  The goal of international trade theories is to explain the exchange of goods
and services between different countries, aiming to benefit from it. Albeit the
idea is very simple and known since ancient history, smart policy and business
strategies need to be implemented by each subject, resulting in a complex as
well as not obvious interplay. In order to understand such a complexity,
different theories have been developed since the sixteenth century and today
new ideas still continue to enter the game. Among them, the so called classical
theories are country-based and range from Absolute and Comparative Advantage
theories by A. Smith and D. Ricardo to Factor Proportions theory by E.
Heckscher and B. Ohlin. In this work we build a simple hydrodynamic model, able
to reproduce the main conclusions of Comparative Advantage theory in its
simplest setup, i.e. a two-country world with country A and country B
exchanging two goods within a genuine exchange-based economy and a trade flow
ruled only by market forces. The model is further generalized by introducing
money in order to discuss its role in shaping trade patterns. Advantages and
drawbacks of the model are also discussed together with perspectives for its
improvement.
