Hi there, Does anybody have the information on commercial software that can simulate debris flows? Ideally, the package can reproduce the three-dimensional landslide movement with options for different rheological models.

Thanks.

Andy:

As you may know the real physics of debris flows are very complex and poorly understood. It is a classic multiphase flow problem with many complications of self-organization (particle gathering and dispersal, fluid leaking, etc.) as a function of transport distance. The physics can change dramatically along the path as well as vertically within the flow, depending on the importance of particle collisions, change in local particle size as a result of breaking of clasts, entrainment of bed, etc.

The notion of 'rheology' is tricky in multiphase flow and really depends on how much phase relative motion you expect. There are standard corrections to the shear viscosity of a fluid by the addition of particles, but they assume that the continuum is an effective mixture, where phase relative motion has a much longer time scale than the bulk motion of the flow. They also are based on the assumption of very simple flow kinematics, which may be okay for pipe flow but maybe not for 'run-out' flows.

In addition these are also 'free surface flows' AND lubricating (and leaking) flows, so extra vexing for numerical analysis. It is doubtful one can use any of the available codes based on a Navier-Stokes formulation without extensive tuning and hand-wringing.

I guess my point is to dig deeply into the geotechnical engineering literature, where both boundary element and finite element approaches have been used. You really need an approach that can address the suspension to slurry transition. I've published on this but it is ad hoc, maybe okay for wild scientific speculation but not good enough for engineering practice.

Strictly speaking, landslides (slumps) are not the same as debris flows.

Dear George,

Thank you very much for your response. It is very imformative. However, I would be more grateful if you could give me some reference for the publications you mentioned.

Thanks again.

Hi Andy:

I'm sorry to seem so glum about the complications, it's just that the assumptions that make for a (semi)robust continuum to many of the workers who gather at this web forum are rarely met in your problem. My main field of research is in multiphase geophysical flows and debris flows are the hardest- don't take anything you read too seriously. Any multiphase theory has limits of application, and debris flows cross the boundries of those theories. If I were you I would fire up my search engine and hunt further.

I did this and found the following- perhaps start here:

http://www.granular.com/POWDER/papers_tag.html

There are some papers that may be of interest to you here. The key isue for you is how much water you have in the flow- but that is not a matter for our CFD colleagues...