SISYPHE v5p9 tutorial RCEM, Sept 2009

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Loren Underwood
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1 SISYPHE is a morphodynamical model, which has been developed to obtain realistic estimates of bed movements and sediment transport patterns driven by currents and/or waves. The bottom evolution equation is solved, using either a finite element or a finite volume method, yielding the bottom evolution and the solid transport rate at each node of the model. An additional transport equation can be solved for the suspended sediment concentration, in order to account properly for the effect of the suspension under non-equilibrium situations. The model formulation also includes the effects of non-uniform grain size and vertical stratification in the bed. SISYPHE is part of the TELEMAC system and is developed by the Laboratoire national d hydraulique et environnement of Electricité de France (LNHE-EDF, Chatou, France). As such the model is compatible with the other modules of the TELEMAC system. In particular, the hydrodynamics driving the morphodynamical model (currents in a river environment, waves in a coastal environment, or a combination of both in an estuarial environment for example) can be derived from TELEMAC-2D (-3D) and/or TOMAWAC computations. For more information see telemacsystem.com. In the case of relatively small bed evolutions, it is possible to use constant, steady state hydrodynamics from a previous TELEMAC-2D (-3D) computation. In this case, the flow is updated at each time step in an effort to conserve both the flow rate and the free surface elevation (velocities are locally increased where deposition occurs and decreased where erosion takes place). It is also possible to couple the hydrodynamic (TELEMAC-2D or TOMAWAC) and morphodynamical (SISYPHE) solvers for a better representation of the hydrodynamics and its response to the changing bed profile. Originally SISYPHE was developed to model bed load transport. Depending on the environmental conditions (driving conditions, type of sediment, etc.), a number of formulations are available to choose from. The users can also use their own formulations through user subroutines. SISYPHE has since then evolved to include the pick-up and transport of suspended material. It should be noted that only a limited number of formulations are available at this stage. Applications of SISYPHE include the prediction of sedimentation rates within ports and the assessment of alternative design for coastal harbours, river flow and deposit in the lee of a dike.

2 CAS file and user subroutines Similarly to other TELEMAC modules, SISYPHE relies on a CAS file or parameter file to describe the processes to be modelled and the driving conditions. A typical CAS file will include the following (general) keywords: STEERING FILE FORTRAN FILE GEOMETRY FILE X1 X7 LIEBOR EBOR X10 X11 N K BOUNDARY CONDITIONS FILE LIEBOR & EBOR: bottom evolution (depth) LIEBOR = 2, 0 : solid LIEBOR = 4 : free at liquid boundary LIEBOR = 5 : imposed to EBOR at liquid boundary When Q is free, LIEBOR is free; when Q is imposed, so is LIEBOR. LIQBOR & QBOR: sediment (bed-load) flow If you want to impose a load at the boundary, set LIEBOR to 4 (file or CONLIT) and LIQBOR to 5 (CONLIT) RESULTS FILE VARIABLES FOR GRAPHIC PRINTOUTS REFERENCE FILE the most notable being B bottom elevation, E bottom evolution, QSBL bed load transport rate of sediment, CSi concentration for class i, QSSUSP suspended transport rate of sediment For comparison and validation IF VALIDATION = Yes PREVIOUS SEDIMENTOLOGICAL COMPUTATION FILE IF COMPUTATION CONTINUE = Yes

3 Principal keywords related to the sediment properties: Non cohesive sediments (D50 > 60 µm) WATER DENSITY Default value kg/m 3 WATER VISCOSITY Default value 1.E-6 m 2 /s SEDIMENT DENSITY Default value kg/m 3 COEFFICIENT FUNCTION OF THE POROSITY Default value is 1.6 NUMBER OF SIZE-CLASSES OF BED MATERIAL INITIAL FRACTION FOR PARTICULAR SIZE CLASS MEAN DIAMETER OF THE SEDIMENT SETTLING VELOCITIES Default value is 1 for each sediment class. Default value is 1 for each sediment class. Default value is 10 mm for each sediment class. If this keyword is not in the CAS file, the subroutine vitchu-sisyphe is used to calculate the settling velocity based on the grain size (Stockes, Zanke or Van Rijn formulae). Cohesive sediment properties COHESIVE SEDIMENTS VOLUME CONCENTRATION OF THE COHESIVE BED.Default value is 0.08 Use the subroutines User_Krone_part.f to define the parameter of the Krone and Partheniades erosion deposition law, critical erosion velocity and deposition velocity (M, u*ce, u*cd).

