CFD Online Discussion Forums - 5.7.1 solver doing max coeff loops.

Hello people,

Have you ever seen a case that the residuals (U,V,W,P) converge in the inner coefficent loops but the solver keeps doing the maximum set coeff. loops for every time step in a transient simulation? Details of the ccl is given below:

 SOLVER CONTROL:
 ADVECTION SCHEME:
 Blend Factor = 0.75
 Option = Specified Blend Factor
 END
 CONVERGENCE CONTROL:
 Maximum Number of Coefficient Loops = 5
 END
 CONVERGENCE CRITERIA:
 Residual Target = 5e-05
 Residual Type = RMS
 END
 TRANSIENT SCHEME:
 Option = Second Order Backward Euler
 END
 END

As stated, I have defaults definitions (i.e. no expert parameters) but the solver keeps solving all 5 coeff. loops as can be seen in the output presented.

<BODY LANG="en-US" DIR="LTR"> 

 ============================================= =========================
 TIME STEP = 230 SIMULATION TIME = 2.12E-01 CPU SECONDS = 8.31E+05
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 1
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 1.02 | 1.9E-04 | 3.7E-03 | 1.6E-02 OK|
 | V-Mom | 1.00 | 2.0E-04 | 4.0E-03 | 5.5E-03 OK|
 | W-Mom | 1.00 | 1.9E-04 | 3.7E-03 | 1.7E-02 OK|
 | P-Mass | 0.92 | 1.0E-05 | 1.1E-03 | 24.3 5.4E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 0.67 | 5.2E-04 | 3.5E-02 | 10.9 7.3E-02 OK|
 | vv-RS | 1.02 | 4.0E-04 | 1.4E-02 | 10.9 6.8E-02 OK|
 | ww-RS | 0.79 | 8.0E-04 | 1.4E-01 | 5.9 6.8E-02 OK|
 | uv-RS | 0.91 | 4.7E-04 | 1.5E-02 | 15.8 4.9E-02 OK|
 | uw-RS | 1.17 | 1.2E-03 | 3.2E-02 | 10.9 7.4E-02 OK|
 | vw-RS | 1.15 | 4.6E-04 | 1.6E-02 | 15.8 4.2E-02 OK|
 | E-Diss.K | 1.49 | 7.1E-04 | 6.0E-02 | 12.3 2.6E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 2 CPU SECONDS = 8.32E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.52 | 1.0E-04 | 1.7E-03 | 1.3E-01 ok|
 | V-Mom | 0.48 | 9.7E-05 | 3.0E-03 | 1.0E-01 ok|
 | W-Mom | 0.53 | 1.0E-04 | 1.8E-03 | 1.3E-01 ok|
 | P-Mass | 1.57 | 1.6E-05 | 1.3E-03 | 10.3 4.8E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 3.00 | 1.6E-03 | 3.9E-02 | 10.9 4.2E-02 OK|
 | vv-RS | 0.87 | 3.5E-04 | 1.0E-02 | 10.9 8.1E-02 OK|
 | ww-RS | 1.67 | 1.3E-03 | 1.0E-01 | 10.9 6.9E-02 OK|
 | uv-RS | 1.33 | 6.2E-04 | 2.0E-02 | 10.9 8.4E-02 OK|
 | uw-RS | 0.27 | 3.3E-04 | 1.9E-02 | 10.9 8.1E-02 OK|
 | vw-RS | 1.22 | 5.6E-04 | 1.8E-02 | 10.9 9.1E-02 OK|
 | E-Diss.K | 0.80 | 5.7E-04 | 8.4E-02 | 12.3 7.3E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 3 CPU SECONDS = 8.32E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.57 | 5.7E-05 | 1.2E-03 | 1.8E-01 ok|
 | V-Mom | 0.55 | 5.4E-05 | 1.6E-03 | 1.3E-01 ok|
 | W-Mom | 0.57 | 5.7E-05 | 1.2E-03 | 1.8E-01 ok|
 | P-Mass | 1.13 | 1.9E-05 | 1.5E-03 | 10.3 2.0E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 0.45 | 7.0E-04 | 2.7E-02 | 10.9 4.7E-02 OK|
 | vv-RS | 1.19 | 4.2E-04 | 2.0E-02 | 10.9 6.5E-02 OK|
 | ww-RS | 1.08 | 1.4E-03 | 3.0E-01 | 5.9 9.6E-02 OK|
 | uv-RS | 0.82 | 5.1E-04 | 1.7E-02 | 10.9 9.5E-02 OK|
 | uw-RS | 3.61 | 1.2E-03 | 3.5E-02 | 10.9 7.1E-02 OK|
 | vw-RS | 0.90 | 5.1E-04 | 1.8E-02 | 10.9 8.4E-02 OK|
 | E-Diss.K | 0.42 | 2.4E-04 | 3.6E-02 | 12.3 3.6E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 4 CPU SECONDS = 8.33E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.78 | 4.4E-05 | 1.5E-03 | 1.7E-01 ok|
 | V-Mom | 0.73 | 3.9E-05 | 1.1E-03 | 1.3E-01 ok|
 | W-Mom | 0.78 | 4.4E-05 | 1.2E-03 | 1.6E-01 ok|
 | P-Mass | 0.54 | 1.0E-05 | 6.1E-04 | 10.3 3.2E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 1.35 | 9.4E-04 | 2.6E-02 | 10.9 6.9E-02 OK|
 | vv-RS | 0.91 | 3.8E-04 | 1.2E-02 | 10.9 8.0E-02 OK|
 | ww-RS | 0.85 | 1.2E-03 | 2.1E-01 | 10.9 6.1E-02 OK|
 | uv-RS | 1.11 | 5.7E-04 | 1.9E-02 | 10.9 8.4E-02 OK|
 | uw-RS | 0.41 | 4.8E-04 | 2.0E-02 | 10.9 7.9E-02 OK|
 | vw-RS | 0.94 | 4.8E-04 | 1.5E-02 | 10.9 8.9E-02 OK|
 | E-Diss.K | 1.06 | 2.6E-04 | 4.0E-02 | 12.3 6.2E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 5 CPU SECONDS = 8.34E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.78 | 3.4E-05 | 1.2E-03 | 1.6E-01 ok|
 | V-Mom | 0.78 | 3.1E-05 | 7.9E-04 | 1.2E-01 ok|
 | W-Mom | 0.82 | 3.6E-05 | 1.4E-03 | 1.6E-01 ok|
 | P-Mass | 0.95 | 9.5E-06 | 1.1E-03 | 10.3 4.3E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 0.65 | 6.1E-04 | 3.2E-02 | 10.9 6.5E-02 OK|
 | vv-RS | 0.90 | 3.4E-04 | 1.5E-02 | 10.9 5.4E-02 OK|
 | ww-RS | 0.60 | 7.3E-04 | 2.3E-02 | 5.9 9.9E-02 OK|
 | uv-RS | 0.65 | 3.7E-04 | 1.2E-02 | 10.9 8.7E-02 OK|
 | uw-RS | 1.97 | 9.4E-04 | 2.6E-02 | 10.9 5.9E-02 OK|
 | vw-RS | 0.93 | 4.4E-04 | 1.8E-02 | 10.9 8.2E-02 OK|
 | E-Diss.K | 0.82 | 2.1E-04 | 2.6E-02 | 12.3 5.9E-03 OK|
 +----------------------+------+---------+---------+------------------+


