SpectraSim
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Workflow, results & reports

One path through the work.

A step-by-step wizard is the only navigation. No model tree, no ribbon — the next thing to do is always obvious.

SpectraSim guides a silencer simulation through twelve wizard steps — Physics, Geometry, Model, Material, Boundary Conditions, Advanced, Numerics, Simulation Control, Mesh, Run, Results and Postprocessing. Defaults are set automatically and marked “auto”; every override is marked “user”. The result is an HTML and PDF report with quality checks and an optional methods appendix.

Navigation
Step wizard only — no model tree, no ribbon
CAD input
STEP, IGES, STL
Reports
HTML and PDF
Data export
CSV, Excel, TSV, PNG, SVG, VTK
Project file
One .spsim file
The wizard

Which steps does a SpectraSim simulation go through?

Twelve steps in the sidebar, in this order. A tick marks a finished step; every step is saved when you leave it. In an acoustics-only project the Model step is hidden and the flow steps show their acoustic settings.

Download and follow along

  1. Physics

    Choose what to solve — fluid flow, heat transfer, acoustics, in any combination — and the acoustic medium: uniform, or taken from the CFD fields. Later steps show only the settings the chosen physics need.

    Physics step [MISSING M12 — screenshot]

  2. Geometry

    Load STEP, IGES or STL, confirm the units, and click faces to assign inlets, outlets, walls, internal walls and perforated walls. Multi-body models become flow regions automatically; Replace CAD keeps every setting.

    Geometry step [MISSING M12 — screenshot]

  3. Model

    Incompressible or compressible, steady or transient, turbulence model k-ω SST.

    Shown when fluid flow is solved
    Model step [MISSING M12 — screenshot]

  4. Material

    Dry air or engine exhaust gas, its temperature and the ambient pressure. Density, viscosity, heat capacity and speed of sound follow from them.

    Material step [MISSING M12 — screenshot]

  5. Boundary Conditions

    One card per boundary: inlet velocity or flow rate, outlet pressure, wall roughness and wall heat loss, the loss model of each perforated wall, and the acoustic port of each inlet and outlet.

    Boundary Conditions step [MISSING M12 — screenshot]

  6. Advanced

    Absorptive packing: flow resistivity (typed, or estimated from bulk density), Forchheimer factor and, with acoustics on, the acoustic model of the material.

    Advanced step [MISSING M12 — screenshot]

  7. Numerics

    Pressure–velocity coupling, under-relaxation, convection schemes and the start of the run — every value auto by default, chosen from the rest of the case.

    Numerics step [MISSING M12 — screenshot]

  8. Simulation Control

    Convergence targets, iteration limit and cores; with acoustics on, the frequency sweep, insertion loss and radiated SPL.

    Simulation Control step [MISSING M12 — screenshot]

  9. Mesh

    Automatic sizing with boundary layers, Generate mesh, and a quality check against the solver’s limits before you solve. With acoustics on, the size rules of the acoustic mesh.

    Mesh step [MISSING M12 — screenshot]

  10. Run

    A setup check, then live progress with ETA, residual and Δp₀ charts, the two quality gates, pause and stop, and a run queue for unattended studies.

    Run step [MISSING M12 — screenshot]

  11. Results

    KPIs with their quality signal, 3-D plots in the model view, charts and tables, and the report on request.

    Results step [MISSING M12 — screenshot]

  12. Postprocessing

    Curves from several runs and imported measurements on one chart, with operations and error metrics.

    Postprocessing step [MISSING M12 — screenshot]
Design principles

Built the way engineers check work.

Four rules from the program’s own design guide decide how every screen behaves.

  • 01

    The number first, then its credibility

    Every result is shown with its unit and a quality signal next to it: gate, convergence, y⁺.

  • 02

    Defaults are visible, not hidden

    Values the program computes are marked auto and can be reset; your overrides are marked user. Nothing changes silently.

  • 03

    Explain once, in place

    A one-sentence ⓘ tooltip on every field; the full theory in the F1 help panel.

  • 04

    Blocked means “here is the fix”

    A disabled step, locked field or failed gate always says why and points to the field that resolves it.

Results & postprocessing

How do I see the field and compare it with a test?

The Results step draws 3-D plots as layers in the CAD viewer, beside a tree of values, charts, tables and quality gates. A colour legend with auto, manual, symmetric or log range, a click probe, a section plane and a separate chart window come with it.

  • Wall pressure, y⁺, wall temperature and heat flux
  • Velocity slices with a position slider
  • Streamlines and arrows, animated on request
  • Isosurfaces of velocity, pressure or temperature
  • Acoustic pressure on the walls at any frequency, with phase animation

Send to Postprocessing stores a frozen copy of any curve, table or value with its provenance. The Postprocessing step overlays curves from several runs and imported measurements (txt, csv, xlsx, MATLAB .mat), interpolates, averages into 1/1 or 1/3 octave bands, and reports the rms, median and maximum difference over a chosen range.

SpectraSim
Screenshot: Postprocessing — transmission loss of two runs against a measured curve [MISSING M12 — screenshot showing the name SpectraSim]
Reports & export

What does a SpectraSim report contain, and which formats can I export?

