1. Fluid Dynamics: Thrust Lesson 7

2. What is Fluid Dynamics?  Fluid dynamics helps engineers and scientists make sense of : how fluid moves how fluid moves how fluids affect moving objects how fluids affect moving objects  Velocity is how fast something moves Many things behave like a fluid Air Air Gas Gas Liquid Liquid Electricity Electricity Traffic Traffic  Fluids are hard to contain since they take many shapes based on their environment

3. Forces: What Makes the Sea Perch Move???  Forces are everywhere: Force of Gravity Person Applied Force to Ball Magnetic Force © alandberning

4. Forces and Sea Perch Movement *Large Picture of Sea Perch moving through hula hoop toward object*  Two main forces affect the movement of the Sea Perch. Thrust: force that allows Sea Perch to move forward Thrust: force that allows Sea Perch to move forward Drag: force that prevents Sea Perch from moving faster once in motion Drag: force that prevents Sea Perch from moving faster once in motion Thrust Drag

5. Thrust vs. Drag Thrust = Drag = 0 Pedaling is a way of applying thrust The breeze in your hair is drag  The rate at which you increase your speed on the bike is acceleration.  However, the faster you go the stronger the breeze This makes the bike harder to pedal This makes the bike harder to pedal  Eventually you can’t go any faster no matter how hard you pedal Now you have reached terminal velocity Now you have reached terminal velocity © krakow.bicycles © dewonn43 © Mariano Kamp

6. Thrust vs. Drag: Mathematically  When a force is applied to a mass you accelerate:  m is mass: the amount of matter in an object  a is acceleration: the rate at which you increase your vel  F thrust: the force of thrust  F drag: the force of drag  What happens when you reach terminal velocity? F thrust = F drag and a = 0 F thrust = F drag and a = 0

7. VehicleThrustDrag Caused by peddling Caused by air Caused by propellers Caused by water How is a Bike Similar to the Sea Perch? © RoRRo

8. Propellers Cause Thrust  What happens when a propeller rotates: 1. It pushes fluid away from the vehicle 2. It pulls fluid towards the vehicle

9. How Does Fluid Density Affect Propellers? *Picture of Fan*  Water has about 1000 times the density of air  A gallon of water is 1000 times heavier than a gallon of air  Pushing fluid with greater density requires more thrust  Thrust force in water is then 1000 times greater than the thrust force in air Propeller pushes water Fan pushes air