Abstract: The subzonal pressure is obtained with subzonal Lagranian masses and corresponding densities. It results in subzonal corner forces and eliminates hourglass motion and spurious vorticity.We extend the compatible Lagranian hydrodynamics algorithm including subzonal pressures to unstructured zone and develope the code.Numerical examples of Saltzman piston demonstraste that this algorithm captures shock discontinuity,eliminates hourglass motion and restraines spurious vorticity accuratly and efficiently.

Key words: corner force, unstructured subzonal pressure, hourglass motion