A large amount of output is potentially available from some simulations. Click the Outputs button on the Calculations screen to define which of these outputs are required. The outputs are grouped into blade, tower and other outputs.
The Aerodynamic information, Performance coefficients and Power curve calculations are unaffected, as they produce a pre-defined set of outputs.
7.21.1 Blade coordinate systems and outputs
To configure blade outputs, click Blade outputs on the Calculation Outputs Specification screen.
Blade outputs include aerodynamic information (including distributed aerodynamic loadings), blade loads and motions. For each of these categories, the information may be generated at any or all of the blade stations (see 3.1). Click Select Output Stations to determine which information is required at which stations. Click Add to define additional points where interpolated loads will be output.
Having defined the blade stations required, specify for each type of output whether that information is required on the First blade, All blades, or not at all (None).
The loads can be specified independently about the following axes: Principal axes, Root Axes, Aerodynamic Axes and User Axes. Within each group, the loads are labeled Mx, My, Mxy, Mz, Fx, Fy, Fxy, Fz.
It’s important to note that the Principal Axes and Root Axes stations coincide with the underlying finite beam element model nodes. The Principal Axes coordinate vectors align with the finite beam elements. The Root Axes coordinates have the same origin rotated to align with the blade root.
The Aerodynamic and User Axes potentially have origins that do not coindicide with the underlying finite element beam model nodes. These load outputs are found by transforming the finite element loads (in the Principal Axes coordinates) to the Aerodynamic or User Axes coordinate centre. The tranformation accounts for additional Mx and My bending moments that are generated at the Aerodynamic or User Axis centre by the element axial force Fz in the Principal Axes system, due to the offset in the aerofoil plane between these two coodinate centres. This effectively estimates the load that would have occurred if the load was carried through an axis at the Aerodynamic Axis or User Axis centre. There is some approximation in this method as the Aerodynamic and User Axes loads are not the true load path. Any changes to the the blade dynamics (e.g. deflections or loads) that might result from such a change in load path are not accounted for.
Principal axes: The positive z-axis follows the local deflected neutral axis at each blade station towards the blade tip. The positive y axis is defined by the principal axis orientation. The positive x axis is orthogonal to the y and z and follows the right hand rule. For output loads, the origin of the axes is on the neutral axis at each local deflected blade station. (see diagram below)
![[Pasted image 20250610111507.png]]Blade principal axes coordinate system
Note that there is a subtle difference between the “principal axis” frame and the “blade local element frame”.
The “blade local element frame” is orientated so that the X vector in this coordinate system points directly between adjacent nodes on the blade. The other two coordinate system vector directions are determined by the “principal axis twist” angle. This is explained in more detail in DNV GL technical note UKBR-110052-T-31-A
The “principal axis” frame is used for load output in Bladed. The principal axis orientation is calculated by taking the average orientation of the two blade elements at the node where the elements join. This is illustrated below. The two adjoining local element frames are shown in green and red. The principal axes output frame is shown in blue.
Note that the element local coordinate system has its x direction along the element, unlike the “principal axes” coordinate system which has z along the element axis.
Relationship between blade "local element axes" and "principal axes coordinates"
### Root axes
Root axes: The orientation of the axes is fixed to the blade root and does not rotate with either twist or blade deflection. The axis set does rotate about the z axis with pitch. For output loads, the origin of the axes is on the neutral axis at each local deflected blade station.
**Aerodynamic axes**: The x axis is perpendicular to the local aerodynamic chord line and the positive y axis is aligned along the local aerodynamic chord line from leading edge to trailing edge. The z-axis is parallel to the local deflected neutral axis at each blade station and increases towards the blade tip. For output loads, the origin of the axes is on the chord line at 25% chord from the leading edge at each local deflected blade station.
**User axes**: The origin of the axes is specified as percentages of chord, parallel and
perpendicular to the chord at each blade station. The user can specify whether the z-axis is
parallel to the root axis or the local neutral axis, and independently whether the y-axis is aligned
to the principal axis orientation, the aerodynamic twist or the root axis.
**用户坐标系**: 坐标原点以弦长的百分比为准，并在每个叶片位置平行于弦长方向和垂直于弦长方向定义。用户可以指定 z 轴是否平行于根轴或局部中性轴，并且可以独立地指定 y 轴是否与主轴方向、气动扭角或根轴对齐。
**The coordinate system for the blade deflections is as follows:**
z-axis Radially along the blade root Z axis
x-axis Perpendicular to z, and pointing towards the tower for an upwind turbine, or away from the tower for a downwind turbine.
y-axis Perpendicular to blade axis and shaft axis, to give a right-handed co-ordinate system independent of direction of rotation and rotor location upwind or downwind of the tower.
