TYPES OF FLUID FLOWS

By: KAUSAR HUSSAIN SE:- CIVIL ROLL:-64*

FLUIDS IN MOTIONReal flow vs. ideal flow non-steady / steady state compressible / incompressible rotational / irrotational viscous / frictionless

Types of fluid Flow 1. Real and Ideal Flow:Friction = 0Ideal Flow ( =0)Energy loss =0Friction = oReal Flow ( 0)Energy loss = 0IdealRealIf the fluid is considered frictionless with zero viscosity it is called ideal.In real fluids the viscosity is considered and shear stresses occur causing conversion of mechanical energy into thermal energy

TYPES OF FLUID FLOWLaminar flow Each particle of the fluid follows a smooth path The paths of the different particles never cross each other The path taken by the particles is called a streamlineTurbulent flow An irregular flow characterized by small whirlpool like regions Turbulent flow occurs when the particles go above some critical speed

Onset of Turbulent FlowThe SeaWifS satellite image of a von Karman vortex around Guadalupe Island, August 20, 1999

LAMINAR AND TURBULENT FLOWIn laminar flow, the fluid flows in layers parallel to each other. No mixing.In turbulent flow, the velocity is fluctuating with time and a strong mixing occurs between fluid layers.

5. Laminar and Turbulent Flow:In Laminar Flow:Fluid flows in separate layersNo mass mixing between fluid layersFriction mainly between fluid layersReynolds Number (RN ) < 2000Vmax.= 2VmeanIn Turbulent Flow:No separate layersContinuous mass mixing Friction mainly between fluid and pipe wallsReynolds Number (RN ) > 4000Vmax.= 1.2 VmeanVmeanVmaxVmaxVmean

5. Laminar and Turbulent Flow (cont.):

Uniform Flow means that the velocity is constant at certain time in different positions (doesnt depend on any dimension x or y or z(3. Uniform and Non uniform Flow Non- uniform Flow means velocity changes at certain time in different positions ( depends on dimension x or y or z( YYxxuniformNon-uniform

Rotational and irrotational flows:The rotation is the average value of rotation of two lines in the flow. (i) If this average = 0 then there is no rotation and the flow is called irrotational flow

*4. One , Two and three Dimensional FlowA flow field is best characterized by its velocity distribution.A flow is said to be one-, two-, or three-dimensional if the flow velocity varies in one, two, or three dimensions, respectively. However, the variation of velocity in certain directions can be small relative to the variation in other directions and can be ignored.The development of the velocity profile in a circular pipe. V = V(r, z) and thus the flow is two-dimensional in the entrance region, and becomes one-dimensional downstream when the velocity profile fully develops and remains unchanged in the flow direction, V = V(r).

4. One , Two and three Dimensional Flow : Two dimensional flow means that the flow velocity is function of two coordinatesV = f( X,Y or X,Z or Y,Z ) One dimensional flow means that the flow velocity is function of one coordinate V = f( X or Y or Z ) Three dimensional flow means that the flow velocity is function of there coordinatesV = f( X,Y,Z)xy

1 DIMENSIONAL FLOWPipe flow:Function of radial position, r, only !Duct flow:Function of axial distance, x, only !Not very good assumption but many practical flows could be modeled as 1 D flow

2 DIMENSIONAL FLOW

3 DIMENSIONAL FLOW

NEWTONIAN VS. NON-NEWTONIAN*Newtonian fluids: water, air.Pseudoplastic fluids: paint, printing ink.Dilatant fluids: dense slurries, wet cement.Bingham fluids: toothpaste, clay.Casson fluids: blood, yogurt.Visco-elastic fluids: polymers (not shown in graph because viscosity is not isotropic). (Pa)

FLOW CLASSIFICATIONSIncompressible vs. compressible flow.Incompressible flow: volume of a given fluid particle does not change.Implies that density is constant everywhere.Essentially valid for all liquid flows.Compressible flow: volume of a given fluid particle can change with position.Implies that density will vary throughout the flow field.Compressible flows are further classified according to the value of the Mach number (M), where.

M < 1 - Subsonic.M > 1 - Supersonic.*

FLOW CLASSIFICATIONSSingle phase vs. multiphase flow.Single phase flow: fluid flows without phase change (either liquid or gas).Multiphase flow: multiple phases are present in the flow field (e.g. liquid-gas, liquid-solid, gas-solid).Homogeneous vs. heterogeneous flow.Homogeneous flow: only one fluid material exists in the flow field.Heterogeneous flow: multiple fluid/solid materials are present in the flow field (multi-species flows).*

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