The amount of friction depends on the fluid viscosity and the velocity gradient (that is, the relative velocity between fluid layers). The velocity gradients are set up by the no-slip condition at the ...

or \(= {ms}^{-2}\). A negative gradient shows the rate of 'slowing down' or deceleration. Velocity-time graphs show velocity on the vertical axis. Acceleration is still represented by the gradient.

A negative gradient shows the rate of “slowing down” or deceleration. Velocity-time graphs show velocity on the vertical axis. Acceleration is still represented by the gradient. Key fact The ...

An important observation is that fluid flow is always irreversible. It is irreversible because fluids have viscosity, and whenever velocity gradients appear in the flow there will be friction and ...

Doppler is used to quantify the severity of aortic stenosis by measuring the pressure gradient across the aortic valve and by calculating the aortic valve area (AVA). The velocity of blood flow ...