 ============================================= =========================
 TIME STEP = 231 SIMULATION TIME = 2.13E-01 CPU SECONDS = 8.34E+05
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 1
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.99 | 1.9E-04 | 3.6E-03 | 1.6E-02 OK|
 | V-Mom | 0.99 | 2.0E-04 | 4.0E-03 | 5.4E-03 OK|
 | W-Mom | 0.99 | 1.9E-04 | 3.6E-03 | 1.6E-02 OK|
 | P-Mass | 0.76 | 8.0E-06 | 7.9E-04 | 24.3 5.6E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 2.10 | 1.1E-03 | 3.2E-02 | 10.9 5.3E-02 OK|
 | vv-RS | 0.85 | 3.4E-04 | 1.1E-02 | 10.9 6.6E-02 OK|
 | ww-RS | 0.98 | 7.8E-04 | 7.9E-02 | 10.9 5.0E-02 OK|
 | uv-RS | 1.20 | 5.7E-04 | 2.0E-02 | 10.9 8.9E-02 OK|
 | uw-RS | 0.78 | 9.4E-04 | 3.2E-02 | 10.9 6.1E-02 OK|
 | vw-RS | 0.94 | 4.3E-04 | 1.3E-02 | 10.9 8.9E-02 OK|
 | E-Diss.K | 1.03 | 7.3E-04 | 8.1E-02 | 12.3 3.2E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 2 CPU SECONDS = 8.35E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.52 | 9.7E-05 | 1.9E-03 | 1.3E-01 ok|
 | V-Mom | 0.48 | 9.6E-05 | 3.0E-03 | 1.0E-01 ok|
 | W-Mom | 0.51 | 9.6E-05 | 1.7E-03 | 1.3E-01 ok|
 | P-Mass | 2.05 | 1.6E-05 | 1.4E-03 | 10.3 4.7E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 1.23 | 1.3E-03 | 4.5E-02 | 10.9 3.2E-02 OK|
 | vv-RS | 0.95 | 3.3E-04 | 1.6E-02 | 10.9 6.7E-02 OK|
 | ww-RS | 1.80 | 1.4E-03 | 1.8E-01 | 10.9 5.4E-02 OK|
 | uv-RS | 0.85 | 4.8E-04 | 1.3E-02 | 10.9 7.9E-02 OK|
 | uw-RS | 0.97 | 9.0E-04 | 2.9E-02 | 10.9 6.1E-02 OK|
 | vw-RS | 1.31 | 5.6E-04 | 2.3E-02 | 10.9 7.9E-02 OK|
 | E-Diss.K | 0.60 | 4.4E-04 | 7.3E-02 | 12.3 5.9E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 3 CPU SECONDS = 8.36E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.58 | 5.6E-05 | 1.4E-03 | 1.8E-01 ok|
 | V-Mom | 0.56 | 5.4E-05 | 1.3E-03 | 1.3E-01 ok|
 | W-Mom | 0.59 | 5.7E-05 | 1.1E-03 | 1.7E-01 ok|
 | P-Mass | 1.00 | 1.6E-05 | 9.6E-04 | 10.3 1.9E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 0.20 | 2.7E-04 | 1.9E-02 | 10.9 9.1E-02 OK|
 | vv-RS | 1.29 | 4.2E-04 | 2.1E-02 | 10.9 7.4E-02 OK|
 | ww-RS | 0.45 | 6.4E-04 | 1.4E-01 | 10.9 7.2E-02 OK|
 | uv-RS | 1.09 | 5.3E-04 | 2.2E-02 | 10.9 9.2E-02 OK|
 | uw-RS | 0.96 | 8.7E-04 | 3.1E-02 | 10.9 7.9E-02 OK|
 | vw-RS | 0.75 | 4.2E-04 | 1.3E-02 | 15.9 4.1E-02 OK|
 | E-Diss.K | 0.63 | 2.8E-04 | 2.6E-02 | 12.3 3.9E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 4 CPU SECONDS = 8.37E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.75 | 4.2E-05 | 9.9E-04 | 1.8E-01 ok|
 | V-Mom | 0.72 | 3.9E-05 | 8.0E-04 | 1.3E-01 ok|
 | W-Mom | 0.75 | 4.3E-05 | 1.4E-03 | 1.6E-01 ok|
 | P-Mass | 0.61 | 9.9E-06 | 8.3E-04 | 10.3 3.0E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 4.89 | 1.3E-03 | 4.9E-02 | 10.9 5.0E-02 OK|
 | vv-RS | 0.84 | 3.6E-04 | 1.7E-02 | 10.9 5.9E-02 OK|
 | ww-RS | 1.93 | 1.2E-03 | 4.1E-02 | 10.9 5.3E-02 OK|
 | uv-RS | 0.85 | 4.5E-04 | 1.2E-02 | 10.9 7.0E-02 OK|
 | uw-RS | 0.60 | 5.2E-04 | 1.6E-02 | 10.9 5.9E-02 OK|
 | vw-RS | 1.28 | 5.4E-04 | 2.3E-02 | 10.9 6.7E-02 OK|
 | E-Diss.K | 1.00 | 2.8E-04 | 4.4E-02 | 12.3 3.8E-03 OK|
 +----------------------+------+---------+---------+------------------+
 ----------------------------------------------------------------------
 COEFFICIENT LOOP ITERATION = 5 CPU SECONDS = 8.37E+05
 ----------------------------------------------------------------------
 |

