Reynolds number. how to calculate a new diameter when given a new velocity?

Question

say you calculate the NRE for a given diameter, velocity, density and viscosity but you then want to use those same values and calculate a new pipe diameter for a new velocity, is the NRE that you calculated initially what you would use to find the new diameter for a new velocity?

Answer 1

Do you want the dynamic similarity implied by a constant Reynolds number? Then you should use the same NRE. But if you are keeping the flow rate constant, then the ratio D changes as the inverse square root of V, not as the simple inverse, so NRe will change.

Answer 2

the linked fee at which the employing forces are cancelled out by employing the resistive forces. Terminal velocity relies upon very plenty upon the form of the object that's dealing with the direction that's moving. as quickly as an merchandise has reached terminal velocity, the object isn't accelerating (a=0), subsequently it is not rushing up or slowing down. that's a relentless velocity till the employing forces or the resistive forces exchange. regularly, Terminal velocity is barely a threat once you're coping with fluid friction as against touch friction like static or kinetic friction. employing Forces Forces that attempt to reason action: interior the case of falling it may be gravity (weight). interior the case of a vehicle it may be the strain from the engine (in the process the friction on tires). from time to time an merchandise could have distinctive employing forces. (ie. an airplane in a dive, has the engine pushing it down on a similar time gravity is pulling it down) Resistive Forces The forces that attempt to stand up to action. The tension of fluid friction (from a liquid or gasoline) performs the significant function in coming up terminal velocity. Fluid Friction Fluid friction differs from touch friction by using fact the quantity of fluid friction relies upon on how briskly the object is moving in the process the fluid. The extra beneficial the linked fee, the extra beneficial the friction. it somewhat is often felt in case you're in a pool of water. attempting to stroll from one area of the pool to the different is plenty less complicated than attempting to run. it somewhat is by using fact the speedier you progression, the extra durable the fluid pushes against you. once you study touch friction you detect that velocity has no result on the quantity of kinetic friction.