Common Questions for Simulation Engineers at UFI Filters | Engineer’s Interview Blueprint

Interviews for Simulation Engineer positions can be tricky, especially when companies like UFI Filters expect candidates to demonstrate not only technical expertise but also problem-solving skills.  

You’ve probably mastered topics like thermodynamics and CFD analysis, but what happens when they throw unexpected questions about mesh refinement, flow separation, or Y+ at you? 

This blog aims to prepare you for just that.  

We’ve gathered real interview questions from UFI Filters that were asked during their Simulation Engineer hiring process.  

These questions will give you a solid sense of what to expect, helping you feel more confident as you prepare for your next interview. 

Let’s get started.  

1. What are the phenomena happening at the wall boundary in a pipe flow? 

At the wall boundary in a pipe flow, the velocity of the fluid is zero due to the no-slip condition. The boundary layer forms here, where shear stress, pressure gradients, and viscous forces dominate. 

2. What is a Newtonian fluid? 

A Newtonian fluid is a fluid where the viscosity remains constant, regardless of the applied stress or strain rate. Examples include water and air, where the flow behavior is predictable under different flow conditions. 

3. How do you design an engine? 

Designing an engine involves several stages: defining performance requirements, choosing the appropriate fuel and combustion cycle, designing mechanical components (e.g., pistons, crankshaft), and optimizing for factors like emissions and efficiency. 

4. According to BS6, what are the emission values for a project on emissions? 

BS6 sets stricter emission standards for pollutants like NOx, particulate matter, and hydrocarbons. For instance, BS6 allows NOx emissions of 80 mg/km for diesel vehicles and 60 mg/km for petrol vehicles. 

5. What is the flame speed of gasoline? 

The flame speed of gasoline typically ranges from 30 to 40 cm/s under normal conditions, depending on the air-fuel mixture and combustion environment. 

6. What is the difference between ANSYS and OpenFOAM software? 

ANSYS is a commercial simulation software known for its user-friendly interface, wide range of solvers, and comprehensive customer support. 

OpenFOAM is open-source, offering more flexibility for customization but requiring more manual setup and coding expertise. It’s ideal for those who need custom solvers or simulations. 

7. What is adiabatic flame temperature? 

Adiabatic flame temperature is the maximum temperature that can be achieved in a combustion process if no heat is lost to the surroundings. It provides insights into the efficiency of the combustion process. 

Mesh and Turbulence Questions 

8. What was your mesh strategy in the tool test and why? 

I used a fine mesh near critical regions such as the wall boundary to capture gradients in velocity and pressure accurately. A coarser mesh was used in areas away from these gradients to save computational resources. 

9. Why is the mesh size finer near the square wall? 

The mesh is finer near the square wall to accurately resolve the boundary layer, where steep velocity and pressure changes occur. This is crucial for capturing the physics of flow separation and drag. 

10. What is turbulence, and what changes occur in the Navier-Stokes equation for a turbulent model? 

Turbulence is characterized by chaotic, unpredictable flow patterns. In the Navier-Stokes equation, additional terms like turbulent viscosity and Reynolds stresses are introduced to account for the fluctuating velocity components in turbulent flow. 

11. What is Y+, and why do we use it? 

Y+ is a non-dimensional number used in CFD to assess how well the near-wall region is resolved. It determines whether the mesh can capture the boundary layer correctly. It's essential for turbulence modeling near walls. 

12. In which type of flow do you use the Y+ method? 

The Y+ method is commonly used in turbulent flows to ensure accurate resolution of the boundary layer, especially when using wall functions or turbulence models like k-omega. 

13. Why is it important to resolve the near-wall boundary layer? 

Resolving the near-wall boundary layer is crucial for accurately predicting drag, heat transfer, and separation points. Poor boundary resolution can lead to incorrect simulation results. 

14. What is K, Omega, and Epsilon in turbulent models? 

K (turbulent kinetic energy): Represents the energy contained in turbulent eddies. 

Omega (specific dissipation rate): Describes the rate of dissipation of turbulent kinetic energy. 

Epsilon: Refers to the rate at which turbulent kinetic energy is converted into heat. 

15. Where is the boundary layer separation in the tool test result? 

The boundary layer separation occurs where the fluid flow detaches from the surface, often due to an adverse pressure gradient. This results in increased drag and turbulence. 

16. What is CHT, and what do you do after obtaining the results of a CHT simulation? 

CHT (Conjugate Heat Transfer) involves simulating heat transfer between solids and fluids. After obtaining CHT results, I analyze temperature gradients, check for potential hotspots, and make design adjustments to improve heat dissipation or insulation. 

Flow Dynamics and Refinement Questions 

17. What equations would you activate for flow over a flat plate, given temperature data? 

In addition to the Navier-Stokes equations for momentum, I would activate the energy equation to account for heat transfer if temperature is a key factor. 

18. How do you calculate drag force on squares in a tool test? 

Drag force is calculated using the drag coefficient (Cd), fluid density, velocity, and surface area. The formula is: 

Drag Force=12⋅ρ⋅v2⋅Cd⋅A\text{Drag Force} = \frac{1}{2} \cdot \rho \cdot v^2 \cdot Cd \cdot ADrag Force=21 ⋅ρ⋅v2⋅Cd⋅A 

19. Why do we refine the mesh? 

Mesh refinement is used to improve the accuracy of simulations, especially in regions with high gradients (such as near boundaries or obstacles). It ensures the solution converges to a more precise result. 

20. How does flow separation affect drag? 

Flow separation increases drag by creating a larger wake region behind the object. This turbulent wake causes higher pressure drag, reducing overall efficiency. 

21. How do you refine the mesh in OpenFOAM? 

In OpenFOAM, mesh refinement can be done using tools like snappyHexMesh or blockMesh. Refinement focuses on areas with steep gradients (such as boundary layers), improving accuracy without increasing computational cost too much. 

22. For a square obstacle, what areas would you refine in the mesh? 

Refinement should be done around the leading edges of the obstacle, the near-wall region, and the wake behind the square, as these areas experience high velocity and pressure changes. 

23. How do you calculate the thickness layer for refinement? 

The thickness layer for refinement is calculated based on the boundary layer thickness, which can be estimated using the Reynolds number. This ensures the mesh captures the physics of the boundary layer accurately. 

Conclusion 

Preparing for a Simulation Engineer interview doesn’t have to be stressful when you know what to expect.  

Focus on refining your simulation engineer skills, understand how to apply them in practical scenarios, and soon you’ll find yourself one step closer to landing that simulation engineer job. 

Stay focused, keep practicing, and get ready to tackle your next interview with confidence! 

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!