Blade [Span] sensorA blade is divided into a number of Blade aerodynamical station, where aerodynamic properties are evaluated. The number of blade aerodynamical stations and their locations is defined in the Blade shape file. The blade span shows the properties of each Blade aerodynamical station along the blade. Therefore, the x-axis of the graphs of the Blade [Span] sensor is not time but distance to the blade root.
The Blade [Span] sensor can be opening by clicking the right side of the sensor icon on the Blade part and selecting Blade Span, as shown in the picture below
The output of the Blade [Span] sensor are the same as the Blade aerodynamical station sensor, but their values along the blade is given rather than their evolution in time. Thus, all values in this sensor are (also) for the same (i.e. current) point in time.
The Blade [Span] sensor has the following fields, computed with the BEM algorithm:
|Angle of attack||deg||The angle between the relative wind (projected into the deformed plane of the airfoil) and the chordline|
|Cl/Cd||-||Ratio of lift over drag coefficients|
|Local wind speed||m.s-1||Wind speed at the station in the horizontal plane. Note that this is only the magnitude of the wind at the blade stations: it does not include the effects of tilt, yaw, cone angles or the deflections of the blade|
|Relative velocity||m.s-1||Magnitude of the sum of the wind velocity, rotational velocity and induced velocity|
|Reynolds number||-||Reynolds number at the station, calculated with the chordlenght, the relative velocity and the kinematic viscosity as defined in the Environment part|
|Mach number||-||Mach number at the station, calculated as the ratio between the relative velocity and the speed of sound (taken as 343 m.s-1)|
|Axial induction factor||-||as calculated with the BEM method|
|Tangential induction factor||-||as calculated with the BEM method|
|Induced velocity||-||Induced velocity in the direction of the relative wind, as calculated with the BEM method|
|Induced tangential velocity||-||Induced velocity in the rotational direction of the blade station, as calculated with the BEM method|
|Lift force, distributed||N.m-1||Distributed aerodynamic force in the direction of the incoming wind|
|Drag force, distributed||N.m-1||Distributed aerodynamic force in the direction perpendicular to the incoming wind|
|Thrust force||N.m-1||Aerodynamic force in the main shaft direction, divided by the length of the element (see Section 4 in Steady BEM)|
|Thrust force, normalized||-||Thrust force divided by ρ⋅U2⋅R, where ρ is the air density, U is the wind speed at the hub (mean wind speed for turbulent wind) and R is the rotor radius.|
|Torque force||N.m-1||Aerodynamic force in the direction of rotation of the blade aerodynamical station (see Section 4 in Steady BEM)|
|Torque force, normalized||-||Torque force divided by ρ⋅U2⋅R, where ρ is the air density, U is the wind speed at the hub (mean wind speed for turbulent wind) and R is the rotor radius|
|Steady BEM iterations||-||The number of iterations used in the Steady BEM algorithm. Note: For Unsteady BEM (which is the default and set by the Aerodynamics->Advanced->BEM mode parameter) only the initial (first) solution is Steady and thus uses iterations. Thus, during an Unsteady BEM simulation the values will not change.|
|Deflection (out-of-plane)||m||Out-of-plane displacement of the blade aerodynamical station.|
|Deflection (in-plane)||m||In-plane displacement of the blade aerodynamical station.|
|Moment (magnitude)||Nm||Magnitude of the bending moment.|
Note: by definition, no angle of attack is defined for circular blade sections (typically the innermost sections of the blade). Therefore, no value for the angle of attack, lift and drag coefficients are displayed for these stations
1 Output file
The output file for the Blade [Span] sensor looks slightly different than the other output files, since it contains both the time and the span variation of the data. In this file, each field is tab separated, and within the output the data at each Blade aerodynamical station are space separated.
The position of each station is provided before the time series, as highlighted in red in the image below.