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*PDRAG
Data format:
An arbitrary number of cards with 5 values each
IP IVEL COEF ITABLE VECH
Status :
Optional
Purpose :
To define local drag coefficients
Restrictions :
The node IP and table ITABLE must have been previously defined. The total number of nodes where drag and lift coefficients are introduced may not exceed MAXBOU which is a version dependent parameter.
Details :
| Parameter | Description |
|---|---|
| IP | Identification number of the node where the |
| coefficient has to be applied | |
| IVEL | Index for the direction of the relative fluid velocity 1 - horizontal , 2 - vertical |
| COEF | Corresponding drag coefficient ( factor of $ |
| ITABLE | Reference table for the possible fluid velocity dependence description of the drag coefficient COEF. For constant drag coefficient set ITABLE=0 and VECH is ignored. |
| VECH | Velocity step of the description table ITABLE (see note) |
Note
- Usual calculation of COEF :
COEF = 0.5 * RHO * CD * S
with CD drag coefficient, and S cross section perpendicular to the direction specified by IVEL. Standard values of CD for a vertical cylinder with two hemispherical caps are : horizontally 1.2 - vertically 1.4
- For a velocity \(\vec{U}\) ((I-1) * VECH < \(||U||\) < I*VECH) the lift force applied to node IP will be interpolated between COEF * TABLE(I-1,ITABLE) * \(||U||\vec{U}\) and COEF * TABLE(I,ITABLE) * \(||U||\vec{U}\)
- Drag forces are defined only in global axis.
Example : *PDRAG c [.] [.] [kg/m] 11 1 250 2 250
