.TRANSFORM.Fluid.ClosureRelations.PressureLoss.Functions.Diffusers.K_conicalDiffuser

Information

Resistance coefficient K for a gradual expansion (conical diffuser) per Rennels & Hudson (2012), referenced to the velocity head in the smaller (inlet) cross-section, i.e. used as dp = K*m_flow^2/(2*rho*min(A)^2).

The input angle is the total included cone (divergence) angle. The correlation is piecewise in this angle and the diameter ratio beta = d_small/d_large; the pieces are constructed to be continuous in value across the 20°/60° breakpoints and across beta = 0.5. At angle = 180° the correlation reduces to the Borda-Carnot sudden-expansion limit K = (1 - beta^2)^2.

References

Rennels, D. C. & Hudson, H. M. Pipe Flow: A Practical and Comprehensive Guide. John Wiley & Sons (2012).

Interface

function K_conicalDiffuser
  extends TRANSFORM.Icons.Function;
  input SI.Area crossAreas[2] = {0.25, 1.0} "Cross-sectional areas (order does not matter)";
  input SI.ReynoldsNumber Re "Reynolds number (referenced to the smaller section)";
  input SI.Angle angle "Total included cone (divergence) angle";
  input SI.Length roughness = 0 "Average height of surface asperities";
  input SI.ReynoldsNumber Re_lam = 2300 "Laminar transition Reynolds number";
  input SI.ReynoldsNumber Re_turb = 4000 "Turbulent transition Reynolds number";
  output Units.NonDim K "Resistance coefficient";
end K_conicalDiffuser;