本帖最后由 周舟 于 2016-5-9 13:41 编辑
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MESH SMOOTHING There is a subclass of ALE modeling referred to as mesh smoothing in which the mesh conforms to the exterior boundary of the ALE material and the elements are reshaped using any of several smoothing algorithms. After the elements are smoothed, material advection occurs. Although this smoothing approach is available in LS-DYNA, it is less general and less robust than the case in which the ALE mesh need not conform to the material boundaries. Thus the ALE smoothing approach in LS-DYNA is not discussed any further in these modeling guidelines. Instead, when ALE is discussed, focus will be on the general ALE approach. In addition, all the fluid elements are set up to be an ALE multi-material group so that each element has a specific material property and the ALE formulation tracks the motion of the elements in the numerical simulation. Note that the ALE control settings are essential. In our numerical model, the number of time steps between mesh smoothing and advection cycles, which could speed up run time but reduce stability, is determined to be unity based on the consideration of computational stability. The first order advection method is applied and it is efficient and accurate for the water. An option is selected (the AFAC value is set at -1) to ensure that no significant element distortion is allowed in the numerical simulation; only expansion and contraction are permitted.
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