Circuit Simulator - Animated electronic circuit simulator using ideal components to visualize voltage and current.
AQUASIM - In order to support environmental scientists in finding an «adequate» model of the system...
LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.
STOAT - STOAT - a dynamic sewage treatment works modelling package
Solve Elec - Solve Elec is a free educational program to draw and analyze electrical circuits.
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming