Introduction to Fluid Mechanics

1. Introduction to Fluid Mechanics Bellagio Fountain

2. Lecture 8 • Introduction to Fluid Mechanics • Approximate Running Time - 21 minutes • Distance Learning / Online Instructional Presentation • Presented by • Department of Mechanical Engineering • Baylor University • Procedures: • Select “Slide Show” with the menu: Slide Show|View Show (F5 key), and hit “Enter” • You will hear “CHIMES” at the completion of the audio portion of each slide; hit the “Enter” key, or the “Page Down” key, or “Left Click” • You may exit the slide show at any time with the “Esc” key; and you may select and replay any slide, by navigating with the “Page Up/Down” keys, and then hitting “Shift+F5”.

3. Lecture 8 Topics • Outline • Measuring Devices for Measuring Drag • Basics of Fluid Mechanics • Flight Characteristics of Baseballs & Golf Balls Dr. Carolyn Skurla Speaking

4. Lab: Drag Force Experiment • Performing a fluid mechanics experiment • Collect experimental data • Perform integration of experimental data • Equipment: • Wind tunnel • Cylinder • Pressure transducer • Pitot-static tube

5. So, What is Fluid Mechanics? • The study of fluids in motion • Solid -> Can resist a shear stress by a static deformation • Fluid -> Cannot resist a shear stress • Any shear stress applied to a fluid will result in motion of that fluid • There are two classes of fluids: • Liquids • Gases (White, 1994)

6. Thermodynamic Properties of a Fluid • Pressure, p • Compression stress at a point in a fluid • Differences, or gradients, of pressure often drive a fluid flow • Temperature, T • Measure of internal energy level of a fluid

7. Thermodynamic Properties of a Fluid • Density,  • Mass per unit volume • Highly variable in gases (i.e.,  =f(p)) • Nearly constant in liquids • Almost incompressible • Assumed to be imcompressible to make analysis easier • Specific Weight,  • Weight per unit volume

8. Pressure Transducer: Manometer • How do we measure pressure, p ? • Change in elevation of a liquid is equivalent to a change in pressure • Therefore, a static column of liquid can be used to measure pressure difference between 2 points (White, 1994)

9. Pressure Transducer: Manometer • Manometer units are in·H2O • How do I convert in·H2O to more standard units for pressure? SI UnitsEnglish

10. y x 1 2 v = Flow velocity ds Pressure – Velocity Relationship A

11. 1 2 v = Flow velocity ds Pressure – Velocity Relationship A

12. Pitot-Static Tube Static Point Static Pressure, (pS ) Static Velocity, (vS) Stagnation Point Stagnation Pressure, (p0 ) Stagnation Velocity, (v0) Differential Pressure Transducer (Manometer)

13. Pitot-Static Tubes • ps= Static pressure (in the moving stream) • Nominal air pressure in atmosphere • p0= Stagnation pressure • Air pressure in the pitot tube • vs= Static velocity • Speed of air passing the pitot tube • Equivalent to speed of plane through the air • v0= Stagnation velocity = 0

14. Pitot-Static Tube Sample Problem 2

15. Velocity • When there is friction between the fluid and the solid surface • No slip of the fluid at the boundary • Velocity = 0 • A boundary layer forms near the solid surface • Shear stress is greatest adjacent to the boundary layer at the surface (White, 1994)

16. Laminar vs. Turbulent Flow • Laminar -> smooth and steady. • Turbulent -> fluctuating and agitated.

17. Reynolds Number • Dimensionless parameter • Correlates viscous behavior of all newtonian fluids •  = density •  = viscosity • V = characteristic velocity of flow • L = length scale of flow • Most important parameter in fluid mechanics • Governs transition from laminar to turbulent flow

18. This Concludes Lecture 8