AnyLogic - AnyLogic has changed simulation modeling and expanded its application into complex business environments. The unmatched flexibility of multimethod modeling allows users to capture the complexity of virtually any system, at any level of detail.
ns-3 - a discrete-event network simulator for internet systems
Simio - Facility design simulation & production scheduling
Paessler Multi Server Simulator - Paessler Multi Server Simulator is inexpensive and robust software that helps you power massive-scale testing.
PowerFLOW - Learn more about how PowerFLOW CFD solutions utilize complex geometry to perform aerodynamic, aeroacoustic and thermal management simulations.
Cisco VIRL - Cisco VIRL is a next-gen network virtualization and orchestration platform that enables you to accomplish multiple tasks like creating and customizing simulated networks with third-party and Cisco objects by means of a graphical utility.