However the shape doesn't look so good. The shuttle goes too high, more than 10 meters...But in distance that's ok !
I have read in the thesis that there are different values for Cl :
0.07 @ 10°
0.21 @ 20 °
0.35 @ 30°
Do you think I should adjust Cl all along the motion ?
And also, What is the difference between your approach and this one :
Quote:
4.2.1 The Main Program
The format of the main program can be seen in Figure 4.19. It reads in the necessary data, some of which is input directly by the user. The rest is read from data files which contain the experimental design parameters measured as described in Chapters 2 and 3. The main program calls the necessary subroutines for the trajectory prediction and writes the resulting trajectory data into a file, i.e. the time, horizontal and vertical distances, resultant and component velocities, incidences and direction of the velocity vector.
4.2.2 Subroutine for 2D Particular Motion; TRAJEC
The flow chart shown in Figure 4.20 describes the subroutine program which is used for predicting the shuttlecock trajectory with and without incidence. (For particular motion, with no incidence, TRAJEC is similar but does not call the 2D angular subroutine, TURN).
4.2.2.1 Interpolation of the Drag Coefficient, Cd
Two standard subroutines, SPLINE and SPLINT, from Press et al [27] were used to carry out a cubic spline interpolation method for setting the value of the drag coefficient Cd at a particular velocity. This was required as the coefficient varies with Reynolds number and therefore varies throughout the trajectory. (This is described in Chapter 2.)
• SPLINE: given the two arrays of data for the drag parameter at the corresponding velocity and the first derivatives of the interpolating function at the first and last data points, this subroutine computes an array of the same length containing the second derivatives of the interpolating function at the tabulated points.
• SPLINT: given the two arrays of data for the drag parameter at the corresponding velocity and the array of second derivatives computed by SPLINE, this subroutine will return a value of the drag parameter at a given velocity.
4.2.2.2 Integration of the Differential Equations of Motion
Two standard Fortran subroutines from Press et al [27] were used to carry out a fourth-order Runge-Kutta integration on the equations of motion:
• DERIVS4: given the horizontal and vertical velocities at a certain time this subroutine computes the accelerations at that time. In this case the equations that were used were the shuttlecock equations of motion, Equations 3.1 and 3.2.
• RK44: given the horizontal and vertical accelerations of the shuttlecock with the corresponding velocities at a certain time this subroutine uses the fourth-order Runge-Kutta method to advance the solution over a given time step and to compute the incremented velocities at the new time.
A suitable time step size for the Runge-Kutta method was found to ensure an accurate prediction with no divergence. It was found in the following way. A theoretical value for the range of a shuttlecock in a vacuum given certain initial conditions was calculated. This assumed no aerodynamic forces. By varying the time step, the optimum value was chosen such that the computed range agreed with the theoretical range as accurately as possible. This is shown in Tables 4.2 and 4.3. The optimum time step for the computer program proved to be 0.005 seconds.
Umm, i know it's a long post. Just tell me if you want to stop that thread..
thx
Fransoa
