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skills/fluidsim/references/solvers.md

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+# FluidSim Solvers
+
+FluidSim provides multiple solvers for different fluid dynamics equations. All solvers work on periodic domains using pseudospectral methods with FFT.
+
+## Available Solvers
+
+### 2D Incompressible Navier-Stokes
+
+**Solver key**: `ns2d`
+
+**Import**:
+```python
+from fluidsim.solvers.ns2d.solver import Simul
+# or dynamically
+Simul = fluidsim.import_simul_class_from_key("ns2d")
+```
+
+**Use for**: 2D turbulence studies, vortex dynamics, fundamental fluid flow simulations
+
+**Key features**: Energy and enstrophy cascades, vorticity dynamics
+
+### 3D Incompressible Navier-Stokes
+
+**Solver key**: `ns3d`
+
+**Import**:
+```python
+from fluidsim.solvers.ns3d.solver import Simul
+```
+
+**Use for**: 3D turbulence, realistic fluid flow simulations, high-resolution DNS
+
+**Key features**: Full 3D turbulence dynamics, parallel computing support
+
+### Stratified Flows (2D/3D)
+
+**Solver keys**: `ns2d.strat`, `ns3d.strat`
+
+**Import**:
+```python
+from fluidsim.solvers.ns2d.strat.solver import Simul  # 2D
+from fluidsim.solvers.ns3d.strat.solver import Simul  # 3D
+```
+
+**Use for**: Oceanic and atmospheric flows, density-driven flows
+
+**Key features**: Boussinesq approximation, buoyancy effects, constant Brunt-Väisälä frequency
+
+**Parameters**: Set stratification via `params.N` (Brunt-Väisälä frequency)
+
+### Shallow Water Equations
+
+**Solver key**: `sw1l` (one-layer)
+
+**Import**:
+```python
+from fluidsim.solvers.sw1l.solver import Simul
+```
+
+**Use for**: Geophysical flows, tsunami modeling, rotating flows
+
+**Key features**: Rotating frame support, geostrophic balance
+
+**Parameters**: Set rotation via `params.f` (Coriolis parameter)
+
+### Föppl-von Kármán Equations
+
+**Solver key**: `fvk` (elastic plate equations)
+
+**Import**:
+```python
+from fluidsim.solvers.fvk.solver import Simul
+```
+
+**Use for**: Elastic plate dynamics, fluid-structure interaction studies
+
+## Solver Selection Guide
+
+Choose a solver based on the physical problem:
+
+1. **2D turbulence, quick testing**: Use `ns2d`
+2. **3D flows, realistic simulations**: Use `ns3d`
+3. **Density-stratified flows**: Use `ns2d.strat` or `ns3d.strat`
+4. **Geophysical flows, rotating systems**: Use `sw1l`
+5. **Elastic plates**: Use `fvk`
+
+## Modified Versions
+
+Many solvers have modified versions with additional physics:
+- Forcing terms
+- Different boundary conditions
+- Additional scalar fields
+
+Check `fluidsim.solvers` module for complete list.