Oscillating airfoil for wind energy
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Hi,
I am trying to simulate an airfoil oscillating vertically over a 6m displacement. i want to write UDFs to describe different relationships between the pitch of the airfoil and the vertical displacement. first i am trying a sinusoidal relationship so the foil is at max angle of attack at the centre of the displacement and the there is also a spring force pulling it back to the centre of the range. the foil is a symmetrical NACA0012 of chord length 1m in a constant air speed of 10m/s i aim to find the best pitch motion that will completes a complete oscillation the quickest. to do this i am using an interpreted six degrees of freedom UDF shown below: #include "udf.h" DEFINE_SDOF_PROPERTIES(fmotion5, prop, dt, time, dtime) { real x[ND_ND]; real THETA[2]; real vel[ND_ND]; real a ; #define PI 3.14159265; real K=10; real THETAMAX =0.349; real SPRING; SPRING=-K*(x[1]); prop[SDOF_MASS] = 5; prop[SDOF_IZZ] = 0.00001; -3<=x[1]<=3; prop[SDOF_ZERO_TRANS_X]=TRUE; prop[SDOF_ZERO_TRANS_Z]=TRUE; prop[SDOF_ZERO_ROT_X]=TRUE; prop[SDOF_ZERO_ROT_Y]=TRUE; prop[SDOF_LOAD_F_Y]=SPRING ; a = ((vel[1])/(sqrt(vel[1]*vel[1])))*THETAMAX*cos(asin((x[1])/3)); THETA[2]=a; } I can only interpret the UDF due to the restrictions on the university computer i am using. When i hook the UDF in, the airfoil shows no motion and i sometimes get negative cell volumes. Can anyone help me on this? I am quite new to CFD by the way. Thanks in advance Henry |
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