Unity3D改变粒子运行速度

ParticleSystem.Particle[] particles = new ParticleSystem.Particle[particleSystem.particleCount];
particleCount = particleSystem.GetParticles(particles);
for(int i = 0; i < particleCount; i++)
{
particles[i].velocity = new Vector3(particleSpeed, 0, 0);
}
particleSystem.SetParticles(particles, particleCount);