How to Prepare for a CFD Engineer Interview | Engineer’s Interview Blueprint

Landing a role as a CFD Engineer can be both exciting and challenging.  

The real challenge for many candidates is anticipating the types of questions they might face.  

In this blog, we’ve gathered real interview questions specifically tailored for CFD Engineers.  

If you're preparing for an interview, these refined questions and answers will help you understand what to expect and how to present your knowledge effectively. 

Let’s get started.  

1. If in Ahmed body project instead of velocity boundaries which other approach can we use to get the results? 

In an Ahmed body simulation, instead of using velocity boundary conditions, you could use a pressure boundary condition. This approach specifies pressure at the inlet or outlet to control the flow, while the solver calculates velocity based on the pressure difference. 

2. What is the Bernoulli equation? 

The Bernoulli equation describes the conservation of mechanical energy in a fluid flow. It relates pressure, velocity, and height along a streamline and is represented as: 

P+12ρv2+ρgh=constantP + \frac{1}{2} \rho v^2 + \rho gh = \text{constant}P+21 ρv2+ρgh=constant 

Where PPP is pressure, ρ\rhoρ is fluid density, vvv is velocity, and ggg is the gravitational constant. 

3. What are the modes of heat transfer? 

Heat can transfer in three modes: 

• Conduction: Transfer of heat through a solid material. 
• Convection: Heat transfer due to fluid motion. 
• Radiation: Emission of heat through electromagnetic waves. 

4. What is thermal conductivity? 

Thermal conductivity is the property of a material that indicates its ability to conduct heat. A high thermal conductivity means the material transfers heat efficiently. Metals, for example, have high thermal conductivity. 

5. Define kinematic viscosity. 

Kinematic viscosity is the ratio of a fluid’s dynamic viscosity to its density. It represents the internal resistance of the fluid to flow under the influence of gravity. The formula is: 

ν=μρ\nu = \frac{\mu}{\rho}ν=ρμ  

Where ν\nuν is kinematic viscosity, μ\muμ is dynamic viscosity, and ρ\rhoρ is density. 

6. What is unsteady uniform flow and steady uniform flow? 

• Steady uniform flow: The velocity of fluid particles remains constant at any point over time. 
• Unsteady uniform flow: The velocity changes with time but remains the same at all points along the flow direction. 

7. What are the types of clearance in a turbine? 

Turbine clearances include radial clearance (the gap between the blade tips and the casing) and axial clearance (the gap along the axis between rotor components). These clearances are critical for avoiding contact and ensuring efficiency. 

8. What is y+? 

Y+ is a dimensionless number used in CFD to represent the distance between the first grid point in the mesh and the wall, in terms of the viscous sublayer. It helps in ensuring that the boundary layer is resolved correctly, especially for turbulence modeling. 

9. What is K-epsilon and K-omega in turbulence equations? 

• K-epsilon model: A two-equation turbulence model that calculates turbulent kinetic energy (K) and its dissipation rate (epsilon), often used for high Reynolds number flows. 
• K-omega model: Similar to K-epsilon, but it uses specific dissipation rate (omega) instead of epsilon, and is preferred for near-wall modeling and low Reynolds number flows. 
• What is a control volume? A control volume is a finite region in space over which mass, momentum, and energy balances are applied in CFD simulations to analyze the flow of fluids or heat transfer. 

10. What is the relation between the thermal boundary layer and hydrodynamic boundary layer? 

The thermal boundary layer is where heat transfer occurs, and the hydrodynamic boundary layer deals with velocity gradients. The thickness of the thermal boundary layer depends on the fluid’s Prandtl number, and it can be thinner or thicker than the hydrodynamic boundary layer. 

11. Why do you need Y+ in CFD simulations? 

Y+ helps in capturing the boundary layer accurately in turbulent flows. It determines whether the mesh near the wall resolves the viscous sublayer or whether wall functions need to be applied to approximate near-wall behavior. 

12. What are the forces acting on water droplets inside a glass? 

Forces include surface tension, gravitational force, and buoyancy force. These forces balance to determine whether the droplet remains intact or spreads out on the surface. 

13. What is the difference between K-epsilon and K-omega? 

K-epsilon is better for free-stream flows, while K-omega performs better near walls and for flows with adverse pressure gradients. K-omega can better capture boundary layer separation. 

14. What is the Biot number and Nusselt number? 

Biot number relates the internal thermal resistance of a body to the thermal resistance at its surface. 

Nusselt number indicates the enhancement of heat transfer in a fluid flow due to convection compared to conduction. 

15. What is boundary layer separation? 

Boundary layer separation occurs when the fluid flow detaches from the surface of a body due to adverse pressure gradients, leading to increased drag and turbulent wake regions. 

16. What is drag force?

Drag force is the resistance experienced by an object moving through a fluid. It depends on the shape of the object, the flow velocity, fluid properties, and surface roughness. 

17. What are turbulence models in CFD? 

Turbulence models like RANS (Reynolds-Averaged Navier-Stokes), LES (Large Eddy Simulation), and DNS (Direct Numerical Simulation) are used to approximate turbulent flow behavior, with each model varying in accuracy and computational cost. 

Conclusion 

Preparing for a CFD Engineer interview requires a deep understanding of both fundamental fluid mechanics and the practical application of these concepts in real-world projects. 

Take your time to review these questions and hone your problem-solving skills.  

A well-prepared answer not only demonstrates your technical knowledge but also shows how you apply CFD in practical scenarios—setting you apart from other candidates in your pursuit of a successful CFD Engineer career. 

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!