Physical Phenomena

When using CFD to study a fluid dynamics problem there are numerous details that should be considered in order to insure useful results.  Some of these issues are not obvious and are the focus of the articles in this section titled Physical Phenomena.

A question that often arises is at what Reynolds numbers is a computational model likely to be accurate?  The article Reynolds Number Restrictions in CFD addresses this question by providing a discussion of both high and low Reynolds numbers where limitations may seriously affect a simulation.  Another important question is whether or not it is necessary to use numerical approximations that satisfy the basic fluid conservation laws of mass, momentum and energy.  Generally, it would be thought that satisfying these laws is a good thing, but as the article To Conserve or Not  explains, this is not always the case.

Along similar lines, it is not always recognized that there are two, not one, conditions for a fluid to be incompressible; and there is also more than one possible specification for a pressure or outflow boundary, depending on the physical situation that is to be modeled.  These topics are covered in the articles The Incompressibility Assumption and several articles that discuss Boundary Conditions.

Boundary conditions: grid overlay