Viscous Daming Coefficient (VDC) is freqeuntly used in contact interface definitions (*CONTACT) to damp out oscillations normal to the contact segment. It is specified in percentage of the critical damping where a value of 90 is 90% of critical damping. In one recent applications using SPH for gravity initialization of a filled fluid container, using a critical damping coefficient of 90 (%) significantly reduced the noise in the particle contact interaction with the lagrange elements. The attached image shows the force time history with and without VDC.

(Click image to enlarge)