Mass balance problemMass balance problemhttps://oss.deltares.nl/c/message_boards/find_thread?p_l_id=1806675&threadId=8760062019-10-21T00:11:08Z2019-10-21T00:11:08ZRE: Mass balance problemIrene Phttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806675&messageId=9106662016-05-02T15:49:36Z2016-05-02T15:49:36ZHi Richard,<br /><br />thank you for your answer. You are right, there was a loss of sediment through the open boundaries of the domain. In order to reduce the amount of sediment loss, I increased the dimension of the grid. Now the loss of sediment is very low, so this issue is negligible. <br />However, now the sum of the suspended and deposited cohesive sediment exceeds the initial concentration inside the lagoon. What could be the cause of this result?<br /><br />Thank you for your support,<br /><br />IreneIrene P2016-05-02T15:49:36ZRE: Mass balance problemRichard Measureshttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806675&messageId=8802812016-03-28T22:51:52Z2016-03-28T22:51:52ZHi Irene,<br /><br />I had one thought regarding this: Are you including sediment which leaves or enters through your boundary condition in your mass balance. I.e. if water containing sediment is leaving through your tidal boundary then this will represent a loss to the system and vice versa. If your mass balance is tidally varying then this could be the cause?<br /><br />Cheers,<br />RichardRichard Measures2016-03-28T22:51:52ZMass balance problemIrene Phttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806675&messageId=8760052016-03-23T14:33:20Z2016-03-23T14:33:20ZHello everyone,<br /><br />I am using Delft3D Flow to simulate sediment concentration under the influence of tide in a system of shallow bays. <br />The boundary conditions in the model are water level, while in the initial conditions I set a constant concentration of mud inside the lagoon. Moreover, I am considering only the sediment deposition, so I imposed no erosion in the model (a critical bed shear stress for erosion equal to 100 and the erosion parameter equal to 0). <br /><br />Once the simulation was done, I checked the mass balance inside the entire domain, but it doesn't work. The difference between the initial mass of sediment and the sum of suspended and deposited sediment is not equal to 0, it increases right after the first time step and at a certain point it becomes negative. I made a lot of attempts, changing some parameters in the model, such as the Foster filter, the morphological factor (equal to 1 and greater than 1), but it didn't change the result. <br /><br />I evaluated the mass of the suspended sediment as the product of the suspended concentration and the volume of water (= water depth times the grid cell area). The mass of deposited sediment was given by the product of the volume of deposited sediment (the height of sediment at the bottom and the grid cell area) and the dry bed density.<br /><br />I don't understand what is missing in my bass balance and why I get large differences in these values.<br /><br />Thank you in advance for your help!<br /><br />IreneIrene P2016-03-23T14:33:20Z