Unsteady Simulations

Unsteady Simulations#

Unsteady (time-accurate) simulations capture the dynamic behavior of flows that change significantly over time. Flow360 provides powerful capabilities for resolving transient flow phenomena with high fidelity and computational efficiency.

🌀 2D Cylinder Vortex Shedding

Learn how to set up and analyze vortex shedding behind a 2D cylinder, a classic benchmark for unsteady flow phenomena.

Unsteady 2D Cylinder

When to Use Unsteady Simulations#

Unsteady simulations are necessary when:

  • The flow field changes significantly with time

  • You need to capture periodic or transient phenomena (vortex shedding, buffeting)

  • The problem involves large separated regions or wake interactions

  • You’re analyzing acoustic phenomena or aerodynamic noise

  • You’re investigating dynamic stability or fluid-structure interaction

  • The Reynolds number exceeds critical values for your geometry

Key Unsteady Simulation Concepts#

  • Setting appropriate time step sizes based on flow physics

  • Understanding physical vs. dual time stepping approaches

  • Determining sufficient total simulation time for statistical convergence

  • Selecting output frequency for capturing transient phenomena

  • Setting subiterations per physical time step

Time Stepping Best Practices#

  • Time step size: Small enough to resolve the highest frequency of interest

  • Statistical convergence: Run for multiple periods of the slowest phenomenon

  • Physical time steps: Typically 50-100 steps per period of interest

  • Subiterations: Sufficient to reduce residuals by 1-2 orders of magnitude per time step

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