Target GATE & ESE 2022 (Fluid Mechanics)

 Do You Know?

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• Hot Wire Anemometer: It is used for measurement of instantaneous velocity and temperature at a point in flow but it is an ideal tool for measurement of velocity fluctuations in time in turbulent flow.
• Orifice Meter: It is cheap device which is used to measure the volume flow rate means discharge.
• Pitot Tube: Used for measurement velocity of flow.

👉     Preston Tube: Used for Boundary shear stress measurement.     

👉     Submerged broad crested weir  (Cd = 0.83 to 0.85)

👉          Free broad crested weir ( Cd = 0.85 to 1)

👉       For ogee spillway ( Cd = 1.19 Cds), where Cds is the discharge coefficient for sharp crested weir. 

👉       Cd value increases for ogee due to adhering Nappe

👉 Rehbock formula gives the expression for discharge over a rectangular suppressed weir.

                                  Q = 2/3 (0.605 + 0.08 H/Z + 0.001/H) sqrt (2g). BH^1.5 

 👉 Francis found that due to end contraction the effective width of the nappe is reduced by o.1H.

                                                              Leff = (L - 0.1 nH)

👉 Cipolletti notch (or weir) is a trapezoidal notch which gives discharge equal to the discharge that would pass over a rectangular notch. 

                                                     Q = 2/3 Cd sqrt(2g) LH^1.5

👉 Ventilation of Nappe: When there is no ventilation of nappe, discharge increases because the Nappe is pulled down due to negative pressure created in the zone below nappe.

👉  Let Q be the discharge in free Nappe then

        For depressed Nappe Qd = (1.06-1.07) Q

        For Adhering Nappe  Qa = 1.25 Q

👉 Orifice is an opening in the tank and Mouthpiece is short length of tube

👉 Coefficient of resistance of Orifice (Cr) is defined as the ratio of Loss of KE through orifice to actual KE.

                                               Cr = (1/Cv^2 -1)

      where Cv is the coefficient of velocity. 

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