add pvt examples

README.md

@@ -137,6 +137,20 @@ print(f"Compressor power: {comp.getPower()/1e6:.2f} MW")
 
 See the [examples folder](https://github.com/equinor/neqsim-python/tree/master/examples) for more process simulation examples, including [processApproaches.py](https://github.com/equinor/neqsim-python/blob/master/examples/processApproaches.py) which demonstrates all four approaches.
 
+## PVT Simulation (PVTsimulation)
+
+NeqSim also includes a `pvtsimulation` package for common PVT experiments (CCE/CME, CVD, differential liberation, separator tests, swelling, viscosity, etc.) and tuning workflows.
+
+- Documentation: `docs/pvt_simulation.md`
+- Direct Java access examples: `examples/pvtsimulation/README.md`
+
+## Transient Multiphase Flow (Two-Fluid Model)
+
+NeqSim includes a mechanistic **Two-Fluid Transient Multiphase Flow Model** for pipeline simulation.
+
+- Jupyter notebook demo (direct Java access): `examples/jupyter/two_fluid_model.ipynb`
+- Upstream documentation (NeqSim Java): https://github.com/equinor/neqsim/blob/master/docs/wiki/two_fluid_model.md
+
 ### Prerequisites
 
 Java version 8 or higher ([Java JDK](https://adoptium.net/)) needs to be installed. The Python package [JPype](https://github.com/jpype-project/jpype) is used to connect Python and Java. Read the [installation requirements for Jpype](https://jpype.readthedocs.io/en/latest/install.html). Be aware that mixing 64 bit Python with 32 bit Java and vice versa crashes on import of the jpype module. The needed Python packages are listed in the [NeqSim Python dependencies page](https://github.com/equinor/neqsim-python/network/dependencies).

docs/pvt_simulation.md

@@ -0,0 +1,80 @@
+# PVTsimulation (PVT experiments, characterization, tuning)
+
+NeqSim’s `pvtsimulation` package contains common PVT laboratory experiments (CCE/CME, CVD, DL, separator tests, swelling, viscosity, etc.) and utilities for tuning fluid characterization to match measured data.
+
+This repository supports two ways of running these experiments from Python:
+
+1. **Python wrappers** in `neqsim.thermo` / `neqsim.thermo.thermoTools` (quickest)
+2. **Direct Java access** via `from neqsim import jneqsim` (full control, more outputs, tuning)
+
+## Experiment coverage
+
+| Experiment | Java class | Python wrapper | Example |
+| --- | --- | --- | --- |
+| Saturation pressure (bubble/dew point) | `jneqsim.pvtsimulation.simulation.SaturationPressure` | `neqsim.thermo.saturationpressure()` | `examples/pvtsimulation/pvt_experiments_java_access.py`, `examples/pvtsimulation/pvt_tuning_to_saturation.py` |
+| Constant mass expansion (CCE/CME) | `...ConstantMassExpansion` | `neqsim.thermo.CME()` | `examples/pvtsimulation/pvt_experiments_java_access.py`, `examples/pvtsimulation/pvt_tuning_cme.py` |
+| Constant volume depletion (CVD) | `...ConstantVolumeDepletion` | `neqsim.thermo.CVD()` | `examples/pvtsimulation/pvt_experiments_java_access.py`, `examples/pvtsimulation/pvt_tuning_cvd.py` |
+| Differential liberation (DL) | `...DifferentialLiberation` | `neqsim.thermo.difflib()` | `examples/pvtsimulation/pvt_experiments_java_access.py` |
+| Separator test | `...SeparatorTest` | `neqsim.thermo.separatortest()` | `examples/pvtsimulation/pvt_experiments_java_access.py` |
+| Swelling test | `...SwellingTest` | `neqsim.thermo.swellingtest()` | `examples/pvtsimulation/pvt_experiments_java_access.py` |
+| Viscosity | `...ViscositySim` | `neqsim.thermo.viscositysim()` | `examples/pvtsimulation/pvt_experiments_java_access.py`, `examples/pvtsimulation/pvt_tuning_viscosity.py` |
+| GOR / Bo | `...GOR` | `neqsim.thermo.GOR()` | `examples/pvtsimulation/pvt_experiments_java_access.py` |
+
+Other available simulations (direct Java access):
+
+- `jneqsim.pvtsimulation.simulation.WaxFractionSim` (wax appearance / wax fraction vs T,P; requires wax model setup)
+- `jneqsim.pvtsimulation.simulation.ViscosityWaxOilSim` (wax + viscosity)
+- `jneqsim.pvtsimulation.simulation.DensitySim`
+- `jneqsim.pvtsimulation.simulation.SlimTubeSim` (slim-tube style displacement simulation)
+
+## Direct Java access: key patterns
+
+### Passing arrays
+
+Many PVTsimulation methods expect Java `double[]`. With JPype you can pass:
+
+- A Python list (often auto-converted), or
+- An explicit `double[]` using `jpype.types.JDouble[:]`
+
+Example:
+
+```python
+from jpype.types import JDouble
+from neqsim import jneqsim
+
+pressures = [400.0, 300.0, 200.0]
+temperatures = [373.15, 373.15, 373.15]
+
+cme = jneqsim.pvtsimulation.simulation.ConstantMassExpansion(oil)
+cme.setTemperaturesAndPressures(JDouble[:](temperatures), JDouble[:](pressures))
+cme.runCalc()
+```
+
+### Experimental data for tuning
+
+For several experiments, NeqSim expects `double[1][n]` experimental data, i.e. a single row with `n` values aligned with your pressure/temperature points:
+
+```python
+cme.setExperimentalData([[0.98, 1.02, 1.10]])  # relative volume values
+cme.runTuning()
+```
+
+## Fluid characterization + PVT lumping
+
+See `examples/pvtsimulation/fluid_characterization_and_lumping.py` for a typical black-oil characterization workflow using:
+
+- `addTBPfraction(...)` and `addPlusFraction(...)`
+- `getCharacterization().setLumpingModel("PVTlumpingModel")`
+- `getCharacterization().characterisePlusFraction()`
+
+## Run the examples
+
+```bash
+python examples/pvtsimulation/pvt_experiments_java_access.py
+python examples/pvtsimulation/pvt_tuning_to_saturation.py
+python examples/pvtsimulation/pvt_tuning_cme.py
+python examples/pvtsimulation/pvt_tuning_cvd.py
+python examples/pvtsimulation/pvt_tuning_viscosity.py
+```
+
+Tuning scripts default to skipping the actual tuning step; set `run_tuning = True` inside the script when you are ready to tune against measured data.