## General Mechanical

#### How can we apply hydrodynamic added mass in ansys workbench?

• Rana Nasser
Subscriber

Hi Everyone,

Using  MASS21 element in ANSYS APDL to apply hydrodynamic added mass to structural elements is the only approach that I have found to  apply the hydrodynamic effect on structural elements in ANSYS, but in my study I'm using workbench not APDL. Is there another way to apply the hydrodynamic effect in workbench?

• Sandeep Medikonda
Ansys Employee

Hi Rana,

Another element with a full mass matrix capability is MATRIX 27, In the help looks for: help/ans_elem/Hlp_E_MATRIX27.html

You can always add an APDL script in Mechanical as well. Check out this video:

I am not sure of the scenario you are dealing with but if you are looking to work with Ocean Loading from a Hydrodynamic Analysis, check out Chapter 13 in the Mechanical APDL>Advanced Analysis Guide.

Lastly, If you just want to apply fluid pressure in Mechanical, Follow these steps:

• On the Environment context toolbar: click Loads>Hydrostatic Pressure. Or, right-click the Environment tree object or the Geometry window and select Insert>Hydrostatic Pressure.

• Define the Scoping Method. Hydrostatic Pressure can only be scoped to faces.

• Select all of the faces that will potentially enclose the fluid.

Or...

If you are working with a surface body, specify the Shell Face, defined as the side of the shell (Top or Bottom) on which to apply the hydrostatic pressure load.

• Specify the magnitude and direction of the Hydrostatic Acceleration. This is typically the acceleration due to gravity, but can be other acceleration values depending on the modeling scenario. For example, if you were modeling rocket fuel in a rocket’s fuel tank, the fuel might be undergoing a combination of acceleration due to gravity and acceleration due to the rocket accelerating while flying.

• Enter the Fluid Density.

• Specify the Free Surface Location, defined as the location of the top of the fluid in the container. You can specify this location by using coordinate systems, by entering coordinate values, or by clicking a location on the model.

• Mesh the model, then highlight the Hydrostatic Pressure load object to display the pressure contours.

Hope this helps.

Regards,

Sandeep

• sk_cheah
Subscriber

Hi Rana,

As you hinted MASS21 to represent hydrodynamic loads, I assume you're interested in dynamic, not static analysis. Acoustic elements could be used to represent sloshing. Here's an example. You could use APDL scripts in Workbench as described by Sandeep.

Kind regards,
Jason

• Rana Nasser
Subscriber

Saandeep and Jason Thank you so much for you help!

Actually my problem is a dynamic problem, I'm doing a simulation for a regulator (small dam) and I need to take the effect of the water that passing through the regulator vents in to concederation in the modal analysis of the regulator and also in a transient analysis for the regulator under the effect of an acceleration due to external excitation. Is there any suggestions?!

Because of the large dimensions and number of elements that used to build the model I always have problems in using APDL to solve my problem, so I'm trying to find a solution based on using workbench module as much as I can.

• Sandeep Medikonda
Ansys Employee

Hi Rana,

Are you running into any specific errors?

It is my understanding that behind the scenes, a mechanical model is always generating an APDL script before solving it.

Regards,

Sandeep

• Gumang
Subscriber
Hallo Rana, nI am looking for ways to apply the added mass for performing modal analysis on basics geometries in water in Ansys or in Workbench. Do you have any tipps for me. nThanking you nKind Regards nUmang n