### Aerodyn: Some input parameters for unsteady aerodynamic case

Posted:

**Fri Jun 03, 2016 10:30 pm**Hi,

I am using Aerodyn v15.02 to calculate a horizontal axis tidal turbine in two cases: steady and unsteady.

However, I encounter the requirements of providing some input parameters in unsteady aerodynamic case.

Specifically, they are:

1. C_nalpha: the slope of the 2D normal force coefficient curve in the linear region.

2. Cn1: the critical value of C0n at leading-edge separation for positive AoA and should be extracted from airfoil data at a given Reynoldâ€™s number and Mach number; Cn1 can be calculated from the static value of Cn at either the break in the pitching moment or the loss of chord force at the onset of stall; Cn1 is close to the condition of maximum lift of the airfoil at low Mach numbers.

3. Cn2: the critical value of C0n at leading-edge separation for negative AoA and should be extracted from airfoil data at a given Reynoldâ€™s number and Mach number; Cn2 can be calculated from the static value of Cn at either the break in the pitching moment or the loss of chord force at the onset of stall; Cn2 is close to the condition of maximum lift of the airfoil at low Mach numbers.

I do not know how to capture these parameters.

So, I will be very grateful if someone can show me how to capture them.

Thank you very much for this help.

I look forward to hearing from you.

Best regards,

Ngoc Ha Tran.

I am using Aerodyn v15.02 to calculate a horizontal axis tidal turbine in two cases: steady and unsteady.

However, I encounter the requirements of providing some input parameters in unsteady aerodynamic case.

Specifically, they are:

1. C_nalpha: the slope of the 2D normal force coefficient curve in the linear region.

2. Cn1: the critical value of C0n at leading-edge separation for positive AoA and should be extracted from airfoil data at a given Reynoldâ€™s number and Mach number; Cn1 can be calculated from the static value of Cn at either the break in the pitching moment or the loss of chord force at the onset of stall; Cn1 is close to the condition of maximum lift of the airfoil at low Mach numbers.

3. Cn2: the critical value of C0n at leading-edge separation for negative AoA and should be extracted from airfoil data at a given Reynoldâ€™s number and Mach number; Cn2 can be calculated from the static value of Cn at either the break in the pitching moment or the loss of chord force at the onset of stall; Cn2 is close to the condition of maximum lift of the airfoil at low Mach numbers.

I do not know how to capture these parameters.

So, I will be very grateful if someone can show me how to capture them.

Thank you very much for this help.

I look forward to hearing from you.

Best regards,

Ngoc Ha Tran.