1. A multi-purpose versatile modular pulse duplicator system that simulates cardiovascular hemodynamic functions, the system comprising: a plurality of modules each having a first straight through channel, wherein the plurality of modules are detachably and fluidly coupled to each other forming a fluidly connecting circulating flow via said first straight through channel of each module; wherein at least two of the plurality of modules each have a second straight through channel crisscrossing in a right angle with the first straight through channel of the same module, and the first and second straight through channels of the same module are fluidly connected to each other; wherein each of said first straight through channels has an inflow port and an outflow port, and the inflow and outflow ports of the first straight through channels each have a diameter that is the same as a diameter of the first straight through channel; wherein the diameter of the first straight through channel is constant throughout an entire length of the first straight through channel; wherein each of said second straight through channels has an inflow port and an outflow port, and the inflow and outflow ports of the second straight through channels each have a diameter that is the same as a diameter of the second straight through channel; wherein the diameter of the second straight through channel is constant throughout an entire length of the second straight through channel; wherein at least one inflow or outflow port is covered by a cap; wherein one of the plurality of modules is a pump module having a linear motor disposed thereon to drive a fluid in the circulating flow; and wherein the plurality of modules are adapted to be detached from each other becoming free standing pieces, and be reattached to each other having a different sequence order or having a different quantity of modules, forming yet another fluidly connecting circulating flow via said first straight through channel of each module.