In diffusion limited aggregation( DLA) model,particle aggregation in parallel field is investigated. It shows that symmetry of particle aggregation is destroyed and particle density is increased. Aggregation pattern transforms fractal into compaction and growth location of aggregation transforms into saturated growth region. As intensity of parallel force field is stronger,aggregation grows faster and particle density is higher.

A modified DLA model is used to simulate particle aggregations formed by random particle released from a local source.It shows that growth structure of aggregations are relative to position of the particle source.Growth velocity toward particle source is faster.It is also shown that particle distribution in growth plane is related to relative distance and relative size of the particle source.A law of particle distribution depends on particle source is shown.It may help in understanding azimuth of particle source from the growth stiucture of aggregations,and to estimate relative distance and relative size of the particles source.