Explore topic-wise MCQs in Computational Fluid Dynamics.

This section includes 8 Mcqs, each offering curated multiple-choice questions to sharpen your Computational Fluid Dynamics knowledge and support exam preparation. Choose a topic below to get started.

1.

Consider the continuity equation ( frac{ partial rho}{ partial t}+ nabla.( rho vec{V})=0 ). For a steady flow this equation becomes ___________

A. ( nabla.( rho vec{V})=0 )
B. ( nabla.( vec{V})=0 )
C. (div( vec{V})=0 )
D. (curl( vec{V})=0 )
Answer» B. ( nabla.( vec{V})=0 )
Discussion
2.

Consider the continuity equation ( frac{ partial rho}{ partial t}+ nabla.( rho vec{V})=0 ). For an incompressible flow, this equation becomes ___________

A. ( nabla.( rho vec{V})=0 )
B. ( frac{ partial( rho vec{V})}{ partial t}=0 )
C. (div( vec{V})=0 )
D. (div( rho vec{V})=0 )
Answer» D. (div( rho vec{V})=0 )
Discussion
3.

Consider an infinitesimally small fluid element with density (of dimensions dx, dy and dz with mass m and volume V) moving along with the flow with a velocity ( vec{V}=u vec{i}+v vec{j}+w vec{k} ). The continuity equation is ( frac{D rho}{Dt}+ rho nabla. vec{V}=0 ). Where does this second term come from?

A. Integral
B. The rate of change of element s volume
C. Elemental change in mass
D. Local derivative
Answer» C. Elemental change in mass
Discussion
4.

Consider an infinitesimally small fluid element with density (of dimensions dx, dy and dz with mass m and volume V) moving along with the flow with a velocity ( vec{V}=u vec{i}+v vec{j}+w vec{k} ). What is the time rate of change of mass of this element?

A. ( frac{D( rho delta V)}{Dt} )
B. ( frac{ partial( rho delta m)}{ partial t} )
C. ( frac{ partial( rho delta V)}{ partial t} )
D. ( frac{D( rho delta m)}{Dt} )
Answer» B. ( frac{ partial( rho delta m)}{ partial t} )
Discussion
5.

Consider an infinitesimally small fluid element with density (of dimensions dx, dy and dz) fixed in space and fluid is moving across this element with a velocity ( vec{V}=u vec{i}+v vec{j}+w vec{k} ). What is the final reduced form of net mass flow across the fluid element?

A. ( frac{ partial rho}{ partial t} )
B. ( rho vec{V} dx ,dy ,dz )
C. ( nabla.( rho vec{V}) )
D. ( nabla.( rho vec{V}) )dx dy dz
Answer» E.
Discussion
6.

According to the conservation law, Net mass flow across the fluid element is equal to the rate of change of mass inside the element . But, stating the final equation, Net mass flow across the fluid element + the rate of change of mass inside the element = 0 . Why is the operation not subtraction?

A. Irrespective of the law, the sum is always zero
B. The two terms are always opposite in sign
C. Change in sign is not considered
D. Rate of change may be increase or decrease
Answer» C. Change in sign is not considered
Discussion
7.

Consider an infinitesimally small fluid element with density (of dimensions dx, dy and dz) fixed in space and fluid is moving across this element with a velocity ( vec{V} = u vec{i} + v vec{j} + w vec{k} ). The rate of change in mass of the fluid element is given by ____________

A. ( frac{ partial( rho u)}{ partial x} + frac{ partial( rho v)}{ partial y} + frac{ partial( rho w)}{ partial z} )
B. ( frac{ partial rho}{ partial t} )
C. ( frac{ partial rho}{ partial t}(dx ,dy ,dz) )
D. ([ frac{ partial( rho u)}{ partial x} + frac{ partial( rho v)}{ partial y} + frac{ partial( rho w)}{ partial z}]dx ,dy ,dz )
Answer» D. ([ frac{ partial( rho u)}{ partial x} + frac{ partial( rho v)}{ partial y} + frac{ partial( rho w)}{ partial z}]dx ,dy ,dz )
Discussion
8.

Consider an infinitesimally small fluid element with density (of dimensions dx, dy and dz) fixed in space and fluid is moving across this element with a velocity ( vec{V}=u vec{i}+v vec{j}+w vec{k} ). The net mass flow across the fluid element is given by ______

A. ([ frac{ partial( rho u)}{ partial x} + frac{ partial( rho v)}{ partial y} + frac{ partial( rho w)}{ partial z}]dx ,dy ,dz )
B. ([ frac{ partial( rho u)}{ partial x} + frac{ partial( rho v)}{ partial y} + frac{ partial( rho w)}{ partial z}] )
C. [ ]dx dy dz
D. ([ frac{ partial( rho)}{ partial x} + frac{ partial( rho)}{ partial y} + frac{ partial( rho)}{ partial z}]dx ,dy ,dz )
Answer» B. ([ frac{ partial( rho u)}{ partial x} + frac{ partial( rho v)}{ partial y} + frac{ partial( rho w)}{ partial z}] )
Discussion