Simulation Setup

Simulation Setup#

This guide walks you through configuring a CFD simulation in Gradient Dynamics Studio. Simulation setup is done in the Simulation tab of a CFD project.

Prerequisites#

Before setting up a simulation, you need a mesh. You can:

  1. Generate a mesh in a Meshing project and import it

  2. Use the mesh generated within the same project

  3. Use an existing mesh from a previous project

Setup Overview#

A simulation configuration consists of five parts:

  1. Solver type — Density-based (recommended) or pressure-based

  2. Turbulence model — The physics model for turbulent flow

  3. Boundary conditions — What happens at each surface (inlets, outlets, walls)

  4. Solver settings — Numerical algorithm and convergence parameters

  5. Run parameters — Maximum iterations, convergence criteria

Step-by-Step Configuration#

1. Select Solver Type#

Choose between Density-Based (recommended) and Pressure-Based solvers from the dropdown at the top of the Simulation tab.

Density-based is the default and recommended choice for the vast majority of applications. It is optimized for the GPU-native Cartesian AMR mesh and delivers the best performance. See Solver Settings for a detailed comparison.

Use Pressure-based only if your application specifically requires an incompressible formulation.

2. Select Turbulence Model#

Choose the turbulence model from the dropdown. The default is k-ω SST, which works well for most external and internal flow applications.

Available models depend on your subscription tier — see Turbulence Models for details on each model.

3. Set Boundary Conditions#

Studio auto-detects boundary types from your surface names:

  • Surfaces named inlet → Velocity inlet

  • Surfaces named outlet → Pressure outlet

  • All other surfaces → Wall (no-slip)

You can override any auto-detected condition. See Boundary Conditions for all available types and parameters.

4. Configure Solver Settings#

For most cases, the defaults work well:

  • Density-based: Explicit Runge-Kutta, CFL 1.5, AUSM+ flux scheme, 2nd order spatial

  • Pressure-based: SIMPLE, pre-configured relaxation factors, AMG preconditioner

See Solver Settings for advanced tuning options.

5. Set Run Parameters#

Parameter

Description

Typical Value

Max iterations

Maximum solver iterations

500 – 2000

Convergence criterion

Residual threshold for completion

1e-5 (density) / 1e-4 (pressure)

Tip

Start with 500 iterations. If residuals haven’t converged, you can extend the run. Most RANS simulations converge within 300–1000 iterations.

Credit Cost Estimation#

Before running, Studio shows the estimated credit cost based on:

  • Mesh size (number of cells)

  • Expected runtime

  • GPU resources required

The estimate is shown when you click Run Simulation, before confirming.

Quick Setup with the AI Assistant#

For the fastest setup, use the AI Assistant:

“Set up a density-based simulation at 30 m/s with k-omega SST”

The assistant will:

  1. Select the density-based solver

  2. Select k-ω SST turbulence model

  3. Set inlet velocity to 30 m/s

  4. Configure outlet as pressure outlet (0 Pa)

  5. Apply default solver settings

  6. Ask for your confirmation before running

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