Wind-Tunnel Similarity Matcher

Compare Reynolds and Mach matching for a scaled model and compute the tunnel speed needed for Re similarity.

visual calculatorAerodynamics & External Flow

Read the flow shape before trusting the number.

This page turns a CFD setup into regime, scale, and dominant-effect cues. Adjust the calculator below and compare the moving graphic with the computed result.

input scale

model

check

wind tunnelsimilarityReynoldsMach

formula

KaTeX rendered

\begin{aligned}\text{Re = rho U L / mu}\\[0.35em]\text{M = U/a}\\[0.35em]\text{U\_model,Re-match = U\_proto L\_proto/L\_model}\end{aligned}

ASCII source

Re = rho U L / mu, M = U/a, U_model,Re-match = U_proto L_proto/L_model

prototype U (m/s)prototype L (m)scale P/Mtunnel U (m/s)rho (kg/m^3)mu (Pa s)T (K)

Re match0.133x

Mach match1.333x

model length (m)

0.4000

Re model / prototype

0.1333

Mach model / prototype

1.3333

U for Re match (m/s)

600.000

Mach model

0.2351

Small models match Mach easily but usually miss Reynolds unless pressure, density, or tunnel speed is increased.

wind tunnel similarity Reynolds Mach