20 + Interview Questions in Some Simple Cfd Techniques in Computational Fluid Dynamics Page 1 InterviewSolution

1.	How many steps does the Alternating Direction Implicit (ADI) scheme involve?(a) One step(b) Two steps(c) Three steps(d) Four stepsThis question was addressed to me in exam.I'd like to ask this question from CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» The correct choice is (b) Two steps For explanation I WOULD say: The WHOLE process is to INITIATE from the known VALUES at the time-step t and move on to the required time-step t+Δ t. For this marching, the ADI SCHEME uses two steps. The solution does not directly move to the final step t+Δ t.

Discussion

2.	The following plot represents flow velocity. Which of these points has the highest acceleration?(a) 1(b) 2(c) 3(d) 4This question was addressed to me at a job interview.This question is from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right OPTION is (b) 2 The explanation: High acceleration means highly varying velocity. In a contour plot, the POINTS with high gradient are REPRESENTED by close lines. Point 2 has lines very close to each other. Therefore, point 2 has the HIGHEST acceleration.

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3.	Is adaptive meshing possible in current CFD packages? If yes, which software offers it?(a) No(b) Yes, ANSYS Fluent 12.0(c) Yes, PHOENICS(d) Yes, ANSYS 8.0I have been asked this question by my college professor while I was bunking the class.My question comes from Simple CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» CORRECT answer is (b) Yes, ANSYS Fluent 12.0 For explanation: Adaptive meshing allows to change or REFINE MESH during the solution of the PROBLEM. This was not possible in earlier versions. From ANSYS Fluent 12.0, we get adaptive meshing.

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4.	Which one is a post-processing Software?(a) FieldView(b) CFD GEOM(c) CCM++(d) TyphonThis question was addressed to me in an interview.This is a very interesting question from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» CORRECT ANSWER is (a) FieldView To elaborate: FieldView is a CFD post-processing SOFTWARE. FieldView is a data handling and VISUALIZING tool that can be used for CFD post-processing.

Discussion

5.	Which is a pre-processing software?(a) ANSYS ICEM CFD(b) ANSYS Mechanical(c) ANSYS CFX(d) EnSightI have been asked this question by my college director while I was bunking the class.This question is from Simple CFD Techniques topic in section Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right answer is (a) ANSYS ICEM CFD To ELABORATE: ICEM stands for INTEGRATED COMPUTER Engineering and Manufacturing. This is a SOFTWARE that allows us to CREATE models and mesh it for generating grids.

Discussion

6.	The order of accuracy of the ADI scheme in the time direction is ___________(a) third-order(b) fourth-order(c) first-order(d) second-orderThis question was posed to me in an online quiz.Asked question is from CFD Techniques in section Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» The correct ANSWER is (d) second-order To explain: The truncation error of the ADI scheme in the time direction is of order two. The ADI scheme is second-order ACCURATE in the time direction. It USES two time-steps to move from the STEP t to t+Δt.

Discussion

7.	Which of these is important while solving a system with implicit methods?(a) Linearizing the difference equation(b) Linearizing the partial differential equation(c) Normalizing the difference equation(d) Normalizing the partial differential equationThis question was addressed to me in an internship interview.The question is from CFD Techniques topic in chapter Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right CHOICE is (a) Linearizing the difference equation To explain: The nature of the original PDE should not be changed while SOLVING the problem. If the problem is non-linear in PDE, to make it solvable by the implicit SCHEME, the difference equation should be linearized.

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8.	Full form of FOAM in OpenFOAM?(a) Field Optimization and Manipulation(b) Flow Optimization and Manipulation(c) Field Operation and Manipulation(d) Flow Operation and ManipulationThis question was posed to me during an interview.My question is taken from Simple CFD Techniques in chapter Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» RIGHT choice is (c) Field OPERATION and Manipulation Explanation: OpenFOAM stands for open-source Field Operation and Manipulation. It was ORIGINALLY named as FOAM when CREATED by Henry Weller in the late 1980s.

Discussion

9.	Which of these plots are irrelevant to CFD post-processing?(a) Contour plots(b) Vector plots(c) xy plots(d) Bar plotsI had been asked this question during an interview.I need to ask this question from Simple CFD Techniques topic in chapter Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» The correct option is (d) Bar plots Easy explanation: Contour plots give a GLOBAL VIEW of the variation in flow PROPERTIES. xy plots show the variation of a flow property with respect to an independent variable. Vector plots DISPLAY vector quantities at discrete grid points. Bar plots cannot be USED in CFD.

