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Using the Coanda Effect to aid lift 

Using the Coanda Effect to aid lift 

Source publication
https://www.researchgate.net/profile/Dr_Stephen_Prior/publication/228895415/figure/fig5/AS:668418894200836@1536374891279/Henri-Coandas-patent-for-a-propelling-device-3_Q640.jpg 2x” type=”image/jpeg”/> Henri Coanda's patent for a propelling device [3].
Air circulation around
Using the Coanda Effect to aid lift
Aesir Coanda Effect UAV [2].
Performance of the GFS-UAV N-01A body and AXI 2217 /20 motor & GWS 1060 prop.
10° AoA Ring Airfoil test rig.
Investigating the use of the Coanda Effect to create novel unmanned aerial vehicles
Article
Full-text available
  • Dec 2009
  • Chris Barlow

    Chris Barlow

  • Darren Lewis

    Darren Lewis

  • Stephen D Prior

    Stephen D Prior

  • […]
  • Bob Collins

    Bob Collins

Context 1
… the results of this experiment, we obtained the necessary information to produce a ring wing for testing. During this experiment we found that a drop in lift occurs when the nozzle is in the neutral position, which is caused by the leading edge of the airfoil to behaving as a wall, restricting and slowing down the airflow. The most efficient method of circulation on the airfoil was found to be when the nozzle is blowing only over the top surface and inducing air through the central hole in the ring wing to boost circulation around the bottom surface, (see Figures 13 & 14). This method of achieving lift on an airfoil is very similar to the effect of circulation on an airplane wing, as discussed in the section "Conventional Fixed Wing Design". Once this configuration was found, we began to experiment with ways of using the Coanda Effect to increase lift efficiency. A perimeter ring of circular cross section was positioned below the trailing edge of the ring airfoil in a position where it can use the Coanda Effect to entrain more air, and direct the air leaving the trailing edge so that it is more effective at producing vertical thrust. By experimenting with the gap between the airfoil trailing edge and this new ring, we were able to increase the lift by around 3%. With the current prototype, only a small amount of lift can be achieved, which would not be sufficient for the UAV to take off. More experiments need to be carried out to apply the theory in this paper to our prototype in order to increase lift to an acceptable level. One proposed experiment involves using a fan to increase the velocity of air circulation around the wing, as we know that lift increases with air velocity squared. More experimentation is needed with the perimeter ring to use the Coanda Effect to redirect the air at the trailing edge more effectively. Also the introduction of Coanda jets similar to figure 4 should, in theory, increase the amount of entrainment from above the wing. Once these experiments are carried out, and with other institutions such as Delft University of Technology in The Netherlands investing a lot of time into similar research [14], the feasibility of using the Coanda Effect for a commercial Unmanned Aerial Vehicle should soon become more …

View

Context 2
… so many restrictions for the pilot of a UAV to consider, in an ideal world UAVs would operate without the requirement for human control. Many companies are in development of autonomous UAVs but so far there are few UAVs on the market which are fully autonomous. Autonomy is a very challenging solution from the developers' perspective but it will ultimately lead to the most efficient systems. In simple terms, a stream of air at high velocity will attach to a curved surface rather than follow a straight line in its original direction. This stream will also entrain air from around it to increase the overall mass flow rate of the stream of air. This phenomenon can be harnessed to produce lift in two ways. Firstly, it can be used to change the direction of airflow to point downwards, resulting in vertical thrust. Secondly, it can be used to entrain air from above which causes a region of low pressure above the body, which results in lift. It is a common misunderstanding that the resulting lift of an airfoil can be explained using the Bernoulli Equation. The explanation is often quoted by academics erroneously, stating that because the distance over the top of the airfoil is greater than the underside, the air over the top goes faster than the underside air to rejoin at the trailing edge and thus the increased speed reduces pressure above causing lift [4]. This is in fact only half true as the air does not rejoin the same airstream at the trailing edge (see Figure 2). Lift on a conventional airfoil is generated by circulation around the wing (see Figure 3). As air is accelerated downwards, it causes the pressure below the wing to increase, and the pressure above to decrease, resulting in lift [6]. The Coanda Effect can be applied to a conventional fixed wing aircraft, to improve lift by up to 300% [4]. By storing compressed air in a plenum chamber (see Figure 4) at the leading and/or trailing edges of a wing, a narrow high-pressure jet of air is forced over the surface, thus preventing flow separation. A UK based company; Aesir (formerly GFS Projects Limited) are developing a UAV which is based on the Coanda …

