[Fluid Mechanics] Topic 1 - Introduction to Fluid Mechanics

49 flashcards · Other · by Ahmed Adil

  1. What is a fluid?

    Fluid is a substance that deforms continuously, under the action of the shear stress of any magnitude.

  2. Fluid (Liquid or Gas) – Has definite mass and volume at a constant pressure and temperature but has no definite shape

  3. Liquids are incompressible but we can calculate small compressibility of liquids

  4. Gases are compressible and will expand or contract to fill their containers

  5. What is Fluid Mechanics?

    the study of the behavior of fluids and fluid systems

  6. Fluid systems can be either at rest (static) or in motion (dynamic)

  7. Dynamic systems can be divided into:  kinetics  Kinematics

  8. Kinetics deals with?

    problems involving the force caused by moving fluids

  9. Kinematics deals with?

    velocities and other areas of fluid motion WITHOUT considering the forces involved

  10. Name 4 characteristics of ideal fluid with some examples

     Completely incompressible  Has zero thermal expansion  Shows no shear stress  Shows no energy losses when flowing Examples: Doesn't exist, only considered when studying fluid systems

  11. Name 4 characteristics of real fluid with some examples

     Compressible  Has thermal expansion  Produces shear stress  Loses energy when flowing Examples: Water, oil, CO2, glycerin, Acid, etc.

  12. To simplify calculations, we consider most liquids incompressible

  13. External Flow versus Internal

    External flow: The flow of an unbounded fluid over a surface such as a plate. Internal flow: The flow of a completely bounded fluid by solid surfaces such as a pipe.

  14. Water flow in a pipe is internal flow, and airflow over a ball is external flow

  15. The flow of a liquids in a duct is called open channel flow if the duct is only partially filled with the liquid and there is a free surface

  16. Weight = mass x gravity Force = mass x acceleration

  17. What is pressure? mention the formula and the unit (SI and US)

    Amount of perpendicular force applied on a unit area of a substance or on a surface pressure = force / area N/m2 or Pascal (Pa) psi lb/in2

  18. 1 kpsi = ? psi

    1000

  19. What do we calculate with this formula? and what is its unit (SI and US)?

    Bulk modulus of elasticity for liquids Pascal Pa PSI Pound per Square Inch lb/in2

  20. What is bulk modulus of elasticity (for liquids)?

    A property of liquid that measures the resistance of a liquid to uniform compression

  21. The higher the bulk modulus of elasticity is the lower compressible the liquid is

  22. The lower the bulk modulus of elasticity is the higher compressible the liquid is

  23. For gases, compressibility is calculated using laws of thermodynamics

  24. Define Compressible versus Incompressible Flow and give one example

    Compressible flow: the density of the fluid change during the flow e.g. high speed gas flow Incompressible flow: the density of the fluid remain constant during the flow e.g. water flowing through a pipe

  25. Write the density formula and mention its units in SI and US

    Density = mass / volume kg/m3 or g/cm3 lbm/ft3 or slug/ft3

  26. Specific volume is equal to the inverse of density

  27. Specific volume = volume / mass

  28. What do we calculate with this formula? and what is the name of the symbol on the left?

    specific weight gamma

  29. What do we calculate with this formula?

    specific gravity

  30. How do we calculate the specific gravity in terms of specific weight

  31. Mass kg in SI unit can also be expressed as? (in US unit)

    pound mass lbm

  32. Meter m in SI unit can also be expressed as? (in US unit)

    foot ft or inch in

  33. Which SI unit does the weight and force share?

    Newton N

  34. Write the two formulas of specific weight

    specific weight = weight / volume specific weight = density x gravity

  35. lb is often used informally to refer to both weight and force lbf is for force lbm is for mass

  36. What do we calculate with this formula?

    specific weight

  37. Viscosity is

    the fluid resistance to flow

  38. Viscosity is a property of a real fluid that: Causes sticking and interaction between fluid molecules, and between fluid and the walls Causes resistance to easy flowing or motion of the fluid molecules Causes shear stress Is the major source of energy losses in most fluid systems especially pipes and ducts is relatively unaffected by pressure but easily affected by temperature changes

  39. Define shear stress

    A stress that acts parallel with cross section of material.

  40. Name the different types of stress 1) compression 2) tension 3) shear

  41. Measures the resistance of a fluid to flow and how easily the fluid can deform under mechanical stress

    Dynamic Viscosity

  42. measures the resistance of the liquid to flow in the presence of gravity.

    Kinematic Viscosity

  43. v = μ / ρ We calculate kinematic viscosity with this formula, where v = kinematic viscosity (m^2/s) μ = dynamic viscosity (N*s/m^2) ρ = density (kg/m^3)

  44. Newtonian fluids have a constant viscosity when force rate changes and linear relationship between the rate of shear strain and shear stress. Non-Newtonian fluids are those that do not have a constant viscosity when force rates changes and have a variable relationship between the rate of shear strain and shear stress.

  45. Mention examples of Newtonian fluids and Non-Newtonian fluids

    Newtonian: Water, air, oil, gasoline, alcohol, kerosene and glycerin Non-Newtonian: Ketchup, toothpaste, molten polymer, paint, blood and shampoo

  46. The pulling force of water molecules below the surface that makes the surface molecules act like a film. The film can hold light objects on the surface.

    surface tension

  47. Surface tension

  48. During a steady- flow process, fluid properties within the control volume may change with position but not with time

  49. The term steady implies no change with time. The opposite of steady is unsteady, or transient