# How to build a coordinate system with arbitrary direction by using HyperMesh

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Hi all,

I want to do a drop simulation, but the direction of the rigid wall is not parallel to the global axis direction. So I think a new system with one plane parallel to the rigid wall should be defined.

I think first I should define a system parallel to global system, then rotate the new system to the target direction.

The system panel was used to define the system, however I found the system was a moving system, so how to define a fix system in HyperMesh?

Best Wishes

Roy

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Another question: what's the difference between /SKEW and /FRAME ?  From the manual, no difference was found out.

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Hi Roy,

Create the system using the Create by axis direction option which will create fix frame or skew.

Two reference definitions are available for skew and frame in RADIOSS:

Skew reference:

It is a projection reference to define the local quantities with respect to the global reference. In fact, the origin of the skew remains at the initial position during the motion even though a moving skew is defined. In this case, a simple projection matrix is used to compute the kinematic quantities in the reference.

Frame reference:

It is a mobile or fixed reference. The quantities are computed with respect to the origin of the frame which may be in motion or not depending on the kind of reference frame. For a moving reference frame, the position and the orientation of the reference vary in time during the motion. The origin of the frame defined by a node position is tied to the node.

Please go through Help Menu regarding Skew and Frame which explains this concept with example.

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16 hours ago, George P Johnson said:

Hi Roy,

Create the system using the Create by axis direction option which will create fix frame or skew.

Two reference definitions are available for skew and frame in RADIOSS:

Skew reference:

It is a projection reference to define the local quantities with respect to the global reference. In fact, the origin of the skew remains at the initial position during the motion even though a moving skew is defined. In this case, a simple projection matrix is used to compute the kinematic quantities in the reference.

Frame reference:

It is a mobile or fixed reference. The quantities are computed with respect to the origin of the frame which may be in motion or not depending on the kind of reference frame. For a moving reference frame, the position and the orientation of the reference vary in time during the motion. The origin of the frame defined by a node position is tied to the node.

Please go through Help Menu regarding Skew and Frame which explains this concept with example.

Hi George P,

What's the difference between the two methods (create by axis direction or create by node reference) to define a system? The figure was showed in first floor.

Best Wishes

Roy

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Could anyone explain the difference?

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Hi Roy,

While creating system using node reference user is defining axis using the nodes as reference. With the nodes user is defining the axis in that particular direction.

Whereas using axis direction, user is directly referring the axis and plane.

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