FhSim  3.1.0
Marine systems simulation
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hydrodynamics::LocalThroughFlow Struct Reference

#include <LocalThroughFlow.h>

Public Attributes

double a3 = 0.07
 Third drag harmonic; 0.07 gives the MF2022 Eq. 10 ratio C_D(45 deg) / C_D(0) = 0.61.
 
double b4 = 0.10
 Fourth lift harmonic; 0.10 from KF2012 section 2.5.2 and the Rudi et al. (1988) data (Fig. 5, p. 224).
 

Detailed Description

Parameters of the LocalThroughFlow law (plan contract C2).

The panel sees the velocity arriving at the net, U_n = f U with f = (1 + r) / 2 and r = min(1.08 - 0.97 Sn, 1) (MF2022 Eqs. 7 and 11, pp. 041301-5 and -6; the clamp below Sn = 0.0825 is the owner's decision, MARE-0109), instead of the free stream U:

  • Re_t = f |U| t / (nu (1 - Sn)), KF2012 Eq. 11 (p. 223) at f U;
  • cd = C_D,cyl(Re_t) Sn (2 - Sn) / (2 (1 - Sn)^2) f^2, KF2012 Eqs. 9 and 10 (pp. 222-223);
  • cl = f^2 times the cl of KF2012 section 2.5.1 (p. 223) taken from cd / f^2 (lead ruling R59; MF2022 normalise lift and drag with the same factor, p. 041301-7);
  • C_D(theta) = cd (a1 cos(theta) + a3 cos(3 theta)), C_L(theta) = cl (b2 sin(2 theta) + b4 sin(4 theta)), KF2012 Eq. 14 (p. 223), with a1 = 1 - a3 and b2 = 1;
  • F = 1/2 rho A |U|^2 (C_D U-hat + C_L L-hat), KF2012 Eq. 1 and Fig. 3 (p. 221);
  • plus the in-plane twine friction of TwineCrossFlow when the netting has bar data, so that the load is not zero for flow along the panel (TwineFriction.h, MARE-0111).

The f^2 factor scales cd and cl independently of theta (lead ruling R1): MF2022 derived (1 + r) / 2 at theta = 0 and assumed the inclination effect small (p. 041301-7), and a3 was fitted under that assumption.

The law already includes the panel's own induction, so it is meant for FlowReference::FreeStream only; rejecting AtPanel is Accepts in PanelLoadLaw.h.

Review issues:

0110 — Default load law misses lift at high solidity and the angle dependence of Rudi, Løland and Zhan (A6 disabled tests)

0131 — Default law: replace the two-harmonic angle form with three harmonics, refitted to MF2022, Rudi, Løland and Zhan

The documentation for this struct was generated from the following file: