Topic 4: Flow Rate and Viscosity

• Recall that fluids can be liquids or gases. • The characteristic of fluid thickness and thickness is viscosity. • "sticky" liquids are called viscous liquids. Example) Honey, molasses, syrup • Low viscosity liquids are "water", juice, pop music, milk. • Gas is also viscous but it is difficult to imagine because you can not see gas.

And please look at their property. However, their viscosity is different from that of liquids. • Flow rate is the speed at which fluid flows within a unit time. • "Flow" means that the particles are sliding because the particles are weak.

Internal friction between liquid particles • Liquid particles flow against one another and produce friction. • The amount of internal friction depends on the type of particle.

Example of their mutual attractiveness Example: Water particles are not attractive for syrup particles. When they flow with each other, the water particles easily slide against each other due to low attractive force, the internal friction is small and the flow velocity is high. The syrup particles attract each other, the internal friction is very large and the flow rate is very slow (ie the flow rate is very slow).

Temperature change of liquid viscosity • The higher the temperature, the higher the energy, the more dynamic movement will occur.

Particles mean more collisions and particles spread further. • Due to internal friction, particles easily slide.

Reduce the viscosity. • Liquid particles become slippery and easy to flow with each other.

Usage: Make sauce and cosmetic by making sauce, engine oil 10W-40 ~ 10W-5 every season

• As gas particles acquire energy and travel faster, they collide more frequently and in fact decelerate with each other.

However, when the energy is low, the gas particles move at a slower rate, with lower collisions and flow velocities. In short, it flows very fast

The shear stress due to the viscosity of the fluid depends on the flow velocity. However, the viscosity itself did not change. In fact, the flow is not important, the speed at which the fluid is sheared. For example, dv / dy is important and direct v is not important.

Poiseuille's law applies to laminar flow of incompressible fluid through the length and radius of the viscosity of the pipe. The direction of flow is from large to low. The flow rate is proportional to the pressure difference and inversely proportional to the length of the tube and the viscosity of the fluid. The flow rate increases with the fourth power of the radius. The intravenous (IV) system supplies saline to the patient at a needle speed with a radius of 0.150 mm and a length of 2.50 cm. Assuming that the viscosity of the salt solution is the same as that of water, what kind of pressure is needed at the entrance of the needle to cause this flow? The patient's intravenous blood gauge pressure was 8.00 mm Hg. (temperature

A common question about peristaltic pumps is how viscosity affects flow. Simply put, if the viscosity rises the flow rate will go down. That said, there are a variety of factors that need to be understood when considering a peristaltic pump in applications where it is necessary to pump up a viscous fluid. * Since the physical properties and shape of the selected pipe are related to the viscous fluid, it directly affects the flow capacity of the peristaltic pump. The tube bounces after it is compressed by the pressure roller. "Rebound" is the cause of suction. Generally, the greater the elongation of the elastomer, the stronger the ability to lift the viscous fluid. This is exactly the same as our Prothane II ™ tube. Geometrically, the larger the ratio of the wall to the inner diameter, the better the pumping out of the pipe as the pipe bounces back better during constant bending in the pump.