Enters the Realm of FSI

The need to study the interaction between fluids and structures is critical to many industries and applications where CFD is applied. FIDAP 8.5 is equipped to solve these problems, where stress and deflection in solid regions must be computed and coupled with the fluid flow solution. For example, in the biomedical arena, flows involving deforming arterial walls, grafts, and other tissues and devices are common. In the materials processing industries, it is often desired to compute the stress and deflection in polymer or aluminum extrusion dies. Many thin film coating processes, such as roll coating and blade coating, involve deformable materials and components. Web flotation and tape transport systems include thin flexible membranes moving through air. The deformation and f low-induced vibration of slender structures can be very important in applications such as tube bundles, marine risers, and antennas. Thermal stresses and deformations due to changes in temperature can be important in many applications, such as semiconductor crystal growth and micro-electro-mechanical systems (MEMS).

While many engineers solve FSI problems by transferring files from a CFD solver to a structural solver and back, the availability of FIDAP 8.5 makes this unnecessary.

FIDAP 8.5 is well-suited for solving these problems, and more. It solves for the linear and non-linear elastic response of the solid. Problems can be steady or unsteady. Thermoelasticity problems (stresses arising from temperature gradients and thermal expansion) can be analyzed and the structural properties can be temperature-dependent. Postprocessing of the deformed structure, stresses, strains, and forces is provided. The new FSI features are fully compatible with the other extensive analysis capabilities in FIDAP. For example, FSI analyses can include free surfaces or filling (using the volume of fluid model) and can take full advantage of multi-CPU machines via parallel processing for quicker turnaround.

Vibrations of a flexible beam are caused by vortices shed from the square cylinder as air flows from left to right. Contours of pressure are shown in the fluid above the beam; velocity vectors appear in the lower half of the figure.

While many engineers solve FSI problems by transferring files from a CFD solver to a structural solver and back, the availability of FIDAP 8.5 makes this unnecessary. All aspects of problem definition, solution control, and postprocessing are accessed from FIDAP's GUI or read from a batch command file.

FSI problems can be solved at different levels of complexity. For simple problems, where the deflection of the structure is small, the coupling between fluid and structure is weak and the two calculations can actually be accomplished in separate steps.

A more challenging (and more interesting!) situation arises when the calculation of the structural deformation affects the flow field and vice versa. A classic example of such a strongly coupled system is flow-induced vibration. In such problems, the most crucial step can often be the handling of the computational grid as it deforms. In FIDAP 8.5, a new elasticity-based remeshing algorithm has been implemented which minimizes mesh distortion when large deflections of the structure take place.

Contours of velocity magnitude in an artery with a compliant vein graft. The outward deflection of the graft is at a maximum at this time step. The mesh in the compliant wall section is also shown.

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