For poroelastic acoustics, Biot's theory-based mixed displacement-pressure finite element harmonic solver is now available for axisymmetric elements, including FLUID244. For details, see Poroelastic Acoustics in the Theory Reference.

Use the new KEYOPT(1) = 1 to specify the membrane option for SHELL294. This option reduces the computational load by assuming no temperature variation through the thickness of the shell. It can be useful when the in-plane temperature variation is dominant.

Use the new KEYOPT(2) to specify a nonlinear temperature-dependent convection film coefficient for current generation thermal elements SOLID279, SOLID291, and PLANE293.

Now, in addition to frequency-based view factor updating at the substep level, you can specify kinematic-based view factor updating to only update when geometric changes in the radiation surfaces exceed prescribed thresholds using the VFUP command. This can be a more efficient updating strategy than frequency-based criteria which update view factors whether or not deformation or kinematic motion has significantly changed the radiation facet geometries. It is particularly useful when you have no knowledge about body deformation prior to the simulation.

A new nonlinear stabilization option is available through the STABILIZATION argument on the RADOPT command. Setting STABILIZATION equal to one can help radiosity solutions converge faster by allowing the film coefficient and bulk temperatures to vary with temperature during the Newton-Raphson loop. Setting STABILIZATION equal to two gives additional stabilization for problems with temperature-dependent emissivity.

Use the new KEYOPT(14) to specify a nonlinear temperature-dependent convection film coefficient for the coupled-field elements PLANE222, PLANE223, SOLID225, SOLID226, and SOLID227.

You can now enable the enhanced strain or the simplified enhanced formulation in a structural-thermal-electric-diffusion analysis by setting KEYOPT(6) = 2 or 3, respectively, on PLANE222 and SOLID225 coupled-field elements. The enhanced strain formulation improves solution accuracy in bending-dominated and nearly incompressible problems by preventing shear and volumetric locking, respectively.

User-programmable features (UPFs) are available for coupled-field elements PLANE222, PLANE223, SOLID225, SOLID226, and SOLID227 by setting KEYOPT(12) = 1. Coupled-field UPFs enable you to customize element characteristics, material models, loads, constitutive equations, and output items. The coupled-field UPFs are integrated into the element standard workflow, so you can customize element properties of interest without writing a user element or material model from scratch. Several utility functions are available to help you access element results and other element information, making it easier to program nonlinearities. See Customizing a Coupled-Field Element in the Programmer's Reference for details.