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Dashboard

The Flow360 dashboard provides real-time monitoring capabilities for CFD simulations, offering visualization of convergence metrics and aerodynamic coefficients. This document describes the key features and interpretation of the dashboard components.

Nonlinear Residuals Monitor

The nonlinear residuals monitor displays the convergence history of the simulation, presenting both absolute and relative residuals for key flow variables:

  • cont: Continuity equation residual
  • momx: X-momentum equation residual
  • momy: Y-momentum equation residual
  • momz: Z-momentum equation residual
  • ener: Energy equation residual
  • nuHat: Turbulence model - modified viscosity residual (SA exclusive)
  • k: Turbulence model - turbulence kinetic energy residual (SST exclusive)
  • omega: Turbulence model - specific dissipation rate residual (SST exclusive)

The residuals are plotted on a logarithmic scale against physical time steps, allowing users to:

  • Monitor convergence behavior
  • Assess solution stability
  • Determine when steady-state has been achieved

Interpretation Guide

  • Decreasing residuals indicate proper convergence
  • Oscillatory behavior may suggest physical unsteadiness or numerical issues
  • Plateauing residuals might indicate reaching machine precision or solution stagnation

Interactive Features

  • Toggle between absolute and relative non-linear residual views
  • Select and deselect individual residuals
  • Choose a time range on the bottom bar of the residuals plot
  • Save residuals data as an image

Forces and Moments

Lift and Drag Coefficients

  • CL: Lift coefficient
  • CD: Drag coefficient

Force Coefficients in Component Directions

  • CFx: X-direction force coefficient
  • CFy: Y-direction force coefficient
  • CFz: Z-direction force coefficient

Moment Coefficients

  • CMx: Rolling moment coefficient
  • CMy: Pitching moment coefficient
  • CMz: Yawing moment coefficient

Statistics

The dashboard provides statistical data for force coefficients, averaged over the last 10% of steps. This feature helps in:

  • Determining final converged values
  • Assessing solution stability
  • Quantifying solution uncertainty
  • Making informed decisions about simulation completion

Time history

Each coefficient is plotted against physical time steps, enabling:

  • Real-time monitoring of aerodynamic performance
  • Assessment of force and moment convergence
  • Identification of periodic behaviors or instabilities
  • Verification of expected aerodynamic characteristics

Interactive Features

  • Click on a plot to enlarge it

💡 Tips

  1. Convergence Assessment

    • Monitor both residuals and force coefficients
    • Look for at least 3-4 orders of magnitude drop in residuals
    • Verify force coefficient stability

  2. Solution Validation

    • Compare force coefficients with expected ranges
    • Check for physical consistency in moment coefficients
    • Verify symmetry properties where applicable

  3. Troubleshooting

    • Use residual behavior to identify numerical issues
    • Monitor force oscillations for physical unsteadiness
    • Cross-reference with mesh quality metrics when necessary

❓ Frequently Asked Questions

  • Why are my residuals not decreasing?

    This could be due to several factors, examples include:

    • Insufficient mesh quality in critical regions
    • Inappropriate CFL number settings
    • Physical instabilities in the flow
    • Incorrect boundary conditions

  • What is considered a "converged" solution?

    A solution is typically considered converged when:

    • Residuals have dropped by 3-4 orders of magnitude
    • Force coefficients have stabilized (variations < 0.1%)
    • The solution behavior matches expected physical trends

  • How do I interpret oscillating force coefficients?

    Oscillating force coefficients may indicate:

    • Natural flow unsteadiness (e.g., vortex shedding)
    • Need for time-accurate simulation
    • Numerical instabilities

    Check if the frequency of oscillations matches expected physical phenomena.

  • Can I export the dashboard data?

    Yes, you can:

    • Save residuals plot as image using the download button
    • Export numerical data in CSV format using the assets window
    • Use Python API to download simulation results

  • Why do some residuals plateau while others continue decreasing?

    This is common and can occur due to:

    • Machine precision limitations
    • Local flow features affecting specific equations

    As long as force coefficients are stable, this usually isn't concerning.

  • How do I zoom in on a specific time range?

    Use the bottom bar of the residuals plot to:

    • Click and drag to select a time range
    • Use the handles to adjust the range
    • Click to change your range's position