I have purchased a wind turbine with a power of 300 W, the start up wind speed is 2.5 m/s, rated wind speed is 11 m/s, and the survival wind speed is 45 m/s, and what I'm going to do is to make an educational modeling for how to generate electrical power using a wind turbine, I mean that I will provide the wind using an axial fan, My question is, how can I predict the power of the fan and its max flow rate required to make the turbine rotate at its maximum power?
You need to push air through the turbine at 11 m/s, or just above. That's what the rated windspeed means: it's the lowest windspeed at which the turbine hits rated power, at standard atmospheric pressure.
The volume of air you need is determined by the area of the rotor. Let's say it's $\alpha m^2$. So you know you need to push through $11\alpha m^3/s$.
So assuming you have some shroud or something so that all the air pushed by the fan passes through the turbine rotor, then that's the rate of air that the fan moves. Then you need the specific fan power, to know how much power you'll draw - let's say it's $\phi kJ/m^3$. Multiply that by the air volume, to get the power requirement of the fan. In the above case, that would be $11\alpha\phi kW$. You'll want to add a bit of contingency to that, to account for things.
In the end, your required power in is going to be your power out, divided by your turbine efficiency, and then divided by your fan efficiency.