Implement Morris surface tension model #584
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## main #584 +/- ##
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- Coverage 70.53% 70.22% -0.31%
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Files 96 96
Lines 5976 6143 +167
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+ Hits 4215 4314 +99
- Misses 1761 1829 +68
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This was referenced Aug 15, 2024
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Conflicts: src/schemes/fluid/entropically_damped_sph/rhs.jl src/schemes/fluid/entropically_damped_sph/system.jl src/schemes/fluid/weakly_compressible_sph/system.jl test/schemes/fluid/fluid.jl
Conflicts: src/schemes/fluid/entropically_damped_sph/system.jl test/examples/examples.jl
Conflicts: src/schemes/fluid/entropically_damped_sph/system.jl
Conflicts: test/examples/examples.jl
Conflicts: test/examples/examples.jl
efaulhaber
requested changes
Feb 19, 2025
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| ### Features | ||
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| - Adds the classic **Continuum Surface Force (CSF)** model based on Morris 2000 (#584), which computes |
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Why bold? Nothing else is bold in this file.
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| ### Artificial (numerical) viscosity | ||
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| - Goal: Stabilize the simulation, capture shocks, and prevent unphysical particle interpenetration. |
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- What do you mean by unphysical particle interpenetration?
- It should be mentioned that this is mostly used when modeling inviscid flow to stabilize the simulation and not to add physical viscosity. Also that we usually want to add as little artificial viscosity as possible to stabilize the simulation but not to change the physical behavior.
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| - Goal: Stabilize the simulation, capture shocks, and prevent unphysical particle interpenetration. | ||
| - Method: Adds a dissipative (artificial) term to the momentum equations. | ||
| - Typical Use: High-speed flows with strong shocks, astrophysical simulations, or situations where numerical damping is needed for stability. |
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Is there any situation where we would use a fluid without any kind of viscosity? If not, the typical use is all simulations where we want to model inviscid flow.
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| - Goal: Model the actual viscous stresses of a fluid, aligned with a target Reynolds number or experimentally measured fluid properties. | ||
| - Method: Introduces a force consistent with the Navier–Stokes viscous stress term. | ||
| - Typical Use: Low-speed, incompressible or weakly compressible flows where matching real fluid behavior is important. |
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Artificial viscosity is often used for low-speed weakly compressible flows as well. This is a bit confusing IMO. @LasNikas ?
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| #### ArtificialViscosityMonaghan | ||
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| - Best For: Compressible/high-speed flows, shock capturing, general purpose damping. | ||
| - If you need: Stability in challenging flow regimes with potentially large density/pressure variations. | ||
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| #### ViscosityMorris | ||
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| - Best For: Moderate to low Mach number flows where realistic viscous behavior is desired. | ||
| - If you need: Straightforward approach to physical viscosity that still works well in weakly compressible scenarios. | ||
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| #### ViscosityAdami | ||
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| - Best For: Incompressible or weakly compressible flows requiring accurate shear stress treatment. | ||
| - If you need: Good boundary layer representation and accurate laminar flow with minimal compressibility effects. |
| The computed curvature is then used to determine forces acting perpendicular to the interface. | ||
| While this method provides accurate surface tension forces, it does not explicitly conserve momentum. | ||
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| In the Morris model, surface tension is computed based on local interface curvature ``\kappa`` and the unit surface normal ``\hat{n}``. |
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Not sure why the period is put in the next line. Can you maybe slightly reformulate this sentence?
| ``` | ||
| This formulation focuses directly on geometric properties of the interface, making it relatively straightforward to implement when a reliable interface detection | ||
| (e.g., a color function) is available. However, accurately estimating ``\kappa`` and ``n`` may require fine resolutions. | ||
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| @@ -120,32 +187,57 @@ A(r) = \frac{0.007}{h_c^{3.25}} | |||
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| ### Morris Surface Tension Model | |||
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| The method estimates curvature by combining particle color gradients and smoothing functions to derive surface normals. | |||
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Are color gradients explained somewhere? If so, could you please add a link here?
| - ``\hat{n}``: Unit normal vector, | ||
| - ``I``: Identity matrix. | ||
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| That can be calculated as |
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Suggested change
| That can be calculated as | |
| This divergence can be computed numerically in the SPH framework as |
| This model implements the momentum-conserving surface tension approach outlined by | ||
| [Morris2000](@cite). It calculates surface tension forces using the gradient of a stress | ||
| This model implements the momentum-conserving surface tension approach outlined by Morris | ||
| [Morris2000](@cite). It calculates surface tension forces using the divergence of a stress | ||
| tensor, ensuring exact conservation of linear momentum. This method is particularly | ||
| useful for simulations where momentum conservation is critical, though it may require | ||
| numerical adjustments at higher resolutions. |
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Please add a link to the surface tension docs section. Also for the other models, which are explained in more details in the docs. This is useful when someone is only looking at the docs within the Julia help.
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