This book on finite element-based computational methods for solving incompressible viscous fluid flow problems shows readers how to apply operator splitting techniques to decouple complicated computational fluid dynamics problems into a sequence of relatively simpler sub-problems at each time step, such as hemispherical cavity flow, cavity flow of an Oldroyd-B viscoelastic flow, and particle interaction in an Oldroyd-B type viscoelastic fluid. Efficient and robust numerical methods for solving those resulting simpler sub-problems are introduced and discussed. Interesting computational results are presented to show the capability of methodologies addressed in the book.
This book discusses finite element based computational methods for solving incompressible viscous fluid flow problems. Fundamental aspects of the computational methodologies, and extensions for advanced engineering applications are also presented.
In this article we present a numerical method for simulating the sedimentation of balls in a three-dimensional channel filled with an Oldroyd-B fluid. We have combined a distributed Lagrange multiplier/fictitious domain method with a factorization approach from Lozinski and Owens [J. Non-Newtonian Fluid Mech. 112 (2003) 161] via an operator splitting technique. The method is validated by comparing obtained results with those reported in literature. Then the study of fluid elasticity on the formation of ball chain (up to six balls) in Oldroyd-B fluids are presented to demonstrate the capability of our methods. For a higher value of elastic number, a longer chain of balls can be formed while settling in an Oldroyd-B fluid as observed experimentally. (A stable six-ball chain settling in an Oldroyd-B fluid is shown at the right.)
In this article, we have investigated, via numerical simulation, the interaction of two identical balls settling in a vertical square tube filled with a viscoelastic fluid. For two balls released in Oldroyd-B fluids, one on top of the other initially, we have observed two possible scenarios, among others: either the trailing ball catches up the leading one to form a doublet (dipole) or the balls separate with a stable final distance. If the ball density is slightly larger than the fluid density, the two balls form a doublet, either vertical or tilted. If one further increases the ball density, the two balls still form a doublet if the initial distance is small enough, but for larger initial distances at higher elasticity numbers, the balls move away from each other and their distance reaches a stable constant. Factors influencing doublet formation are (possibly among others) the ball density, the ball initial distance, and the fluid elasticity number. When settling in FENE-CR (finite extendable non-linear elastic - Chilcott and. Rallison) fluids, low values of the coil maximal extension limit enhance ball separation. (The effect of the initial distance on forming a doublet in an Oldroyd-B fluid is shown at the right two figures. The right top one shows that two balls keep a constant distance.)