Lecture 1

• weather (clouds, rainbows, hail, fog)

• soil erosion

• waves, sea spray

• water repellent surfaces

• dewdrops

• volcanic activity (viscous drops)

• medical devices, e.g. inhalers, infusion

• pharmaceutics, e.g. medication in pill form (coating drops with solid particles)

• food processing industry, e.g. powder generation (spray drying, spray freeze drying)

• agriculture, e.g. irrigation of crops or use of plant protective agents

• combustion engines (fuel injection), e.g. cars, space crafts

• power generation, e.g. high fogging in gas turbines

• fire extinction, e.g. sprinklers, Aqueous Film Forming Foams (AFFF)

• printing, e.g. on paper, 3D-printing or printing of micro-electronics

• coating/spray painting

• icing on plane wings

• liquid-repellent surface (hydrophobic, olio-phobic, omni-phobic)

• atomizers, e.g. deodorant spray, perfumes, hairspray

• coffee stains

• Leidenfrost effect on hot surfaces

• water repellent surfaces, e.g. clothing, mobile phone displays

• misty mirrors or glasses

• tears of wine

• Liquid - Solid interaction

• Liquid - Gas interaction

• Liquid - Liquid interaction

• Liquid - Light Beam interaction

• single droplet

• droplet chains/arrays

• liquid jets

• bubbles

• sprays

• liquid strands

• liquid films

Droplet:

• shape

• size

• velocity

• inner circulation

• fluid properties

• temperature distribution

• concentration of the ingredients and their distribution in the drop

Surrounding medium:

• velocity field

• level of turbulence

• temperature field

• concentration of the ingredients

Solid surface

• contact angle

• surface roughness / structure

• temperature

• heat capacity / thermal conductivity

• geometric quantities

• fluid properties

• temperature - heat transfer

• velocities / flow field

Molecular dynamic approach:

Within liquid phase intermolecular attractions pull equaly in every direction. On the surface intermolecular attractions pull only in the direction of the liquid.

Mechanical approach - Capillary Force:

Surface tension as a force per unit length, directed towards the liquid: 𝝈 = 𝑭/𝟐L

Mechanical approach - Surface Energy:

𝝈 = 𝒅𝑾/𝒅𝑨 is energy that must be supplied to increase the surface area by one unit