The blade geometry is defined at each blade station (see 3.1) clicking on the data item to be defined or changed. The following data is required at each station:
Distance: This can be entered as a distance along the blade or as a distance along the blade root Z-axis. Select the appropriate option at the base of the screen.
• Distance along blade: the distance from the blade root to the current blade station, along the blade neutral axis, which does not have to be a straight line. It must be zero for the first station. If distance is entered along the blade root Z-axis, this value is calculated based on the distance along the blade root Z-axis and the neutral axis.
• Distance along blade root Z-axis: the distance of the blade station along the nominal pitch axis (with no pre-sweep or pre-cone). If distance is entered along the blade, this value is calculated based on the distance along the blade and the neutral axis.
• Chord: the distance from the leading edge to the trailing edge, i.e. along the chord line.
• Aerodynamic Twist: the local angle of the chord line. More positive values of twist and set angle push the leading edge further upwind. (See diagram below)
• Thickness: the thickness of the blade as a percentage of the chord at that station.
• Neutral axis (x): the distance from the blade root Z-axis to the neutral axis in the x direction. This would be non-zero if for example the blade was pre-bent. (See diagram below)
• Neutral axis (y): the distance from the blade root Z-axis to the neutral axis in the y direction. (See
diagram below)
• Neutral axis, local (x’): the perpendicular distance from the chord line to the neutral axis in local
coordinates, as a percentage of the chord. (See diagram below)
• Neutral axis, local (y’): the distance along the chord line from the leading edge to the neutral axis
in local coordinates, as a percentage of the chord. (See diagram below)
• Foil section: an index number defining the aerofoil section (see 3.8) at that station
• Moving/Fixed: differentiates between a fixed part of the blade and a part which is movable to
achieve aerodynamic regulation or braking, either by bodily changing the pitch of that part of the
blade, or by deploying an aileron, flap or other aerodynamic control (see 4.1) surfaces.
To configure hub outputs, click Other Outputs on the Calculation Outputs Specification screen.
The co-ordinate system for the hub load and deflection outputs from the calculations is based on the ‘GL’ convention, with some modifications as specified below.
Hub loads in fixed frame of reference:
XN Along shaft axis, and pointing towards the tower for an upwind turbine, or away from the tower for a downwind turbine (the picture shows an upwind turbine).
ZN Perpendicular to XN, such that ZN would be vertically upwards if the tilt angle were zero.
YN Horizontal, to give a right-handed co-ordinate system independent of direction of rotation and rotor location upwind or downwind of the tower.
Co-ordinate system for stationary hub loads
要配置轮毂输出，请在“计算输出规范”屏幕上点击“其他输出”。
来自计算的轮毂载荷和挠度输出的坐标系基于“GL”惯例，并根据以下说明进行了一些修改。
![[Pasted image 20250610154850.png]]
轮毂载荷（固定参考系）：
XN 沿轴向，对于迎风式风轮，指向塔架；对于背风式风轮，则背离塔架（图片显示的是迎风式风轮）。
ZN 与 XN 垂直，如果倾斜角度为零，则 ZN 将垂直向上。
YN 水平方向，以提供一个与旋转方向和风轮位于迎风或背风位置无关的右手坐标系。
静止轮毂载荷坐标系
![[Pasted image 20250610155051.png]]
Hub loads in rotating frame of reference:
XN Along shaft axis, and pointing towards the tower for an upwind turbine, or away from the tower for a downwind turbine (the picture shows an upwind turbine).
ZN Perpendicular to XN, such that ZN would be aligned with blade 1 axis if the cone angle were zero.
YN Perpendicular to XN and ZN, to give a right-handed co-ordinate system independent of direction of rotation and rotor location upwind or downwind of the tower.
Origin At hub centre (intersection of blade and shaft axes).
Figure 7-9: Co-ordinate system for rotating hub loads
旋转坐标系下的叶片中心载荷：
轮毂的旋转坐标系随叶片旋转，ZR跟随叶片1
XN 沿轴向，对于迎风式风轮指向塔架，对于顺风式风轮则背向塔架（图示为迎风式风轮）。
ZN 与 XN 垂直，如果锥角为零，则 ZN 将与叶片 1 轴对齐。
YN 与 XN 和 ZN 垂直，构成一个右手坐标系，该坐标系与旋转方向和风轮位于迎风侧或顺风侧无关。
原点 位于叶片中心（叶片和轴的交点）。
图 7-9：旋转叶片中心载荷坐标系
## 7.21.3 Anti-clockwise and downstream rotor coordinate systems
The rotor and blade output coordinate systems for all permutations of clockwise, anti-clockwise, downstream and upstream rotors are shown in the following four figures.
