在写毕业论文，做地暖管地面热分析模拟，模型是有四块板拼接成的，板中布置有管道，建模完成后接触一直提示出错，哪位大侠能指点一二，不胜感激！
这是提示的错误：
The slave and master pair (assembly__pickedsurf187, assembly__pickedsurf186) is invalid. Stress-displacement element surfaces and acoustic element surfaces cannot couple using *contact pair.
No bulk modulus is defined for acoustic element 2 instance part-1-1. All acoustic elements must have nonzero bulk modulus defined using *material and *acoustic medium.

Initialization of acoustic element material point data for element 2 has failed because no bulk modulus exists for thiselement.