Fluids Part 1 A look at the characteristics of fluids, flow rate, viscosity and temperature Mr. Williams Grade 8 Science

So What Do We Know About Fluids? With a partner, discuss what a fluid is and how you would define it? Share your thoughts with the class. Name a Fluid… Most of you probably said water, right?

Fluids Are fluids only liquids? Liquids are fluids, but so are gases! Liquids and gases can be thick and thin. Some things float in liquids and some things sink Fluids share properties with other substances They take up space and are made of matter What do you think are some properties of fluids?

Fluids Help Us Everyday Engineers use water to harness the power of electricity Vacuum cleaners use air to suck up dirt and dust Hydraulics use cylinders to move fluids in a lot of machinery

Can you name other machines that use fluids?

Fluids Are Needed For Life The Earth holds a balance of different fluids (water and atmosphere) to sustain life You have fluids that keep you alive in your body Blood (arteries and veins) Oxygen (lungs) Intravenous fluids are used for hospital patients to keep them alive when suffering from illness or injury. Do fluids function the same way in living things as they function in the systems we create?

Go With the Flow In Groups of 4 or 5 make 10 small pieces of paper. On Each paper write down a fluid OR the name of a machine or system that uses fluids. Separate the words into categories. Use glue or tape to tape the different items onto the paper. Give each category a name Discuss with other groups when you are done

Fluids Everywhere Fluids – materials that have no fixed shape and are free to flow, such as liquids and gases. Two fluids that are essential for human life are water and air. Both cover and surround our planet. Not only do we use fluids, but the human body is comprised of about 60-70% water.

Overview In this portion of the unit we will be discovering the properties of fluids specifically to how they move. More specifically we will look at: Laminar vs. Turbulent flow Viscosity Mass, Volume and Weight of matter Density Buoyancy

How fluids flow around objects Many objects that we use often involve moving through a fluid (usually water or air). As an object moves it causes the particles around it to move as well. These particles can move in straight, or almost straight lines known as laminar flow, or the particles will be unable to move in straight lines, this is known as turbulent flow.

Laminar Flow Shapes that produce a more laminar flow produce less drag and are considered streamlined or aerodynamic. For airplanes, this means better fuel consumption, less wind and faster speeds. Wind tunnels are often used today to test for drag and measure airflow. Can you think of some industries that would use these techniques?

Turbulent Flow Turbulent flow is choppy and irregular. This type of flow mixes particles together and creates resistance and drag. As water flows past rocks in a river, some of it curls back behind the rocks to form much calmer water called eddies. Scientist and engineers try to use their knowledge of flow patterns to reduce or eliminate turbulence. Objects that are streamlined have shapes that reduce turbulence and create more laminar flow.

Flow Rate and Viscosity You have probably noticed that not all fluids flow at the same rate. Water for example is able to flow much faster out of the tap than honey flows from a jar. Flow rate – is a measure of how quickly fluids move. This is measured in a volume per unit time (ex. L/s or mL/min)

Flow Rate Flow rate measures the volume of a fluid moving past a certain point in a given amount of time. There are a number of different factors that cause flow rate to increase or decrease. They are: 1. The type of fluid that is flowing Thin fluids flow faster than thick ones 2. The force pushing the fluid The stronger the force the faster the flow rates 3. The size of the pipe or opening the fluid is flowing through Larger openings allow for faster flow 4. The type of surface that the fluid is flowing over Smoother surfaces allow for faster flow

Measuring Flow Rate To test for a substances viscosity we can measure its flow rate, meaning, how fast the substance will flow in a given amount of time. We use the formula: Flow rate = Volume (of a substance) (mL) time (sec/min) For example: What is the flow rate of 400mL of Corn Syrup if it takes 345 sec to empty the bottle. Flow rate = 400mL 345sec Flow rate = 1.15mL/sec

Viscosity Have you tried to pour ketchup out of a glass bottle? It can be a very difficult experience. How about maple syrup? If you are finding it difficult for the fluid to flow you are dealing with the principle of viscosity. Viscosity – A measure of how easily a fluid’s particles are able to slide past one another. Viscosity is also sometimes referred to as its “thickness” or its resistance to flowing and movement Different substances are composed of different particles and therefore have different forces of attraction.

Viscosity Contd. We often use the words thick or thin to describe viscosity, but this does not give us enough information. An instrument that measures viscosity is called a viscometer. Look at the water strider to the right…how is it able to stay on the surface of the water without sinking???

Cohesion and Adhesion Cohesion – Is a measure of how strongly the particles of a fluid attract each other Fluids that have slower flow rates have particles with greater cohesion. Which fluid would have higher cohesion…water, maple syrup or a cup of coffee? Adhesion – Is the attraction between the particles of one substance and the particles of another substance Fluids sometimes adhere to the side of the containers that they are in. For example, have you noticed that when you drink a glass of milk there is some left on the side of the glass?

Viscosity and Temperature Have you ever put a syrup bottle in the fridge instead of the cupboard…hmmm, you might have a flow problem if you have. What we find is that for many fluids, temperature affects their viscosity, or their ability to flow. The higher the temperature, the less viscous a substance becomes, meaning that it is easier for substances to flow at higher temperatures.

Understanding Fluid Flow Fluids play a very important role in our lives and therefore we need to learn and control their flow. Fluid mechanics is the study of how fluids behave, both at rest and in motion. Part of this study is fluid dynamics which deals with fluids in motion. Fluid dynamics is then broken into two different areas. 1. Aerodynamics – the study of moving gasses 2. Hydrodynamics – the study of moving liquids

Controlling Fluid Flow Food Industry: Fluid flow is important in the making of certain margarine and shortening. Through this process hydrogen gas is bubbled through liquid oils (usually vegetable oil). If this gas mixes too quickly it produces “trans fat”. Water Power: Dams are used throughout the world to control the flow of water. In fact, 60% of Canada’s electrical energy comes from the production of hydro- electric power. Although dams do not produce the same carbon- burning problems that coal and oil do, they still use agricultural land and can flood some forests.

Controlling Fluid Flow Cont’d Blood Flow: Blood is one of the most important fluids in your body, yet we rarely give it a lot of thought. Blood thinners are medicines given to individuals whose blood clots too easily. A condition called hemophilia is a condition where some people do not form blood clotting as easily when injured.