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Give practical applications of super-hydrophobic or super-oleophobic surfaces.
Give practical applications of super-hydrophobic or super-oleophobic surfaces.
In which phenomena we can 'feel' the action of surface tension at a macroscopic level?
In which phenomena we can 'feel' the action of surface tension at a macroscopic level?
Give an estimation of the Reynolds number associated with the fall of a glass bead of 1 cm at velocity 10 cm/s in water.
Give an estimation of the Reynolds number associated with the fall of a glass bead of 1 cm at velocity 10 cm/s in water.
About 100
Give an estimation of the Reynolds number associated to the rise of liquid into a thin capillary of radius 100 microns.
Give an estimation of the Reynolds number associated to the rise of liquid into a thin capillary of radius 100 microns.
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In the rising of liquids in capillary tubes, which statement is true?
In the rising of liquids in capillary tubes, which statement is true?
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Tick the assertions which are true for a laminar cylindrical pipe flow (Poiseuille flow).
Tick the assertions which are true for a laminar cylindrical pipe flow (Poiseuille flow).
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What are the typical situations where the flows are mainly ruled by viscous forces?
What are the typical situations where the flows are mainly ruled by viscous forces?
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What are the operations and applications especially suitable in microfluidic channels?
What are the operations and applications especially suitable in microfluidic channels?
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From the rheometric curves of a suspension of particles in a Couette rheometer, which assertions seem to be true?
From the rheometric curves of a suspension of particles in a Couette rheometer, which assertions seem to be true?
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How can we define the rheology of the fluid besides?
How can we define the rheology of the fluid besides?
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When a solid sphere of several centimetres radius freely falls in the air, which statement is true?
When a solid sphere of several centimetres radius freely falls in the air, which statement is true?
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Give an approximate value of the Reynolds number and shear-rate in the experimental microfluidic cell (capillary radius 12 microns).
Give an approximate value of the Reynolds number and shear-rate in the experimental microfluidic cell (capillary radius 12 microns).
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What are the effects of the concentration of fibrinogen in the properties of blood?
What are the effects of the concentration of fibrinogen in the properties of blood?
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What is the action of dextran in the blood suspension?
What is the action of dextran in the blood suspension?
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What are the advantages of the microfluidic cell used in the experiments?
What are the advantages of the microfluidic cell used in the experiments?
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In your opinion, what would be the next steps of such a study?
In your opinion, what would be the next steps of such a study?
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Study Notes
Super-Hydrophobic and Super-Oleophobic Surfaces
- Practical applications include water-proof textiles, underwater bubble generators, anti-fouling surfaces, self-cleaning surfaces, and spreading of pesticides on plant leaves.
Surface Tension
- Phenomena where surface tension is visible at a macroscopic level include slow-down of liquid sliding down a vertical plate, insects walking on top of water pools, spherical shape of oil drops in water, and impregnation of soils with water.
Reynolds Number
- Estimation of Reynolds number for a 1 cm glass bead falling at 10 cm/s in water: about 100.
- Estimation of Reynolds number for liquid rising in a thin capillary of radius 100 microns: about 10.
Capillary Tubes
- Height of rise in capillary tubes is inversely proportional to the tube radius.
- Height of rise is not zero in a space shuttle.
Laminar Cylindrical Pipe Flow (Poiseuille Flow)
- Velocity profile is parabolic and maximal on the cylinder axis.
- Flow is governed by viscosity.
- Velocity is zero along the cylinder walls.
Typical Situations for Viscous Forces
- Flows mainly ruled by viscous forces include imbibition of a porous soil, swimming of bacteria, sedimentation of powder particles, and flow of blood in the aorta.
Microfluidic Channels
- Operations and applications suitable for microfluidic channels include conveying of yield-stress fluids, blood sample bio-analysis, preparation of emulsions, and tumor cell sorting.
Rheology of Fluids
- In a suspension of particles, viscosity increases with volume fraction and shows shear-thickening behavior at small shear rates.
- Rheology of a fluid can be defined as non-Newtonian, shear-thickening, viscoelastic, or yield-stress fluid.
Falling Solid Sphere in Air
- Archimedes force is negligible for a solid sphere falling in air.
- Terminal velocity is proportional to the square of the radius of the sphere.
Plasma Protein Fibrinogen in Microcapillary Flows
- Approximate value of Reynolds number and shear rate in the experimental microfluidic cell: Re = 0.012 and γ = 80-1.
- Effects of fibrinogen concentration on blood properties include increased viscosity for any shear rate and stronger effects for high shear rates.
- Dextran allows spanning larger values of shear rate and promotes cluster formation at intermediate concentrations.
- Advantages of the microfluidic cell include clear visualization of individual RBCs and clusters, high shear rates, and well-controlled flow rates.
Future Steps of the Study
- Next steps could include improving visualization, exploring higher shear rate ranges, coating micro channel walls with endothelial cells, and determining velocity profiles around clusters and individual RBCs.
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Description
This quiz tests your knowledge of fluid dynamics concepts, including super-hydrophobic and super-oleophobic surfaces, surface tension, and their practical applications.