Generate report builds an HTML and a PDF report of the run on request, with its pictures, quality checks and the settings that produced it. A report builder sets the title, author, company logo, notes and the saved chart and 3-D views to include.

Report and export formats
Output Format Notes
Report HTML and PDF Title, author, company logo, notes, saved views, quality checks; optional “Solver and methods” appendix
Charts PNG, SVG, CSV Or copy the image or the data to the clipboard
Tables CSV, copy as TSV Pastes straight into a spreadsheet
Acoustic results Excel workbook (.xlsx) Transmission loss, bands and port data
3-D fields VTK For ParaView; Open in ParaView when it is installed
Project .spsim Settings, CAD and results in one file
Branded templates — Planned customer-branded report templates
Help that teaches

Press F1 on any field.

A help panel opens on the field’s article: what the setting does, the theory and equations behind it, the default and why it was chosen, the valid range, and references in author–year form to one bibliography. Every parameter has its article; a few are still marked Draft while their theory is completed.

The panel on the right is an illustration of the layout, not a published article. A public theory section built from the Help: yes — owner request 2026-11-01; published at /docs/help/ by npm run sync:help.

Help → TheoryF1

Acoustic model of the packing

The packing is treated as an equivalent fluid with a complex, frequency-dependent characteristic impedance and propagation constant. The empirical models need only the flow resistivity R:

Zc=ρ0c0[1+C5X−C6−i C7X−C8],kc=ωc0[1+C1X−C2−i C3X−C4]Z_c = \rho_0 c_0\left[1 + C_5 X^{-C_6} - i\,C_7 X^{-C_8}\right], \qquad k_c = \frac{\omega}{c_0}\left[1 + C_1 X^{-C_2} - i\,C_3 X^{-C_4}\right]

with X = ρ0f/R and the constants C1…C8 of the selected model.

Models
Delany–Bazley · Miki · Komatsu · user defined · JCA / JCAL Experimental
Default
Miki needs only R, and stays physically realisable outside its fitted band.

References: Delany and Bazley (1970); Miki (1990); Komatsu (2008).

Projects

One file per project.

SpectraSim project file icon
muffler-a.spsim

Settings, CAD and results in one file. Double-click it to open the project. A project saved by an older version opens and is converted on opening; the file on disk changes only when you save, and you are asked before a save converts it.

Samples

Which sample projects are built in?

Five small cases that run in minutes, from File → Open a sample… Each names the result it can be compared with.

Built-in sample projects
Sample Physics Set-up and comparison
Straight pipe Flow A 50 mm pipe, 0.6 m long, air at 20 m/s: pressure drop against the Darcy–Weisbach friction loss.
Sudden expansion Flow 30 mm to 60 mm, air at 10 m/s: total-pressure loss against Borda–Carnot.
Expansion chamber Acoustics 30 mm pipes, a 90 mm chamber 0.5 m long, 50–1500 Hz: transmission loss against the plane-wave formula.
Resonator with packing Acoustics A perforated 50 mm tube in a 100 mm cavity filled with fibre packing: perforate and packing models together.
Through-flow resonator Flow + acoustics The same tube and cavity without packing, air at 15 m/s: the CFD grazing flow feeds the acoustic perforate model.
Quick answers

Workflow, answered

Which CAD formats does SpectraSim import?
STEP, IGES and STL. The units are confirmed on import, because CAD files do not reliably carry them, and a model made of several solid bodies is split into its flow regions automatically. Replace CAD loads a changed model and keeps every setting.
Can I compare SpectraSim results with my measurements?
Yes. The Postprocessing step imports measured curves from txt, csv, xlsx or MATLAB .mat files, overlays them with results from several runs, and computes the rms, median and maximum difference over a chosen frequency or flow range.
Which export formats does SpectraSim write?
HTML and PDF reports; CSV, Excel and copy-as-TSV for data; PNG and SVG for charts; VTK for 3-D fields in ParaView. The project itself is one .spsim file with the settings, the CAD and the results.
Are sample projects included?
Yes, five: Straight pipe and Sudden expansion (flow), Expansion chamber and Resonator with packing (acoustics), and Through-flow resonator (flow and acoustics). Each runs in minutes and names the analytical result it can be compared with.
Do I have to set every solver value myself?
No. SpectraSim sets numerics, mesh and convergence values from the model and marks them auto. Typing a value marks it user; Reset to auto brings the computed value back, so every override stays visible in the project and the report.

References

  1. Delany, M. E. and Bazley, E. N. (1970). Acoustical properties of fibrous absorbent materials.Applied Acoustics, 3(2), 105-116. doi:10.1016/0003-682X(70)90031-9
  2. Komatsu, T. (2008). Improvement of the Delany-Bazley and Miki models for fibrous sound-absorbing materials.Acoustical Science and Technology, 29(2), 121-129. doi:10.1250/ast.29.121
  3. Miki, Y. (1990). Acoustical properties of porous materials: modifications of Delany-Bazley models.Journal of the Acoustical Society of Japan (E), 11(1), 19-24. doi:10.1250/ast.11.19

From STEP file to report, in one guided path.

Every licence includes every feature. Or let our engineers run the study for you.

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