The Marangoni convection approximation automatically adjusts the melt temperature conductivity to approximate the heat transfer through the melt pool via convection.
*MRNG
r1
r2
r1: r*8 Temperature offset, subtracted from the Solidus temperature, to define the width of the ramp
r2: r*8 Conductivity scaling factor
Marangoni convection occurs in the melt pool during welding and additive processes, wherein the advection of the molten material incurs a large amount of convective heat transfer. In the Local Simulation thermal model this behavior cannot be captured directly as it is purely a solid model. However, following the advice of Goldak et al [1], this can be approximated by using a very high thermal conductivity for temperatures in the liquid phase. This is typically done by multiplying the highest temperature conductivity and setting it at or near the solidus temperature. This card automatically applies the Marangoni Convection approximation at a temperature offset r1 below the Solidus temperature in the *LATE card, multiplying the highest temperature conductivity by r2. The effect on the conductivity is illustrated in the figure below. This effect is only applied during the generation of PRMs of type Hot Spot and Lack of Fusion.
Plot of Thermal Conductivity vs Temperature using the Marangoni approximation
Required Cards: *LATE
[1] John Goldak, M Bibby, J Moore, R House, and B Patel. Computer modeling of heat flow in welds. Metallurgical transactions B, 17:587-600, 1986.