Discussion

10.	Which of the following properties will need a plot like this?(a) Pressure(b) Temperature(c) Velocity(d) LiftI had been asked this question during an internship interview.Query is from Simple CFD Techniques in chapter Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» The correct option is (c) VELOCITY Explanation: The GIVEN plot is a VECTOR plot. Velocity is the directional flow property of a fluid. To represent its DIRECTION and magnitude, we can USE the vector plot.

Discussion

11.	The order of accuracy of the ADI scheme in the x and y-directions are __________ and __________(a) second-order and first-order(b) first-order and second-order(c) second-order and second-order(d) second-order and third-orderThis question was addressed to me in exam.The above asked question is from CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Correct answer is (c) second-order and second-order The explanation is: The TRUNCATION errors of the ADI SCHEME in the x and the y-directions are O(Δx^2) and O(Δy^2). Therefore, the order of ACCURACY of the ADI scheme in the x and the y-directions are TWO and two respectively.

Discussion

12.	The intermediate step of the ADI scheme is at __________(a) t+\(\frac{\Delta t}{3}\)(b) t+\(\frac{\Delta t}{2}\)(c) t-\(\frac{\Delta t}{2}\)(d) t+\(\frac{\Delta t}{4}\)I got this question in an internship interview.The query is from CFD Techniques topic in section Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right answer is (b) t+\(\frac{\DELTA t}{2}\) The explanation is: The first STEP of the ADI scheme is from t to t+\(\frac{\Delta t}{2}\). The second step of the ADIscheme is from t+\(\frac{\Delta t}{2}\) to t+Δt. Here, the intermediate step t+\(\frac{\Delta t}{2}\) is extra for the process and the RESULTS here are not actually needed.

Discussion

13.	The second step of the ADI scheme is swept over __________ direction.(a) both the x and y(b) the x(c) the y(d) the timeThis question was posed to me during an interview for a job.My doubt is from CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» The correct CHOICE is (C) the y The best I can explain: The second step of the ADI scheme uses the time domain from t+\(\FRAC{\DELTA t}{2}\)to t+Δt. Here, the y-derivative is treated IMPLICITLY after replacing the derivatives with central differences. The solutions are swept in the y-direction here.

Discussion

14.	Which plot will you choose if you want your users to read quantitative data from your data visualization?(a) Contour plot(b) Vector plot(c) xy plot(d) Mesh plotThis question was addressed to me in semester exam.My question is taken from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right CHOICE is (C) xy plot The explanation is: xy plot SHOWS the quantitative VARIATION of a dependent variable with some independent variable. So, a user can use it readily to GET quantitative data at a particular point.

Discussion

15.	The ADI scheme is particularly suitable for ____________ problems.(a) parabolic and elliptic(b) parabolic and hyperbolic(c) hyperbolic(d) parabolicI got this question in semester exam.My question comes from CFD Techniques in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Correct choice is (a) parabolic and ELLIPTIC The BEST EXPLANATION: The ADI SCHEME is useful to solve many fluid flow problems including the heat conduction and the MASS diffusion problems. It is particularly suitable for the parabolic and elliptic problems.

Discussion

16.	Which of these statements is correct about the first step of the ADI scheme?(a) x-derivative is treated implicitly(b) y-derivative is treated implicitly(c) Time derivative is treated implicitly(d) Thomas algorithm is not usedThis question was posed to me in examination.I want to ask this question from CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» The correct choice is (a) x-derivative is treated IMPLICITLY The explanation is: In the first step with the time interval \(\frac{\Delta t}{2}\), the spatial derivatives are replaced USING the central DIFFERENCE scheme. Only the x-derivative is treated implicitly. Then the resulting equations are solved using the TDMA METHOD.

Discussion

17.	Which one is an open source CFD solver tool?(a) OpenFOAM(b) ANSYS Fluent(c) TGrid(d) ParaViewThis question was posed to me by my college professor while I was bunking the class.Query is from Simple CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right choice is (a) OpenFOAM Best explanation: OpenFOAM is an OPEN source CFD toolbox based on C++. It ALLOWS us to develop customized solvers. Some of the other open source SOFTWARE are CFL3D, Typhon, OVERFLOW, and Wind-US. ANSYS fluent is licensed software. TGrid and ParaView are for pre-processing and post-processing respectively.

