Newton's Parallel Plate Experiment
In this experiment, the apparatus consists of two horizontal parallel plates with a sufficiently large spacing (h) between them. The space is filled by a fluid. Now the top plate is moved with a velocity, U. The distance in the fluid affected by the motion of the upper plate is denoted by . The distance is the penetration depth in the fluid arising from a disturbance on its boundary (the plate movement).The force required to sustain the plate motion is given by,
![](../images/eqn_addn_chap1/image004.gif)
Now can be approximated as (which you will learn in later chapters). Here is coefficient of momentum transport (kinematic viscosity) that determines the extent of motion transport in a stationary fluid medium. The kinematic viscosity ( ) is related to dynamic viscosity ( ) as
![](../images/eqn_addn_chap1/image014.gif)
where is the density of the fluid.
So, we can approximate as (upon considering the fluid incompressible). Hence, the force required can be reframed as,
![](../images/eqn_addn_chap1/image019.gif)
So, this experiment can be used to calculate the coefficient of dynamic viscosity of a fluid for a given value of density of the fluid , velocity of the plate, U and the area of the plate, A and the force applied, F.
![](../images/fig_addn2.jpg)
u(y) is the velocity profile along the y-axis.
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