bed shear stress in shallow watersbed shear stress in shallow watershttps://oss.deltares.nl/c/message_boards/find_thread?p_l_id=1806765&threadId=21983922020-04-09T05:34:14Z2020-04-09T05:34:14Zbed shear stress in shallow watersRachel Allenhttps://oss.deltares.nl/c/message_boards/find_message?p_l_id=1806765&messageId=21983912019-02-27T01:03:44Z2019-02-27T01:03:44Z<p>Hi,</p> <p>I'm looking in to bed shear stress model outputs, and comparing to some ADV data collected in a shallow estuary (1-2 m MLLW, in San Francisco Bay). I'm a relatively new user for the Delft models, so I apologize if this is not the correct place for this question...</p> <p>1) where are the bed shear stresses from currents, waves, and currents and waves reported? I'm currently running the flow and wave modules in Delft3D4, and I've found that the trim file gives "bed shear stress", "staggered bed shear stress", and "max bed shear stress", and the trih file gives "bed shear stress". I assume that these are bed shear stresses from currents and waves, tau_m (FLOW manual eq. 9.195) and tau_max (eq. 9.197). But section 9.7.5 of the FLOW manual discusses tau_c and tau_w, I'd love to determine if I can output those parameters from the model as well, and I haven't yet figured out how to do this from reading the manual.</p> <p>2) how does the model account for wave penetration to the bed when computing bed shear stress? My understanding is that wave spectra are reported for the surface, so tau_peak is the peak wave period at the surface. But in this shallow estuary with tidal water level changing from 1 m above bed to 3 m above bed, 2 second waves may penetrate to the bed on low water, but not on high water. So, since tau_w is computed from u_orb, which is computed from omega (the wave frequency), the relevant omega to use at the bed may not be the same as at the surface where the waves are computed. I would guess that this is accounted for in the model, but I haven't figured out how yet... </p> <p>Thank you for your help!</p> <p>Best,</p> <p>Rachel</p>Rachel Allen2019-02-27T01:03:44Z