Continuity
Incompressible mass conservation\[\nabla\!\cdot\!\mathbf{u}=0\]
The velocity field is divergence-free under the low-speed, constant-density approximation used by the preview and browser solver.
Current Reynolds—
Current Mach—
Dynamic pressure—
Blockage—
Both modes
Momentum
Incompressible Navier–Stokes\[\frac{\partial\mathbf{u}}{\partial t}+(\mathbf{u}\!\cdot\!\nabla)\mathbf{u}=-\frac{1}{\rho}\nabla p+\nu\nabla^2\mathbf{u}\]
The displayed pressure, shear, wake, and force fields are interpreted against the conservation of momentum.
Reynolds number
Inertial-to-viscous scaling\[Re=\frac{\rho U_\infty L}{\mu}=\frac{U_\infty L}{\nu}\]
Uses the selected characteristic length, free-stream speed, density, and dynamic viscosity.
Mach number
Compressibility indicator\[M=\frac{U_\infty}{a},\qquad a=\sqrt{\gamma R T}\]
Compressibility effects become increasingly important above approximately \(M=0.3\); the interface flags that regime.
Dynamic pressure
Reference pressure scale\[q_\infty=\frac{1}{2}\rho U_\infty^2\]
Dynamic pressure normalizes aerodynamic forces and the pressure-coefficient visualization.
Force coefficients
Drag, lift, and side force\[C_D=\frac{D}{q_\infty A_{ref}},\quad C_L=\frac{L}{q_\infty S_{ref}},\quad C_Y=\frac{Y}{q_\infty A_{ref}}\]
Reference areas remain explicit because coefficient comparisons are only meaningful when normalization is consistent.
Pressure coefficient
Surface-pressure normalization\[C_p=\frac{p-p_\infty}{q_\infty}\]
The surface heat map uses this nondimensional pressure scale; preview values are interpretive rather than mesh-converged CFD.
Sutherland viscosity
Temperature-dependent air viscosity\[\mu(T)=\mu_0\left(\frac{T}{T_0}\right)^{3/2}\frac{T_0+S}{T+S}\]
The implementation uses the equivalent standard-air form with \(S\approx110.4\,\mathrm{K}\).
Blockage ratio
Model-to-test-section area\[\beta=\frac{A_{model,max}}{A_{tunnel}}\]
Large blockage can accelerate the tunnel flow and bias force estimates relative to far-field conditions.
Drag power
Mechanical power against drag\[P_D=D\,U_\infty\]
This is the ideal mechanical rate required to overcome aerodynamic drag at the selected speed, before drivetrain or propulsive losses.
Atmospheric boundary layer
Building inflow profile\[U(z)=U_{ref}\left(\frac{z}{z_{ref}}\right)^{\alpha}\]
Urban, suburban, and open-country profiles represent the height-dependent approach flow relevant to building aerodynamics.
D3Q19 evolution
Browser numerical solve\[f_i(\mathbf{x}+\mathbf{c}_i\Delta t,t+\Delta t)=f_i(\mathbf{x},t)-\frac{1}{\tau}\left(f_i-f_i^{eq}\right)\]
The browser worker uses a coarse athermal lattice-Boltzmann domain for comparative visualization, not certification-grade CFD.
Source hierarchy
Equations and defaults are tied to primary technical reports, peer-reviewed methods, and established wind-engineering guidance. Links open the cited source or DOI.
- 01U.S. Standard Atmosphere, 1976.
NOAA, NASA, and U.S. Air Force. Atmospheric pressure, density, temperature, and derived-property reference model.
NASA Technical Reports Server · Report 19770009539 - 02Ladson, C. L. (1988).
Effects of Independent Variation of Mach and Reynolds Numbers on the Low-Speed Aerodynamic Characteristics of the NACA 0012 Airfoil Section.
NASA TM-4074 · NACA 0012 validation data - 03Menter, F. R. (1994).
Two-equation eddy-viscosity turbulence models for engineering applications. AIAA Journal, 32(8), 1598–1605.
doi:10.2514/3.12149 - 04Lallemand, P., & Luo, L.-S. (2000).
Theory of the lattice Boltzmann method: dispersion, dissipation, isotropy, Galilean invariance, and stability. Physical Review E, 61, 6546–6562.
doi:10.1103/PhysRevE.61.6546 - 05Richards, P. J., & Hoxey, R. P. (1993).
Appropriate boundary conditions for computational wind engineering models using the \(k\text{-}\varepsilon\) turbulence model.
doi:10.1016/0167-6105(93)90124-7 - 06Franke, J., Hellsten, A., Schlünzen, H., & Carissimo, B. (Eds.). (2007).
Best Practice Guideline for the CFD Simulation of Flows in the Urban Environment. COST Action 732.
COST Action 732 - 07Blocken, B. (2015).
Computational Fluid Dynamics for urban physics: importance, scales, possibilities, limitations and ten tips and tricks towards accurate and reliable simulations.
doi:10.1016/j.buildenv.2015.02.015 - 08Barlow, J. B., Rae, W. H., & Pope, A. (1999).
Low-Speed Wind Tunnel Testing (3rd ed.). Wiley. Tunnel design, corrections, blockage, instrumentation, and uncertainty.
ISBN 978-0-471-55774-6 - 09NASA Glenn Research Center.
Drag, lift, Reynolds number, Mach number, and dynamic-pressure educational derivations used to document the interface variables.
NASA Glenn · Drag equation
Fast comparative interpretation
Surface pressure, separation risk, wake shape, and force vectors are generated from geometry, orientation, atmosphere, and nondimensional scaling. They are designed to make aerodynamic consequences visible while controls are manipulated.
- Responsive during model rotation and parameter changes
- Useful for teaching, screening, and A/B comparison
- Not a locally mesh-converged pressure solution
Coarse browser D3Q19 field
The worker advances an athermal lattice-Boltzmann domain and reports convergence behavior and a central velocity slice. Resolution is intentionally bounded by browser memory and device performance.
- Velocity field is smoothed for display without changing solver values
- Low-Mach, fixed-geometry, single-phase assumptions
- Grid independence and experimental validation remain required
Why boundary-layer profiles matter
Wind speed near the ground is not uniform. Terrain roughness and upstream development create a vertical velocity and turbulence profile that materially changes facade pressures, roof separation, pedestrian-level flow, and wake recovery.
- Uniform inflow for idealized general tests
- Open-country, suburban, and urban profiles for structures
- Profile choice is recorded in exported runs
Required before engineering use
Use benchmark geometry and experimental datasets, refine the domain and grid, quantify blockage and wall effects, test turbulence and boundary-condition sensitivity, and report numerical and experimental uncertainty.
- NACA 0012 is included as a low-speed validation reference
- Sphere and bluff-body presets provide qualitative checks
- Certification decisions require validated engineering workflows
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Governing equations, numerical method, validation, and interpretive limitsOpen source PDF ↗
▣Aerodynamic_Flow_Model_Tester_Methodology.pdfInline viewer↗
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RUN DATA & REPRODUCIBILITY
Uploaded geometry remains in browser memory. Export a configuration, viewport image, or browser report with model, atmosphere, tunnel, and solver metadata.