2. Physical phenomena of fluid flow

• It is assumed to be constant

• i.e. flowing liquids are assumed to be incompressible and temperature resistant

• It can be assumed to be constant

• Mach Number < 0.3 and constant temperature flowing gases can be assumed to be incompressible

Ideal Gas Law - p⋅V=m⋅R⋅T

• p: Pressure of the gas [Pa or N/m²]

• V: Volume of the gas [m³]

• m: Mass of the gas [kg]

• R: Specific gas constant [J/(kg·K)]

• T: Absolute temperature [K]

• m/V: Density ρ

• Mach Number (Ratio of the velocity of the flow/object to the speed of sound)

• Reynolds Number (laminar/turbulent)

  —> Same Reynolds Number —> Physical similiarities of flows

  
  

—> Is to be assumed to be constant

Temperature dependence

• Gases: High viscosity, high temp. (p = const.)

• Liquids: Low viscosity, high temp. (p = const.)

Shear rate dependence

= measure of the rate at which neighboring layers of fluid move relative to each other

—> Channel flow: Maximum near the wall

1. Newtonian Fluid

   • Viscosity = constant

   • Water or air

2. Shear Thickening

   • Viscosity increasing —> by increasing shear rate

   • Cornstarch in water

3. Shear Thinning

   • Viscosity decreasing —> by increasing shear rate

   • Ketchup and paint

Water column of 10 m —> pressure difference of 1 bar

1. Mass conservation

   —> Pipe with different cross sections

   —> Continuity equation

• If ρ (rho) = const.: V dot = v A = const. = v1 A1 = v2 A2

  
  

1. Energy conservation

   —> Bernoulli’s equation (incrompressible, inviscid, steady flows)

• With static pressure = p

• With dynamic pressure = 1/2 ρ v²

• Total pressure is dynamic pressure + static pressure

1. Prandtl Tube

   —> Measure static and total pressure

   —> Calculate dynamic pressure and velocits

2. Venturi Tube

   —> Measure pressures and cross sectional areas

   —> Calculate velocity

   
   

• Boundary Layer

• Type of flow

• Flow Separation

• Drag forces

• Laminar flow: Smooth and steady flow, flow in one direction

• Transition

• Turbulent flow: Irregular and unsteady flow, flow with fluctuations

Area is chord length times span (width)