# Rheology of Fluids

Document Preview:

Chapter 6 Rheology of Fluids 1. Viscosity 2. Types of fluids 3. Factors affecting viscosity 4. Measurement of viscosity
Fluidity and Viscosity • Concentration • Temperature • Solute and solvent • Structure and size of solute molecules
Liquid flows in a pipe Velocity v v v
1. Viscosity Definition: resistance to flow. F F ?L Fluid Fluid Layers ?l X ? x Velocity gradient F = shear force (N), v = velocity (m/s), x = fluid thickness (m), L = distance (m).
Viscosity F ?dv and F ? 1 dx ? FA ? dv dx or by introducing a coefficient?, FA =? · dv dx t = FA =? · A· dv dx A =? · dv dx let ?? = dv dx , t =??? and ? = t?? F = shear force (N), v = velocity (m/s), x = fluid thickness (m), A = area of the plate (m2), t = shear stress (Pa), ? ? = shear rate (s-1), and ? = viscosity (Pa·s)
Viscosity (represented by the symbol ? “eta”) is the ratio of the shearing stress (F/A) to the velocity gradient (?v/?x or dv/dx) in a fluid.

## ORDER ASSIGNMENT HELP

• TIMELY DELIVERIES
• ZERO PLAGIARISM
• GUARANTEED PASS
• AFFORDABLE PRICING
• FREE REVISIONS

The more usual form of this relationship, called Newton’s equation, states that the resulting shear of a fluid is directly proportional to the force applied and inversely proportional to its viscosity. The similarity to Newton’s second law of motion (F = ma) should be apparent. ? = FA ?v ?x or ? = FA dv dx = t?? dt vs F m dv dx dv AF =? . =
Viscosity ? ? t a dl dx ?? ??? ?1 dt t a ?? or t =? ?? ? = t?? slope= viscosity, ? (Pa.s) Shear stress (Pa) Shear rate (s-1) Newtonian (ideal) fluid
Ø? Absolute (dynamic) viscosity SI unit: Pa·s, mPa·s CGS unit: Poise (dyne·s/cm2, or g/cm·s) (P), centipoise (cP) 1 mPa·s = 1 cP = 0.01 P Ø? Kinematic viscosity ? ? ? = ? = t?? Unit: m2/s, cm2/s (Stokes), mm2/s (centistokes) Unit of Viscosity
simple liquids T (ºC) ? (mPa·s) alcohol, ethyl (grain) 20 1.1 alcohol, isopropyl 20 2.4 alcohol, methyl (wood) 20 0.59 blood 37 3 -4 ethylene glycol 25 16.1 ethylene glycol 100 1.98 freon 11 (propellant) -25 0.74 freon 11 (propellant) 0 0.54 freon 11 (propellant) +25 0.42 freon 12 (refrigerant) +15 0.20 glycerin 20 1420

You can hire someone to answer this question! Yes, essay96.com has paper writers dedicated to completing research and summaries, critical thinking tasks, essays, coursework, and other homework tasks. It's fast and safe.