View

Citations

  • … Part of the flow being drawn by the actuator can be utilized for lift (like in a helicopter), and part of it will be utilized for establishing radial flow for Coandă jet blanket on the surface of the body. This saucer like Coandă MAV with annular structure has been developed and investigated by many researchers, such as Barlow et al. (2009), Hatton (Nedelcut (2010)) and Saeed (2010), and basically can be idealized as illustrated in Figure 5b. Momentum analysis is carried out in order to identify the Coandă effect related aerodynamic forces and the Coandă MAV performance parameters. …
    First Principle Analysis of Coandă Micro Air Vehicle Aerodynamic Forces for Preliminary Sizing
    Article
    • Jan 2016
    • AIRCR ENG AEROSP TEC
    • Riyadh Ibraheem

      Riyadh Ibraheem

    • Harijono Djojodihardjo

      Harijono Djojodihardjo

    • Abd Rahim Abu Talib

      Abd Rahim Abu Talib

    • Mohd Rafie

  • … A review on the progress done on pneumatic circulation control was carried out by Englar [14], and on active flow control by Jahanmiri [15]. One of the recent applications of blowing is unmanned aerial vehicles to secure lift augmenting and flow control as proposed by Barlow et al. [16]. Pfingsten and Radespiel [17] stated that with active flow control a gapless high-lift device is capable of generating the high lift coefficients needed for climb and landing. …
    Experimental Investigation of the Flow Field Characteristics under Active Flow Control
    Article
    Full-text available
    • Jan 2014
    • Int J Fluid Mech Res
    • Ibrahim Olwi

      Ibrahim Olwi

  • Complexity Aspects in Design for Sustainability
    Article
    • M. J. T. Schroijen

  • Numerical Research on Aerodynamic Efficiency of a VTOL GFS UAV
    Conference Paper
    Full-text available
    • Jan 2015
    • Yifei Zhang
    • Lijun Xu
    • Haixin Chen

      Haixin Chen

  • Experimental Study of an Unmanned Aerial Vehicle under the Combined Coanda and Magnus Effects
    Conference Paper
    Full-text available
    • Aug 2016
    • Mohsen Jahanmiri

      Mohsen Jahanmiri

    • Malihe Najafi

      Malihe Najafi

  • An Innovative Technique to Increase Lift of a Coanda UAV
    Article
    Full-text available
    • Mar 2017
    • Maliheh Najafi

      Maliheh Najafi

    • Mohsen Jahanmiri

      Mohsen Jahanmiri

  • Modeling and control of a saucer type Coandä effect UAV
    Conference Paper
    • May 2017
    • Jameson Y. Lee
    • Seung Hwan Song
    • Hyun Wook Shon
    • Hyouk Ryeol Choi

      Hyouk Ryeol Choi

    • Woosoon Yim

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DiscoverHover CURRICULUM GUIDE #8
BERNOULLI’S PRINCIPLE AND THE COANDA EFFECT

© 2004 World Hovercraft Organization

NAME

DATE

A closer look at how propellers cause forward thrust will reveal that the hovercraft
moves forward by pushing air behind it. Exactly how does the propeller push
air behind it? To understand this we turn to a principle that was discovered
about 300 years ago, Bernoulli’s Principle.

Daniel Bernoulli
1700-1782

Bernoulli’s Principle: An increase in the velocity of any
fluid is always accompanied by a decrease in pressure.

Since air behaves exactly like a fluid, Bernoulli’s principle
applies. Any time the wind is blowing or a fan blows air, the pressure of the
moving air becomes less than it would be if the air wasn’t moving. As an aside,
this characteristic plays a huge role in how weather systems work! If you can
cause air to move faster on one side of a surface than the other, the pressure
on that side of the surface will be less than the pressure on its other side.

