/UPWM/SUPG (Obsolete)

Engine Keyword This describes the Streamline Upwind Petrov Galerkin formulation.

Format

/UPWM/SUPG

fac

Definition

Field Contents SI Unit Example
fac Scale factor applied on Petrov Galerkine weighting function.

Default = 1.00 (recommended value).

  

Comments

  1. The streamline upwind Petrov-Galerkine (SUPG) is an optimal upwinding technique which acts only in the flow direction.
  2. If this keyword is used, the usual upwind method for momentum advection is no longer used. As a consequence, the coefficient η 1 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4TdG2aaS baaSqaaiaaikdaaeqaaaaa@388A@ from /UPWIND (Obsolete) Starter is also not used.
  3. The Galerkin (shape function φ) are modified to integrate the momentum convection term [(u - w). ∇]u, which leads to a Petrov Galerkin method using weight function W* such as:(1)
    W * = φ + f a c k ' ( u − w ) 2 u j ∂ φ ∂ x j

    Where, k' is a function of the Reynolds number, material velocity and element length, and fac is a scale factor. fac = 1.00 is the standard value for SUPG formulation (recommended).

  4. /UPWM/SUPG is activated by default in 2D and 3D analysis, as it returns the most accurate results.
  5. It is available for multi-material LAW51.
  6. The upwinding technique is introduced to add numerical diffusion to the scheme which, otherwise is generally under-diffusive and thus unstable. The usual method is first: order accurate and strongly depends on the mesh aspect. In some cases (see examples below) the classical method might lead to locally erratic velocities with unsuitable meshes. SUPG method provides more accurate results, if the phenomenon is sensitive to mesh aspect. It is recommended to systematically activate it.
    Modeling situation:

    blast_wave
    Figure 1. Blast Wave Modeling
    A regular mesh is used although this phenomenon has spherical evolution. Result are obtained with multi-material LAW51.
    Velocity Result - Classical UPWIND:

    classical_upwind
    Figure 2. Blast Wave Evolution with Usual Method
    Classical UPWIND method for momentum transportation is not suitable with spherical evolution and regular mesh.
    Velocity Result - SUPG:

    blast_wave_supg
    Figure 3. Blast Wave Evolution with SUPG Method
    SUPG method for momentum advection removes mesh sensitivity. It is no longer required to have a spherical mesh to model spherical phenomena.