open TELEMAC-MASCARET The mathematically superior suite of solvers

Hello,
I have a question about the definition of dry condition in Telemac.
Experimental work shows that wave front celerity in completely dry condition bed is less than that in condition with initial water depth.That is probably due to loss of water which infiltrates in the bed under dry condition, give the porosity and permeability of the sediment bed. Now I have a question how dry condition in telemac works. Does dry mean saturate condition with no air in the content of saturate soil?
I tried to compare wave front in dry vs wet(initial water)condition in Telemac but the result is in contrast to experimental result.I would really appreciate if you could answer my question.

Hello,

Water going into the sand and back is not considered so far in Telemac. The reason of faster propagation on wet bed is that the celerity of the shallow water waves is added to the velocity of the flow. Then you should be aware that such flows, a front advancing on dry land, is far from the assumptions of the shallow waters. Another thing is that in such computations the advection scheme is very important. You can see in the Malpasset dam break test case the difference between the method of characteristics and the NERD scheme (case small, changing TYPE OF ADVECTION = 1;5 into TYPE OF ADVECTION = 14;5). The wave front goes faster.

With best regards,

Jean-Michel Hervouet

Thank you so much for your quick reply.I will consider your points in my modeling.
you mentioned that the reason of faster propagation on wet bed is that the celerity of the shallow water waves is added to the velocity of the flow.Considering the initial water depth with zero velocity, could we still say that the velocity of flow is added to the celerity of shallow water wave?could not we say that it is because of energy dissipation due to seepage which originate from the interface between the fluid and the sediment bed.

Thank you in advance,
Sanaz

Hello,

Yes of course in reality the water going underground also slows down the wave progressing on dry bed.

JMH