Greetings. I am new to this platform, and I am currently working on my master’s thesis.
Here I have little problem, what I am sharing as a screen. This is part of upstream surface of dam (blue curved surface) where I am trying to simulate hydrostatic pressure. For this I was trying to use surface load BC (linear force generator), but I have problem because of surface curvature. Can anyone suggest me if there is better way to do it or how to use Global linear force for surface condition in GiD properly.
GiD is a neutral pre/postprocessor, it don’t define any condition for a specific simulation. The conditions are defined by each problemtype, then “surface load BC” is defined by some problemtype loaded in GiD. What is this problemtype? (to see if there is some special condition to define a hydrostatic pressure)
I cannot see in Atena/Static any special boundary condition to facilitate define a hydrostatic pressure load.
Maybe you must cut the geometric surfaces affected with this pressure, to be splitted in a surface over the water level and a surface under the level (can create an auxiliary planar surface at this water level and use intersect surfaces),and then can assign a boundary condition only to the surfaces under the level.
and this boundary surface maybe can be represented with a ‘Load Force for Surface’ with coordinate system ‘LOCAL LINEAL’ , with local values px=py=0 and pz=water depth (local z’ points in the surface normal direction) It seems that for LINEAL you can define two points and its two values , e.g. a point in the water level, with pressure=0 and other under the water with p=density*depth, but I don’t know what is really doing this condition in Atena, must see its manual or ask its developers.
It is also possible to write a small Tcl script that can ask GiD for some element faces (marked somehow, e.g. by this condition) and then calculate the pressure for its depth (z water level-z center) and assign or modify the field of this condition with this recalculated value for each element, but it is more advanced (see the GiD customization manual commands to know the scripting commands)
Thanks for your time. That’s exactly what I have done. I cut the surface in several segments and created “Load for surface” condition, because I had problem with curved surface, which has several radiuses and Linear gradient was not really useful, because it creates really parallel forces of global axes while I needed perpendicular force for surface. I was hoping if there was some tool what automatically gives load perpendicular direction to surface but as it seems there is not. Thanks anyways - I will find some primitive solution
The coordinate system ‘LOCAL’ in ‘Load Force for Surface’ just mean that the pressure values are relative to the local axis of the surface, and the z’ local is the surface normal, and for a perpendicular pressure Pxlocal and Pxlocal are 0 and Pzlocal is the pressure (positive in the normal direction and negative in opposite direction. Must check and swap if necessary the normal of these surfaces: the mesh elements with inherit the same normal)
But this pressure in case of hydrostatic is not a constant value, must be a linear value and truncated to zero over the water surface. I am not sure if this can be defined with the current ‘LOCAL LINEAL’ option of Atena (must ask them), otherwise is necessary to calculate for each element a Pzlocal value (can be constant as an approximation, with small element size). In theory you can manually calculate the value element by element (e.g. for its z center) and assign manually the condition to each mesh element, but is a hard work, that can be automatized with an Tcl script doing the same.