Note that for simplicity these diagrams do not include blade mounting cone, blade mounting sweep. The blade pitch and set angle are shown at zero in these diagrams.
风轮和叶片的输出坐标系，针对顺时针、逆时针、向下游和向上游风轮的所有排列方式，见下四幅图。
请注意，为了简化起见，这些图未包含叶片安装锥度和叶片展向。图中显示的是零变桨角度和零扭角。
![[Pasted image 20250610155315.png]]Blade and rotor coordinate systems for a clockwise upstream rotor
![[Pasted image 20250610155646.png]]Blade and rotor coordinate systems for an anticlockwise upstream rotor
![[Pasted image 20250610155658.png]]Blade and rotor coordinate systems for a clockwise downstream rotor
![[Pasted image 20250610155729.png]]
Blade and rotor coordinate systems for an anticlockwise downstream rotor
## 7.21.4 Tower outputs
Click Tower outputs on the Calculation Outputs Specification screen.
Tower loads may be generated at any or all of the tower stations (see 4.5). Click Select Output Stations to determine at which stations the loads are to be output. For the monopile tower model, click Add to define additional points where interpolated loads will be output.
Having defined the tower stations required, specify for each individual output whether that information is required. For the loads, this can be specified independently for each of the forces and moments.
There is also an option to Refine deflections. With this option disabled, the tower deflection outputs are modal deflections. Modal deflections give a good estimate of overall tower motion, but may not be very precise in predicting the small deflections at foundation stations. This can lead to a poor estimate of the foundation reaction loads given the applied loads on the rest of the turbine.
With the Refine deflections feature enabled, the tower deflections are re-calculated at each output time step using the underlying finite element model with the external loads applied. The refined deflections give a more accurate estimate of the deflections at the foundation nodes, hence the foundation reaction forces are more accurate, especially for non-linear foundations. With Refine deflections selected, Bladed will iterate at each output time step to find the foundation applied loads based on the refined deflections. This will ensure that the applied loads, tower deflections and foundation reactions correspond correctly.
Note that the modal deflections are used to estimate the foundation loads when solving the structural system at each integrator time step. To use the refined deflections at every time step would require iteration on each time step, causing a significant increase in simulation time. The assumption with this modelling choice is that error in foundation load estimate due to using modal deflections doesn’t affect the overall turbine dynamics significantly. It is therefore reasonable to only calculate the foundation reaction loads based on refined deflection on each output time step.
The co-ordinate system for tower outputs is based on the GL convention, as described below.
![[Pasted image 20250610160454.png]]
XT Pointing South.
ZT Pointing along deflected tower centre line.
YT Pointing East.
Origin At each tower station.
Note that for steady-state calculations the wind is deemed to come from the North.
Figure 7-14: Co-ordinate system for tower loads (monopile only) and deflections
Note that the coordinate system system for tower loads moves with tower modal deflections, so that the coordinate system remains aligned with the deflected member axis.
需要注意的是，塔架载荷的坐标系会随着塔架模态挠度而移动，以保持坐标系与挠曲构件轴对齐。
Loads and deflections for multi-member towers
The loads are output with reference to the local member coordinate system for each member. The member x-axis is always aligned along the member. The member z axis is perpendicular to the member x-axis and aligned according to the direction cosines for the member z-axis as specified in the tower screen. These are the direction cosines of the z-axis relative to the global GL coordinate system. For example, a vertical member with z-axis direction cosine of 0.0 in the x-direction, 1.0 in the y-direction and 0.0 in the z-direction would be a member where the local x-axis corresponds to the GL z-axis, the local y-axis corresponds to the GL x-axis and the local z-axis corresponds to the GL y-axis.
The deflections are output in the GL coordinate system.
Bladed multi-member output convention: local x-y plane:
The same sign convention applies to the applied pitching moment, pitch bearing friction and pitch actuator torque. A positive applied pitching moment means that the blade aerodynamic, gravitational and other applied forces act in such a way as to drive the pitch in the positive (feathering) direction.
Pitch system loads and deflections:
For pitch angles, rates and accelerations, the positive direction is the direction in which the leading edge moves upwind, i.e. towards the feathered position:
The yaw bearing is located at the “nacelle node” as specified in the support structure screen. For monopile towers, the yaw bearing is assumed to be located at the top tower station.
The co-ordinate system for yaw bearing loads is the same as for the top tower station except that it rotates with the nacelle yaw angle.
Yaw bearing output is defined opposite to the GL z-axis, with clockwise from North being positive.
