Surface Normals

The calculation of surface normals is a crucial step in multimaterial mode MPM.

Introduction

The surface normal is a key component of multimaterial mode MPM calculations. First, normals are needed to find the component of the velocity in the approaching direction, which is used to detect contact. Second, the normals are needed implement contact mechanics or |imperfect interfaces. Practical experimental using multimaterial mode MPM simulations has revealed that accuracy of results is very sensitive to the method used to find the normals.

Normal Vector Options

When multimaterial mode MPM was initially developed, contact was handled separately for each material's velocity field and the normal vector was found from that material's mass gradient. NairnMPM has implemented new methods that seem to work better. No one method works for all problems, which is why multiple options are available. This section describes the available options.

Each Material's Gradient

Show picture two materials with two normals

Maximum Gradient

Show full vs partial

Average Gradient

Show top with two edges

Maximum Volume

Just describe

Custom Specified Normal

Developer flags and maybe more options int he future