B-2 Physics Fluid Dynamics Quiz

Module: B-2 Physics, Topic 2.2.4 Fluid Dynamics

• This topic covers fluid dynamics, a branch of physics focusing on fluids (liquids and gases).
• Upon successful completion, students should be able to:
  • Describe specific gravity and density in relation to fluids
  • Describe viscosity, fluid resistance, streamlining effects, and compressibility effects in fluids.
  • Describe static, dynamic, and total pressure.
  • State Bernoulli's Theorem and the venturi's operation.
• Solids, Liquids, and Gases are the three states of matter.
  • Solids have a definite shape and volume, are not easily compressible and do not flow.
  • Liquids have a definite volume, take the shape of their container, are not easily compressible, and flow.
  • Gases have indefinite shape and volume, are easily compressible, and flow.
• Density is a substance's weight per unit volume.
  • Usually measured in pounds per cubic foot (lb/ft³) or grams per cubic centimeter (g/cm³).
  • Varies with temperature for liquids and solids (standard temperature is 4°C).
  • Varies with temperature and pressure for gases (standard conditions typically 0°C and 76cm Hg pressure).
• Specific gravity (S.G.) is a pure number, calculated by comparing the weight of a substance to the weight of an equal volume of water. The standard for liquids and solids is water at 4°C and for gases it is air at 0°C.
• A hydrometer is a device used to measure the specific gravity of liquids.
• Viscosity is a fluid's resistance to flow.
  • Liquids with low viscosity flow easily (e.g., gasoline).
  • Liquids with high viscosity flow slowly (e.g., tar).
  • Viscosity in liquids decreases with increasing temperature and increases with increased pressure (in liquids).
  • Viscosity in gases is not affected by pressure (under normal conditions); it increases with increasing temperature in gases.
• Streamlining is shaping an object to reduce drag, by allowing the fluid to flow smoothly around the object (e.g., an aircraft body or wing):
  • A flat object experiences more drag/ resistance from fluid flow compared to a curved shape object.
  • The front of a streamlined object should be well rounded.
  • The body should gradually curve back to a tapered rear section.
• Compressibility describes the ability of fluid molecules to be compressed and bounce back to their original density.
  • Liquids are largely considered incompressible.
  • Gases can be either compressible or incompressible, depending on the speed of the flow
• Effects of compressibility:
  • At low speeds, compressibility doesn't significantly affect fluid dynamics.
  • High speeds lead to a change in airflow density, meaning some of the energy of the object's movement goes into compressing the air.
• Pressure in fluids:
  • Static pressure is the pressure due to the weight of the fluid (atmospheric pressure).
  • Dynamic pressure is the pressure due to the fluid's motion (proportional to velocity).
  • Total pressure is the sum of static and dynamic pressure.
• Bernoulli's Theorem states that in a steady flow of an incompressible and inviscid fluid, the sum of pressure and kinetic energy per unit volume remains constant.
• The venturi effect is the reduction in fluid pressure when a fluid flows through a constricted section of a pipe.
  • Fluid velocity increases at the narrow section to maintain flow rate.
  • Pressure decreases at the narrow section because of the increased velocity.