Essential CFD Engineer Interview Questions from Praan

Preparing for a CFD Engineer interview can feel overwhelming, especially when you’re unsure what types of questions will be asked.  

Job seekers often face a mix of technical challenges and project-based queries, making it crucial to understand the specific expectations of the hiring company.  

Whether it's explaining multiphase modeling, discussing SIMPLE algorithms, or walking through the details of a Conjugate Heat Transfer (CHT) project, the ability to confidently answer interview questions can be the key to landing the job. 

To help you get a clear picture, we’ve compiled a list of real interview questions asked by Praan during their recruitment process for CFD Engineers.  

These questions will give you insights into what to expect, how to articulate your experience, and how to showcase your problem-solving abilities in a way that sets you apart. 

1. What is DPM, and how is it used in Fluent? 

DPM (Discrete Phase Model) in Fluent is used to simulate the behavior of discrete particles, droplets, or bubbles within a fluid. It’s commonly applied in processes like spray modeling, particle tracking, and fuel injection systems. 

2. Can you explain multiphase modeling? 

Multiphase modeling simulates interactions between multiple phases, such as gas, liquid, or solid, within a system. It’s used in applications like oil-water separation, boiling, or air-bubble interactions in fluids. 

3. Can you discuss any project mentioned in your resume? 

This is where you provide a detailed explanation of a project, focusing on the challenges, the tools (like CFD or FEA software) used, and the results or key takeaways from the project. 

4. What is Conjugate Heat Transfer (CHT)? 

CHT is used to model heat transfer between solid and fluid regions, which is essential in cooling systems, electronics, and heat exchangers. It considers both conduction in solids and convection in fluids. 

5. How do you calculate time step size in CFD? 

Time step size is determined by the Courant number, which is based on the mesh size and fluid velocity. The smaller the time step, the more accurate the simulation, though it increases computational time. 

6. What are some real-life applications of CFD? 

CFD is used in industries like automotive, aerospace, and HVAC for tasks like aerodynamic design, airflow optimization, and pollutant dispersion modeling. It helps engineers simulate real-world problems without physical prototypes. 

7. How proficient are you with design and FEA? 

Here, you'd discuss your experience with design software (like CATIA or SolidWorks) and FEA tools (like Ansys or Abaqus) in any relevant projects you've worked on. 

8. What kind of design projects have you worked on? 

Provide specific examples of design projects that involved CFD or FEA, highlighting challenges, solutions, and outcomes to demonstrate your practical experience. 

9. Which CFD software do you prefer, and why? 

Discuss the advantages of different CFD software tools based on your experience. For instance, Fluent is known for its versatility, OpenFOAM for its flexibility and open-source nature, and STAR-CCM+ for its user-friendly interface. 

10. Explain the SIMPLE and PISO algorithms. 

• SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is used for steady-state problems and pressure-velocity coupling. 

• PISO (Pressure-Implicit with Splitting of Operators) is ideal for transient simulations, offering faster convergence for time-dependent problems. 

11. What steps would you consider for designing and optimizing an air purifier? 

You would begin by defining the geometry, simulating airflow and particle capture, analyzing pressure drops, and iterating to improve efficiency. Material selection and placement of filters also play a crucial role in optimization. 

12. How do you validate your CFD results? 

Validation involves comparing CFD results with experimental data, or established benchmarks, to ensure accuracy. If discrepancies arise, you may refine the mesh, boundary conditions, or turbulence models. 

13. How do you check mesh quality? 

Mesh quality is assessed using parameters like skewness, aspect ratio, and orthogonality. High-quality mesh ensures better simulation accuracy and faster convergence. 

14. What’s the difference between SIMPLE, SIMPLEC, and COUPLED? 

• SIMPLE is more stable but slower. 

• SIMPLEC (SIMPLE-Consistent) speeds up convergence but may sacrifice some accuracy. 

• COUPLED solves momentum and continuity equations simultaneously, leading to faster convergence, often used in highly transient or complex simulations. 

15. Do you have experience with automation in CFD? 

Automation in CFD can involve scripting or using tools like Python to streamline repetitive tasks, improve efficiency, or conduct parametric studies without manual intervention. 

16. How do you simulate natural convection? 

Natural convection simulation involves setting buoyancy-driven flow, where temperature differences cause fluid movement. Boundary conditions should account for heat sources, and mesh refinement is crucial for accurate results. 

17. Which programming languages are you familiar with? 

CFD engineers often work with languages like Python or MATLAB for scripting, automation, or handling large datasets. Discuss any programming experience that supports your CFD work. 

18. What design tools are you familiar with? 

Mention any design tools you’ve used, such as SolidWorks, CATIA, or Autodesk Inventor, and highlight their role in your projects related to CFD and FEA. 

19. When you initialize a solution, what happens in the background in ANSYS? 

Initialization in ANSYS involves setting initial conditions for flow, pressure, and temperature fields. It helps stabilize the solution before iterating toward convergence. 

20. Between Eulerian-Eulerian and Eulerian-Lagrangian models, which is more accurate and which consumes less time? 

• Eulerian-Eulerian is used for systems where both phases are continuous, offering higher accuracy but longer computation times. 

• Eulerian-Lagrangian tracks discrete particles within a continuous phase, often consuming less time but may be less accurate for systems with complex interactions between phases. 

Conclusion 

Remember, interviews are not just about testing your technical knowledge—they’re an opportunity to showcase how you solve problems, think critically, and add value to the company.  

Now that you know what to expect, practice your responses, and you’ll be one step closer to landing that coveted CFD Engineer role!  

With Skill-Lync's Post Graduate Programs, you'll build a rock-solid foundation in all these critical concepts, making you interview-ready in no time. Plus, our Career Experts offer hands-on support through mock interviews, resume workshops, LinkedIn profile optimization, and much more! 

Sign up for a FREE course demo today, and let’s start your  journey toward landing that dream job!