1. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 1Autumn Quarter Transport Phenomena Lab 4

2. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 2Autumn Quarter Topics to be covered Transport Phenomena –Energy –Mass –Momentum (fluid) Viscosity and rheology Falling ball viscometers –examine the effect of viscosity on object falling through the fluid.

3. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 3Autumn Quarter Transportation applications Energy –Fighter jet cooling –Radiators –Air conditioners Mass –Intracellular transfer Momentum (i.e. fluid) –Pumps –Airplane flight –Water flow Applications all over engineering: –Mechanical –Chemical –Aeronautical –Biomedical –Civil –Industrial Systems –Materials Science

4. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 4Autumn Quarter Energy and Mass Transport Mechanisms Energy Transport Mass Transport Flow Direction N2N2 O2O2 valve Difference in temperature is the driving force for heat transfer. Difference in concentration is the driving force for mass transfer.

5. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 5Autumn Quarter Momentum (Fluid) Transport Flow types –Turbulent flow –Laminar flow Velocity Gradient Viscosity Reynolds Number

6. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 6Autumn Quarter Momentum transport Mechanisms Difference in pressure is the driving force, causing fluid to flow Turbulent flow (Eddy) Flow Direction If pressure drop is large, flow will be relatively large - fluid motion is chaotic and transfer is with blocks of molecules moving in all directions, causing eddy currents.

7. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 7Autumn Quarter Momentum transport Mechanisms If pressure drop is small across the object, fluid motion is smooth and transfer is molecular. That is, momentum transfers from molecule to molecule through the fluid. Fluid flows in layers Difference in pressure is the driving force, causing fluid to flow Laminar flow ( Molecular)

8. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 8Autumn Quarter Velocity Gradient (dVx/dy) There is a gradient of velocity as you move from the stationary to the moving plate, and the liquid tends to move in layers with successively higher speed In case of fluid through a pipe, the velocity of flow varies from zero at the walls to a maximum along the centerline of the pipe.

9. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 9Autumn Quarter Viscosity – A fluid flow property Internal property of a fluid that offers resistance to flow – it is a measure of how easily a fluid can flow. Results from cohesion and molecular momentum exchange between fluid layers – as flow occurs, these appear as shearing stresses between moving layers. It can also be viewed as a resistance to shear force, more viscous the fluid is, higher the resistance.

10. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 10Autumn Quarter Coefficient of Viscosity (μ) Under conditions of laminar flow, the force (F) required to move a plate at constant speed against the resistance of a fluid is proportional to the area of the plate (A) and to the velocity gradient (dV x /dy) perpendicular to the plate. F = μ A (dV x /dy) (or) τ = μ (dV x /dy) where, τ is shear stress per unit area Newtons Law of Viscosity Unit (SI): kg m -1 s -1 (preferred) or Pa-s

11. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 11Autumn Quarter Reynolds Number (Re) Re is a dimensionless parameter that describes flow and is defined as Re = DV ρ/µ –D: Characteristic length scale (such as diameter of a pipe, diameter or length of a body) (m) –V: Characteristic Velocity (m/s) –ρ: Density of fluid (kg/m3) –µ: Viscosity of fluid (kg/ms) –Ratio µ/ρ is called Kinematic Viscosity of fluid, usually expressed in (m2/s)

12. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 12Autumn Quarter Re and Critical Velocity At a critical value of Re, flow will change from laminar to turbulent - the flow velocity at which this occurs is called the critical velocity. Critical Re changes based on application – there are no analytical methods for predicting critical Re available due to complex origins of turbulence.

13. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 13Autumn Quarter Re and Critical Velocity For fluid flow through pipes, critical Re  2000 –Re < 2000 for laminar –Re >> 2000 for turbulent –2000 < Re < 4000 is transition region – laminar or turbulent Critical Re changes for different flow types: –  1 for object moving in a fluid (this lab) –  1000 for flow between parallel walls –  500 for flow in a wide open channel

14. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 14Autumn Quarter Falling Sphere Viscometer Requires a transparent vertical tube filled with test fluid and the object (a sphere). When object starts to drop (free fall), it accelerates downward till it reaches a maximum velocity – called terminal velocity (Vt). Terminal velocity affected by –Density, viscosity of the fluid –Shape, size, density of object Measure terminal velocity. VtVt Assume: Sphere attains terminal velocity here

15. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 15Autumn Quarter Falling Sphere Viscometer Sphere at terminal velocity (Vt) Fd = Fg – Fb Fg Fd Fb When body attains terminal velocity, body experiences no acceleration – forces acting on the body are in equilibrium. Magnitude of terminal velocity should result in a low Re – critical Re is about 1. Gravitational Force (Fg) depends on: –Density of sphere –Radius of sphere –Acceleration due to gravity

16. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 16Autumn Quarter Falling Sphere Viscometer Force due to buoyancy (Fb) depends on: –Density of fluid –Radius of sphere –Acceleration due to gravity Drag force (Fd) is the resistance of the fluid to motion of body given by Stokes law, depends on: –Absolute viscosity of fluid –Terminal Velocity (Vt) –Radius of sphere Fg Fd Fb Fd = Fg – Fb

17. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 17Autumn Quarter Falling Sphere Viscometer VtVt Design should consider: Wall effects Ratio of diameter of sphere to diameter of cylinder should be as small as possible. Bottom effects To ensure minimal error, we stop recording before a specific height from the bottom of cylinder. Terminal velocity of object through fluid Should yield Re << 1 for laminar flow. Start recording after sphere attains terminal velocity. Assume sphere attains terminal velocity here Bottom effect considerations

18. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 18Autumn Quarter Lab Report Requirements - in pairs Analysis and discussion of the two fluids at your table plus a third fluid from the lab website –Position/time plots with trendlines Analysis and discussion of the velocities from each group in the class –Comparison of group data against class Determination of Reynolds number and viscosity for each fluid

19. Engineering H191 - Drafting / CAD The Ohio State University Gateway Engineering Education Coalition Lab 4P. 19Autumn Quarter Today’s Goals Collect data using the LabVIEW application –Save at least 6.csv files – 3 per fluid using the two fluids at your table Collect 6 sample V t (3 per fluid) and report to the front, as described at end of procedure: –Open your.csv files and determine V t by fitting trendlines and calculating total velocity