支撑结构屏幕中，偏航轴承位于“吊舱节点”处。对于单桩塔架，假设偏航轴承位于塔顶位置。
偏航轴承载荷的坐标系与塔顶位置的坐标系相同，但会随着吊舱偏航角度旋转。
偏航轴承输出定义为与GL z轴相反，以北为正，顺时针方向为正。
## 7.21.8 Variables that follow “rotor direction is positive” convention
There are a number of other variables for which the positive direction is the ‘normal running’ direction. This applies to controller and drive train variables such as rotor and generator speeds, torques and azimuthal positions, drive train and generator torques etc.
• Summary information: includes principal operational and environmental indicators.
• Software performance: useful for diagnosing slow simulations, and finding a suitable step length for Real Time Test simulations.
• Specific node outputs: This is an advanced feature, intended for users with some knowledge of the Multibody Dynamics approach used within Bladed. See the description below.
Clicking the Specific node outputs… button will open the Node Outputs screen, which allows you to add, delete or edit entries in the node outputs list. This is a list of structural nodes at which you want to see kinematic (position, velocity, acceleration) or loads outputs.
To see a tree diagram of node identifiers and the components they are connected to, run Bladed once without altering the project details (a 1-second simulation is enough), and then open the verification (.$VE) file in a text editor. Any node and component identifiers you enter must be exactly as they appear in this tree, and the component must be connected directly to the node. For each node, choose the type – Loads or kinematics – and the coordinate system in which you want the outputs to be expressed. Specify a name for the output group; this is the name that will appear in the list of outputs in the dataviewer. You can also choose to have the outputs calculated at a position (Offset) other than that of the node itself. This option should be used with care, as it must represent a position in space that is physically on the turbine structure, otherwise the outputs will be meaningless.
These outputs describe the wind speed and direction, as well as the sea surface elevation and seismic motions, if present. All speeds are relative to the hub or rotor motion, so any motion of the nacelle is reflected in these outputs.
Hub wind speed magnitude: This is the overall relative flow speed magnitude experienced by the hub.
Cup anemometer wind speed: This is the horizontal component of the hub wind speed magnitude.
Hub longitudinal wind speed: The component of the horizontal wind speed aligned with the hub longitudinal direction (includes rotation due to yaw angle).
Hub lateral wind speed: The component of the horizontal wind speed aligned with the hub lateral direction (includes rotation due to yaw angle).
Hub vertical wind speed: The component of the flow speed magnitude in the vertical direction.
Wind direction at hub: Direction, as an angle to North (clockwise looking down).
Wind upflow at hub: Upflow, as an angle to the vector of flow direction in the horizontal plane. Positive angle is upwards.
Rotor average longitudinal wind speed: Component of the overall flow speed along the hub X axis, averaged over the rotor plane. The rotor is effectively treated as a non-rotating disc.
Rotor average longitudinal wind direction: Direction, as an angle to North (clockwise looking down), averaged over the rotor plane as above.
Sea surface elevation: Instantaneous sea surface Z in global coordinates, at global X=0, Y=0.
In this section the outputs of the aerodynamics module are explained. To understand the outputs, the definitions of the rotor axial/tangential direction are defined in the figures below. Note that “axial” indicates in direction of normal vector “n” and tangential indicates in the direction of tangent vector “t”. Further note that the radial vector “r” assumes an un-coned rotor.
• Pitch Angle – The current pitch angle of the blade
• Pitch rate – The current rate of pitching of the blade
• Pitch acceleration – The current acceleration of pitching of the blade
• Demand Pitch Angle/Rate – The input demand from the controller into the actuator system
• External Pitch Bearing Moment – This is the load that comes from the blade due to aerodynamic and inertial loading, acting on the bearing. When the rotor is clockwise, the sense of the load is opposite to that of GL Blade z-axis, but is the same sense for an anti-clockwise rotor.
• Pitch Bearing Friction – The total friction (kinetic or static) acting on the pitch freedom.
• Pitching Inertia – The total pitching inertia consisting of the outboard blade inertia plus the referred motor rotational inertia if a rotary actuator is defined.
• Pitch actuator torque (rotary actuator drive or no drive defined) –The torque provided by the pitch motor. Defined on the motor side of the gear ratio.
• Pitch actuator force (linear actuator drive) –The force provided along the line of the actuator ram.
• Controller demanded pitch angle/rate (setpoint trajectory planning defined) –The input demand from the controller before being limited by setpoint trajectory planning.
• Limited demanded pitch angle/rate (setpoint trajectory planning defined) –The demand after it has been limited by setpoint trajectory planning.
• Motor position/rate/acceleration (When a flexibility in the actuator drive is defined) –Kinematics the motor side of the gear ratio and drive flexibility
