Engineering H191 - Drafting / CADTransport Phenomena Lab 4 Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. 1 2 . Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Drafting / CAD 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.Engineering H191 . Engineering H191 . fluid) – Pumps – Airplane flight – Water flow • Applications all over engineering: – Mechanical – Chemical – Aeronautical – Biomedical – Civil – Industrial Systems – Materials Science Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Drafting / CAD Transportation applications • Energy – Fighter jet cooling – Radiators – Air conditioners • Mass – Intracellular transfer • Momentum (i.e. 3 . Engineering H191 . 4 Autumn Quarter The Ohio State University Gateway Engineering Education Coalition .Drafting / CAD Energy and Mass Transport Mechanisms Energy Transport Flow Direction Difference in temperature is the driving force for heat transfer. Mass Transport N2 valve O2 Difference in concentration is the driving force for mass transfer. Lab 4 P. Drafting / CAD Momentum (Fluid) Transport • Flow types – Turbulent flow – Laminar flow • Velocity Gradient • Viscosity • Reynolds Number Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. 5 .Engineering H191 . causing fluid to flow Laminar flow ( Molecular) If pressure drop is small across the object.Drafting / CAD Momentum transport Mechanisms Difference in pressure is the driving force. momentum transfers from molecule to molecule through the fluid. Fluid flows in layers Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Engineering H191 . fluid motion is smooth and transfer is molecular. That is. 6 . Drafting / CAD 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. • It can also be viewed as a resistance to shear force. Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. these appear as shearing stresses between moving layers. 7 . higher the resistance.Engineering H191 . • Results from cohesion and molecular momentum exchange between fluid layers – as flow occurs. more viscous the fluid is. Drafting / CAD Coefficient of Viscosity (μ) Under conditions of laminar flow. 8 . τ is shear stress per unit area Newtons Law of Viscosity Unit (SI): kg m-1 s-1 (preferred) or Pa-s Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. 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 (dVx/dy) perpendicular to the plate.Engineering H191 . F = μ A (dVx/dy) (or) τ = μ (dVx/dy) where. usually expressed in (m2/s) Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. 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.Engineering H191 . 9 .Drafting / CAD 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. Drafting / CAD Re and Critical Velocity • At a critical value of Re. 10 . • Critical Re changes based on application – there are no analytical methods for predicting critical Re available due to complex origins of turbulence.the flow velocity at which this occurs is called the critical velocity. Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Engineering H191 . flow will change from laminar to turbulent . Engineering H191 .Drafting / CAD Re and Critical Velocity • For fluid flow through • Critical Re changes for pipes. 11 . critical Re 2000 different flow types: – 1 for object moving in a fluid (this lab) – Re < 2000 for laminar – 1000 for flow between parallel walls – Re >> 2000 for turbulent – 500 for flow in a wide open channel – 2000 < Re < 4000 is transition region – laminar or turbulent Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. Engineering H191 . density of object • Measure terminal velocity. size. it accelerates downward till it reaches a maximum velocity – called terminal velocity (Vt). • When object starts to drop (free fall).Drafting / CAD Falling Sphere Viscometer Vt Assume: Sphere attains terminal velocity here • Requires a transparent vertical tube filled with test fluid and the object (a sphere). viscosity of the fluid – Shape. Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P. • Terminal velocity affected by – Density. 12 . • Gravitational Force (Fg) depends on: – Density of sphere – Radius of sphere – Acceleration due to gravity Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 Sphere at terminal velocity (Vt) Fd = Fg – Fb Fd Fb Fg P. • Magnitude of terminal velocity should result in a low Re – critical Re is about 1.Drafting / CAD Falling Sphere Viscometer • When body attains terminal velocity. body experiences no acceleration – forces acting on the body are in equilibrium.Engineering H191 . 13 . 14 .Engineering H191 . depends on: – Absolute viscosity of fluid Fd Fb – Terminal Velocity (Vt) – Radius of sphere Fg Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Drafting / CAD Falling Sphere Viscometer • Force due to buoyancy (Fb) depends on: – Density of fluid Fd = Fg – Fb – Radius of sphere – Acceleration due to gravity • Drag force (Fd) is the resistance of the fluid to motion of body given by Stokes law. The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Drafting / CAD Falling Sphere Viscometer Terminal velocity of object Design should consider: Assume sphere attains terminal velocity here through fluid Should yield Re << 1 for laminar flow. we stop recording before a specific height from the bottom of cylinder. Bottom effect considerations Bottom effects To ensure minimal error. Vt Wall effects Ratio of diameter of sphere to diameter of cylinder should be as small as possible. 15 Autumn Quarter .Engineering H191 . Start recording after sphere attains terminal velocity. 16 .Drafting / CAD 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 Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Engineering H191 . csv files and determine Vt by fitting trendlines and calculating total velocity Autumn Quarter The Ohio State University Gateway Engineering Education Coalition Lab 4 P.Drafting / CAD 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 Vt (3 per fluid) and report to the front. 17 . as described at end of procedure: – Open your .Engineering H191 .