Fluid Mechanics Question: Calculation of kinematic velocity

In summary, the person is asking for help with a fluid mechanics problem involving absolute and kinematic viscosity. They provide the necessary equations and their solution, and ask for feedback on their work. They also mention their instructor's method for handling units.
  • #1
thelovemonkey
12
0
hey guys I am new to the forum... i am a first year civil engineering student trying to do a second year course over this summer holiday. for fluid mechanics i was given this h/w problem. could you please tell me if I am correct and if not make explain where i went wrong and how to correct it?



Homework Statement


at 25 C a fluid has an absolute viscosity of 0.0978 Poise and a Specific Gravity of 0.997. Compute:
a. absolute viscosity in Ns/m^2
b. Kinematic viscosity in SI units


Homework Equations



Specific Gravity(SG)= Density of substance(Ds)/ Density of Water(Dw)

Kinematic Viscosity (KV) = Absolute Viscosity in SI units/ Density of Substance(Ds)

1 Poise= 0.1 Ns/m^2


The Attempt at a Solution




A.
if
1 Poise= 0.1 Ns/m^2

then

o.00978 Poise = 0.1 x 0.00978 Ns/m^2 = 0.000978 Ns/m^2


B.

KV= Abs. Viscosity/ Ds

SG= Ds/Dw

Ds= SG x Dw = 1000 kg/m^3 x 0.997 = 997kg/m^3


KV = (0.000978 Ns/m^2)/ (997 kg/m3)

=> KV= 9.8 x 10^-7 Nsm/Kg
 
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  • #2
Yes your work is correct.
 
  • #3
the lecturer showed us a pretty neat way to handle these units...

Nsm/Kg ->

since N= Kg/m^2
then

units = m^2/ S


very late don't have time to rbeak down
 

1. What is kinematic velocity in fluid mechanics?

Kinematic velocity in fluid mechanics refers to the velocity of a fluid flow without taking into account the density of the fluid. It is a measure of the rate at which the fluid particles move and is typically measured in meters per second (m/s).

2. How is kinematic velocity calculated?

Kinematic velocity can be calculated by dividing the fluid's dynamic viscosity by its density. The formula for calculating kinematic velocity is v = μ/ρ, where v is the kinematic velocity, μ is the dynamic viscosity, and ρ is the density of the fluid.

3. What are some common units for kinematic velocity?

The most commonly used unit for kinematic velocity is meters per second (m/s). However, other units such as feet per second (ft/s) and centimeters per second (cm/s) may also be used.

4. How does kinematic velocity differ from dynamic velocity?

Kinematic velocity and dynamic velocity are both measures of fluid flow, but they differ in that dynamic velocity takes into account the density of the fluid, while kinematic velocity does not. Dynamic velocity is typically used in fluid dynamics calculations, while kinematic velocity is used in applications such as heat transfer and mass transfer.

5. What factors can affect kinematic velocity?

Kinematic velocity can be affected by various factors, including the type of fluid, its temperature and pressure, and the presence of any external forces such as gravity or friction. Changes in these factors can alter the fluid's dynamic viscosity and density, thus impacting the kinematic velocity.

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