/CAA

Block Format Keyword Describes the computation Aero-Acoustic formulation for Eulerian or quasi-Eulerian simulations. Internal forces are computed with finite volume formulation. It improves results for under integrated elements. By default artificial viscosity is canceled, (qa,qb) default values are zero.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/CAA

Comments

  1. To use "Computation Aero-Acoustic" formulation and specific options, it is necessary to use the option /CAA in the input deck.
  2. /CAA is fully consistent only for Eulerian formulation. /CAA is recommended for Eulerian formulation, but not for ALE (except if ALE is quasi-Eulerian).
  3. This option has no influence with fully-integrated elements. It is recommended only with one integration point elements.
  4. This option uses a finite volume formulation to compute internal forces.

    caa_finite_volume
    Figure 1.
    F k N i = ∭ Ω σ ⋅∇ Φ N i ⋅ e k dΩ MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaDa aaleaacaWGRbaabaGaamOtamaaBaaameaacaWGPbaabeaaaaGccqGH 9aqpdaWdtaqaaiaaho8aaSqaaiabfM6axbqab0Gaey4kIiVaey4kIi Vaey4kIipakiabgwSixlabgEGirlaahA6adaWgaaWcbaGaamOtamaa BaaameaacaWGPbaabeaaaSqabaGccqGHflY1caWHLbWaaSbaaSqaai aadUgaaeqaaOGaamizaiabfM6axbaa@516B@ F k N i =p ∭ S N i n ⋅ e k dS+ ∭ Ω σ dev ⋅∇ Φ N i ⋅ e k dΩ MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOramaaDa aaleaacaWGRbaabaGaamOtamaaBaaameaacaWGPbaabeaaaaGccqGH 9aqpcaWGWbWaa8WeaeaacaWHUbaaleaacaWGtbWaaSbaaWqaaiaad6 eadaWgaaqaaiaadMgaaeqaaaqabaaaleqaniabgUIiYlabgUIiYlab gUIiYdGccqGHflY1caWHLbWaaSbaaSqaaiaadUgaaeqaaOGaamizai aadofacqGHRaWkdaWdtaqaaiaaho8adaWgaaWcbaGaamizaiaadwga caWG2baabeaaaeaacqqHPoWvaeqaniabgUIiYlabgUIiYlabgUIiYd GccqGHflY1cqGHhis0caWHMoWaaSbaaSqaaiaad6eadaWgaaadbaGa amyAaaqabaaaleqaaOGaeyyXICTaaCyzamaaBaaaleaacaWGRbaabe aakiaadsgacqqHPoWvaaa@65E5@
    Correct with:
    • Parallelepipedic shape, or
    • Fully integrated elements
    Improve internal forces calculation, in general for:
    • One integration point elements
    • Trapezoidal shapes
  5. Finite volume formulation implies better internal forces estimations.
    In the case of a homogeneous fluid pressure, equilibrium on nodes will be verified even with non-trapezoidal shapes like truncated pyramid. This may not be the case with volume integration, due to hypothesis on shape functions for one integration point element. (Refer to Reduced Integration Method in the Theory Manual).

    caa_finite_volume2
    Figure 2.
  6. Numerical viscosities default values (qa,qb) are set to 0.

    This is suitable for low Mach number problem, otherwise these parameters should be non-zero.

  7. For old CFD input (input deck V43 or V46 format), this option will be automatically activated running Radioss.
  8. For other Block Format input (V41 and V44), it is allowed to add this option in the input deck file to enable this feature running Radioss.