Discontinuous v_smooth in dp_edgedOverall_MFLOW

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Modified by dietmarw on 29 Jun 2013 17:30 UTC
This part of the code in dp_edgedOverall_MFLOW shows a discontinues signal for v_smooth when abs(dp) becomes larger than dp_lam (or vice versa). Unsure if this is on purpose, but it causes simulations to fail if this function is part of an implicit system equations to be solved (nonlinear systems in Dymola).

//mean velocity under smooth conditions w.r.t. flow regime

  Modelica.SIunits.Velocity v_smooth=if abs(dp) > dp_lam then (2*abs(dp))!^0.5*(
      A*C1*zeta_LOC*IN_var.rho)!^(-0.5) else (2*(d_hyd/IN_var.eta)!^exp/(A*C1*
      zeta_LOC*B*(IN_var.rho)!^(1 - exp)))!^(1/pow)*
      Modelica.Fluid.Dissipation.Utilities.Functions.General.SmoothPower(
      abs(dp),
      dp_min,
      1/pow) "Mean velocity under smooth conditions";

---

Reported by edo.drenth on 29 Jun 2013 17:15 UTC
This part of the code in dp_edgedOverall_MFLOW shows a discontinues signal for v_smooth when abs(dp) becomes larger than dp_lam (or vice versa). Unsure if this is on purpose, but it causes simulations to fail if this function is part of an implicit system equations to be solved (nonlinear systems in Dymola).

//mean velocity under smooth conditions w.r.t. flow regime

  Modelica.SIunits.Velocity v_smooth=if abs(dp) > dp_lam then (2*abs(dp))!^0.5*(

      A*C1*zeta_LOC*IN_var.rho)!^{(-0.5) else (2*(d_hyd/IN_var.eta)!}exp/(A*C1*

      zeta_LOC*B*(IN_var.rho)!^{(1 - exp)))!}(1/pow)*

      Modelica.Fluid.Dissipation.Utilities.Functions.General.SmoothPower(

      abs(dp),

      dp_min,

      1/pow) "Mean velocity under smooth conditions";

---

Migrated-From: https://trac.modelica.org/Modelica/ticket/1188

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Modified by dietmarw on 29 Jun 2013 17:30 UTC

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Comment by otter on 3 Jul 2013 13:05 UTC
If possible, should be fixed for MSL 3.2.1

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Comment by wischhusen on 12 Jul 2013 07:26 UTC
Right. It should be handeled in the same way like the bend transition in dp_curvedOverall_MFLOW for different flow regimes.

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Comment by wischhusen on 13 Jul 2013 14:23 UTC
Transition introduced with b93e545.

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Comment by otter on 14 Jul 2013 07:20 UTC
Closing the ticket, since seems to be fixed

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Comment by edo.drenth on 6 Sep 2013 15:39 UTC
The change does not seem to solve the problem at hand.

Without having read all the sources mentioned in the code, the tests I have performed make me believe there is a fundemental design flaw. The v_lam and v_turb have significant different value when the transition is to take place as fucntion of dp. The transition then is self-amplifying and has an almost instant pressure drop. This works fine as long as the model is not part of an implicit system to be solved. I guess when the transition is made when v_turb and v_lam are equal this problem will not occur, but then it may violate the physical results obtained in the referencef litterature. Any thoughts?

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Comment by wischhusen on 17 Jun 2014 09:03 UTC
#1188 Revised functions dp_edgedOverall_DP and dp_edgedOverall_MFLOW. Please check if problem is still present.

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Modified by beutlich on 18 Jun 2014 09:13 UTC

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Comment by wischhusen on 2 Dec 2014 09:57 UTC
Fixed with 5613528, 7befe78, 14ae5bd.

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Changelog modified by wischhusen on 2 Dec 2014 09:57 UTC
MSL 3.2.1 build 3, Maintenance 3.2.1 and 3.2 build 16

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Modified by beutlich on 19 Mar 2015 11:37 UTC

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Changelog removed by beutlich on 19 Mar 2015 11:37 UTC

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Modified by beutlich on 19 Mar 2015 11:39 UTC

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Modified by wischhusen on 27 Mar 2015 10:14 UTC

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Changelog modified by wischhusen on 27 Mar 2015 10:14 UTC
Corrected the tranisiton between laminar and turbulent region

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Modified by beutlich on 22 Jul 2015 22:03 UTC

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Changelog modified by beutlich on 22 Jul 2015 22:03 UTC
Corrected the transition between laminar and turbulent region