User Forum of Software BASEMENT

tristan

User

Registered: 2014-09-09

Posts: 4

Modelling bridges/culverts

Hallo,

does somebody have experiences in modelling of bridges and culverts in "Baseplane"?
I think to use the inner gate boundery option may be a way to represent submerged bridges/culverts. What is the best way?

Christian Volz

User

Registered: 2014-09-04

Posts: 31

Re: Modelling bridges/culverts

Dear tristan,

at the moment we do not have a special treatment of bridges or culverts implemented in BASEMENT. Such a feature is planned for future releases, however.
We usually recommend the following approaches, which are sufficient for many applications:

- to model the influence of the reduced cross sectional area due to the bridge piers, we recommend to artificially reduce the cross section width by the widths of the bridge piers. If the water does not reach the bottom level of the bridge, nothing more needs to be done.

- if the water may reach the bottom level of the bridge or culvert, we recommend (as you suggested) to implement an inner gate boundary. This allows for modelling backwater effects caused by the bridge structure. It does not, however, consider effects of pressurized flow, which may be a limitation epsecially regarding culverts.

Best regards
Christian

michelk

Advanced_User

Registered: 2014-09-17

Posts: 33

Re: Modelling bridges/culverts

Hi,

is there an update on the issue, or already a beta-implementation of a culvert? Has anybody tried to use BaseExtern in conjunction with 1D-Floris (which allows closed cross-sections)? BTW is it planned to implement closed cross-sections in Basechain as well ?

Greetings, Michel

Christian Volz

User

Registered: 2014-09-04

Posts: 31

Re: Modelling bridges/culverts

Hi michel

there is a first simple implementation of a HQ-inner-boundary. The discharge through the inner boundary is hereby computed as function of the upstream water-levels. This h-q-table must be given by the user, who is free to define it as he wants. This boundary may be helpful to simulate some aspects of a culvert. If you need it urgently, we can send you a BASEMENT version. Probably, there will also be a new release within a few  weeks.

We think about implementing closed cross-sections in BASEchain (Preissmann-Slot). It is however not scheduled at the moment and does not have the highest priority. So we can not say when it will be implemented.

regards!

Hering

User

Registered: 2015-11-25

Posts: 5

Re: Modelling bridges/culverts

Modeling bridges or culverts till now I have only two possibilities:
1) bridge or culvert as gate
Backwater effect: considered
pressure flow: not considered
overtopping: not considered
manning in bridge/culvert: not considered

2) bridge or culvert as water level flow table
Backwater effect: not considered
pressure flow: considered
overtopping: considered
manning in bridge/culvert: considered
problem: the HEC-RAS result cannot adapt to backwater effects

Your model is very fine.
Only the modeling of bridges and culverts seems to be a big problem.
Can I hope for a solution in near future?

PaoloTamagnone

User

Registered: 2016-07-01

Posts: 8

Re: Modelling bridges/culverts

Hi,
I was trying to model a culvert in my domain.
I used the inner_boundary:

INNER_BOUNDARY {
type = hqrelation
string_name1 = sbocco_bealera_abbaziale
string_name2 = imbocco_bealera_abbaziale
file = culvert.txt outflow of scale

where stringdef are defined by the points of interest within my mesh.
when I start the simulation basement will fail with this error:

ERROR -> The Edge string 'sbocco_bealera_abbaziale' is not correct!
                   Edges must be boundary edges!
                   Please correct the edge string in the command file.
why?

2 stringdef must necessarily be defined on the mesh boundary?

regards

sajjad

User

Registered: 2014-10-01

Posts: 101

Re: Modelling bridges/culverts

Hi,

the inner boundary definition requires that you create a gap in the mesh across which a hyd structure is to be defined through inner boundary. The upstream and downstrem stringdefs which show the limits of the structure are defined across this gap.

For more understanding, pl download the files about basement tutorial/test case for flow control. In the 2dm mesh file u can see implemented a weir through inner boundary with a miniscule gap created while meshing.

It is my suggestion to admin to modify the inner boundary definition procedure whereby the requirement of gap creation is removed and we can declare the cells falling inside the structure as redundant i.e SV equations r not solved there. This will facilitate things for the user.

Regards

Last edited by sajjad (2016-07-01 15:26:39)

qtheiler

User

Registered: 2015-07-30

Posts: 60

Re: Modelling bridges/culverts

Hi everybody,

Because this post becomes old (2 years ago). I would like to know from the Developer if you have some new information about the culvert as Hec Ras do? I have a flow Under two bridges and I woul like to modelize it. I was hoping to do a coupling model (1D and 2D) and using a culvert on the 1D model. Unfortunatley it seems that there isn't any such structure. Do you have some advice? Have anybody any example that he has used that was good? Thank's in advance.

alaquas

User

Registered: 2015-08-27

Posts: 9

Re: Modelling bridges/culverts

Hi

I tried to model a culvert using the inner boundary condition. Although during the simulation, the water level at DL_in reaches up to 427.0 m there is no flow through the culvert (stringdef history of DL_in and DL_out are zero during the entire simulation time). Did I use the boundary correct? Any suggestions how to implement the culvert in a different way?

Thanks in advance!

INNER_BOUNDARY {
    type         = hqrelation
    string_name1 = DL_out
    string_name2 = DL_in
    file         = DL.txt
}
The file DL.txt contains the water level in m and the corresponding Q in m3/s.
420.5    0
423.5    63
426.5    114

Stephan Kammerer

Developer

Registered: 2015-03-31

Posts: 67

Re: Modelling bridges/culverts

Check your node strings for the Inner Boundary, as string_name1 you have to define the upstream edge of the culvert (in your case) string_name2 is the downstream edge, where the water re-enters the computational domain.

alaquas

User

Registered: 2015-08-27

Posts: 9

Re: Modelling bridges/culverts

Thanks for the hint! When using the description behind the question mark in BASEMENT_v2 it said that 'string_name_1' corresponds to the expected outflow boundary...
I will change the position of DL_out and DL_in and run the simulation again.