  In this article we introduce the concept and the first implementation of a
lightweight client-server-framework as middleware for distributed computing. On
the client side an installation without administrative rights or privileged
ports can turn any computer into a worker node. Only a Java runtime environment
and the JAR files comprising the workflow client are needed. To connect all
clients to the engine one open server port is sufficient. The engine submits
data to the clients and orchestrates their work by workflow descriptions from a
central database. Clients request new task descriptions periodically, thus the
system is robust against network failures. In the basic set-up, data up- and
downloads are handled via HTTP communication with the server. The performance
of the modular system could additionally be improved using dedicated file
servers or distributed network file systems.
  We demonstrate the design features of the proposed engine in real-world
applications from mechanical engineering. We have used this system on a compute
cluster in design-of-experiment studies, parameter optimisations and robustness
validations of finite element structures.
