in the sandy beach, "Fluidized bed"The sand will become wavy like water. A movie that reproduces this phenomenon by using a bath bath is being released on YouTube.

Liquid Sand Hot Tub - Fluidized air bed - YouTube


Engineers who are former NASA engineersMark RoberI am sitting on a bath with sand. Naturally, the ground is hard as if it is sitting on a sandy beach.


However, when Pocopoko and air bubbles come up from under the sand, Rober sinks and goes as if he got caught in a bog.


This means that by ejecting gas from the bottom of small particle size particles like sand, solid particles will behave like a liquid "Fluidized bedThe application of the phenomenon phenomenon. When you watch the movie, you can see the mysterious appearance that the sand put in the container waves like a liquid.


Usually, when the fluidized bed is coated with powder paint ... ...


To store cerealssiloIt is used for.


Even if you put the nymo toys used in the water on the sand, if you do not normally move at all ... ...


Within the fluidized bed, the toy will advance as if swimming in the water.


When the ball is pressed against the sand, the ball sinks as the sand waves.


The phenomenon of fluidized bed itself is not new. The picture of the fluidized bed reproduction experiment which was carried out about 60 years ago remains as a picture. However, Rober says he wanted to do experiments on the fluidized bed for many years, but he could not find information on the Internet.


So Rober decided to develop the original mechanism with reference to the system applied fluidized bed which is used industrially.


Investigating the fluidized bed, Rober noticed that in any system, there are many holes in the pipe for sending air to the sand.


And repeated as many as 25 failures ......


The following mechanism is completed.

PVC pipes with a diameter of about 1.27 cm are spread under a container in a ladder shape.


At this time, a hole is made in the pipe so that the angle between the hole and the hole becomes 90 degrees, and holes are drilled from the 2 side.



Drill holes at 25 mm intervals.


Firmly adhere so that sand does not get inside the pipe ... ...


Put fine sand or glass beads in the container containing the pipe.


To send air, use air compressor.


When doing a large-scale experiment it is OK if you rent a nitrogen cylinder like this.


The basic structure is as above. To do experiments on the fluidized bed with the bath size, it is enough to scale up the above mechanism, so in the movie, the created video is swept forward in the fast forward.


Cut the pipe ... ....


I will bend it in the required shape.


I am destroying the bath oath gently.


Putting a hole with a hole ... ...


The necessary equipment is stored inside the bath.


I connect a bottle and a bath.


Complete filling the sand with a bath.


It is Rober standing on the sand ... ...


Once the system is operational and the air bubbles out, it was sunk and Zubuzubu without being stood.


So, suddenly the time of science. I will explain what kind of science is in the background of the fluidized bed.


Fluidization of sand occurs when the force which the sand rises upward with the air sent from the pipe and the force which tries to fall down by gravity are equalized. So, when you look at each sand, it is like a ping - pong ball floating in the air by the wind from the dryer.


When the ping-pong ball is floating, gravity and air attracting force are the same ... ...


Suddenly a big force is added ......


The equilibrium collapses, and the ping-pong ball moves to the side of the greater force.


In other words, if the force that the sand rises upward by the force of the air is moderate, the fluidized bed will occur ...


If the power of the air is too big, it will fail.


When the magnitude of force is just right, the particles of sand can move around.


It is the same reason why air is sent into the water when people dive into the pool. As the particles move around, the bubbles play a role like a cushion.


When putting things in fluidized sand, some will float up and some will sink below. This is due to buoyancy.


Buoyancy is determined by fluid density × volume of object × gravity.


Pressure gradientWhen it exists in the body, force is applied to the object from various directions. And when we are in the deep part of the water or under the human pyramid, a lot of force will be applied to the object. This is because a lot of water on my body tries to push people down when it is in a deep water.


At this time, the forces from various directions cancel each other out, and the force that levitates upwardResultant forceIt is left as. This is buoyancy.


When the buoyant force is larger than the gravity, the object floats up and it sinks when it is small.


The previous explanation was the buoyancy of water, but even in the air, helium emerges because it has greater buoyancy than the atmosphere.


So, which of the buoyancy of the ball and balloon that Rober has in hand is big?


As you can see from the expression above, the buoyancy is not related to the density of the object. Only volumes are relevant. So the larger the volume of the rubber ball, the greater the buoyancy will be.


So why the ball falls down and the balloon floats in the air, this is because the gravitational force of the thick rubber ball and the air is greater than the buoyant force.


Whether the object floats or sinks depends on the result of the tug of war, as was the case in the first tug of war. Although the balloon has less buoyancy than the ball, the buoyancy increases more than the gravity on the helium and thin rubber in the balloon, so it will float up to the sky.


And finally, we stop the levitation where the density of the air becomes the same as the density of helium. This is because the power of the tug of war will be even at this point.


The mechanism of sand bath that fluidized it. Because the science as described above is in the background, when the system is not in operation, it is only to landing to jump into the sand ... ...


After operation it is like playing like a pool.


In addition, putting a huge drum can into the sand ... ...


As the hot water in the bath was overflowing, the sand was overflowing.