Discussion

18.	When was the first commercial CFD package released?(a) 1991(b) 1983(c) 1985(d) 1981I have been asked this question in a national level competition.I would like to ask this question from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Correct choice is (d) 1981 For explanation: PHOENICS is the first commercial CFD package RELEASED in the YEAR 1981. This can SIMULATE fluid flow, heat and mass transfer, CHEMICAL REACTIONS, combustion, etc.

Discussion

19.	Which of these is a popular version of the ADI scheme?(a) Operator splitting(b) Approximate factorization(c) ALU algorithm(d) SIMPLE algorithmThis question was addressed to me at a job interview.My query is from CFD Techniques in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» CORRECT answer is (B) Approximate factorization To explain I WOULD say: The major objective of the ADI scheme is to make the Thomas ALGORITHM for tri-diagonal matrices applicable to multi-dimensional PROBLEMS. This scheme has other versions too. One of the popular versions of the ADI scheme is the approximate factorization scheme.

Discussion

20.	If there are N grid points in both the x and y-directions, how many times does the ADI scheme use the Thomas algorithm?(a) N/2(b) 2(c) N^2(d) 2NThis question was posed to me by my college professor while I was bunking the class.The origin of the question is CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics
Answer» Right option is (d) 2N The EXPLANATION is: In the first STEP of the ADI SCHEME, the Thomas algorithm is used N times to SOLVE in the x-direction. Similarly, in the y-direction, again the Thomas algorithm is used N times to get the solutions. Totally, the Thomas algorithm is used 2N times.

Discussion

Explore topic-wise InterviewSolutions in .

How many steps does the Alternating Direction Implicit (ADI) scheme involve?(a) One step(b) Two steps(c) Three steps(d) Four stepsThis question was addressed to me in exam.I'd like to ask this question from CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics

The following plot represents flow velocity. Which of these points has the highest acceleration?(a) 1(b) 2(c) 3(d) 4This question was addressed to me at a job interview.This question is from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics

Which one is a post-processing Software?(a) FieldView(b) CFD GEOM(c) CCM++(d) TyphonThis question was addressed to me in an interview.This is a very interesting question from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics

The order of accuracy of the ADI scheme in the time direction is ___________(a) third-order(b) fourth-order(c) first-order(d) second-orderThis question was posed to me in an online quiz.Asked question is from CFD Techniques in section Some Simple CFD Techniques of Computational Fluid Dynamics

Which of these plots are irrelevant to CFD post-processing?(a) Contour plots(b) Vector plots(c) xy plots(d) Bar plotsI had been asked this question during an interview.I need to ask this question from Simple CFD Techniques topic in chapter Some Simple CFD Techniques of Computational Fluid Dynamics

Which of the following properties will need a plot like this?(a) Pressure(b) Temperature(c) Velocity(d) LiftI had been asked this question during an internship interview.Query is from Simple CFD Techniques in chapter Some Simple CFD Techniques of Computational Fluid Dynamics

The second step of the ADI scheme is swept over __________ direction.(a) both the x and y(b) the x(c) the y(d) the timeThis question was posed to me during an interview for a job.My doubt is from CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics

The ADI scheme is particularly suitable for ____________ problems.(a) parabolic and elliptic(b) parabolic and hyperbolic(c) hyperbolic(d) parabolicI got this question in semester exam.My question comes from CFD Techniques in portion Some Simple CFD Techniques of Computational Fluid Dynamics

Which one is an open source CFD solver tool?(a) OpenFOAM(b) ANSYS Fluent(c) TGrid(d) ParaViewThis question was posed to me by my college professor while I was bunking the class.Query is from Simple CFD Techniques in division Some Simple CFD Techniques of Computational Fluid Dynamics

When was the first commercial CFD package released?(a) 1991(b) 1983(c) 1985(d) 1981I have been asked this question in a national level competition.I would like to ask this question from Simple CFD Techniques topic in portion Some Simple CFD Techniques of Computational Fluid Dynamics

Which of these is a popular version of the ADI scheme?(a) Operator splitting(b) Approximate factorization(c) ALU algorithm(d) SIMPLE algorithmThis question was addressed to me at a job interview.My query is from CFD Techniques in portion Some Simple CFD Techniques of Computational Fluid Dynamics