English Component

11\25\13

11/26/13

Bernoulli’s principle is the main factor in explaining flight. Bernoulli’s principle states as the speed of a moving fluid (liquid or gas) increases, the pressure of the fluid decreases. This principle has various applications such as a carburetor where air is moving and comes to the restriction (the throttle plate opening and closing) and increases speed, which decreases the pressure. When looking at it in terms of fluid moving from a wide pipe to a narrow pipe (the restriction) you can see that the same volume of fluid needs to fit through the narrow pipe. The result is that the fluid increases speed to get through resulting in a decrease in pressure. Since the speed of the fluid through the pipe is increased, the kinetic energy is increased. This principle is a conservation of energy because the increase in kinetic energy is balanced by the decrease in pressure.

12/5/13

To start the experiment we first orient the hair dryer so that the outlet is pointing directly upwards. Turn it on and place a ball carefully in the flow from the hairdryer. How does it work you may ask? A good understanding of the Bernoulli effect comes along with terminal velocity. The ball is held up by the wind blast putting the ball at it’s terminal velocity. The ball moves up if the wind is faster than terminal or moves down towards faster air if the air speed is less than terminal velocity. The ball will always settle in at the right point where terminal velocity air is moving up and flowing around the ball. In other words, it will balance in the air, appearing to levitate, by gently move the hairdryer from side to side, the ball will stay in the air stream, i.e. will also move back and forth. The upward pressure from the hairdryer balances the downward force of gravity, keeping the ball 'levitating'. The more impressive part of this trick is, being able to move the ball along with the hairdryer and angle it, which is based on the Bernoulli principle.

11/27/13

A question that interests many people is, how do airplanes fly? Bernoulli’s principle is the main factor in explaining flight. When looking at the energy involved with his principle, Potential energy plus kinetic energy, equals constant total energy. In steady airflow, the total energy will remain constant but the pressures will change. As kinetic energy increases from higher flow speed, the potential energy will decrease. Any restrictions to the flow will result in an increase in velocity. As a vehicle increases its speed the dynamic pressure will increase because more molecules of air are hitting your hand. This is why your hand feels a lot of pressure and moves back when it is held out the window. When air is denser this pressure will increase as well, and static pressure acts on all sides of an airplane and results in being cancelled out. The propeller of an airplane creates thrust and moves the airplane forward. The airfoil of the wing is the main factor in what causes lift for an airplane.

12/10/13

As written in the previous journal, the Bernoulli principle states that, fast moving fluids (including gases such as air) are at a lower pressure than slow moving fluids. So the air stream from the hairdryer is at a much lower pressure than the air outside. If we look at a ball that is smaller than the diameter of the air stream, it can be balanced within it. If the ball starts 'falling' out of the air stream to one side then the higher pressure of the air outside the air stream will push the ball back into the center. In Bernoulli principle faster air produces less pressure and the larger pressure (slower air) on the outside will cause the ball to be re-centered. If you watch the ball you can see it being re-centered almost all the time. This is the process that enables the ball to balance inside the air stream and is able to stay within the air stream as the hairdryer is moved around.

Daniel Bernoulli was born on January 29, 1700 in Groningen, Netherlands. The Bernoulli family was well known for their excellence in mathematics and physics. His father was Johann Bernoulli, was a mathematician in Groningen. His older brother Nicolaus, also had an impact in mathematics. Continuing his studies Bernoulli studied in Italy until the age of 24 and received a doctorate in medicine. The next year he left Italy to St. Petersburg, Russia, as a professor of mathematics. He returned to Switzerland after 8 years due to his health, continued his teaching career in anatomy and botany, then changed to experimental and speculative philosophy(theoretical physics). He has been called the father of mathematical physics. Bernoulli is best known for his work on hydrodynamics, but he also did pioneering work on the kinetic theory of gases. Daniel Bernoulli was very honored during his lifetime and was considered one of the greatest mathematicians and physicists of all time along with many others.

11/29/13

When an airplane is flying steady, the pressure over the upper surface of the wing is decreased compared to normal static pressure. The static pressure on the under side of the wing is increased resulting in more air molecules against the under side of the wing. The result is lift and the aerodynamic forces acting on an airplane. Many factors affect the amount of lift that a wing can produce. These items include the lifting efficiency of the wing, dynamic pressure, and the surface area of the wing. As you can see Bernoulli’s principle have many different aspects concerning the flow of fluid, velocity, and pressure. The principle is the basis for explaining why the wings of an airplane produce lift resulting in an airplane being able to fly.

12/12/13