One of the most widely used applications of Bernoulli’s principle is in the
airplane wing. Wings are shaped so that the top side of the wing is curved while
the bottom side is relatively flat. In motion, the front edge of the wing hits
the air, and some of the air moves downward below the wing, while some moves
upward over the top. Since the top of the wing is curved, the air above the
wing must move up and down to follow the curve around the wing, while the air
below the wing moves very little. The air moving on the top of the curved wing
must travel farther before it reaches the back of the wing; consequently it
must travel faster than the air moving under the wing, to reach the back edge
at the same time. The air pressure on the top of the wing is therefore less
than that on the bottom of the wing, according to Bernoulli’s principle.
The higher pressure air on the bottom of the wing pushes up on the wing with
more force than the lower pressure air above the wing pushes down. This results
in a net force acting upwards called lift. Lift pushes
the wings upwards and keeps the airplane in the air.

Though Bernoulli’s principle is a major source of lift in an aircraft
wing, a Romanian engineer by the name of Henri Coanda discovered another effect
that plays an even larger role in producing lift.

Henri Coanda
1886 – 1972

Although generally unrecognized, Coanda was actually the first
person to build and fly a jet powered aircraft. It is commonly believed that
the first jet engines were developed during World War II. Dr. Hans Von Ohain
designed the first German jet aircraft, which made its first flight on August
27, 1939. Unaware of Dr. Von Ohain’s work, A British engineer named Sir Frank
Whittle also independently designed a jet aircraft, which first flew on May
15, 1941.

Although these two men are generally thought of as the fathers of jet aircraft,
Henri Coanda built and "flew" the first recorded jet aircraft about
30 years earlier. The somewhat amusing first flight is best described in Coanda’s
own words:

"It was on 16 December 1910. I had no intention of
flying on that day. My plan was to check the operation of the engine on the
ground but the heat of the jet blast coming back at me was greater than I
expected and I was worried in case I set the aeroplane on fire. For this reason
I concentrated on adjusting the jet and did not realize that the aircraft
was rapidly gaining speed. Then I looked up and saw the walls of Paris approaching
rapidly. There was no time to stop or turn round and I decided to try and
fly instead. Unfortunately I had no experience of flying and was not used
to the controls of the aeroplane. The aeroplane seemed to make a sudden steep
climb and then landed with a bump. First the left wing hit the ground and
then the aircraft crumpled up. I was not strapped in and so was fortunately
thrown clear of the burning machine."


The Coanda- 1910, the world’s first jet aircraft

Unfortunately Coanda couldn’t obtain funding to continue
his research after the wreck, and so his contribution to jet propulsion never
became widespread. If he had been able to continue his work, France could
have had a jet-powered air force before WW II began. Even though he didn’t
build another jet aircraft, he did make a very important contribution to how
the aircraft wings produce lift when he discovered what is now called the
Coanda Effect.

Coanda Effect: A moving stream of fluid in contact with
a curved surface will tend to follow the curvature of the surface rather than
continue traveling in a straight line
.

To perform a simple demonstration of this effect, grab a spoon
and find a sink. Get a small stream of water coming down from the sink, then
place the bottom of the spoon next to the stream. Notice how the water curves
along the surface of the spoon. If you hold the spoon so that it is free to
swing, you should be able to notice that the spoon is actually being pulled
towards the stream of water.

The same effect occurs with an airplane wing. If the wing is
curved, the airflow will follow the curvature of the wing. In order to use
this to produce lift, we need to understand something called angle
of attack
. This gives the angle between the wing and the direction
of the air flow, as shown in the following diagram.

The angle of attack indicates how tilted the wing is with respect
to the oncoming air. In order to produce lift, or an upward force acting on
the wing, Newton’s third law says that there must be an equal force acting
in the opposite direction. If we can exert a force on the air so that it is
directed down, the air will exert an upward force back on the wing. Look at
how the Coanda effect directs the airflow for different angles of attack in
the diagrams below.

