Transient Analysis of a Car
 

Hi everyone,
I am a beginner in CFD.I am doing transient analysis of a car as a part of my aerodynamics project.
I am using half-car model(symmetry) for my simulation.
Earlier,i did steady state cfd analysis with Realizable K-epsilon turbulence model ,Coupled Scheme
Flow courant number-50
Under relaxation factors are
Pressure-0.25
Momentum-0.25
Turbulence -0.85
and i used a mesh with skewness of 0.92 max
The solution got converged for steady state simulation.
Now the problem is for transient Simulation the solution is diverging after 20 time steps(600th iteration and above)Time step size is 0.01
Could you help me with some ideas how to improve mesh quality and recommend which scheme,time-step size to be used in order to get convergence?Thanks in advance..