Which scenario would typically require an unsteady CFD simulation?

Which scenario would typically require an unsteady CFD simulation?

• A. Transient gusts hitting a wing
• B. Steady flow around a cylinder
• C. Steady pipe flow
• D. Uniform steady temperature field

Answer: (A)

Unsteady CFD is required when the flow changes with time. Transient gusts hitting a wing create time-varying inflow conditions and angle of attack, so pressure fields and lift respond dynamically as the gust passes. To capture this evolving behavior, you need a time-accurate (unsteady) solver with appropriate time stepping. In contrast, a flow described as steady around a cylinder, steady pipe flow, or a uniform steady temperature field is time-invariant, so a steady-state solver suffices.

Unsteady CFD is required when the flow changes with time. Transient gusts hitting a wing create time-varying inflow conditions and angle of attack, so pressure fields and lift respond dynamically as the gust passes. To capture this evolving behavior, you need a time-accurate (unsteady) solver with appropriate time stepping. In contrast, a flow described as steady around a cylinder, steady pipe flow, or a uniform steady temperature field is time-invariant, so a steady-state solver suffices.