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WorksheetsDay 41-Oct 31-worksheet-Diploma-Drag & lift & vortex flow
Total questions: 15
Worksheet time: 10mins
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 Cd varies as —
Cd ∝ Re
Cd ∝ 1/Re
Cd ∝ Re²
Cd = 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) .
Fill in the blank: The force perpendicular to the direction of motion of a fluid flow over a body is known as (a) .
Fill in the blank: When Re<0.2 , the flow is called (a) flow, and Stokes law is valid.
In free vortex flow, velocity is inversely proportional to ________.
Radius
Area
Density
Time
Stokes drag on a tiny sphere. Water at 20°C has density = 1000 kg/m³ and viscosity = 1.0×10−3 Pa·s. A small sphere of diameter D=50 micrometers moves at velocity U=0.002 m/s. (a) Find Reynolds number
(a)
Stokes drag on a tiny sphere. Using the same data in question number 14 and Stokes law (b) find the drag force on the sphere (in newtons).
(a)
