- #1
richard9678
- 93
- 7
I don't understand units associated with kinematic viscosity.
Let's recap dynamic viscosity (η):
η = Shear stress (τ) / rate of shear strain (m/s)/m)
η = F/A / (velocity (m/s) / gap distance (m))
η = Force( N) / Area (m2) / (velocity (m/s) / gap distance (m))
Stress (F/A) is pressure, Newtons per metre squared, so unit is Pascals. When you cancel the two m's out in the divisor, you are left with:
η = N/m2 or Pascals / s (Pascal Seconds).
The equation to convert dynamic viscosity to kinematic velocity is:
ν = η / ρ
ν = η N m-2 s / ρ Kg m-3
I get this. The numerator is saying Newtons per square meter (pressure in Pascals) per second (Pascal seconds) and the divisor is saying Kg per cubic metre)
Since 1 Kg = N m-1 s2, this simplifies to dimensions of m2 s-1
I don't get how things simplify.
I know that the Stoke is the unit, and it's a unit of position and time.
Thanks.
Let's recap dynamic viscosity (η):
η = Shear stress (τ) / rate of shear strain (m/s)/m)
η = F/A / (velocity (m/s) / gap distance (m))
η = Force( N) / Area (m2) / (velocity (m/s) / gap distance (m))
Stress (F/A) is pressure, Newtons per metre squared, so unit is Pascals. When you cancel the two m's out in the divisor, you are left with:
η = N/m2 or Pascals / s (Pascal Seconds).
The equation to convert dynamic viscosity to kinematic velocity is:
ν = η / ρ
ν = η N m-2 s / ρ Kg m-3
I get this. The numerator is saying Newtons per square meter (pressure in Pascals) per second (Pascal seconds) and the divisor is saying Kg per cubic metre)
Since 1 Kg = N m-1 s2, this simplifies to dimensions of m2 s-1
I don't get how things simplify.
I know that the Stoke is the unit, and it's a unit of position and time.
Thanks.
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