4 Sediment transport parameters: RATIO BETWEEN SKIN FRICTION AND MEAN DIAMETER BED LOAD BED-LOAD TRANSPORT FORMULA Default value : KSPRATIO = 3 Ksp= KSPRATIO D50 Default value is YES 10 bed-load or total load transport formulations have been implemented in SISYPHE. (3), (30) and (9) should not be used if suspension is to be considered as well. (4), (5), (8) and (9) model the transport under the combined action of currents and waves. SHIELDS PARAMETER Default value is SLOPING BED EFFECT Koch and Flokstra BETA VALUE Empirical coefficient of the formula b= 1.3 FORMULA FOR SLOPE EFFECT Default = 1 : Koch and Flochstra as a function of 2. Soulsby SUSPENSION REFERENCE CONCENTRATION FORMULA EQUILIBRIUM INFLOW CONCENTRATION INITIAL SUSPENSION CONCENTRATION 'CONCENTRATION PER CLASS AT BOUNDARIES' CORRECTION ON CONVECTION VELOCITY (1) Zyserman and Fredsoe formula (2) Bijker concentrations on the boundary are calculated assuming equilibrium conditions Default value is 0 Imposed concentrations on the boundary Default is NO

5 Those parameters need only to be specified if the model is used alone. They will not be accounted for, if Sisyphe is coupled internally with Telemac: The flow field can be either given in the fortran, within the user-subroutine condim_sisyphe.f Or it can be prescribed from a previous Telemac run. TIME STEP NUMBER OF TIME STEPS HYDRODYNAMIC FILE LAW OF BOTTOM FRICTION FRICTION COEFFICIENT Previous Telemac 2d results choice between wave induced ripple height (1), Chezy (2), Strickler (3), Manning (4), or Nikuradse (5) formulations; default law is Strickler When Sisyphe is coupled internally to Telemac, those keywords need to be specified in Telemac steering file COUPLING WITH SISYPHE STEERING FILE COUPLING PERIOD SISYPHE Ratio between SISYPHE and TELEMAC-2D time steps (must be an integer) In the coupled runs, the time step of Sisyphe is equal to the hydrodynamic time multiplied by the coupling period. Therefore it does not need to be specified. The total friction is also calculated by the hydrodynamic model and key words like FRICTION LAW and FRICTION COEFFICIENT are no longer needed.

6 Principal keywords related to suspended sediment transport SUSPENSION SETTLING VELOCITIES OPTION FOR THE DISPERSION DISPERSION ALONG THE FLOW DISPERSION ACROSS THE FLOW.!! if the user wants to activate transport by suspension, not only has this keyword to be set to YES, but the user subroutine USER_KRONE_PART.f also has to be modified to define sensible values for erosion and deposition critical shear velocities. By default, these values are such that there is no erosion and no deposition. for each sediment class. If this keyword is not in the CAS file, the subroutine vitchu-sisyphe is used to calculate the settling velocity based on the grain size (Stockes, Zanke or Van Rijn formulae). Default option is 1, whereby dispersion along and across the flow are set to a constant value by the user. Default value is 1.E-2 Default value is 1.E-2 For waves effect : EFFECT OF WAVES WAVE FILE name of a file containing the results a previous wave computation made on the same mesh. (use of TOMAWAC)

7 User subroutines Following is a list and short description of the FORTRAN subroutines available to the user in the context of SISYPHE: condim_sisyphe.f : Initial conditions condim_susp.f : Initial conditions for suspension conlit.f : Boundary conditions for suspension (EBOR=bed evolution; CBOR=suspended sediment concentration). Useful for time varying simulations since conlit is called at each timestep. A fixed bottom elevation / depth is usually imposed at the boundaries with an inflow, whereas free evolution of the bottom is usually imposed at the boundaries with an outflow. corrxy.f : Mesh geometry modification (in BIEF) corstr_sisyphe.f : Time varying roughness coefficient gf_user.f : Grain feeding init_compo.f : Bed composition init_constant.f : Definition of physical constants (gravity ) noerod.f : No erodable bottom nomvar_sisyphe.f : Name of stored variables predes.f : Computation of new variables qsform.f : User transport formula strche.f : Space varying roughness coefficient user_krone_part.f : Definition of Krone/Partheniades law for cohesive sediments (M,VITCD, threshold for deposition and VITCE, threshold for erosion)

Sisyphe v6.3 User's Manual

Sisyphe v6.3 User's Manual NATIONAL HYDRAULICS AND ENVIRONMENT LABORATORY NUMERICAL AND PHYSICAL MODELLING IN RIVER AND COASTAL HYDRODYNAMICS 6 quai Watier - 78401 CHATOU CEDEX, +33 (1) 30 87 79 46 Front Page January 13 2014 Sisyphe