Viscous Flow MCQs : Here you will find MCQ Questions related to "Viscous Flow" in Fluid Mechanics. These Viscous Flow MCQ Questions Will help you to improve your Fluid Mechanics knowledge and will prepare you for various Examinations like Competitive Exams, Placements, Interviews and other Entrance Exmaniations.
Which of the following flows have the highest critical Reynolds number (lower)?
A. Flow in a pipe
B. Flow between parallel plates
C. Flow in an open channel
D. Flow around spherical body
Explanation: The approximate lower critical Reynolds number for Flow in a pipe, flow between parallel plates, flow in an open channel and flow around the spherical body are 2000, 1000, 500 and 1 respectively. Hence, the maximum is for internal pipe flow.
How is Reynolds number defined as?
A. Ratio of pressures in the inlet to the outlet of a pipe
B. The product of velocity of the flow and the diameter of the pipe, divided by the kinematic viscosity of fluid
C. The product of density of the fluid, velocity of the flow and the diameter of the pipe, divided by the dynamic viscosity of fluid
D. Ratio of inertia force to viscous force
Explanation: The question demands the definition and not the commonly used formula of Reynolds number. Some of them denote the formula of Reynolds number. The definition of Reynolds number is the ratio of inertia force to viscous force in a pipe flow.
Which of the factors primarily decide whether the flow in a circular pipe is laminar or turbulent?
A. The Prandtl Number
B. The Pressure gradient along the length of the pipe
C. The dynamic viscosity coefficient
D. The Reynolds Number
Explanation: High Reynolds number flows (> 4000) are turbulent flows, whereas low Reynolds number flows (< 2100) are laminar flows. The viscosity coefficient is a part of the Reynolds number, but isn’t the only criteria for decision.
For a fully-developed pipe flow, how does the pressure vary with the length of the pipe?
Explanation: In a zero acceleration fully-developed flow in a pipe, the pressure gradually decreases linearly along the length of the pipe. Hence, the pressure variation is said to be linear
During which case will the power loss be maximum?
A. High viscosity oil
B. Low viscosity oil
C. High viscosity water
D. Low viscosity water
Explanation: A highly viscous oil will offer greater resistance due to which the power loss is maximum. As we know, oil has a greater density than water. Thus, oil is more viscous than water and corresponds to a higher loss of power.
Fluid does not offer resistance to change of__________
Explanation: Shape is one of the most important factors for a fluid. The forces other than gravity that fall on the fluid affects the outcome. Thus, changing the shape of the fluid cannot be controlled.
Why can’t mercury wet a glass?
C. Surface tension
Explanation: Surface tension is an elastic tendency of a fluid. It results due to imbalance of intermolecular attractive forces. Any molecule at the surface of the liquid experiences a net inward force. Mercury having a higher density than water, cannot wet a glass.
Which among the following does not depend on the friction factor?
A. Pipe diameter
B. Fluid density
Explanation: The friction factor(f) depends on the velocity of flow, fluid density, pipe diameter and the viscosity of the pipe. Roughness of the pipe is also an important criteria to determine the friction factor.
How do we calculate losses for a larger range of Reynolds number?
A. Moody chart
B. Bar Chart
C. Scatter chart
D. Column histogram
Explanation: Moody chart is a graph of frictional factor(f) vs Reynolds numbers. It gives various values corresponding to the k/d ratios. Where k is the measure of the wall roughness and d is the pipe diameter
Darcy- Weisbach equation gives relation between__________
A. Pressure and temperature
B. Mass, volume and pressure
C. Head loss and pressure loss
D. Pressure loss only
Explanation: Darcy-Weisbach equation relates the head loss and pressure loss due to friction along a given pipe with a specified length. It contains a dimensionless friction factor called the Darcy friction factor. The equation was named after Henry Darcy and Julius Weisbach.