# Fluid bulk modulus scaling **URL:** \ **Category:** FLAC3D\ **Created:** [March 1, 2022, 11:33am UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304 "2022-03-01T11:33:29Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Gian](https://avatars.discourse-cdn.com/v4/letter/g/f19dbf/32.png) [@Gian](https://forum.itascainternational.com/u/Gian)\ **Post date:** [March 1, 2022, 11:33am UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304/1 "2022-03-01T11:33:30Z")
Guys, I would like to know if anyone knows about the existence of a function to perform the fluid bulk modulus scaling to accelerate calculations in FLAC3D such as the available in FLAC. Also, I would appreciate if someone could confirm if the unsaturated logic is already activated in common flow calculations. All the best, ---
**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\ **Post date:** [March 2, 2022, 6:36pm UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304/2 "2022-03-02T18:36:39Z")
Although not explicitly documented, I believe the similar fluid bulk modulus scaling scheme in FLAC3D is applicable - just replacing the square root of zone area in FLAC (Eq. 1.41 in FLAC fluid manual) by the cubic root of zone volume in FLAC3D. Yes, unsaturated (e.g., to calculate the phreatic surface) is available in FLAC3D. More generalized unsaturated logic, e.g., incorporating soil-water characteristic curves, will be available from next version. ---
**Author:** ![Francesco\_IT](https://avatars.discourse-cdn.com/v4/letter/f/b5a626/32.png) [@Francesco\_IT](https://forum.itascainternational.com/u/Francesco_IT)\ **Post date:** [March 7, 2022, 12:03pm UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304/3 "2022-03-07T12:03:08Z")
Hi, do you know if in the next version also a general implicit solution will be available for faster seepage analyses? Also, this could improve the speed for consolidation analyses using the “uncoupled” scheme, i.e. keeping mechanical and fluid analyses split and cycling between mech and fluid. Thank you in advance. ---
**Author:** ![Francesco\_IT](https://avatars.discourse-cdn.com/v4/letter/f/b5a626/32.png) [@Francesco\_IT](https://forum.itascainternational.com/u/Francesco_IT)\ **Post date:** [June 6, 2022, 4:20pm UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304/4 "2022-06-06T16:20:50Z")
Dear cheng, please, explicitly document the command to activate automatic bulk modulus scaling equivalent to that used in FALC: **SET fastwb on** Moreover, is there a way to record and display the convergence during flow-only analysis? In FLAC there is a FISH function to track the convergence. Thank you in advance. Francesco ---
**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\ **Post date:** [June 6, 2022, 5:39pm UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304/5 "2022-06-06T17:39:26Z")
Yes, next version ahs a general implicit solution even for free-surface water table calculation. Yes, the next version will have one “consolidation” command that keeps mechanical and fluid analyses split and cycling between mech and fluid. ---
**Author:** ![cheng](https://avatars.discourse-cdn.com/v4/letter/c/ecccb3/32.png) [@cheng](https://forum.itascainternational.com/u/cheng)\ **Post date:** [June 6, 2022, 5:45pm UTC](https://forum.itascainternational.com/t/fluid-bulk-modulus-scaling/304/6 "2022-06-06T17:45:08Z")
Currently, FLAC3D does not have an equivalent command as **SET fastwb on** in FLAC. The FISH intrinsic to record and display the convergence during flow-only analysis is: [zone.fluid.ratio](http://docs.itascacg.com/flac3d700/flac3d/zone/doc/manual/zone_manual/zone_fish/zone_intrinsics/fish_zone.fluid.ratio.html#zone.fluid.ratio)