Day 41-Oct 31-worksheet-Diploma-Drag & lift & vortex flow

The drag force acting on a body immersed in a fluid acts —

• Always perpendicular to the flow direction

• Always parallel and opposite to the direction of motion

• Always at 45° to the flow direction

• Always tangential to the streamline

In laminar flow over a sphere, according to Stokes’ law, the drag coefficient C_d varies as —

• C_d ∝ Re

• C_d ∝ 1/Re

• C_d ∝ Re²

• C_d = constant

For a streamlined body, which one of the following statements is correct?

• Pressure drag is dominant

• Friction drag is negligible

• Boundary layer separation occurs near the leading edge

• Pressure drag is very low, viscous drag dominates

The Kármán vortex trail is observed —

• Only at Re < 0.2

• When the flow is laminar and symmetrical

• Behind a cylinder at high Reynolds number

• In irrotational and frictionless flow

Magnus effect is the phenomenon in which —

• A rotating body moving through a fluid experiences a lift force perpendicular to direction of motion

• A stationary object in a rotating fluid experiences drag

• The vortex formation is stopped completely

• none

Terminal velocity of a spherical particle in a viscous fluid depends on —

• Density of the fluid and body only

• Dynamic viscosity, diameter, and density difference

• Pressure of fluid

• Temperature of solid

True/False: For a cylinder at high Reynolds number, pressure drag constitutes nearly 90% of total drag.

• True

• False

True/False: In a free vortex, external torque is continuously required to maintain motion.

• True

• False

Assertion–Reason: Assertion (A): In free vortex flow, velocity varies inversely with radius. Reason (R): The angular momentum of each fluid particle remains constant.

• Both A and R are true, and R is the correct explanation of A

• Both A and R are true, but R is not the correct explanation

• A is true, R is false

• Both A and R are false

Fill in the blank: The component of resultant fluid force in the direction of motion is called (a)   .