Nozzle.mo Documentation / v_out

[Flauipaui]

Hello,

while studying Processes/Nozzle.mo i have seen that the documentation at the end of the document is in my eyes not referring to the model, descriping flow resistances in pipes.

ThermofluidStream/ThermofluidStream/Processes/Nozzle.mo

Line 67 in ef31d9a

<p><span style=\"font-size: 12pt;\">Implementation of a flow resistance pipe with different selectable flow resistance functions (laminar, laminar-turbolent, linear-quadratic).</span></p>

Further, i have seen that you are modeling the flow veloctiy v_out with positive values in case of positive mass flows. I would have expected, as a convention, that the flow velocity v_out is negative since it is leaving the component. I have checked the code, the sign of the variables is not influencing the solution, though (used only: v_out^2). Changing the sign of v_out, thus rather fulfills a convention than correcting errors.

ThermofluidStream/ThermofluidStream/Processes/Nozzle.mo

Line 27 in ef31d9a

v_out = m_flow/(rho_out*A_out);

Let me know that you think.

Bests,

[mimeissner]

both points are true, thank you.
since they are not urgent, we will fix them at a later time.

[Flauipaui]

Hello,

I have just seen that in other models (see below), v_out is meant to be positive (equations based on v_out are designed for positive values of v_out). In case you are willing to introduce a convetion that v_out has negative values, you would need to adapt further models. I'm not sure, if that is in your interest ... and if there is a benefit for you.

ThermofluidStream/ThermofluidStream/Boundaries/DynamicPressureInflow.mo

Line 59 in ef31d9a

v_out = inlet.m_flow/(rho_out*A);

ThermofluidStream/ThermofluidStream/Boundaries/DynamicPressureInflow.mo

Line 71 in ef31d9a

delta_v = v_in - v_out;

It might be easier to add a coment, that v_out has positive values for outgoing flow.

Bests,

[tobolar]

The documentation of Nozzle was fixed with c34a0a4

[nieweber]

Thank you again, your remarks on the sign convention are reasonable.
With PR #147 we have updated the documentation of the dynamic pressure components and added an explanation of the sign convention of the velocity. An internal review on changing the sign convention is still pending.