This diagram shows that increasing the angle of attack increases
how much the air is deflected downwards. If the angle of attack is too great,
the air flow will no longer follow the curve of the wing. As shown in the
bottom of the diagram, this creates a small vacuum just behind the wing. As
the air rushes in to fill this space, called cavitation, it causes heavy vibrations
on the wing and greatly decreases the efficiency of the wing. For this reason,
aircraft wings are generally angled like the middle wing in the diagram. This
wing efficiently directs the airflow downward, which in turn pushes up on
the wing, producing lift.

This method of determining lift is called momentum change. Other methods to
calculate the same lift utilize the difference in pressure fields above and
below the wing. Either method is accurate on its own, but never add the two
methods together.

In addition to producing lift on an aircraft, Bernoulli’s principle and the
Coanda effect play an important role in the operation of a propeller. Examine
a propeller closely and you will find that the blades of the propeller look
like an airfoil, or wing. Essentially, a propeller blade is a wing turned
on its side. Just as wings traveling forward are lifted upward, a rotating
propeller blade is sucked or pushed forward. A propeller blade also has something
that wings don’t: they are twisted. Watch a propeller turn very slowly, and
you will see how the twist of the blade causes it to move the air evenly and
push it backwards. Additionally, the propeller blades are set at an angle.
This is called propeller pitch. The greater the
pitch of the propeller, the more air it can push. Blades of common household
fans are also slightly angled to help move air for cooling. Ideally an equal
quantity of air will pass the blade at its root (the hub of the propeller)
and its tip, but the tip travels much faster than the root. To maintain an
even flow rate as much as possible, the hub pitch (pitch at the root of the
propeller) has to be very steep while the propeller tips have to be almost
flat! This will help insure an even flow of air through the duct.

Continue to Experiment
8.1

DiscoverHover CURRICULUM GUIDE #8
BERNOULLI’S PRINCIPLE AND THE COANDA EFFECT

© 2004 World Hovercraft Organization

NAME

DATE

A closer look at how propellers cause forward thrust will reveal that the hovercraft
moves forward by pushing air behind it. Exactly how does the propeller push
air behind it? To understand this we turn to a principle that was discovered
about 300 years ago, Bernoulli’s Principle.

Daniel Bernoulli
1700-1782

Bernoulli’s Principle: An increase in the velocity of any
fluid is always accompanied by a decrease in pressure.

Since air behaves exactly like a fluid, Bernoulli’s principle
applies. Any time the wind is blowing or a fan blows air, the pressure of the
moving air becomes less than it would be if the air wasn’t moving. As an aside,
this characteristic plays a huge role in how weather systems work! If you can
cause air to move faster on one side of a surface than the other, the pressure
on that side of the surface will be less than the pressure on its other side.

One of the most widely used applications of Bernoulli’s principle is in the
airplane wing. Wings are shaped so that the top side of the wing is curved while
the bottom side is relatively flat. In motion, the front edge of the wing hits
the air, and some of the air moves downward below the wing, while some moves
upward over the top. Since the top of the wing is curved, the air above the
wing must move up and down to follow the curve around the wing, while the air
below the wing moves very little. The air moving on the top of the curved wing
must travel farther before it reaches the back of the wing; consequently it
must travel faster than the air moving under the wing, to reach the back edge
at the same time. The air pressure on the top of the wing is therefore less
than that on the bottom of the wing, according to Bernoulli’s principle.
The higher pressure air on the bottom of the wing pushes up on the wing with
more force than the lower pressure air above the wing pushes down. This results
in a net force acting upwards called lift. Lift pushes
the wings upwards and keeps the airplane in the air.

Though Bernoulli’s principle is a major source of lift in an aircraft
wing, a Romanian engineer by the name of Henri Coanda discovered another effect
that plays an even larger role in producing lift.

Henri Coanda
1886 – 1972

Although generally unrecognized, Coanda was actually the first
person to build and fly a jet powered aircraft. It is commonly believed that
the first jet engines were developed during World War II. Dr. Hans Von Ohain
designed the first German jet aircraft, which made its first flight on August
27, 1939. Unaware of Dr. Von Ohain’s work, A British engineer named Sir Frank
Whittle also independently designed a jet aircraft, which first flew on May
15, 1941.

