10+ CFD Engineer Interview Questions and Answers

Velocity and thermal boundary conditions for outer flow over flat plate and inner flow through pipe.

• Outer flow (flow over flat plate): Velocity boundary condition - free stream velocity parallel to the plate, Thermal boundary condition - constant temperature at the plate surface

• Inner flow (flow through pipe): Velocity boundary condition - parabolic velocity profile, Thermal boundary condition - constant heat flux at the pipe wall

To use tools or software related to CFD, one needs to have a good understanding of the software and its capabilities.

• Learn the basics of the software and its user interface

• Understand the different types of simulations that can be performed

• Know how to set up the simulation and input the necessary parameters

• Be able to interpret the results and make necessary adjustments

• Practice and experiment with different scenarios to gain proficiency

• Examples of CFD software include ANSYS Flu...read more

The equations governing CFD are based on fundamental laws of physics.

• Based on conservation of mass, momentum, and energy

• Navier-Stokes equations are fundamental in fluid dynamics

• Incompressible flow assumes constant density

• Reynolds-averaged Navier-Stokes (RANS) equations are commonly used

The governing equations solved in CFD include the Navier-Stokes equations, continuity equation, and energy equation.

• Navier-Stokes equations describe the motion of fluid substances.

• Continuity equation ensures mass conservation within the fluid domain.

• Energy equation accounts for the transfer of thermal energy within the fluid.

• Other equations like turbulence models may also be solved depending on the simulation requirements.

Aerodynamic refers to the study of the motion of air and other gases, while hydrodynamic refers to the study of the motion of liquids, primarily water.

• Aerodynamics deals with the flow of air around objects, such as airplanes, cars, and buildings.

• Hydrodynamics focuses on the behavior of liquids, including water, in motion, such as in rivers, oceans, and pipes.

• Both fields are crucial in designing efficient vehicles, structures, and systems that interact with air or water.

• Unders...read more

Boundary layer is the layer of fluid adjacent to a solid surface where the flow velocity changes from zero at the surface to the free stream velocity.

• Boundary layer is a region in a fluid flow where viscous effects are significant.

• It is characterized by a gradual increase in flow velocity from the solid surface to the outer flow.

• The boundary layer thickness depends on the Reynolds number and the surface roughness.

• There are two types of boundary layers: laminar and turbulent.

• B...read more

Mesh dependent test in CFD is a test to determine the sensitivity of the simulation results to changes in the mesh resolution.

• Mesh dependent test involves running the CFD simulation with different mesh resolutions to see how the results vary.

• It helps in assessing the accuracy and reliability of the simulation results based on the mesh quality.

• The test is important to ensure that the simulation results are not heavily influenced by the mesh resolution.

• Common metrics used in me...read more

Relaxation factor in CFD controls the rate at which the solution converges towards the final solution.

• Relaxation factor is a parameter used in iterative methods to control the rate of convergence.

• A higher relaxation factor can speed up convergence but may lead to instability.

• Conversely, a lower relaxation factor can improve stability but may slow down convergence.

• Optimal relaxation factor varies depending on the problem and solver being used.

• Common values for relaxation facto...read more

CFD stands for Computational Fluid Dynamics. It is a branch of fluid mechanics that uses numerical analysis to solve and analyze problems related to fluid flow and heat transfer.

• CFD is important in designing and optimizing various engineering systems such as aircraft, automobiles, and power plants.

• It helps in predicting the behavior of fluids and their interaction with solid objects.

• CFD simulations can be used to optimize the design of products and reduce the need for physica...read more

Different viscous models in CFD include laminar, turbulent, and transitional models.

• Laminar model assumes flow is smooth and predictable, suitable for low Reynolds numbers.

• Turbulent model accounts for chaotic and unpredictable flow behavior, suitable for high Reynolds numbers.

• Transitional model combines aspects of both laminar and turbulent models for flows transitioning between the two.

• Examples include Spalart-Allmaras model for turbulence and SST k-omega model for transitio...read more

Yes, I have experience working on cloud-based CFD platforms.

• I have worked on cloud-based CFD platforms such as SimScale and ANSYS Cloud

• I am familiar with cloud computing concepts such as virtual machines and containers

• Working on cloud allows for easy collaboration and scalability

Turbulent flow is dominated by chaotic and unpredictable fluctuations in velocity and pressure.

• Chaotic fluctuations in velocity and pressure

• Unpredictable behavior

• Large-scale vortices and eddies

• High levels of mixing and diffusion

Y+ is a dimensionless wall distance used in CFD to determine the appropriate mesh resolution near the wall.

• Y+ is used to ensure accurate modeling of boundary layer flow near walls.

• It is calculated as the ratio of the distance from the wall to the first cell center to the wall shear stress.

• Y+ values less than 1 indicate a viscous sublayer, while values greater than 30 indicate a fully turbulent flow.

• Properly resolving Y+ is crucial for accurate prediction of wall-bounded flows...read more

CFD stands for Computational Fluid Dynamics.

• CFD is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems involving fluid flow.

• It is commonly used in engineering fields to simulate and optimize the behavior of fluids in various systems.

• Examples of CFD applications include aerodynamics in automotive design, airflow in HVAC systems, and water flow in hydraulic structures.

GPU cooling case simulation involves using CFD software to analyze airflow and temperature distribution within a computer case.

• Utilize CFD software to create a 3D model of the computer case and GPU components

• Define boundary conditions such as fan speeds, heat sources, and material properties

• Run simulations to analyze airflow patterns, temperature distribution, and heat transfer

• Optimize cooling design by adjusting fan placement, airflow direction, or heat sink design

• Validate s...read more

Different turbulence models are used in CFD to simulate turbulent flow behavior.

• Turbulence models include k-epsilon, k-omega, SST, and RANS models.

• Each model has its own strengths and weaknesses, and is chosen based on the specific flow conditions.

• For example, the k-epsilon model is commonly used for industrial applications, while the SST model is preferred for aerospace simulations.