This example shows the necessary steps for studying the flow pattern that appears in a “lateral”, cavity of a by-flowing fluid – one side of the cavity being swept by the outer flow.
The flow pattern will be calculated using the incompressible Navier-Stokes equations for a Reynolds number of 1 (in order to capture turbulence effects that appear at higher Reynolds numbers, a finer mesh would be necessary).
The geometry simply consists of a “box”, representing a cubic cavity, its top face being swept by the passing fluid. This problem is essentially a two-dimensional case, i.e. it could also be calculated in only two dimensions (see Tdyn 2D Tutorial). The problem will be however solved in three dimensions to illustrate the basic capabilities of Tdyn.
- incompressible flow
- viscous, non-turbulent case
- Reynolds number equal to 1
The Reynolds number (Re) is given by the equation shown below. In this equation, L represents the characteristic length of the problem, which in this case is the edge length of the cube, r and m are the density and the viscosity of the fluid respectively, and v is the velocity of the flow on the swept surface.
Re =r· v· L / m
For the example to be solved, we can choose arbitrarily:
- L = 1 m
- v = 1 m/s
- r = 1 kg/m3
- m = 1 kg/m.s
By substituting the variables for their value in the equation above we obtain the Reynolds number:
Re = 1
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