Although these two men are generally thought of as the fathers of jet aircraft,
Henri Coanda built and "flew" the first recorded jet aircraft about
30 years earlier. The somewhat amusing first flight is best described in Coanda’s
own words:

"It was on 16 December 1910. I had no intention of
flying on that day. My plan was to check the operation of the engine on the
ground but the heat of the jet blast coming back at me was greater than I
expected and I was worried in case I set the aeroplane on fire. For this reason
I concentrated on adjusting the jet and did not realize that the aircraft
was rapidly gaining speed. Then I looked up and saw the walls of Paris approaching
rapidly. There was no time to stop or turn round and I decided to try and
fly instead. Unfortunately I had no experience of flying and was not used
to the controls of the aeroplane. The aeroplane seemed to make a sudden steep
climb and then landed with a bump. First the left wing hit the ground and
then the aircraft crumpled up. I was not strapped in and so was fortunately
thrown clear of the burning machine."


The Coanda- 1910, the world’s first jet aircraft

Unfortunately Coanda couldn’t obtain funding to continue
his research after the wreck, and so his contribution to jet propulsion never
became widespread. If he had been able to continue his work, France could
have had a jet-powered air force before WW II began. Even though he didn’t
build another jet aircraft, he did make a very important contribution to how
the aircraft wings produce lift when he discovered what is now called the
Coanda Effect.

Coanda Effect: A moving stream of fluid in contact with
a curved surface will tend to follow the curvature of the surface rather than
continue traveling in a straight line
.

To perform a simple demonstration of this effect, grab a spoon
and find a sink. Get a small stream of water coming down from the sink, then
place the bottom of the spoon next to the stream. Notice how the water curves
along the surface of the spoon. If you hold the spoon so that it is free to
swing, you should be able to notice that the spoon is actually being pulled
towards the stream of water.

The same effect occurs with an airplane wing. If the wing is
curved, the airflow will follow the curvature of the wing. In order to use
this to produce lift, we need to understand something called angle
of attack
. This gives the angle between the wing and the direction
of the air flow, as shown in the following diagram.

The angle of attack indicates how tilted the wing is with respect
to the oncoming air. In order to produce lift, or an upward force acting on
the wing, Newton’s third law says that there must be an equal force acting
in the opposite direction. If we can exert a force on the air so that it is
directed down, the air will exert an upward force back on the wing. Look at
how the Coanda effect directs the airflow for different angles of attack in
the diagrams below.

This diagram shows that increasing the angle of attack increases
how much the air is deflected downwards. If the angle of attack is too great,
the air flow will no longer follow the curve of the wing. As shown in the
bottom of the diagram, this creates a small vacuum just behind the wing. As
the air rushes in to fill this space, called cavitation, it causes heavy vibrations
on the wing and greatly decreases the efficiency of the wing. For this reason,
aircraft wings are generally angled like the middle wing in the diagram. This
wing efficiently directs the airflow downward, which in turn pushes up on
the wing, producing lift.

This method of determining lift is called momentum change. Other methods to
calculate the same lift utilize the difference in pressure fields above and
below the wing. Either method is accurate on its own, but never add the two
methods together.

In addition to producing lift on an aircraft, Bernoulli’s principle and the
Coanda effect play an important role in the operation of a propeller. Examine
a propeller closely and you will find that the blades of the propeller look
like an airfoil, or wing. Essentially, a propeller blade is a wing turned
on its side. Just as wings traveling forward are lifted upward, a rotating
propeller blade is sucked or pushed forward. A propeller blade also has something
that wings don’t: they are twisted. Watch a propeller turn very slowly, and
you will see how the twist of the blade causes it to move the air evenly and
push it backwards. Additionally, the propeller blades are set at an angle.
This is called propeller pitch. The greater the
pitch of the propeller, the more air it can push. Blades of common household
fans are also slightly angled to help move air for cooling. Ideally an equal
quantity of air will pass the blade at its root (the hub of the propeller)
and its tip, but the tip travels much faster than the root. To maintain an
even flow rate as much as possible, the hub pitch (pitch at the root of the
propeller) has to be very steep while the propeller tips have to be almost
flat! This will help insure an even flow of air through the duct.

Continue to Experiment
8.1