Mer 331 Lab Week 2 Viscosity Background Viscosity

Mer 331 Lab – Week 2 Viscosity Background: Viscosity n A fluid is a state of matter that does not permanently resist shear and the resistance to deformation (shear stress) is a function of the rate of deformation (shear rate) n Rheology = science of deformation n Viscometry = measurement of rheological properties n Viscosity is the property of a fluid that resists deformation: molasses vs water, u molasses in January vs molasses in July. u n Newton Law of Viscosity (for Newtonian fluids)

Background: Viscosity Shear Thickening Shear stress as a function of deformation

Background Oobleck: shear thickening http: //io 9. com/5715076/non+newtonian-fluids-theweirdest-liquids-youve-ever-seen http: //en. wikipedia. org/wiki/Bartholome w_and_the_Oobleck http: //www. youtube. com/watch? v=y. Hl. Ac. ASsf 6 U

Background Ketchup, Toothpaste: shear thinning Leaping Shampoo! Versluis M, Blom C, Meer D, Weele K, Lohse D (2006) Leaping Shampoo and the Stable Kaye Effect. Journal of Statistical Mechanics: Theory and Experiment 2006 P 07007. http: //www. youtube. com/watch? v=GX 4_3 c. V_3 Mw

Background: Viscosity Units Absolute (or Dynamic) Viscosity, Units: 1 Poise = 1 g/(cm sec) 1 Pa sec = 1 kg/(m sec) = 1 N sec/m 2 1 Poise = 100 c. P = 0. 1 Pa sec Kinematic Viscosity: = /ρ Units: 1 stoke = 1 cm 2/sec = 0. 0001 m 2/sec

Techniques for Measuring Viscosity n n Capillary Viscometers Rotary Viscometers Falling “Object” Viscometers And many others….

Capillary Viscometers n Capillary Viscometers Measure the flow rate of a fixed volume of fluid through a small orifice u From laminar flow theory we can relate the flow rate, pressure drop to viscosity u = K*time K is a calibration constant Time is measured in seconds is given in c. St

Rotary Viscometers n Use the torque on a rotating shaft to measure a fluids resistance to flow = F * torque F is a calibration constant which you look up in the instrument manual

Falling “Object” Viscometers n Apply F=ma n At terminal speed a=0 FG = F B + F D FG = mg = rp. D 3 g/6 FB = rfluidp. D 3 g/6 The drag on a sphere depends on the flow field: …. FB= Buoyancy FD =Drag FG = Weight

Falling “Object” Viscometers The drag on a sphere depends on the flow field: Reynold’s Number: For Stokes Flow: Re < 0. 1 Therefore: Restrictions: terminal velocity, Re < 0. 1

Gilmont Viscometer = Kt(rball-rfluid) K = 35 Rball, ss = 8. 02 (gm/ml) Rball, glass = 2. 53 (gm/ml) in Cp t in minutes

Lab Write Up You will write a full lab report. Review the information on the course webpage: http: //engineering. union. edu/~andersoa/mer 331/MELab. Reports. htm Include detailed information on the uncertainty analysis: u Table of uncertainty values for each thing you measure (i. e. mass, volume etc). u Report all data with an uncertainty value u Include (hand written) derivation of uncertainty equations with a sample calculation in an appendix. u See handout on lab report expectations.