We can consider several layers in a flowing fluid. Each layer has a sightly different speed compared to the neighboring layers. This force, acting between two layers of as flowing fluid is known as viscous force. And the property due to which this force arises is called viscosity.

Viscosity is a measure of a fluid’s resistance to flow. It describes the internal friction of a moving fluid. A fluidwith large viscosity resists motion because its molecular makeup gives it a lot of internal friction.

A type of fluid flow in which there is a continuous steady motion of the particles; the motion at a fixed point always remains constant. Also called streamline flow; laminar flow; steady flow.

Viscosity is another type of bulk property defined as a liquid’s resistance to flow. When the intermolecular forces of attraction are strong within a liquid, there is a larger viscosity. An example of this phenomenon is imagining a race between two liquids down a windshield.

Units. The SI unit of dynamic viscosity is the newton-second per square meter (N·s/m2), also frequently expressed in the equivalent forms pascal-second (Pa·s) and kilogram per meter per second (kg·m−1·s−1).

two kinds

Dynamic viscosity of water Water has a viscosity of 0.0091 poise at 25 °C, or 1 centipoise at 20 °C. where A=2.414 × 10−5 Pa·s ; B = 247.8 K ; and C = 140 K.

In fluid dynamics, viscosity is the parameter to measure the thickness or thinness of any given fluid. Density is the measure of spaces between two particles in a given fluid. Viscosity and density are the characteristics of a fluid, but there is no direct relation between viscosity and density.

The resistance to flow in turn is directly proportional to the viscosity η . Thus, the flow rate is inversely proportional to the viscosity.

Viscosity is caused by friction within a fluid. It is the result of intermolecular forces between particles within a fluid.

One of the most viscous liquids known is pitch, also known as bitumen, asphalt, or tar. Demonstrating its flow and measuring its viscosity is the subject of the longest continuously running scientific experiment, begun in 1927 at the University of Queensland in Australia.

A fluid that is highly viscous has a high resistance (like having more friction) and flows slower than a low-viscosity fluid. Honey would move slower than water, so honey would have a greater viscosity.

In layman’s terms, viscosity defines a fluid’s resistance to flow. The higher the viscosity of a liquid, the thicker it is and the greater the resistance to flow. Temperature will affect the viscosity of most materials.

The greater a lubricant’s viscosity, the greater pressure or load it can withstand, and the better it maintains separation between moving parts. But there are limits to this relationship. If the viscosity is too high, it won’t flow as readily and your engine will work harder and burn more fuel.

Engine oil viscosity refers to how easily oil pours at a specified temperature. Thin oils have lower viscosity and pour more easily at low temperatures than thicker oils that have a higher viscosity. Thick oils are better at maintaining film strength and oil pressure at high temperatures and loads.

Ketchup, maple syrup, molasses, and corn syrup are all examples of liquids with high viscosities. Molasses has a high viscosity – it is very thick. Vegetable oil has a relatively low viscosity, as does milk. Viscosity is a concern when you need to know how quickly or how slowly a fluid flows.

Now if oil is replaced with honey then a greater force will be required to move the top plate with same velocity. Hence, honey is more viscous than oil. Viscosity of thin liquids like water, alcohol, etc., is less compared to thick liquids like coal tar, blood, glycerine, etc.

Acetone has a viscosity 3x less than water but weighs 2.5 times more.

The least viscous at any temperature must be superfluid liquid helium.

Summary: Blood flows differently than water. Anyone who has ever cut themselves knows that blood flows viscously and rather erratically.