Initial conditions failed to converge

I get the following error for a simple circuit I made to test how accumulators work:

An error occurred during simulation and the simulation was terminated

Caused by:

['AccumulatorTest/Solver Configuration']: Initial conditions solve failed to converge.

Nonlinear solver: Linear Algebra error. Failed to solve using iteration matrix.

all components and nodal across variables involved

Cannot solve for one or more variables, including dynamic variable derivatives:

Time derivative of 'Gas_Charged_Accumulator_TL.T_I' (Temperature of liquid volume)

Time derivative of 'Gas_Charged_Accumulator_TL.p_I' (Pressure of liquid volume)

'Fixed_Displacement_Pump_TL.Phi_A' (Energy flow rate into port A)

... (it lists off several more variables)

Problems possible for transient initialization, as well as stepsize control for transient solve, due to equations of one or more components:

all components involved

'AccumulatorTest/Fixed-Displacement Pump (TL)'

Equation location is:

'C:\Program Files\MATLAB\R2025a\toolbox\physmod\fluids\library\m\+fluids\+thermal_liquid\+pumps_motors\fixed_displacement_pump.sscp' (no line number info)

... (it lists off several more equations)

I have attached the model file. Thanks for the help!

Answer 1

[Jacob Mathew]

Hey @Maximus,

I was able to remove the error "Initial conditions solve failed to converge" by replacing the Ideal Torque Source Block with a Ideal Angular Velocity Block. However, this means the pump is now rotating at a constant rpm than compared to using a torque source which would allow the pump to reach a steady state rpm. This might not be desirable for the analysis you want to perform and might need further tweaking of the model to get the pump to work as intended.

I have attached my model "AccumulatorTestModified.slx" as reference

[Maximus]

Hi Jacob,

Thanks for taking the time to write this answer! Since I was only attempting to test the accumulator, this workaround will work for now, although I do wonder why the Torque block wasn't working. Thanks again!