Block Format Keyword This option allows for a second order MUSCL (Monotonic Upstream-Centered Scheme for Conservation Laws) reconstruction of volumic fraction fields when using Multi-Material laws (LAW51), and for a full second order scheme (time and space) when using material LAW151.


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
BETA IFLAG              


Field Contents SI Unit Example
BETA Compression coefficient for gradient reconstruction. Must be between 0.0. and 2.0.
= 1e-20
Classical upwind scheme (no gradient reconstruction).
= 1.0
Exact second order gradient reconstruction.
= 2.0 (Default)
Over-compressive gradient limiter.


IFLAG Formulation flag for LAW151 second order.
= 0 (Default)
Full second order in time and space for all variables.
= 1
Only volume fraction field is reconstructed with MUSCL method (as for LAW51).




  1. Finite volume schemes classically rely on the computation of a numerical flux along mesh faces (in 3D) or mesh edges (in 2D). A convenient, yet very diffusive, way to get a robust and stable scheme is to use the upwind technique. The MUSCL1 technique combines an upwind approach to a second order reconstruction of the volume fraction field, allowing for a better localization of the interface between fluids, and much less numerical diffusion.
  2. /ALE/MUSCL is only compatible with LAW51 for 2D and 3D modeling. It is currently enabled only for volume fraction. A slight computational overcost is to be expected.
  3. /ALE/MUSCL is also compatible with multimaterial LAW151 and provides a full second order solution (time and space) when IFLAG=0 (default). It is possible to use MUSCL only for the volume fraction field by setting IFLAG=1. The behavior is then the same as for LAW51.
  4. As of Version 2022.0, MUSCL scheme is enabled by default. It can be disabled by using Engine option /ALE/MUSCL/OFF.
1 B. Van Leer, Towards the Ultimate Conservative Difference Scheme, V. A Second Order Sequel to Godunov’s Method, J. Comp. Phys., 87, 408—463, 1979