Target GATE & ESE 2022 (Fluid Mechanics)

 Do You Know ?

👉As per Bernoulli's equation:

      Total head = P/Y + V^2/2g + z

      Piezometric head = P/Y + z

     Velocity head or kinetic head or dynamic head = v^2/2g

      Stagnation head = P/Y + V^2/2g  

👉Cavitation is the formation of vapour bubbles in a flowing liquid in the region where the pressure falls below vapour pressure and sudden collapsing of these vapour bubbles in a region of high pressure causes pitting.

👉 If time of closure (T) is less than equal to 2L/C  → closure is sudden or instantaneous

👉  If time of closure (T) is greater than  2L/C  → closure is gradual or slow.

👉 In case of sudden closure, when pipe is rigid 

                                     P = ρ CV       

      This formula is called Allievi Formula

👉Loss of head in both the cases, sudden expansion and sudden contraction happens due to formation of eddies, but the intensity is more in case of sudden expansion. Loss will be more in case of sudden expansion.

    Another reason for more loss in case of sudden expansion is the deceleration of flow due to area expansion.

👉Surge tanks are used to absorb the increase in pressure due to water hammer phenomenon.

👉 Condition to satisfy Hardy Cross Method (Trial & Error Solution)

     > The flow into any junction must equal the flow out of the junction (Continuity principle)

     > The Darcy-weisbach equation must be satisfied for each pipe (hf = rQ^n)

     > The algebric sum of head loss around any closed circuit will be zero when discharge distribution is correct.  

                

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