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A finite element for incompressible plane flows of fluids with memory
Author(s) -
Bernstein Barry,
Malkus David S.,
Olsen Elwood T.
Publication year - 1985
Publication title -
international journal for numerical methods in fluids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 112
eISSN - 1097-0363
pISSN - 0271-2091
DOI - 10.1002/fld.1650050105
Subject(s) - finite element method , mathematics , compressibility , newtonian fluid , streamlines, streaklines, and pathlines , mixed finite element method , pressure correction method , mechanics , reynolds number , incompressible flow , smoothed finite element method , geometry , mathematical analysis , classical mechanics , flow (mathematics) , physics , boundary knot method , boundary element method , turbulence , thermodynamics
Flows of fluids with single‐integral memory functionals are considered. Evaluation of the stress at a material point involves the deformation history of that point, and a dominant computational cost in finite element approximation is the construction of streamlines. It is shown that the simple crossed‐triangle macro‐element is in many ways an ideal finite element for the difficult non‐linear, non‐self‐adjoint problem. The question as to whether this element produces convergent velocity and pressure solutions is addressed in the light of its failure to satisfy the discrete LBB condition. The effect of the element's ill‐disposed (‘spurious’) pressure modes is discussed, and a pressure smoothing scheme is given which gives good results in Newtonian and non‐Newtonian flows at various Reynolds and Deborah numbers. As an example of the element's success in modelling such flows, the problem of pressure differences in flows over transverse slots is studied numerically. The results are compared with experimental observations of such flows. The effect of fluid memory on the relation between first normal‐stress differences and pressure differences is investigated.