Flow of fluids

Flow of fluidsUdeh chinyere uba

In a mechanical view, a fluid is a substance that does not supportshear stress; that is why a fluid at rest has the shape of its containing vessel. A fluid at rest has no shear stress.1

What is a fluid???

LAMINAR VS TURBULENT FLOW

Laminar floworstreamlineflow occurs when a fluid flows in parallel layers, with no disruption between the layers (no mixing of fluids). Laminar flow tends to occur at lower velocities.

Turbulent flow is characterised by random chaotic property changes.(mixing of fluids, collision of fluid particles)

Note: laminar flow can be turned into turbulent flow by:Increasing amount of fluid per cross section per timeDecreasing the radius of the mediumDecreasing the viscosity of the fluid

BLOOD PRESSURE MEASUREMENTSPressureSoundFlow typeP> systolic pressuresilenceNo flowSys>P> diastolicOscillating soundTurbulent flowDiastolic> pressureNo soundLaminar flow

REGULATION OF BLOOD PRESSUREvasoconstriction and vasodilatation are an important part of controlling bloodpressure.They're probably not the most important part - as we'll see next - but inevitablythey play their role.As the blood vesselsconstrict, there is less room for the blood to go throughand so the pressure goes up; both the systolic blood pressure and diastolicblood pressure will be increased. Conversely, as the vesselsdilate, there is more room for the blood to gothrough, and so the pressures go down.

Ideal FluidsIdeal fluid; a fluid with no frictionAlso referred to as an inviscid (zero viscosity) fluid Fluid is incompressible (isochoric flow)Ideal fluids are just theoretical and do not really exist

Real FluidsParticles are constantly interactingThus, fluid friction is createdShear forces oppose motion of one particle past anotherFriction forces gives rise to a fluid property called viscosityE.g. of real fluids; blood

VOLUMETRIC FLOW RATE

In our body: A, v

Conclusion:A decrease in the diameter and or length of tube leads to a decrease in velocity of blood flowThe more the branches, the less the velocity of blood flowThe higher the cross-section area, the lower the blood velocity

Bernoullis law

Consequences of Bernoullis law:It states that an increase in velocity of fluid leads to a decrease in pressureIn a tube, the centre which has the lowest pressure experiences the quickest flow leading to an increase in the number of particles in the centre. E.g. in blood flow, more cells go with the mainstreamThis is because particles always move to areas of lower energy states/ concentrationPractical example; when u open the window of a moving car, your hair tries to fly out of the car

1 pascal (Pa) = 1 N/m2

CONSEQUENCE OF HAGEN-POISEUILLE LAW