Equation | Rate | RMS Res | Max Res | Linear Solution |
 +----------------------+------+---------+---------+------------------+
 | U-Mom | 0.79 | 3.3E-05 | 1.3E-03 | 1.6E-01 ok|
 | V-Mom | 0.74 | 2.9E-05 | 7.9E-04 | 1.2E-01 ok|
 | W-Mom | 0.75 | 3.2E-05 | 9.0E-04 | 1.5E-01 ok|
 | P-Mass | 0.87 | 8.6E-06 | 1.1E-03 | 10.3 4.0E-02 OK|
 +----------------------+------+---------+---------+------------------+
 | uu-RS | 0.26 | 3.5E-04 | 2.1E-02 | 10.9 6.2E-02 OK|
 | vv-RS | 0.96 | 3.4E-04 | 1.7E-02 | 10.9 6.2E-02 OK|
 | ww-RS | 0.22 | 2.7E-04 | 1.4E-02 | 10.9 9.3E-02 OK|
 | uv-RS | 1.15 | 5.2E-04 | 2.3E-02 | 10.9 7.3E-02 OK|
 | uw-RS | 1.91 | 1.0E-03 | 3.3E-02 | 10.9 6.4E-02 OK|
 | vw-RS | 0.65 | 3.5E-04 | 1.1E-02 | 10.9 9.6E-02 OK|
 | E-Diss.K | 0.65 | 1.8E-04 | 1.8E-02 | 12.3 7.4E-03 OK|
 +----------------------+------+---------+---------+------------------+
</BODY>

Well, anyone got a clue about this issue?

Thanks in advance, S. W.