Wheelset
Wheelset model objects contain properties required for calculating rolling sound powers (requires rolling noise option).
Overview
Each Vehicle can contain any number of Wheelset objects, which include properties for geometry, modal response and roughness. These properties are used, along with Track properties, when calculating rolling sound powers. Note that the rolling noise option must be present in your Train Noise Expert license in order to run rolling noise calculations.
Each of the Wheelsets are assigned a Wheelset library item, and in this way Wheelsets can be reused throughout your project. Wheelsets can be added or deleted, by right-clicking on the appropriate items in the model objects view . The order of the Wheelsets in the model objects view is determined by their distance from the front of the Vehicle.
Rolling sound powers from rolling sources are calculated according to the rolling noise procedure. When calculating the sound pressure levels using the external noise calculation, Train Noise Expert implements the following:
Wheel
Two equivalent point sources are used to model the noise contribution from each wheel, and they are both located at the wheel centre. The first one accounts for the acoustic power from radial vibration and has a monopole directivity. The second one accounts for the acoustic power from axial vibration and has a dipole directivity (with axis in the lateral direction). Each wheelset is composed of two wheels and both the wheels are present in the simulation (i.e. there are 4 point sources per wheelset).
Rail
There are two sources used to model the rail vibration due to the interaction with each wheel. The rail vertical vibration contribution is modelled by a point source having a monopole directivity. The lateral vibration is modelled by a point source with dipole directivity (orientated laterally). The position for rail sources is 0.07 m below the top of rail.
Sleeper
The sleeper acoustic power is represented by a monopole at 0.2 m directly below the top of the rail. Note that this is a standard monopole that radiates in a whole sphere so that it can be reflected in the ground. There is one source on each side of the track for each wheelset.
If including Wheelsets in a model, it is necessary to run the rolling noise calculations before running the external noise calculations.
If you do not have a license for the rolling noise option, then you may instead specify wheels as conventional Point sources (requires appropriate sound power data).
Input Parameters
| Name | Data type | Unit | Comment |
|---|---|---|---|
| Label | Text | - | A label for this Wheelset. This will be used to identify the Wheelset in the calculation and results. Special characters are not allowed. |
| Enabled | Checkbox | - | Specifies whether this Wheelset is enabled in the calculation. This is a convenient method to deactivate a single Wheelset without removing it from the model. |
| Distance from front | Number | m | The distance between the front of the Vehicle and the centre of the Wheelset. |
| Library item | Lib. item | - | The Wheelset library item to be used for this Wheelset instance. |
| Diameter | Number | m | The diameter of the Wheelset. (Note that this only affects the graphics view; the wheel geometry for the calculations is taken from the wheelmodes file.) |
| Normal load | Number | N | The normal load for this Wheelset. This affects the contact filter in the calculations. |
| Roughness input file | File | - | The file location for the wheel roughness is specified here (with ’.to’ file extension ). This setting is only enabled if the roughness input defined for the Situation has been set to allow separate wheel/rail roughness values. |
| Wheel modes input file | File | - | The file location for the wheel modes is specified here (with ’.wheel_modes’ file extension ). |
| Bogie cavity length (Beta feature) | Number | m | The length of the bogie cavity. This is used to calculate the effect of track absorption in the bogie area. |
| Bogie cavity height (Beta feature) | Number | m | The height of the bogie cavity. This is used to calculate the effect of track absorption in the bogie area. |
| Ratio of bogie sides open (Beta feature) | Number | 0-1 | The ratio of open area for the sides of the bogie cavity. This is used to calculate the effect of track absorption in the bogie area. |
| Include transfer functions (Beta feature) | Checkbox | - | Selects whether axlebox and bogie transfer functions are included as part of the rolling noise calculations. If included, the response of the bogie will be calculated and saved in the results folder as ‘roll_bogieResponse.csv’. Note that this is a Beta feature and this functionality may be changed in future releases. |
| Axlebox transfer mobilities (Beta feature) | File | - | The file location for the axlebox transfer mobilities is specified here (with ‘.xlsx’ file extension). |
| Suspension stiffness type (Beta feature) | Choice | - | For calculating the bogie response, the primary suspension stiffness can be specified as constant values (not recommended), or with frequency-dependent transfer stiffness values taken from a file. |
| Suspension stiffness file (Beta feature) | File | - | The file location for the primary suspension transfer stiffness is specified here (with ‘.xlsx’ file extension). This should be in complex values (to include damping). |
| Suspension stiffness (vert) (Beta feature) | Number | N/m | The vertical transfer stiffness of the primary suspension. |
| Suspension stiffness (lat) (Beta feature) | Number | N/m | The lateral transfer stiffness of the primary suspension. |
| Suspension damping (vert) (Beta feature) | Number | N.s/m | The vertical viscous damping of the primary suspension. |
| Suspension damping (lat) (Beta feature) | Number | N.s/m | The lateral viscous damping of the primary suspension. |
| Bogie transfer mobilities (Beta feature) | File | - | The file location for the bogie transfer mobilities is specified here (with ‘.xlsx’ file extension). |