Golf balls have the perfect shape or in other words have the perfect aerodynamics for making it fly. Aerodynamics is therefore a big part of our business and responsibility, but what is actually aerodynamics? Aerodynamics is the way air moves around things. The rules of aerodynamics explains for example on how an airplane is able to fly, why a golf ball can fly and even how we can convey dry materials by means of air. Anything that moves through air reacts to aerodynamics. A rocket blasting off the launch pad and a kite in the sky react to aerodynamics. Aerodynamics also acts on cars, since the air streams around cars while moving.
What are the Four Forces of Flight?
The four forces of flight are lift, weight, thrust and drag. These forces make an object move up and down, and faster (moving forward) or slower. The amount of each force influence how the object moves through the air.
What is Weight?
Everything on Earth has weight. This force comes from gravity pulling down on objects. To fly, a golf ball or a grain of dry material needs something (an energy) to push it in the opposite direction from gravity. The weight of an object controls how strong the push has to be. A kite needs a lot less upward push energy than a jumbo jet does.
What Is Lift?
Lift is the push energy that lets something move up. It is the force that is the opposite of weight. Everything that flies must have lift. For a golf ball or a dry material grain to move upward, it must have more lift than weight. A hot air balloon has lift because the hot air inside is lighter than the air around it. Hot air rises and carries the balloon with it. A helicopter’s lift comes from the rotor blades at the top of the helicopter. Their motion through the air pushes the air downwards and moves the helicopter upward. Lift for an airplane comes from its wings moving through the airstream.
What Is Drag?
Drag is a force that tries to slow something down, resistance. It makes it hard for an object to move. It is harder to walk or run through water than through air. That is because water causes more drag than air. The shape of an object also changes the amount of drag. Most round surfaces have less drag than flat ones. Narrow surfaces usually have less drag than wide ones. The more air that hits a surface, the more drag it makes.
What Is Thrust?
Thrust is the force that is the opposite of drag. Thrust is the push that moves something forward. For a golf ball or dry material grain to fly and to keep moving forward, it must have more thrust than drag. In regard to the golf ball, it gets its thrust from the swing of the golf club. With dry material conveying the thrust is provided by the compressor. The flight will last until the drag causes it to slow down and land.
Golf ball vs dry material grain
So, what are the similarities in regard to aerodynamics of a golf ball and a grain of dry material (for example cement)? First of all, both objects have a somewhat round shape, but do not have a smooth surface. At micro size the cement grain looks like a potato. So, a grain of cement has all kind of uneven dimples in its surface, and a golf ball has it dimples evenly spread over the complete ball. But what does these dimples (and a potato shape) has to do with pneumatic conveying or aerodynamics?
A smooth golf ball hit by a professional golfer would travel only about half as far as a golf ball with dimples does. Most golf balls have between 300 and 500 dimples, which have an average depth of about 0.010 inch. The lift and drag forces on a golf ball are very sensitive to dimple depth: a depth change of 0.001 inch can produce a radical change to the ball’s trajectory and the overall distance it can fly.
A moving object has a high-pressure area on its front side. Air flows smoothly over the contours of the front side and eventually separates from the object toward the back side. A moving object also leaves behind a turbulent wake region where the air flow is fluctuating or agitated, resulting in lower pressure behind it. The size of the wake affects the amount of drag on the object. Dimples on a golf ball create a thin turbulent boundary layer of air that clings to the ball’s surface. This allows the smoothly flowing air to follow the ball’s surface a little farther around the back side of the ball, thereby decreasing the size of the wake. A dimpled ball thus has about half the drag of a smooth ball. Therefore, the shape of a cement grain is very convenient for pneumatic conveying.
Dimples also affect lift. A smooth ball with backspin creates lift by warping the airflow such that the ball acts like an airplane’s wing. The spinning action makes the air pressure on the bottom of the ball higher than the air pressure on the top; this imbalance creates an upward force on the ball. Ball spin contributes about one half of a golf ball’s lift. The other half is provided by the dimples, which allow for optimization of the lift force.
It is therefore understandable that the dimples within a cement grain are perfectly suitable for transporting by air. The difficult part on pneumatic conveying the cement is the keep a perfect balance between all 4 forces of flight in relation to the needed energy optimization. The flow engineers at Lion Bulk Handling keep striving for perfection for the most efficient material flow. We will ensure that your system is efficient, economic and environmental friendly as possible.
If you have any questions, in regard to pneumatic conveying or dry material flow, contact our Lion Bulk Handling team or leave a response in the comment section.
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