.Buildings.Fluid.Examples.ResistanceVolumeFlowReversal

Information

This model demonstrates the impact of the allowFlowReversal parameter on the size of nonlinear systems of equations. The user can change the parameter value in the allowFlowReversal block and rerun the simulation. The results are also demonstrated below for nRes.k = 10, which is the number of parallel branches containing one pressure drop element and one mixing volume each.

This model was created to demonstrate the influence of a new implementation of Buildings.Fluid.Interfaces.ConservationEquation. The old implementation used the actualStream() function whereas the new implementation uses the semiLinear() function. This change allows Dymola to exploit knowledge about the min and max attributes of m_flow. When Dymola knows in which way the medium will flow, nonlinear systems can be simplified or completely removed. This is illustrated by the results below. See issue 216 for a discussion.

Note that Dymola 2015FD01 can only reliable solve the last case. For the other two cases the Newton solver of the nonlinear system does not converge.

These results were generated using Dymola 2015FD01 64 bit on Ubuntu 14.04 and with Evaluate=false.

ResistanceVolumeFlowReversal = true

Sizes of nonlinear systems of equations: {6, 11, 56}
Sizes after manipulation of the nonlinear systems: {1, 9, 12}

ResistanceVolumeFlowReversal = false

Old implementation

Sizes of nonlinear systems of equations: {6, 11, 44}
Sizes after manipulation of the nonlinear systems: {1, 9, 11}

New implementation

Sizes of nonlinear systems of equations: {6, 11, 4}
Sizes after manipulation of the nonlinear systems: {1, 9, 1}

Contents

Name Description
Medium

Revisions


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